tag:blogger.com,1999:blog-1927516228676647102023-11-15T08:59:47.723-08:00Microsoft Encartaghozian karamihttp://www.blogger.com/profile/13214011599962806335noreply@blogger.comBlogger15125tag:blogger.com,1999:blog-192751622867664710.post-23096222539722683322009-01-02T16:36:00.000-08:002009-01-02T16:38:02.358-08:00All about earth<p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 24pt; font-family: "MS Reference Serif","serif";">Earth (planet)<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">I<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">INTRODUCTION</span></p></td></tr></tbody></table><img src="http://farm4.static.flickr.com/3265/2767407807_2d6cd2961d_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Earth<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">An oxygen-rich and protective atmosphere, moderate temperatures, abundant water, and a varied chemical composition enable Earth to support life, the only planet known to harbor life. The planet is composed of rock and metal, which are present in molten form beneath its surface. The Apollo 17 spacecraft took this snapshot in 1972 of the Arabian Peninsula, the African continent, and Antarctica (most of the white area near the bottom).<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">NASA/Science Source/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Earth (planet), one of nine planets in the solar system, the only planet known to harbor life, and the “home” of human beings. From space Earth resembles a big blue marble with swirling white clouds floating above blue oceans. About 71 percent of Earth’s surface is covered by water, which is essential to life. The rest is land, mostly in the form of continents that rise above the oceans.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Earth’s surface is surrounded by a layer of gases known as the atmosphere, which extends upward from the surface, slowly thinning out into space. Below the surface is a hot interior of rocky material and two core layers composed of the metals nickel and iron in solid and liquid form.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Unlike the other planets, Earth has a unique set of characteristics ideally suited to supporting life as we know it. It is neither too hot, like Mercury, the closest planet to the Sun, nor too cold, like distant Mars and the even more distant outer planets—Jupiter, Saturn, Uranus, Neptune, and tiny Pluto. Earth’s atmosphere includes just the right amount of gases that trap heat from the Sun, resulting in a moderate climate suitable for water to exist in liquid form. The atmosphere also helps block radiation from the Sun that would be harmful to life. Earth’s atmosphere distinguishes it from the planet Venus, which is otherwise much like Earth. Venus is about the same size and mass as Earth and is also neither too near nor too far from the Sun. But because Venus has too much heat-trapping carbon dioxide in its atmosphere, its surface is extremely hot—462°C (864°F)—hot enough to melt lead and too hot for life to exist.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Although Earth is the only planet known to have life, scientists do not rule out the possibility that life may once have existed on other planets or their moons, or may exist today in primitive form. Mars, for example, has many features that resemble river channels, indicating that liquid water once flowed on its surface. If so, life may also have evolved there, and evidence for it may one day be found in fossil form. Water still exists on Mars, but it is frozen in polar ice caps, in permafrost, and possibly in rocks below the surface.</span><br /><img src="http://farm4.static.flickr.com/3124/2767407847_8c962cfed0_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Earth from the Moon<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">In the late 1960s, people saw for the first time what Earth looked like from space. This famous photo of Earth was taken by astronauts on the Apollo 8 mission as they orbited the Moon in 1968.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">NASA<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">For thousands of years, human beings could only wonder about Earth and the other observable planets in the solar system. Many early ideas—for example, that the Earth was a sphere and that it traveled around the Sun—were based on brilliant reasoning. However, it was only with the development of the scientific method and scientific instruments, especially in the 18th and 19th centuries, that humans began to gather data that could be used to verify theories about Earth and the rest of the solar system. By studying fossils found in rock layers, for example, scientists realized that the Earth was much older than previously believed. And with the use of telescopes, new planets such as Uranus, Neptune, and Pluto were discovered.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In the second half of the 20th century, more advances in the study of Earth and the solar system occurred due to the development of rockets that could send spacecraft beyond Earth. Human beings were able to study and observe Earth from space with satellites equipped with scientific instruments. Astronauts landed on the Moon and gathered ancient rocks that revealed much about the early solar system. During this remarkable advancement in human history, humans also sent unmanned spacecraft to the other planets and their moons. Spacecraft have now visited all of the planets except Pluto. The study of other planets and moons has provided new insights about Earth, just as the study of the Sun and other stars like it has helped shape new theories about how Earth and the rest of the solar system formed.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">As a result of this recent space exploration, we now know that Earth is one of the most geologically active of all the planets and moons in the solar system. Earth is constantly changing. Over long periods of time land is built up and worn away, oceans are formed and re-formed, and continents move around, break up, and merge.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Life itself contributes to changes on Earth, especially in the way living things can alter Earth’s atmosphere. For example, Earth at one time had the same amount of carbon dioxide in its atmosphere as Venus now has, but early forms of life helped remove this carbon dioxide over millions of years. These life forms also added oxygen to Earth’s atmosphere and made it possible for animal life to evolve on land.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">A variety of scientific fields have broadened our knowledge about Earth, including biogeography, climatology, geology, geophysics, hydrology, meteorology, oceanography, and zoogeography. Collectively, these fields are known as Earth science. By studying Earth’s atmosphere, its surface, and its interior and by studying the Sun and the rest of the solar system, scientists have learned much about how Earth came into existence, how it changed, and why it continues to change.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">II<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">EARTH, THE SOLAR SYSTEM, AND THE GALAXY</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3257/2768255108_52567bf977_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Solar System<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Earth is the third planet from the Sun, after Mercury and Venus. The average distance between Earth and the Sun is 150 million km (93 million mi). Earth and all the other planets in the solar system revolve, or orbit, around the Sun due to the force of gravitation. The Earth travels at a velocity of about 107,000 km/h (about 67,000 mph) as it orbits the Sun. All but one of the planets orbit the Sun in the same plane—that is, if an imaginary line were extended from the center of the Sun to the outer regions of the solar system, the orbital paths of the planets would intersect that line. The exception is Pluto, which has an <i>eccentric</i> (unusual) orbit. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Earth’s orbital path is not quite a perfect circle but instead is slightly <i>elliptical </i>(oval-shaped). For example, at maximum distance Earth is about 152 million km (about 95 million mi) from the Sun; at minimum distance Earth is about 147 million km (about 91 million mi) from the Sun. If Earth orbited the Sun in a perfect circle, it would always be the same distance from the Sun.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The solar system, in turn, is part of the Milky Way Galaxy, a collection of billions of stars bound together by gravity. The Milky Way has armlike discs of stars that spiral out from its center. The solar system is located in one of these spiral arms, known as the Orion arm, which is about two-thirds of the way from the center of the Galaxy. In most parts of the Northern Hemisphere, this disc of stars is visible on a summer night as a dense band of light known as the Milky Way.</span><br /><img src="http://farm4.static.flickr.com/3291/2767408073_e166d2b6b8_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Milky Way Galaxy<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Our own solar system exists within one of the spiral arms of the disk-shaped galaxy called the Milky Way. This false-color image looks toward the center of the Milky Way, located 30,000 light-years away. Bright star clusters are visible along with darker areas of dust and gas.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Morton-Milon/Science Source/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Earth is the fifth largest planet in the solar system. Its diameter, measured around the equator, is 12,756 km (7,926 mi). Earth is not a perfect sphere but is slightly flattened at the poles. Its polar diameter, measured from the North Pole to the South Pole, is somewhat less than the equatorial diameter because of this flattening. Although Earth is the largest of the four planets—Mercury, Venus, Earth, and Mars—that make up the <i>inner solar system</i> (the planets closest to the Sun), it is small compared with the giant planets of the outer solar system—Jupiter, Saturn, Uranus, and Neptune. For example, the largest planet, Jupiter, has a diameter at its equator of 143,000 km (89,000 mi), 11 times greater than that of Earth. A famous atmospheric feature on Jupiter, the Great Red Spot, is so large that three Earths would fit inside it.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Earth has one natural satellite, the Moon. The Moon orbits the Earth, completing one revolution in an elliptical path in 27 days 7 hr 43 min 11.5 sec. The Moon orbits the Earth because of the force of Earth’s gravity. However, the Moon also exerts a gravitational force on the Earth. Evidence for the Moon’s gravitational influence can be seen in the ocean tides. A popular theory suggests that the Moon split off from Earth more than 4 billion years ago when a large meteorite or small planet struck the Earth.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">As Earth revolves around the Sun, it rotates, or spins, on its <i>axis</i>, an imaginary line that runs between the North and South poles. The period of one complete rotation is defined as a day and takes 23 hr 56 min 4.1 sec. The period of one revolution around the Sun is defined as a year, or 365.2422 solar days, or 365 days 5 hr 48 min 46 sec. Earth also moves along with the Milky Way Galaxy as the Galaxy rotates and moves through space. It takes more than 200 million years for the stars in the Milky Way to complete one revolution around the Galaxy’s center.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Earth’s axis of rotation is <i>inclined</i> (tilted) 23.5° relative to its plane of revolution around the Sun. This inclination of the axis creates the seasons and causes the height of the Sun in the sky at noon to increase and decrease as the seasons change. The Northern Hemisphere receives the most energy from the Sun when it is tilted toward the Sun. This orientation corresponds to summer in the Northern Hemisphere and winter in the Southern Hemisphere. The Southern Hemisphere receives maximum energy when it is tilted toward the Sun, corresponding to summer in the Southern Hemisphere and winter in the Northern Hemisphere. Fall and spring occur in between these orientations.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">III<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">EARTH’S ATMOSPHERE<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The atmosphere is a layer of different gases that extends from Earth’s surface to the exosphere, the outer limit of the atmosphere, about 9,600 km (6,000 mi) above the surface. Near Earth’s surface, the atmosphere consists almost entirely of nitrogen (78 percent) and oxygen (21 percent). The remaining 1 percent of atmospheric gases consists of argon (0.9 percent); carbon dioxide (0.03 percent); varying amounts of water vapor; and trace amounts of hydrogen, nitrous oxide, ozone, methane, carbon monoxide, helium, neon, krypton, and xenon.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Layers of the Atmosphere</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3265/2767408187_8281098d01_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Divisions of the Atmosphere<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Without our atmosphere, there would be no life on Earth. A relatively thin envelope, the atmosphere consists of layers of gases that support life and provide protection from harmful radiation.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The layers of the atmosphere are the troposphere, the stratosphere, the mesosphere, the thermosphere, and the exosphere. The troposphere is the layer in which weather occurs and extends from the surface to about 16 km (about 10 mi) above sea level at the equator. Above the troposphere is the stratosphere, which has an upper boundary of about 50 km (about 30 mi) above sea level. The layer from 50 to 90 km (30 to 60 mi) is called the mesosphere. At an altitude of about 90 km, temperatures begin to rise. The layer that begins at this altitude is called the thermosphere because of the high temperatures that can be reached in this layer (about 1200°C, or about 2200°F). The region beyond the thermosphere is called the exosphere. The thermosphere and the exosphere overlap with another region of the atmosphere known as the ionosphere, a layer or layers of ionized air extending from almost 60 km (about 50 mi) above Earth’s surface to altitudes of 1,000 km (600 mi) and more.</span><br /><img src="http://farm4.static.flickr.com/3131/2768255504_2e282fd83f_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Greenhouse Effect<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Earth’s atmosphere and the way it interacts with the oceans and radiation from the Sun are responsible for the planet’s climate and weather. The atmosphere plays a key role in supporting life. Almost all life on Earth uses atmospheric oxygen for energy in a process known as cellular respiration, which is essential to life. The atmosphere also helps moderate Earth’s climate by trapping radiation from the Sun that is reflected from Earth’s surface. Water vapor, carbon dioxide, methane, and nitrous oxide in the atmosphere act as “greenhouse gases.” Like the glass in a greenhouse, they trap infrared, or heat, radiation from the Sun in the lower atmosphere and thereby help warm Earth’s surface. Without this greenhouse effect, heat radiation would escape into space, and Earth would be too cold to support most forms of life.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Other gases in the atmosphere are also essential to life. The trace amount of ozone found in Earth’s stratosphere blocks harmful ultraviolet radiation from the Sun. Without the ozone layer, life as we know it could not survive on land. Earth’s atmosphere is also an important part of a phenomenon known as the water cycle or the hydrologic cycle. <i>See also </i>Atmosphere.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The Atmosphere and the Water Cycle</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3170/2767408335_4044c5ae6b_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Water Cycle<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The water cycle simply means that Earth’s water is continually recycled between the oceans, the atmosphere, and the land. All of the water that exists on Earth today has been used and reused for billions of years. Very little water has been created or lost during this period of time. Water is constantly moving on Earth’s surface and changing back and forth between ice, liquid water, and water vapor. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The water cycle begins when the Sun heats the water in the oceans and causes it to evaporate and enter the atmosphere as water vapor. Some of this water vapor falls as precipitation directly back into the oceans, completing a short cycle. Some of the water vapor, however, reaches land, where it may fall as snow or rain. Melted snow or rain enters rivers or lakes on the land. Due to the force of gravity, the water in the rivers eventually empties back into the oceans. Melted snow or rain also may enter the ground. Groundwater may be stored for hundreds or thousands of years, but it will eventually reach the surface as springs or small pools known as seeps. Even snow that forms glacial ice or becomes part of the polar caps and is kept out of the cycle for thousands of years eventually melts or is warmed by the Sun and turned into water vapor, entering the atmosphere and falling again as precipitation. All water that falls on land eventually returns to the ocean, completing the water cycle.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">IV<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">EARTH’S SURFACE<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Earth’s surface is the outermost layer of the planet. It includes the hydrosphere, the crust, and the biosphere.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Hydrosphere<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The hydrosphere consists of the bodies of water that cover 71 percent of Earth’s surface. The largest of these are the oceans, which contain over 97 percent of all water on Earth. Glaciers and the polar ice caps contain just over 2 percent of Earth’s water in the form of solid ice. Only about 0.6 percent is under the surface as groundwater. Nevertheless, groundwater is 36 times more plentiful than water found in lakes, inland seas, rivers, and in the atmosphere as water vapor. Only 0.017 percent of all the water on Earth is found in lakes and rivers. And a mere 0.001 percent is found in the atmosphere as water vapor. Most of the water in glaciers, lakes, inland seas, rivers, and groundwater is fresh and can be used for drinking and agriculture. Dissolved salts compose about 3.5 percent of the water in the oceans, however, making it unsuitable for drinking or agriculture unless it is treated to remove the salts.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Crust<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The crust consists of the continents, other land areas, and the basins, or floors, of the oceans. The dry land of Earth’s surface is called the continental crust. It is about 15 to 75 km (9 to 47 mi) thick. The oceanic crust is thinner than the continental crust. Its average thickness is 5 to 10 km (3 to 6 mi). The crust has a definite boundary called the Mohorovičić discontinuity, or simply the Moho. The boundary separates the crust from the underlying mantle, which is much thicker and is part of Earth’s interior.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Oceanic crust and continental crust differ in the type of rocks they contain. There are three main types of rocks: igneous, sedimentary, and metamorphic. Igneous rocks form when molten rock, called magma, cools and solidifies. Sedimentary rocks are usually created by the breakdown of igneous rocks. They tend to form in layers as small particles of other rocks or as the mineralized remains of dead animals and plants that have fused together over time. The remains of dead animals and plants occasionally become mineralized in sedimentary rock and are recognizable as fossils. Metamorphic rocks form when sedimentary or igneous rocks are altered by heat and pressure deep underground.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Oceanic crust consists of dark, dense igneous rocks, such as basalt and gabbro. Continental crust consists of lighter-colored, less dense igneous rocks, such as granite and diorite. Continental crust also includes metamorphic rocks and sedimentary rocks.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">C<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Biosphere<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The biosphere includes all the areas of Earth capable of supporting life. The biosphere ranges from about 10 km (about 6 mi) into the atmosphere to the deepest ocean floor. For a long time, scientists believed that all life depended on energy from the Sun and consequently could only exist where sunlight penetrated. In the 1970s, however, scientists discovered various forms of life around hydrothermal vents on the floor of the Pacific Ocean where no sunlight penetrated. They learned that primitive bacteria formed the basis of this living community and that the bacteria derived their energy from a process called chemosynthesis that did not depend on sunlight. Some scientists believe that the biosphere may extend relatively deep into Earth’s crust. They have recovered what they believe are primitive bacteria from deeply drilled holes below the surface.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">D<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Changes to Earth’s Surface<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Earth’s surface has been constantly changing ever since the planet formed. Most of these changes have been gradual, taking place over millions of years. Nevertheless, these gradual changes have resulted in radical modifications, involving the formation, erosion, and re-formation of mountain ranges, the movement of continents, the creation of huge supercontinents, and the breakup of supercontinents into smaller continents.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The weathering and erosion that result from the water cycle are among the principal factors responsible for changes to Earth’s surface. Another principal factor is the movement of Earth’s continents and seafloors and the buildup of mountain ranges due to a phenomenon known as plate tectonics. Heat is the basis for all of these changes. Heat in Earth’s interior is believed to be responsible for continental movement, mountain building, and the creation of new seafloor in ocean basins. Heat from the Sun is responsible for the evaporation of ocean water and the resulting precipitation that causes weathering and erosion. In effect, heat in Earth’s interior helps build up Earth’s surface while heat from the Sun helps wear down the surface.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">D</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">1<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Weathering<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Weathering is the breakdown of rock at and near the surface of Earth. Most rocks originally formed in a hot, high-pressure environment below the surface where there was little exposure to water. Once the rocks reached Earth’s surface, however, they were subjected to temperature changes and exposed to water. When rocks are subjected to these kinds of surface conditions, the minerals they contain tend to change. These changes constitute the process of weathering. There are two types of weathering: physical weathering and chemical weathering.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Physical weathering involves a decrease in the size of rock material. Freezing and thawing of water in rock cavities, for example, splits rock into small pieces because water expands when it freezes. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Chemical weathering involves a chemical change in the composition of rock. For example, feldspar, a common mineral in granite and other rocks, reacts with water to form clay minerals, resulting in a new substance with totally different properties than the parent feldspar. Chemical weathering is of significance to humans because it creates the clay minerals that are important components of soil, the basis of agriculture. Chemical weathering also causes the release of dissolved forms of sodium, calcium, potassium, magnesium, and other chemical elements into surface water and groundwater. These elements are carried by surface water and groundwater to the sea and are the sources of dissolved salts in the sea.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">D</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">2<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Erosion</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3038/2768255844_168e88ca4c_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Glacial Erosion<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Glaciers erode the Earth’s surface through processes such as abrasion, crushing, and fracturing of the material in the glacier’s path. Glaciers move by growing or shrinking, depending on the climate. Moving glaciers erode and transport large quantities of rocks, sand, and other particles along their path. The icy path shown here is a moraine formed by a glacier in Switzerland.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Paolo Koch/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Erosion is the process that removes loose and weathered rock and carries it to a new site. Water, wind, and glacial ice combined with the force of gravity can cause erosion.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Erosion by running water is by far the most common process of erosion. It takes place over a longer period of time than other forms of erosion. When water from rain or melted snow moves downhill, it can carry loose rock or soil with it. Erosion by running water forms the familiar gullies and V-shaped valleys that cut into most landscapes. The force of the running water removes loose particles formed by weathering. In the process, gullies and valleys are lengthened, widened, and deepened. Often, water overflows the banks of the gullies or river channels, resulting in floods. Each new flood carries more material away to increase the size of the valley. Meanwhile, weathering loosens more and more material so the process continues.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Erosion by glacial ice is less common, but it can cause the greatest landscape changes in the shortest amount of time. Glacial ice forms in a region where snow fails to melt in the spring and summer and instead builds up as ice. For major glaciers to form, this lack of snowmelt has to occur for a number of years in areas with high precipitation. As ice accumulates and thickens, it flows as a solid mass. As it flows, it has a tremendous capacity to erode soil and even solid rock. Ice is a major factor in shaping some landscapes, especially mountainous regions. Glacial ice provides much of the spectacular scenery in these regions. Features such as <i>horns</i> (sharp mountain peaks), <i>arêtes</i> (sharp ridges), glacially formed lakes, and U-shaped valleys are all the result of glacial erosion.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Wind is an important cause of erosion only in <i>arid</i> (dry) regions. Wind carries sand and dust, which can scour even solid rock. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Many factors determine the rate and kind of erosion that occurs in a given area. The climate of an area determines the distribution, amount, and kind of precipitation that the area receives and thus the type and rate of weathering. An area with an arid climate erodes differently than an area with a humid climate. The elevation of an area also plays a role by determining the potential energy of running water. The higher the elevation the more energetically water will flow due to the force of gravity. The type of bedrock in an area (sandstone, granite, or shale) can determine the shapes of valleys and slopes, and the depth of streams.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">A landscape’s geologic age—that is, how long current conditions of weathering and erosion have affected the area—determines its overall appearance. Relatively young landscapes tend to be more rugged and angular in appearance. Older landscapes tend to have more rounded slopes and hills. The oldest landscapes tend to be low-lying with broad, open river valleys and low, rounded hills. The overall effect of the wearing down of an area is to level the land; the tendency is toward the reduction of all land surfaces to sea level.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">D</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">3<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Plate Tectonics<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Opposing this tendency toward leveling is a force responsible for raising mountains and plateaus and for creating new landmasses. These changes to Earth’s surface occur in the outermost solid portion of Earth, known as the lithosphere. The lithosphere consists of the crust and another region known as the upper mantle and is approximately 65 to 100 km (40 to 60 mi) thick. Compared with the interior of the Earth, however, this region is relatively thin. The lithosphere is thinner in proportion to the whole Earth than the skin of an apple is to the whole apple. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Scientists believe that the lithosphere is broken into a series of plates, or segments. According to the theory of plate tectonics, these plates move around on Earth’s surface over long periods of time. Tectonics comes from the Greek word, <i>tektonikos</i>, which means “builder.”<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">According to the theory, the lithosphere is divided into large and small plates. The largest plates include the Pacific plate, the North American plate, the Eurasian plate, the Antarctic plate, the Indo-Australian plate, and the African plate. Smaller plates include the Cocos plate, the Nazca plate, the Philippine plate, and the Caribbean plate. Plate sizes vary a great deal. The Cocos plate is 2,000 km (1,000 mi) wide, while the Pacific plate is nearly 14,000 km (nearly 9,000 mi) wide.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">These plates move in three different ways in relation to each other. They pull apart or move away from each other, they collide or move against each other, or they slide past each other as they move sideways. The movement of these plates helps explain many geological events, such as earthquakes and volcanic eruptions as well as mountain building and the formation of the oceans and continents.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">D3</span><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">a</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);"><o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">When Plates Pull Apart</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3245/2767408749_c2b57e5827_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Magma Upwelling<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Mid-ocean ridges occur along boundaries between plates of Earth’s outer shell where new seafloor is created as the plates spread apart. As plates move apart under the ocean, molten rock, or magma, wells up from deep below the surface of the seafloor. Some of the magma that ascends to the seafloor produces enormous volcanic eruptions. The rest solidifies on the edges of the plates as they spread apart, creating new rocky seafloor material.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Archive Photos<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">When the plates pull apart, two types of phenomena occur depending on whether the movement takes place in the oceans or on land. When plates pull apart on land, deep valleys known as rift valleys form. An example of a rift valley is the Great Rift Valley that extends from Syria in the Middle East to Mozambique in Africa. When plates pull apart in the oceans, long, sinuous chains of volcanic mountains called mid-ocean ridges form, and new seafloor is created at the site of these ridges. Rift valleys are also present along the crests of the mid-ocean ridges.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Most scientists believe that gravity and heat from the interior of the Earth cause the plates to move apart and to create new seafloor. According to this explanation, molten rock known as magma rises from Earth’s interior to form hot spots beneath the ocean floor. As two oceanic plates pull apart from each other in the middle of the oceans, a crack, or rupture, appears and forms the mid-ocean ridges. These ridges exist in all the world’s ocean basins and resemble the seams of a baseball. The molten rock rises through these cracks and creates new seafloor.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">D3</span><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">b</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);"><o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">When Plates Collide</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3261/2768256128_93da2e1bfd_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Converging Plates<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The outer layer of the Earth, the lithosphere, is broken into about 20 pieces, called tectonic plates. These plates slowly slide around on the asthenosphere below, periodically colliding with each other.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">When plates collide or push against each other, regions called convergent plate margins form. Along these margins, one plate is usually forced to dive below the other. As that plate dives, it triggers the melting of the surrounding lithosphere and a region just below it known as the asthenosphere. These pockets of molten crust rise behind the margin through the overlying plate, creating curved chains of volcanoes known as arcs. This process is called subduction.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">If one plate consists of oceanic crust and the other consists of continental crust, the denser oceanic crust will dive below the continental crust. If both plates are oceanic crust, then either may be subducted. If both are continental crust, subduction can continue for a while but will eventually end because continental crust is not dense enough to be forced very far into the upper mantle.</span><br /><img src="http://farm4.static.flickr.com/3117/2768256290_7c888e24f8_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Mount Everest<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Mount Everest, the world’s highest mountain at 8,850 m (29,035 ft), is located in the Himalayas. The Himalayas form the highest mountain system in the world, with more than 30 peaks towering 7,600 m (25,000 ft) or more.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Keren Su/Tony Stone Images<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The results of this subduction process are readily visible on a map showing that 80 percent of the world’s volcanoes rim the Pacific Ocean where plates are colliding against each other. The subduction zone created by the collision of two oceanic plates—the Pacific plate and the Philippine plate—can also create a trench. Such a trench resulted in the formation of the deepest point on Earth, the Mariana Trench, which is estimated to be 11,033 m (36,198 ft) below sea level.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">On the other hand, when two continental plates collide, mountain building occurs. The collision of the Indo-Australian plate with the Eurasian plate has produced the Himalayan Mountains. This collision resulted in the highest point of Earth, Mount Everest, which is 8,850 m (29,035 ft) above sea level.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">D3</span><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">c</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);"><o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">When Plates Slide Past Each Other</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3199/2768256472_dd60347534_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">San Andreas Fault, California<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The San Andreas Fault, unlike most faults that stay below the ocean, emerges from the Pacific Ocean and traverses hundreds of miles of land. It runs through California for about 1,000 km (about 600 mi) from Point Arena to the Imperial Valley. The fault marks the boundary between the North American and Pacific tectonic plates; earthquakes are caused by these plates sliding together.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Francois Gohier/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Finally, some of Earth’s plates neither collide nor pull apart but instead slide past each other. These regions are called transform margins. Few volcanoes occur in these areas because neither plate is forced down into Earth’s interior and little melting occurs. Earthquakes, however, are abundant as the two rigid plates slide past each other. The San Andreas Fault in California is a well-known example of a transform margin.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The movement of plates occurs at a slow pace, at an average rate of only 2.5 cm (1 in) per year. But over millions of years this gradual movement results in radical changes. Current plate movement is making the Pacific Ocean and Mediterranean Sea smaller, the Atlantic Ocean larger, and the Himalayan Mountains higher.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">V<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">EARTH’S INTERIOR</span></p></td></tr></tbody></table><br /><img style="width: 466px; height: 275px;" src="http://farm4.static.flickr.com/3017/2767409307_79fc968f94_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Internal Structure of the Earth<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Earth is made up of a series of layers that formed early in the planet’s history, as heavier material gravitated toward the center and lighter material floated to the surface. The dense, solid, inner core of iron is surrounded by a liquid, iron, outer core. The lower mantle consists of molten rock, which is surrounded by partially molten rock in the asthenosphere and solid rock in the upper mantle and crust. Between some of the layers, there are chemical or structural changes that form discontinuities. Lighter elements, such as silicon, aluminum, calcium, potassium, sodium, and oxygen, compose the outer crust.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The interior of Earth plays an important role in plate tectonics. Scientists believe it is also responsible for Earth’s magnetic field. This field is vital to life because it shields the planet’s surface from harmful cosmic rays and from a steady stream of energetic particles from the Sun known as the solar wind.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Composition of the Interior<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Earth’s interior consists of the mantle and the core. The mantle and core make up by far the largest part of Earth’s mass. The distance from the base of the crust to the center of the core is about 6,400 km (about 4,000 mi).<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Scientists have learned about Earth’s interior by studying rocks that formed in the interior and rose to the surface. The study of meteorites, which are believed to be made of the same material that formed the Earth and its interior, has also offered clues about Earth’s interior. Finally, seismic waves generated by earthquakes provide geophysicists with information about the composition of the interior. The sudden movement of rocks during an earthquake causes vibrations that transmit energy through the Earth in the form of waves. The way these waves travel through the interior of Earth reveals the nature of materials inside the planet.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The mantle consists of three parts: the lower part of the lithosphere, the region below it known as the asthenosphere, and the region below the asthenosphere called the lower mantle. The entire mantle extends from the base of the crust to a depth of about 2,900 km (about 1,800 mi). Scientists believe the asthenosphere is made up of mushy plastic-like rock with pockets of molten rock. The term <i>asthenosphere</i> is derived from Greek and means “weak layer.” The asthenosphere’s soft, plastic quality allows plates in the lithosphere above it to shift and slide on top of the asthenosphere. This shifting of the lithosphere’s plates is the source of most tectonic activity. The asthenosphere is also the source of the basaltic magma that makes up much of the oceanic crust and rises through volcanic vents on the ocean floor.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The mantle consists of mostly solid iron-magnesium silicate rock mixed with many other minor components including radioactive elements. However, even this solid rock can flow like a “sticky” liquid when it is subjected to enough heat and pressure. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The core is divided into two parts, the outer core and the inner core. The outer core is about 2,260 km (about 1,404 mi) thick. The outer core is a liquid region composed mostly of iron, with smaller amounts of nickel and sulfur in liquid form. The inner core is about 1,220 km (about 758 mi) thick. The inner core is solid and is composed of iron, nickel, and sulfur in solid form. Because the inner core is surrounded by a liquid region, it can rotate independently. Recent scientific studies indicate that the inner core may actually rotate faster than the rest of the planet, making one full extra spin over a period of 700 to 1,200 years. The inner core and the outer core also contain a small percentage of radioactive material. The existence of radioactive material is one of the sources of heat in Earth’s interior because as radioactive material decays, it gives off heat. Temperatures in the inner core may be as high as 6650°C (12,000°F).<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The Core and Earth’s Magnetism</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3255/2768256746_3a2e9f6bc6_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Earth’s Magnetic Field<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Scientists believe that Earth’s liquid iron core is instrumental in creating a magnetic field that surrounds Earth and shields the planet from harmful cosmic rays and the Sun’s solar wind. The idea that Earth is like a giant magnet was first proposed in 1600 by English physician and natural philosopher William Gilbert. Gilbert proposed the idea to explain why the magnetized needle in a compass points north. According to Gilbert, Earth’s magnetic field creates a magnetic north pole and a magnetic south pole. The magnetic poles do not correspond to the geographic North and South poles, however. Moreover, the magnetic poles wander and are not always in the same place. The north magnetic pole is currently close to Ellef Ringnes Island in the Queen Elizabeth Islands near the boundary of Canada’s Northwest Territories with Nunavut. The south magnetic pole lies just off the coast of Wilkes Land, Antarctica.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Not only do the magnetic poles wander, but they also reverse their polarity—that is, the north magnetic pole becomes the south magnetic pole and vice versa. Magnetic reversals have occurred at least 170 times over the past 100 million years. The reversals occur on average about every 200,000 years and take place gradually over a period of several thousand years. Scientists still do not understand why these magnetic reversals occur but think they may be related to Earth’s rotation and changes in the flow of liquid iron in the outer core.</span><br /><img src="http://farm4.static.flickr.com/3177/2768257032_22c5d54ed0_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Aurora Borealis<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The aurora borealis, commonly known as the northern lights, creates a spectacular light show near Fairbanks, Alaska. Auroras, most frequently seen in the far northern and far southern regions of the globe, are common sights in the Alaskan sky. Luminous displays visible to the naked eye only at night, auroras occur when charged particles from the Sun interact with gases in Earth’s atmosphere.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Jack Finch/Science Source/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Some scientists theorize that the flow of liquid iron in the outer core sets up electrical currents that produce Earth’s magnetic field. Known as the dynamo theory, this theory appears to be the best explanation yet for the origin of the magnetic field. Earth’s magnetic field operates in a region above Earth’s surface known as the magnetosphere. The magnetosphere is shaped somewhat like a teardrop with a long tail that trails away from the Earth due to the force of the solar wind.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Inside the magnetosphere are the Van Allen radiation belts, named for the American physicist James A. Van Allen who discovered them in 1958. The Van Allen belts are regions where charged particles from the Sun and from cosmic rays are trapped and sent into spiral paths along the lines of Earth’s magnetic field. The radiation belts thereby shield Earth’s surface from these highly energetic particles. Occasionally, however, due to extremely strong magnetic fields on the Sun’s surface, which are visible as sunspots, a brief burst of highly energetic particles streams along with the solar wind. Because Earth’s magnetic field lines converge and are closest to the surface at the poles, some of these energetic particles sneak through and interact with Earth’s atmosphere, creating the phenomenon known as an aurora.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">VI<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">EARTH’S PAST<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "Times New Roman","serif"; display: none;"><o:p> </o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Origin of Earth<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Most scientists believe that the Earth, Sun, and all of the other planets and moons in the solar system formed about 4.6 billion years ago from a giant cloud of gas and dust known as the solar nebula. The gas and dust in this solar nebula originated in a star that ended its life in a violent explosion known as a supernova. The solar nebula consisted principally of hydrogen, the lightest element, but the nebula was also seeded with a smaller percentage of heavier elements, such as carbon and oxygen. All of the chemical elements we know were originally made in the star that became a supernova. Our bodies are made of these same chemical elements. Therefore, all of the elements in our solar system, including all of the elements in our bodies, originally came from this star-seeded solar nebula.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Due to the force of gravity tiny clumps of gas and dust began to form in the early solar nebula. As these clumps came together and grew larger, they caused the solar nebula to contract in on itself. The contraction caused the cloud of gas and dust to flatten in the shape of a disc. As the clumps continued to contract, they became very dense and hot. Eventually the atoms of hydrogen became so dense that they began to fuse in the innermost part of the cloud, and these nuclear reactions gave birth to the Sun. The fusion of hydrogen atoms in the Sun is the source of its energy.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Many scientists favor the planetesimal theory for how the Earth and other planets formed out of this solar nebula. This theory helps explain why the inner planets became rocky while the outer planets, except for Pluto, are made up mostly of gases. The theory also explains why all of the planets orbit the Sun in the same plane.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">According to this theory, temperatures decreased with increasing distance from the center of the solar nebula. In the inner region, where Mercury, Venus, Earth, and Mars formed, temperatures were low enough that certain heavier elements, such as iron and the other heavy compounds that make up rock, could condense out—that is, could change from a gas to a solid or liquid. Due to the force of gravity, small clumps of this rocky material eventually came together with the dust in the original solar nebula to form protoplanets or planetesimals (small rocky bodies). These planetesimals collided, broke apart, and re-formed until they became the four inner rocky planets. The inner region, however, was still too hot for other light elements, such as hydrogen and helium, to be retained. These elements could only exist in the outermost part of the disc, where temperatures were lower. As a result two of the outer planets—Jupiter and Saturn—are mostly made of hydrogen and helium, which are also the dominant elements in the atmospheres of Uranus and Neptune.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The Early Earth</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3042/2767409853_5eea7f0e3b_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The Early Earth<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Life originated on Earth about four billion years ago, when oceans dotted with volcanic islands covered most of Earth’s surface and continents were very small. The air was hot and contained almost no breathable oxygen. The Moon was much closer to Earth, and a day was less than 15 hours long. Meteorites fell more frequently, and there was more volcanic activity than there is today.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Within the planetesimal Earth, heavier matter sank to the center and lighter matter rose toward the surface. Most scientists believe that Earth was never truly molten and that this transfer of matter took place in the solid state. Much of the matter that went toward the center contained radioactive material, an important source of Earth’s internal heat. As heavier material moved inward, lighter material moved outward, the planet became layered, and the layers of the core and mantle were formed. This process is called differentiation. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Not long after they formed, more than 4 billion years ago, the Earth and the Moon underwent a period when they were bombarded by meteorites, the rocky debris left over from the formation of the solar system. The impact craters created during this period of heavy bombardment are still visible on the Moon’s surface, which is unchanged. Earth’s craters, however, were long ago erased by weathering, erosion, and mountain building. Because the Moon has no atmosphere, its surface has not been subjected to weathering or erosion. Thus, the evidence of meteorite bombardment remains.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Energy released from the meteorite impacts created extremely high temperatures on Earth that melted the outer part of the planet and created the crust. By 4 billion years ago, both the oceanic and continental crust had formed, and the oldest rocks were created. These rocks are known as the Acasta Gneiss and are found in Canada’s Northwest Territories. Due to the meteorite bombardment, the early Earth was too hot for liquid water to exist and so it was impossible for life to exist.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">C<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Geologic Time</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3014/2767410093_001ce5c19c_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Fossil-bearing Rocks<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Sedimentary rocks, such as this fossil-bearing limestone, can help geologists determine geologic time. Because the bottom layers were deposited first, the oldest fossils are found in the bottom layers of sedimentary rocks. The accumulation of shells or shell fragments and other fossils in limestone provides geologists with a record of the evolution of the animals that used to live in the ancient oceans.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Carolina Biological Supply/Phototake NYC<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Geologists divide the history of the Earth into three eons: the Archean Eon, which lasted from around 4 billion to 2.5 billion years ago; the Proterozoic Eon, which lasted from 2.5 billion to 543 million years ago; and the Phanerozoic Eon, which lasted from 543 million years ago to the present. Each eon is subdivided into different eras. For example, the Phanerozoic Eon includes the Paleozoic Era, the Mesozoic Era, and the Cenozoic Era. In turn, eras are further divided into periods. For example, the Paleozoic Era includes the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian Periods.</span><br /><img src="http://farm4.static.flickr.com/3140/2768257600_4398d530e5_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Geologic Time Scale<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The Archean Eon is subdivided into four eras, the Eoarchean, the Paleoarchean, the Mesoarchean, and the Neoarchean. The beginning of the Archean is generally dated as the age of the oldest terrestrial rocks, which are about 4 billion years old. The Archean Eon ended 2.5 billion years ago when the Proterozoic Eon began. The Proterozoic Eon is subdivided into three eras: the Paleoproterozoic Era, the Mesoproterozoic Era, and the Neoproterozoic Era. The Proterozoic Eon lasted from 2.5 billion years ago to 543 million years ago when the Phanerozoic Eon began. The Phanerozoic Eon is subdivided into three eras: the Paleozoic Era from 543 million to 248 million years ago, the Mesozoic Era from 248 million to 65 million years ago, and the Cenozoic Era from 65 million years ago to the present.</span><br /><img style="width: 365px; height: 215px;" src="http://farm4.static.flickr.com/3202/2768257908_de2212cd66_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Stratigraphic Column<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Fossils preserved in rock strata provide scientists with clues to evolutionary history. This stratigraphic column is based on paleontological evidence and shows the order in which organisms appeared in the fossil-rich Paleozoic era. Each layer represents a particular time frame and shows a representative organism that flourished during that time. Although fossils are rarely found in the idealized and localized fashion shown here, they are often in more or less chronological order. Generally, the oldest fossils appear in lower layers, and the most recent fossils at the top, so that placement may be used as an aid in dating the specimens.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Geologists base these divisions on the study and dating of rock layers or strata, including the fossilized remains of plants and animals found in those layers. Until the late 1800s scientists could only determine the relative ages of rock strata. They knew that in general the top layers of rock were the youngest and formed most recently, while deeper layers of rock were older. The field of stratigraphy shed much light on the relative ages of rock layers.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The study of fossils also enabled geologists to determine the relative ages of different rock layers. The fossil record helped scientists determine how organisms evolved or when they became extinct. By studying rock layers around the world, geologists and paleontologists saw that the remains of certain animal and plant species occurred in the same layers, but were absent or altered in other layers. They soon developed a fossil index that also helped determine the relative ages of rock layers.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Beginning in the 1890s, scientists learned that radioactive elements in rock decay at a known rate. By studying this radioactive decay, they could determine an absolute age for rock layers. This type of dating, known as radiometric dating, confirmed the relative ages determined through stratigraphy and the fossil index and assigned absolute ages to the various strata. As a result scientists were able to assemble Earth’s geologic time scale from the Archean Eon to the present. <i>See also </i>Geologic Time.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">C</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">1<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Precambrian</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3122/2768257976_af9e46d98e_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Cyanobacteria<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Cyanobacteria (formerly blue-green algae) are among the most ancient organisms on earth. These photosynthetic organisms can be single-celled, connected in afilamentous form as shown here, or arranged in simple colonies. Cyanobacteria are capable of enduring a wide variety of environmental conditions ranging from freshwater and marine habitats to snowfields and glaciers. They are capable of surviving and flourishing even at extremely high temperatures.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Peter Parks/Oxford Scientific Films<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The Precambrian is a time span that includes the Archean and Proterozoic eons and began about 4 billion years ago. The Precambrian marks the first formation of continents, the oceans, the atmosphere, and life. The Precambrian represents the oldest chapter in Earth’s history that can still be studied. Very little remains of Earth from the period of 4.6 billion to about 4 billion years ago due to the melting of rock caused by the early period of meteorite bombardment. Rocks dating from the Precambrian, however, have been found in Africa, Antarctica, Australia, Brazil, Canada, and Scandinavia. Some zircon mineral grains deposited in Australian rock layers have been dated to 4.2 billion years.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The Precambrian is also the longest chapter in Earth’s history, spanning a period of about 3.5 billion years. During this timeframe, the atmosphere and the oceans formed from gases that escaped from the hot interior of the planet as a result of widespread volcanic eruptions. The early atmosphere consisted primarily of nitrogen, carbon dioxide, and water vapor. As Earth continued to cool, the water vapor condensed out and fell as precipitation to form the oceans. Some scientists believe that much of Earth’s water vapor originally came from comets containing frozen water that struck Earth during the period of meteorite bombardment. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">By studying 2-billion-year-old rocks found in northwestern Canada, as well as 2.5-billion-year-old rocks in China, scientists have found evidence that plate tectonics began shaping Earth’s surface as early as the middle Precambrian. About a billion years ago, the Earth’s plates were centered around the South Pole and formed a supercontinent called Rodinia. Slowly, pieces of this supercontinent broke away from the central continent and traveled north, forming smaller continents.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Life originated during the Precambrian. The earliest fossil evidence of life consists of prokaryotes, one-celled organisms that lacked a nucleus and reproduced by dividing, a process known as asexual reproduction. Asexual division meant that a prokaryote’s hereditary material was copied unchanged. The first prokaryotes were bacteria known as archaebacteria. Scientists believe they came into existence perhaps as early as 3.8 billion years ago, but certainly by about 3.5 billion years ago, and were anaerobic—that is, they did not require oxygen to produce energy. Free oxygen barely existed in the atmosphere of the early Earth. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Archaebacteria were followed about 3.46 billion years ago by another type of prokaryote known as cyanobacteria or blue-green algae. These cyanobacteria gradually introduced oxygen in the atmosphere as a result of photosynthesis. In shallow tropical waters, cyanobacteria formed mats that grew into humps called stromatolites. Fossilized stromatolites have been found in rocks in the Pilbara region of western Australia that are more than 3.4 billion years old and in rocks of the Gunflint Chert region of northwest Lake Superior that are about 2.1 billion years old.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">For billions of years, life existed only in the simple form of prokaryotes. Prokaryotes were followed by the relatively more advanced eukaryotes, organisms that have a nucleus in their cells and that reproduce by combining or sharing their heredity makeup rather than by simply dividing. Sexual reproduction marked a milestone in life on Earth because it created the possibility of hereditary variation and enabled organisms to adapt more easily to a changing environment. The very latest part of Precambrian time some 560 million to 545 million years ago saw the appearance of an intriguing group of fossil organisms known as the Ediacaran fauna. First discovered in the northern Flinders Range region of Australia in the mid-1940s and subsequently found in many locations throughout the world, these strange fossils appear to be the precursors of many of the fossil groups that were to explode in Earth's oceans in the Paleozoic Era. <i>See also </i>Evolution; Natural Selection.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">C</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">2<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Paleozoic Era</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3211/2767410685_d97ee8bd3e_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The Earliest Animals<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The earliest known animals on Earth were a bizarre collection of life forms that emerged just prior to and during the Cambrian Period, some of which were exquisitely preserved in fossil beds in various parts of the world. Some of the more extraordinary creatures (depicted in this artist's conception) were the formidable predator <i>Anomalocaris</i> (foreground upper right) about to make a meal of <i>Waptia</i>, which it holds in its extended claws. Just below <i>Anomalocaris</i> and slightly to its left is <i>Opabinia</i> using its long, trunklike snout to grasp <i>Burgessochaeta,</i> a bristle worm. The fernlike objects (left and center) are actually animals, as are the primitive sponges (center foreground) that resemble a saguaro cactus. The depictions of these fernlike animals are based on a group of fossils known as the Ediacaran fossils and date from about 550 million years ago.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">D.W. Miller<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">At the start of the Paleozoic Era about 543 million years ago, an enormous expansion in the diversity and complexity of life occurred. This event took place in the Cambrian Period and is called the Cambrian explosion. Nothing like it has happened since. Almost all of the major groups of animals we know today made their first appearance during the Cambrian explosion. Almost all of the different “body plans” found in animals today—that is, the way an animal’s body is designed, with heads, legs, rear ends, claws, tentacles, or antennae—also originated during this period. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Fishes first appeared during the Paleozoic Era, and multicellular plants began growing on the land. Other land animals, such as scorpions, insects, and amphibians, also originated during this time. Just as new forms of life were being created, however, other forms of life were going out of existence. Natural selection meant that some species were able to flourish, while others failed. In fact, mass extinctions of animal and plant species were commonplace. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Most of the early complex life forms of the Cambrian explosion lived in the sea. The creation of warm, shallow seas, along with the buildup of oxygen in the atmosphere, may have aided this explosion of life forms. The shallow seas were created by the breakup of the supercontinent Rodinia. During the Ordovician, Silurian, and Devonian periods, which followed the Cambrian Period and lasted from 490 million to 354 million years ago, some of the continental pieces that had broken off Rodinia collided. These collisions resulted in larger continental masses in equatorial regions and in the Northern Hemisphere. The collisions built a number of mountain ranges, including parts of the Appalachian Mountains in North America and the Caledonian Mountains of northern Europe.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Toward the close of the Paleozoic Era, two large continental masses, Gondwanaland to the south and Laurasia to the north, faced each other across the equator. Their slow but eventful collision during the Permian Period of the Paleozoic Era, which lasted from 290 million to 248 million years ago, assembled the supercontinent Pangaea and resulted in some of the grandest mountains in the history of Earth. These mountains included other parts of the Appalachians and the Ural Mountains of Asia. At the close of the Paleozoic Era, Pangaea represented over 90 percent of all the continental landmasses. Pangaea straddled the equator with a huge mouthlike opening that faced east. This opening was the Tethys Ocean, which closed as India moved northward creating the Himalayas. The last remnants of the Tethys Ocean can be seen in today’s Mediterranean Sea.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The Paleozoic came to an end with a major extinction event, when perhaps as many as 90 percent of all plant and animal species died out. The reason is not known for sure, but many scientists believe that huge volcanic outpourings of lavas in central Siberia, coupled with an asteroid impact, were joint contributing factors.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">C</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">3<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Mesozoic Era</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3264/2768258422_b9f249c124_m.jpg" /><br /><br /><img src="http://farm4.static.flickr.com/3288/2768258650_5dc30528bd_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Extent of Pleistocene Epoch Glaciation<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">During the Pleistocene epoch of the Quaternary Ice Age, glaciers (represented on map in white) covered much of the Earth’s northern hemisphere. Ice Ages consist of glacial periods and warmer interglacial periods. Although the Pleistocene, the Earth’s most recent glacial event, ended 10,000 years ago, many scientists believe that the Earth remains in an interglacial state of the Quaternary Ice Age.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The Cenozoic Era, beginning about 65 million years ago, is the period when mammals became the dominant form of life on land. Human beings first appeared in the later stages of the Cenozoic Era. In short, the modern world as we know it, with its characteristic geographical features and its animals and plants, came into being. All of the continents that we know today took shape during this era.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">A single catastrophic event may have been responsible for this relatively abrupt change from the Age of Reptiles to the Age of Mammals. Most scientists now believe that a huge asteroid or comet struck the Earth at the end of the Mesozoic and the beginning of the Cenozoic eras, causing the extinction of many forms of life, including the dinosaurs. Evidence of this collision came with the discovery of a large impact crater off the coast of Mexico’s Yucatán Peninsula and the worldwide finding of iridium, a metallic element rare on Earth but abundant in meteorites, in rock layers dated from the end of the Cretaceous Period. The extinction of the dinosaurs opened the way for mammals to become the dominant land animals.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The Cenozoic Era is divided into the Tertiary and the Quaternary periods. The Tertiary Period lasted from about 65 million to about 1.8 million years ago. The Quaternary Period began about 1.8 million years ago and continues to the present day. These periods are further subdivided into epochs, such as the Pleistocene, from 1.8 million to 10,000 years ago, and the Holocene, from 10,000 years ago to the present.</span><br /><img src="http://farm4.static.flickr.com/3085/2767411311_de9e648651_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Glaciers<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Discovery Enterprises, LLC<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Early in the Tertiary Period, Pangaea was completely disassembled, and the modern continents were all clearly outlined. India and other continental masses began colliding with southern Asia to form the Himalayas. Africa and a series of smaller microcontinents began colliding with southern Europe to form the Alps. The Tethys Ocean was nearly closed and began to resemble today’s Mediterranean Sea. As the Tethys continued to narrow, the Atlantic continued to open, becoming an ever-wider ocean. Iceland appeared as a new island in later Tertiary time, and its active volcanism today indicates that seafloor spreading is still causing the country to grow. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Late in the Tertiary Period, about 6 million years ago, humans began to evolve in Africa. These early humans began to migrate to other parts of the world between 2 million and 1.7 million years ago.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The Quaternary Period marks the onset of the great ice ages. Many times, perhaps at least once every 100,000 years on average, vast glaciers 3 km (2 mi) thick invaded much of North America, Europe, and parts of Asia. The glaciers eroded considerable amounts of material that stood in their paths, gouging out U-shaped valleys. Anatomically modern human beings, known as <i>Homo sapiens</i>, became the dominant form of life in the Quaternary Period. Most <i>anthropologists</i> (scientists who study human life and culture) believe that anatomically modern humans originated only recently in Earth’s 4.6-billion-year history, within the past 200,000 years. <i>See also </i>Human Evolution.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">VII<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">EARTH’S FUTURE<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">With the rise of human civilization about 8,000 years ago and especially since the Industrial Revolution in the mid-1700s, human beings began to alter the surface, water, and atmosphere of Earth. In doing so, they have become active geological agents, not unlike other forces of change that influence the planet. As a result, Earth’s immediate future depends to a great extent on the behavior of humans. For example, the widespread use of fossil fuels is releasing carbon dioxide and other greenhouse gases into the atmosphere and threatens to warm the planet’s surface. This global warming could melt glaciers and the polar ice caps, which could flood coastlines around the world and many island nations. In effect, the carbon dioxide that was removed from Earth’s early atmosphere by the oceans and by primitive plant and animal life, and subsequently buried as fossilized remains in sedimentary rock, is being released back into the atmosphere and is threatening the existence of living things. <i>See also </i>Global Warming.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Even without human intervention, Earth will continue to change because it is geologically active. Many scientists believe that some of these changes can be predicted. For example, based on studies of the rate that the seafloor is spreading in the Red Sea, some geologists predict that in 200 million years the Red Sea will be the same size as the Atlantic Ocean is today. Other scientists predict that the continent of Asia will break apart millions of years from now, and as it does, Lake Baikal in Siberia will become a vast ocean, separating two landmasses that once made up the Asian continent.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In the far, far distant future, however, scientists believe that Earth will become an uninhabitable planet, scorched by the Sun. Knowing the rate at which nuclear fusion occurs in the Sun and knowing the Sun’s mass, <i>astrophysicists</i> (scientists who study stars) have calculated that the Sun will become brighter and hotter about 3 billion years from now, when it will be hot enough to boil Earth’s oceans away. Based on studies of how other Sun-like stars have evolved, scientists predict that the Sun will become a <i>red giant</i>, a star with a very large, hot atmosphere, about 7 billion years from now. As a red giant the Sun’s outer atmosphere will expand until it engulfs the planet Mercury. The Sun will then be 2,000 times brighter than it is now and so hot it will melt Earth’s rocks. Earth will end its existence as a burnt cinder. <i>See also </i>Sun.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Three billion years is the life span of millions of human generations, however. Perhaps by then, humans will have learned how to journey beyond the solar system to colonize other planets in the Milky Way Galaxy and find another place to call “home.” <o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 15pt;"><span style="font-size: 12pt; font-family: "Times New Roman","serif";"><br /><br />Reviewed By:<br />Alan V. Morgan<o:p></o:p></span></p> <b><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif";">Microsoft ® Encarta ® 2007.</span></b><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif";"> © 1993-2006 Microsoft Corporation. All rights reserved.</span>ghozian karamihttp://www.blogger.com/profile/13214011599962806335noreply@blogger.com0tag:blogger.com,1999:blog-192751622867664710.post-60950049345100928262009-01-02T16:34:00.000-08:002009-01-02T16:35:55.329-08:00All about animals<p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 24pt; font-family: "MS Reference Serif","serif";">Animal<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">I<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">INTRODUCTION</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3200/2771138102_1c2a76f042_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Swallowing Snake<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">BBC Worldwide Americas, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Animal, multicellular organism that obtains energy by eating food. With over 2 million known species, and many more awaiting identification, animals are the most diverse forms of life on earth. They range in size from 30-m (100-ft) long whales to microscopic organisms only 0.05 mm (0.002 in) long. They live in a vast range of habitats, from deserts and Arctic tundra to the deep-sea floor. Animals are the only living things that have evolved nervous systems and sense organs that monitor their surroundings. They are also the only forms of life that show flexible patterns of behavior that can be shaped by past experience. The study of animals is known as zoology.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Animals are multicellular organisms, a characteristic they share with plants and many fungi. But they differ from plants and fungi in several important ways. Foremost among these is the way they obtain energy. Plants obtain energy directly from sunlight through the process of photosynthesis, and they use this energy to build up organic matter from simple raw materials. Animals, on the other hand, eat other living things or their dead remains. They then digest this food to release the energy that it contains. Fungi also take in food, but instead of digesting it internally as animals do, they digest it before they absorb it.</span><br /><img src="http://farm4.static.flickr.com/3075/2770291163_ede055b8ff_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Fierce Hunter<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">A flying eagle snatches a fish from the water with its long, curved talons. It will carry the fish to a feeding place on land before devouring it. Eagles hunt only during the day; by night, they perch safely in their nests or in some other high spot.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Oxford Scientific Films<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Most animals start life as a single fertilized cell, which divides many times to produce the thousands or millions of cells needed to form a functioning body. During this process, groups of cells develop different characteristics and arrange themselves in tissues that carry out specialized functions. Epithelial tissue covers the body’s inner and outer surfaces, while connective tissue binds it together and provides support. Nervous tissue conducts the signals that coordinate the body (<i>see </i>Nervous System), and muscle tissue–which makes up over two-thirds of the body mass of some animals–contracts to make the body move. This mobility, coupled with rapid responses to opportunities and hazards, is one feature that distinguishes animals from other forms of life.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Some kinds of animal movement, such as the slow progress of a limpet as it creeps across rocks, are so slow that they are almost imperceptible. Others, such as the attacking dive of a peregrine falcon or the leap of a flea, are so fast that they are difficult or even impossible to follow. Many single-celled organisms can move, but in absolute terms, animals are by far the fastest-moving living things on earth.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Animal life spans vary from less than 3 weeks in some insects to over a century in giant tortoises. Some animals, such as sponges, mollusks, fish, and snakes, show indeterminate growth, which means that they continue to grow throughout life. Most, however, reach a pre-defined size at maturity, at which point their physical growth stops.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">II<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">TYPES OF ANIMALS</span></p></td></tr></tbody></table><br /><img style="width: 349px; height: 190px;" src="http://farm4.static.flickr.com/3144/2770291311_493d1f7cd0_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Animal Kingdom<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Kingdom Animalia includes more than one million living species, grouped into more than 30 phyla. Vertebrates, members of the phylum Chordata, comprise only one percent of these organisms. Phylum Arthropoda is more successful in sheer numbers, total mass, and distribution than all other groups of animals combined. The remaining animal phyla are composed of mostly marine-dwelling organisms. Illustrated here is the evolutionary relationship between all of these groups.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Like all living things, animals show similarities and differences that enable them to be classified into groups. Birds, for example, are the only animals that have feathers, while mammals are the only ones that have fur. The scientific classification of animals began in the late 18th century. At this time, animals were classified almost entirely by external features, mainly because these are easy to observe. But external features can sometimes be misleading. For example, in the past, comparison of physical features led to whales being classified as fish and some snakes being classified as worms.</span><br /><img style="width: 354px; height: 209px;" src="http://farm4.static.flickr.com/3044/2771138820_543b2abd22_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Body Plans of Animals<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The basic body plan of an animal, shown here in cross section, is one of the characteristics used to classify animals into separate phyla. Cnidarians such as jellyfishes and sea anemones have two layers of tissue, endoderm and ectoderm, surrounding a digestive cavity. In some animals a third layer, mesoderm, develops between the endoderm and ectoderm. Among these, flatworms and ribbon worms are called acoelomates, because they lack a separate body cavity, or coelom. Nematodes have an extra, epithelial-lined cavity called a pseudocoelom, but only animals such as annelids and chordates have a true coelom, a fluid-filled chamber situated actually within the mesoderm.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Presently, animals are classified according to a broader range of characteristics, including their internal anatomy, patterns of development, and genetic makeup. These features provide a much more reliable guide to an animal’s place in the living world. They also help to show how different species are linked through evolution. Scientists divide the animal kingdom into approximately 30 groups, each called a phylum (plural phyla).<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Vertebrates and Invertebrates</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3259/2770291835_98d99e88c9_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Vertebrate Embryos<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Vertebrates that evolved from fish pass through similar embryonic stages. As a flexible notochord develops in the back, blocks of tissue called somites form along each side of it. These somites will become major structures, such as muscle, vertebrae, connective tissue, and, later, the larger glands of the body. Just above the notochord lies a hollow nerve cord. Such similarities formed the basis for German biologist Ernst Haeckel’s biogenetic law, which states that an animal’s embryonic development recapitulates its evolution. Although scientists now know that this law does not hold absolutely, Haeckel’s idea has remained influential.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">One phylum of animals, the chordates, has been more intensively studied than has any other, because it comprises nearly all the world’s largest and most familiar animals as well as humans. This phylum includes mammals, birds, reptiles, amphibians, and fish together with a collection of lesser-known organisms, such as sea squirts and their relatives (<i>see </i>Tunicates). The feature uniting these animals is that at some stage in their lives, all have a flexible supporting rod, called a notochord, running the length of their bodies. In the great majority of chordates, the notochord is replaced by a series of interlocking bones called vertebrae during early development. These bones form the backbone, and they give these animals their name—the vertebrates.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Vertebrates total about 40,000 species. Thanks to their highly developed nervous systems and internal skeletons, they have become very successful on land, sea, and air. Yet vertebrates account for only about 2 percent of animal species. The remaining 98 percent, collectively called invertebrates, are far more numerous and diverse and include an immense variety of animals from sponges, worms, and jellyfish to mollusks and insects. The only feature these diverse creatures share in common is the lack of a backbone.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Some invertebrate phyla contain relatively few species. An extreme example is the phylum Placozoa, which contains just one species. Measuring less than 0.5 mm (0.02 in) across, this unique animal was first discovered in 1883 in a saltwater aquarium in Austria. Its flat body consists of just two layers of cells, making it the simplest known member of the animal kingdom, although not the smallest. Another minor phylum, the loriciferans, was classified in 1983 with the chance discovery of a tiny organism dredged up in marine gravel. Several other species of loriciferans have since been identified, but little is known about how they live.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">At the other end of the spectrum, some invertebrate phyla contain immense numbers of species. These major phyla include the annelids (segmented worms), with 12,000 known species; the nematodes (roundworms), also with 12,000 known species; and the mollusks, including bivalves, snails, and octopuses, with at least 100,000 species. The arthropods, with about 1 million known species, include the insects, spiders, and crustaceans. These figures include only species that have been described and named, which are only a portion of those that actually exist. Some biologists estimate that the total number of nematode species may be as high as a quarter of a million, while the total number of arthropods could exceed 10 million.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Compared to vertebrates, most invertebrates are animals of modest dimensions. Giant squids, which are the largest invertebrates, can exceed 18 m (60 ft) in length, but the great majority of invertebrate animals are less than 2.5 cm (1 in) long. Their small size enables them to exploit food sources and infiltrate habitats that larger animals cannot use, but it also leaves them exposed to changing environmental conditions. This is not often a problem in the sea, but it can create difficulties on land. Land-dwelling invertebrates have to cope with the constant threat of drying out, and most of them quickly become inactive in low temperatures.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Cold-blooded and Warm-blooded Animals</span></p></td></tr></tbody></table><br /><br /><img src="http://farm4.static.flickr.com/3076/2771139112_6830d98bc9_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Penguin Keeping Its Young Warm<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Penguins always return to their ancestral nesting sites to lay their eggs and rear their young. The emperor penguin, the largest of the penguins, lays its single egg during the coldest time of the Antarctic year, when temperatures drop as low as -62 degrees C (-80 degrees F). The egg is incubated on top of the parent’s feet, protected by abdominal folds of skin. Young chicks remain under these abdominal folds until they are able to regulate their own body temperature.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Doug Allan/Oxford Scientific Films<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">On land, some invertebrates manage to overcome the problem of cold by using muscles to warm themselves. For example, many large moths and bumblebees use a special form of shivering to raise their body temperature to 35°C (95°F) before they take off, which allows them to fly in cool weather. Bees also maintain warm conditions in their nests, which speeds up the development of their young. But in invertebrates as a whole, temperature regulation is very unusual. In vertebrates, on the other hand, it has developed to a high degree.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Vertebrates are customarily divided into cold-blooded and warm-blooded animals, but these labels are not very precise. Biologists normally use the terms <i>ectoderm</i> and <i>endoderm</i> to describe temperature regulation more accurately. An ectoderm is an animal whose temperature is dictated by its surroundings, while an endoderm is one that keeps its body at a constant warm temperature by generating internal heat.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Reptiles, amphibians, and fish are ectoderms. Although they do not maintain a constant warm temperature, some of these animals do manage to raise their body temperature far above that of their surroundings. They do this by behavioral means, such as basking in direct sunshine when the surrounding air is cool. Mammals and birds are endoderms. These animals generate heat through their metabolic processes, and they retain it by having insulating layers of fat, fur, or feathers. Because their bodies are always warm, they can remain active in some of the coldest conditions on earth.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">III<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">ANIMAL HABITATS<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Few parts of Earth’s surface are entirely devoid of animal life. Animals cannot survive in places where water is unavailable or permanently frozen, or where temperatures regularly exceed 55° C (130° F). However, in all habitats that lie between these extremes, animal life abounds.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Aquatic Habitats</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3118/2770292139_ab5f75e63a_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Tidal Pool<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The fluctuation of the tide allows for a unique environment along shorelines. The current continually circulates and replenishes a rich supply of nutrients along beaches, but organisms living there must be adapted to both buffeting waves and frequent shifts from open air to complete submersion. Marine organisms adapt to the constantly changing surroundings in a variety of ways. Starfish use suction-cup feet, barnacles fix permanently to large objects like rocks and boats, and seaweed anchors firmly to the ocean floor. When the tide goes out, pockets of water remain trapped in rocks, depressions in the sand, and natural basins called tidal pools, like the one shown here during low tide.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Pat O'Hara Photography<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Animal life first arose in water. Millions of years later, marine and freshwater habitats continue to support a large proportion of the animal life on earth. Aquatic habitats—particularly in the seas and oceans–rarely experience abrupt changes in conditions, which is a major advantage for living things. <o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In the seas and oceans, the greatest diversity of animal life is found in habitats close to shores. The richest of all these habitats are coral reefs, underwater ridges that form in clear water where the minimum temperature is 20° C (68° F) or above. Coral reefs are composed of an accumulation of the remains of coral—invertebrates with stony skeletons—calcareous red algae, and mollusks. One of the reasons for the great diversity of animal life in reefs is that living coral creates a complex three-dimensional landscape, with many different microhabitats. The smallest crevices provide hiding places for scavengers such as crabs and shrimps, while larger ones conceal predators such as octopuses and moray eels. Over half the world’s fish species live in coral reefs, many hiding away by day and emerging after dark to feed.</span><br /><img src="http://farm4.static.flickr.com/3262/2770292223_5031de78fd_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Ratfish<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The ratfish is a member of a species of deep-water fish related to sharks. The deep-water habitat of the ratfish is dark, cold, and vast. Like many deep-water predators, the ratfish uses several senses to track prey; its eyes are used to located bioluminescent prey The poisonous spine in front of the dorsal fin is used defensively.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Dave Fleetham/Tom Stack and Associates<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">On reefs and rocky shores, many animals are sessile, meaning that they spend their entire adult lives fixed in one place. These species, which include sponges, barnacles, and mollusks, as well as reef-building corals themselves, typically spend the early part of their lives as drifting larvae, before settling on a solid surface and changing shape. Sessile animals are common in aquatic habitats because it is relatively easy for them to collect food, which typically is pushed in the animal’s direction by water currents. By contrast, very few sessile animals have evolved on land.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In open water, depth has a marked influence on animal lifestyles. The surface layers of the open sea teem with small and submicroscopic animals, which feed either on algae and other plantlike organisms or on each other. These animals form part of the plankton, a complex community of living things that drifts passively with the currents. Many planktonic animals can adjust the depth at which they float, but larger animals such as fish, squid, and marine mammals, are strong enough to commute between the surface and the depths far below.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Even in the clearest water, light quickly fades with increasing depth. Deeper than about 150 m (500 ft), not enough light penetrates for photosynthesis to occur, so algae are unable to survive. With increasing depth, water pressure rises and temperature falls, ultimately coming close to the freezing point on the ocean floor. Despite these extreme conditions, animal life is found in the ocean’s greatest depths, fueled by the constant rain of organic debris that drifts down from far above. In a habitat where prey is widely scattered, many deep-sea fish can swallow animals larger than themselves, an adaptation that allows them to go weeks or months between meals.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Land Habitats</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3202/2771139598_028a9e16e2_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Zoogeographic Regions<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The world’s land area is divided into six zoogeographic regions, each with different fauna. Within these regions, animals are grouped by the particular habitat they occupy. Land animals will tend toward habitats based on many factors, including indigenous food and availability of natural protection from predators.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">On land, animal habitats are strongly influenced by climate, the combination of precipitation and temperature conditions experienced in a region. At or near the equator, year-round moisture and warmth generates a constant supply of food. Further north or south, seasonal changes become much more pronounced, shaping the type of animals that live in different habitats and their strategies for survival (<i>see </i>Animal Distribution).<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Tropical and subtropical forests are home to by far the largest number of animal species on land. These animals include the majority of the world’s insects, most of its primates, and a large proportion of its birds. Tropical forests have existed longer than any other forests on earth and their plants and animals have evolved an elaborate web of interrelationships.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Much of the animal life of tropical forests is still poorly known, and new species are constantly being discovered. The majority of these newly identified animals are invertebrates, but larger animals have also come to light during the 20th century. Major discoveries have included three large but secretive plant-eating mammals: the okapi, discovered in Central Africa in 1900; the kouprey, discovered in the forests of Cambodia in 1937; and the sao la, which was identified in forests bordering Laos and Vietnam in 1993.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Unlike tropical forests, temperate forests provide animals with an abundance of food during spring and summer, but a dearth during the winter. In this habitat, animals have evolved several different strategies for avoiding starvation during the winter months. Food hoarders, such as squirrels and jay birds, bury surplus food during the fall, and dig it up again when other food supplies run out. Other forest animals, such as the common dormouse, avoid food shortages by hibernation, a period of inactivity when body temperature is lowered. A third group of animals—composed chiefly of birds, but also including some bats and insects–migrates to warmer regions before the winter begins and returns again in spring. In boreal forests, which are found in the far north, the seasonal swings are more extreme. Here only a few species stay and remain active during the winter months.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">For land animals, the most testing habitats are ones that experience intense drought or extreme cold. Desert animals cope with heat and water shortage by behavioral adaptations, such as remaining below ground by day, and also by physiological adaptations. North American kangaroo rats, for example, can live entirely on dry seeds without ever drinking liquid water. They do this by losing very little moisture from their bodies and using all the “metabolic water” that is formed when food is broken down to release energy.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In tundra and on polar ice, winter air temperatures can fall to below -40° C (-40° F), which is far colder than the temperature of the surrounding seas. The smallest inhabitants of tundra, which include vast numbers of mosquitoes and other biting flies, spend winter in a state of suspended animation and are kept alive by chemical antifreeze within their tissues. The few animals that do remain active on land or ice during winter, such as seals and male emperor penguins, rely on a thick layer of insulating fat to prevent their body heat leaking away. Without this fat, they would die within a matter of minutes.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">IV<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">FEEDING<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Animals all feed on organic matter, but their diets and way of obtaining food vary enormously. Some animals are omnivores, meaning that they are capable of surviving on a very wide range of foods. Many other animals, from giant pandas to fleas, have extremely precise requirements and cannot deviate from their highly specialized diet.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Herbivores and Carnivores</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3025/2770292531_bd05e690b8_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Meat Eaters and Plant Eaters<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">In carnivores (<i>right</i>), the front of the skull has a pair of enlarged canine teeth and the lower jaw moves only in an up and down direction, which assists with the capture and holding of prey. In herbivores (<i>left</i>), the canine teeth are absent and the premolars and molars are well developed. The jaw construction also allows for the lateral movement of the lower jaw in relation to the upper jaw, which helps to provide a grinding motion necessary for rendering plant materials into a state suitable for swallowing and digestion.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Dorling Kindersley<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In general, animals eat plants, other animals, or the remains of living things. Plant-eaters, or herbivores, often do not have to search far to find things to eat, and in some cases—for example wood-boring insects—they are entirely surrounded by their food. The disadvantage of a plant-based diet is that it can be difficult to digest and is often low in nutrients.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">To overcome the first of these problems, most herbivores have tough mouthparts for chewing and grinding their food. Many plant-eating animals, from termites to cattle, have complex digestive systems containing microorganisms that break down cellulose and other indigestible plant substances, turning them into nutrients that the animals can absorb. The second problem—lack of nutrients–is harder to sidestep, particularly in a diet made up largely of leaves. As a result, leaf-eaters often have to feed for many hours each day to obtain the nutrients that they need.</span><br /><img src="http://farm4.static.flickr.com/3078/2771139814_6036459a69_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Alligator Snapping Turtle<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The alligator snapping turtle, the largest of the freshwater turtles, has a ridged, camouflaged shell and powerful jaws. When a fish, mistaking a small, wriggling projection on the turtle’s tongue for a worm, swims within reach, the turtle captures it by quickly snapping its jaws shut.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Dorling Kindersley<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Carnivores live on flesh from other animals that is often nutrient-rich and easy to digest but difficult to obtain. Finding and capturing this kind of food calls for keen senses. But even though a hunter has acute vision or a highly developed sense of smell, a large proportion of a hunter’s victims manage to escape. If this happens too often, a predator quickly starves.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Some mammalian predators, such as the lion and wolf, increase their chances of success by hunting in groups. While this strategy enables them to tackle larger prey, a successful kill has to be shared among members of the group. But in the animal world as a whole, many other predators adopt a less energy-intensive approach to catching their food. Instead of actively searching out their prey, they position themselves in a suitable location and wait for their prey to come within striking distance.</span><br /><img src="http://farm4.static.flickr.com/3195/2771139990_2764ca6708_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Anglerfish<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Anglerfish have appendages that serve as fishing rods or lures to attract prey, mainly other fish. They are found in oceans all over the world and generally inhabit deep waters. Certain species can grow to lengths of about 1.5 m (5 ft), and have huge mouths capable of swallowing fish of equal size.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Zig Leszczynski/Animals Animals<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In this method of hunting, camouflage and other forms of deception play a prominent role. Most animals that use a lie-and-wait strategy blend in with their surroundings, but a few use lures to entice their prey within range. A typical example is the alligator snapping turtle of North America, which waves a ribbon of pink flesh on its tongue that resembles a worm. Any fish venturing toward it is swallowed whole.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In predatory animals, teeth or other mouthparts often play a part in catching and subduing food as well as in preparing it for digestion. These mouthparts include canine teeth in carnivorous mammals, venomous fangs in snakes, and poisonous “harpoons” in some marine mollusks. These harpoons can impale and kill small fish. Each harpoon is used just once, and afterwards it is expelled and another is formed in its place.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Other Feeding Strategies</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3275/2771140214_86f95493f9_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Giant Anteater<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Anteaters are native to Central and South America, inhabiting both forest and open-plain regions. The giant anteater, shown here, is the largest of the species, weighing up to 23 kg (50 lb). The animal is well-adapted to hunt for insects, its sole source of food, because of its long front claws and sticky tongue, which can extend to 60 cm (24 in).<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Library of Natural Sounds, Cornell Laboratory of Ornithology. All rights reserved./Miriam Austerman/Animals Animals<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Most predators hunt the largest animals that they can catch without putting themselves unduly at risk. However, some animals concentrate on food items that are much too small to be worth collecting one by one. Instead of catching food individually, they have special feeding adaptations for sweeping it up in bulk.</span><br /><img src="http://farm4.static.flickr.com/3043/2771140404_eee821a29a_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Whale Shark<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Strictly a <i>filter feeder,</i> the whale shark strains plankton and small fish from the upper waters of tropical and subtropical seas by lying motionless beneath the water’s surface. Considered the largest living species of fish, a whale shark may measure more than 15 m (50 ft) in length and weigh more than 18 metric tons. The whale shark poses little risk to humans; however, whale sharks have been known to ram boats that they have mistaken for rival sharks.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">James D. Watt/Animals Animals<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">On land, these animals include insect-eating mammals, such as anteaters and pangolins. Using their long and sticky tongues, they lick up ants and termites and can consume over 20,000 insects a day. In water, this kind of feeding strategy is mirrored by animals called filter feeders, which sieve small animals or food particles from their surroundings. Many of these filter feeders are sessile animals that sieve food from the water immediately around them. Others, such as some whales, scoop up their food while on the move and filter it out in their mouths, using specialized gills or plates of a fibrous material called baleen. This feeding technique is extremely efficient, allowing whales to grow to an immense size.</span><br /><img src="http://farm4.static.flickr.com/3144/2770293387_ed0dcdf95c_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Female Mosquito Sucking Blood<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">There are approximately 2,000 species of mosquitoes ranging from the tropics to the Arctic Circle and from sea level to mountaintops. All mosquitoes belong to the insect order Diptera, which includes all of the flies, or two-winged insects. All species of Dipterans have a single pair of wings for flying and a second vestigial pair called halteres, which act as organs of balance. Female mosquitoes have hypodermic mouthparts which enable them to pierce the skin and suck the blood of mammals, birds, reptiles, and other arthropods. The males have reduced mouthparts and feed instead on nectar and water.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Tim Shepherd/Oxford Scientific Films<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In another feeding technique, predators seek out sources of food that are much larger than themselves but only eat part of their prey—usually its blood. This way of life is has been pursued with great success by several groups of flying insects, such as mosquitoes and horseflies. But in the animal world as a whole, fluid diets are much more common in animals that feed on plants. Aphids, cicadas, and other true bugs use piercing mouthparts to suck sap from plant stems. Many different animals, including moths, butterflies, hummingbirds, and bats, use probing beaks and tongues to reach nectar in flowers.</span><br /><img style="width: 365px; height: 215px;" src="http://farm3.static.flickr.com/2312/2771140922_5705db2064_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Life Cycle of Human Blood Flukes<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Flukes of the genus <i>Schistosoma</i> parasitize two hosts. The young hatch from their eggs in rivers and lakes and enter a specific kind of aquatic snail, where they develop into tadpole-like larvae called cercariae. When the cercariae leave the snail, they burrow through the skin of a human host swimming or wading in infested water. Adult flukes mature in the host’s bloodstream and settle in the veins of the gut. Their eggs, deposited in the lining of the human intestine and bladder, pass back into water via the sewage system, and the cycle begins again. More than 200 million people worldwide suffer from schistosomiasis, a disease characterized by the abscesses and bleeding caused by the flukes’ infestation.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">To avoid the need to track down food, some animals use a highly specialized feeding strategy, called parasitism (<i>see </i>Parasite). A parasite lives on or inside other animals and simply siphons off some of its host’s food or, more commonly, feeds on the host itself. External parasites, such as fleas, have well-developed senses and adaptations that enable them to cling to their hosts. Internal parasites, such as tapeworms and liver flukes, are highly modified for a life inside their hosts. The sense organs of internal parasites are rudimentary or absent because they do not need to find food or avoid enemies. Instead, they devote their time entirely to the twin tasks of feeding and reproduction.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">V<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">BREATHING</span></p></td></tr></tbody></table><br /><img style="width: 352px; height: 193px;" src="http://farm4.static.flickr.com/3255/2770293871_27c86a832a_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Evolution of Air-Breathing Organisms<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Both the lung structure of air-breathing organisms and the swim bladders of most modern fishes evolved from paired air sacs of primitive bony fishes. In the primitive fish, as in the modern bony fishes, these sacs served as a buoyancy device that inflated and deflated to alter the fish’s depth in the water. In other fish, they became primitive lung structures, repeatedly folding inward to maximize oxygen uptake in an oxygen-deprived environment. Both kinds of fishes improved upon a preexisting adaptation but in so doing evolved into very different groups of organisms.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Wherever they live, animals need oxygen in order to survive. By breathing, or respiring, they extract oxygen from their surroundings and dispose of carbon dioxide waste (<i>see </i>Respiration).</span><br /><img style="width: 358px; height: 244px;" src="http://farm4.static.flickr.com/3050/2770294051_1925567006_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">How Fish Breathe<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">A fish breathes by absorbing oxygen from the water it drinks. Water flows into the mouth, through the gills, and out of the body through gill slits. As water flows through the gills, the oxygen it contains passes into blood circulating through gill structures called filaments and lamellae. At the same time, carbon dioxide in the fish’s bloodstream passes into the water and is carried out of the body.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Very small animals do not need any special adaptations for obtaining oxygen. Oxygen simply diffuses in through their body surface, with carbon dioxide traveling out the same way. Larger animals cannot rely on this system because they have a much bigger volume relative to their surface area. To obtain sufficient oxygen, large animals have to boost their oxygen intake by using special respiratory organs. In water, many animals breathe by using gills. A typical gill consists of a stack of thin flaps connected to the animal’s blood supply. Water moves past the flaps in a one-way flow, either when the animal moves, or when it pumps water through its body. The flaps extract oxygen from the water and pass it into the blood, which transfers it to needed tissues. The blood releases carbon dioxide in exchange.</span><br /><img src="http://farm4.static.flickr.com/3223/2771141422_8b00191d03_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Axolotl Showing External Gills<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The axolotl is actually the aquatic larval stage of the brown salamander. Axolotls are of interest to scientists because not all axolotls metamorphose, or change, into adult salamanders. More interestingly, those axolotls that do not transform may become sexually mature while in the larval stage. In captivity, axolotls can be induced to change into adult salamanders by the addition of thyroid extract to the surrounding water.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">G.I. Bernard/Oxford Scientific Films<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Gills do not work on land because their flaps collapse and stick together. Instead, land animals have evolved two different kinds of respiratory organs: tracheal systems and lungs. Tracheal systems are found in insects and many other arthropods. They consist of slender hollow tubes, called tracheae, that reach deep into the body, delivering oxygen from outside. Lungs are hollow cavities that have a large surface area. They are found in vertebrates and also in some invertebrates, such as terrestrial mollusks.</span><br /><img src="http://farm4.static.flickr.com/3063/2770294377_bdc81158ce_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Dolphin Surfacing for Air<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">A Pacific whitesided dolphin breaks the surface of the water while swimming to breathe through a blowhole on the top of its head. Underwater, a dolphin communicates with whistles emitted in single-toned squeals to convey alarm, sexual excitement, and perhaps other emotional states. Dolphins inhabit all the world’s oceans, using their streamlined bodies to reach underwater speeds of 40 km/h (25 mph). This swimming ability coupled with sharp teeth enables dolphins to capture fish and squid, their principal prey.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Library of Natural Sounds, Cornell Laboratory of Ornithology. All rights reserved./K. Findlay, Zoology Department/University of Cape Town<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In tracheae and most lungs, gases move in a two-way flow. Most vertebrates actively pump air in and out of their lungs to step up the rate of gas exchange. By stretching and squeezing their bodies, some arthropods behave in a similar way.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">VI<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">MOVEMENT<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">All animals can move parts of their bodies. The majority are also capable of locomotion—movement of the whole body from place to place. Many simple animals, such as rotifers and flatworms, move with the help of microscopic hairlike structures called cilia. These beat in a coordinated way, propelling the animal through water or making it glide over solid surfaces at the rate of a few inches an hour. Another form of creeping movement, seen in earthworms, involves changes in body shape. The worm’s segments extend and contract in a set sequence, allowing it to force its way through the surrounding soil.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Some of the earthworm’s relatives have flaps called parapodia that help them to move, but even with these, their speed is fairly modest. With a few notable exceptions—such as squid and octopuses, which can move by a form of jet propulsion—the fastest animals by far are ones that have skeletons and jointed limbs.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Jointed Limbs</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3288/2770294543_af64fa6bf8_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Cheetah Running<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The cheetah is believed to be the fastest animal on Earth, reaching speeds of more than 97 km/h (60 mph) while chasing prey. Wildebeests, gazelles, impalas, and other hoofed mammals make up much of the cheetah’s diet. Cheetahs generally stalk their prey to within 10 m (33 ft) and then burst into a sprint to close the gap. Studies indicate that approximately half of the chases initiated by the cheetah are successful.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">National Geographic Society/Worldwide Television News<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Jointed limbs are found in only two groups of animals: the arthropods and vertebrates. An arthropod’s limbs are made of a number of hard tubular segments, which form part of its external skeleton, or exoskeleton. The muscles that operate them are hidden away inside this strong outer framework. In vertebrates, the plan is reversed. The bony skeleton forms an internal framework, with muscles attached around it.</span><br /><img src="http://farm4.static.flickr.com/3195/2770294925_27a39fd1ab_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Pigeon in Flight<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">A bird moves its wings in two ways during flapping flight. The part of the wing closest to the bird’s body moves up and down. Simultaneously, the tip of the wing moves in a circular motion, propelling the bird forward. The way a bird flies depends on the shape of its wings. Most small birds flap their wings the entire time they are airborne, while gulls and other large birds with long, pointed wings soar or glide. The fastest fliers have sharply tapered wings.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Oxford Scientific Films<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">During the course of evolution, both these kinds of limbs have become modified in many different ways. Aquatic animals often have paddlelike limbs that push against the water, enabling them to speed away from predators or after food, or to maneuver their way around confined spaces. On land, the fastest animals, such as the horse and cheetah, have long legs and a flexible backbone, which helps to increase the length of their stride. Land animals that move by jumping often have highly developed hind legs, with extra-large muscles. In fleas, the muscles squeeze an elastic material called resilin, which flicks the legs back when released. This extremely rapid flick is faster than a jump triggered by muscles alone, and it throws a flea up to 30 cm (12 in) into the air.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Many animals can glide, but only insects, birds, and bats are capable of powered flight. The fastest flying insects are dragonflies, which can reach speeds of about 29 km/h (about 18 mph) in short bursts. However, in terms of speed and endurance, birds are by far the most successful animal aviators. Swans and geese can cruise at 64 km/h (40 mph) for many hours at a time, while peregrine falcons can briefly reach 145 km/h (90 mph) when they swoop down on their prey.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Patterns of Movement</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3020/2771142472_edb322335c_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Migrating Wildebeest<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The blue wildebeest, or brindled gnu, migrates annually from Kenya to northern South Africa. Along their migratory route the wildebeests stop at watering holes on the Grameti River, where they become the chief source of food for Nile crocodiles. Scientists speculate that the crocodiles of the Grameti River may feed only once a year, when blue wildebeests arrive during their annual migration.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">John Downer/Oxford Scientific Films<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Being able to move gives animals many advantages, but it also generates its own demands. For any animal, random movement can be unhelpful or even dangerous. To be useful, movement has to be carefully guided.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Animals are guided by their senses, which provide feedback about their changing surroundings. In animals that have radial symmetry (symmetry around a central point), such as jellyfishes, sensory nerves are arranged more or less evenly around the body. This arrangement makes the animal equally sensitive to stimuli from any direction. In bilaterally symmetrical animals (animals made of equal halves), sensory nerves are concentrated in the head. They convey signals to the brain from organs such as ears and eyes, telling an animal about the surroundings that it is about to encounter.</span><br /><img src="http://farm4.static.flickr.com/3048/2770296539_ab08ac69dd_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Monarch Migration<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The monarch butterfly, <i>Danaus plexippus,</i> is known for its extraordinarily long migrations. During the summer months, monarchs can be found throughout the continental United States and parts of Canada, and they migrate to the California coast and central Mexico for the winter. The longest recorded flight for a tagged adult is 2,900 km (1,800 mi). A large number of monarchs spend their winters in the mountains west of Mexico City. Scientists speculate that the mountainous climate provides a favorable mix of moist air and cool, but not freezing, temperatures. These conditions keep the butterfly from drying out and keep its metabolism low enough to conserve fat stores but high enough to maintain life.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">G. G. Dimijian/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">These sensory systems help animals to move toward food and away from possible danger. On a longer time span, they also guide them through much more complex patterns of movement that are essential for their survival. These movements include special kinds of behavior needed to locate a partner, and also seasonal movements or migrations.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Some of the shortest migrations are carried out by microscopic flatworms that live on sandy shores. These worms migrate up to the surface of the sand at low tide and back into it at high tide—a total distance of about 20 cm (about 8 in) roughly twice a day. In the open ocean, many planktonic animals carry out larger daily migrations, rising to the surface at dusk and then sinking at sunrise. By doing this, they reduce the chances of being eaten.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The longest migrations are annual ones, undertaken by animals in response to the changing seasons. By carrying out these journeys, animals can breed in places where food is abundant for just a few months each year. Long-distance annual migration is seen in some plant-eating mammals, such as wildebeest and caribou, and also in whales, but it is most common in animals that fly. Some birds, such as terns and shearwaters, migrate over 32,000 km (20,000 mi) each year. Research has shown that during these epic journeys, they use a variety of cues to help them navigate. These include familiar landmarks, the position of the sun and stars, and the also the orientation of Earth’s magnetic field (<i>see </i>Animal Migration).<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">VII<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">REPRODUCTION<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Like all living things, animals have limited life spans. Although individual animals eventually die, reproduction ensures that they hand on their characteristics to future generations. Animals reproduce at markedly different rates, but all have the potential to increase their numbers if resources allow it. In practice, sharp increases are rare, kept in check by predators and food shortages. <o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Forms of Reproduction<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Animal reproduction takes two overall forms. In the first form, called asexual reproduction, animals produce offspring without needing a partner. Asexual reproduction is most common in simple animals such as flatworms and cnidarians. In flatworms, the parent often develops a constriction in its body, and the rear part eventually tears itself free. The rear part grows a new head, while the front part grows a new tail. Some cnidarians can also divide in two, but many reproduce by a different process, called budding. During budding, a small outgrowth of the body slowly develops into a complete new animal, which eventually takes up life on its own.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Asexual reproduction also occurs in insects such as aphids and in a few unusual vertebrates, such as whiptail lizards. However, in general, it is rarely used as an animal’s sole method of reproduction. This is because asexual reproduction produces offspring that are genetically identical to their parent. They inherit all their parent’s weak points and are equally vulnerable if a disease or other changes in the environment threaten the group’s survival.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">A second and much more common form of reproduction, sexual reproduction, involves two parents. The parents produce sperm and egg cells (gametes), which are brought together to form a fertilized cell (zygote) with a new and unique combination of genes. In this genetic lottery, offspring inherit unique combinations of characteristics that increase the likelihood that at least some individuals in the population can survive changes in the environment.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Sexual reproduction is used by the vast majority of the world’s animals. However, a significant number of species, particularly in the world of insects, use both forms of reproduction at different stages of their life cycles. They reproduce asexually when food is abundant, but turn to sexual reproduction when conditions become more severe.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Reproductive Strategies</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3215/2771143896_2fa8390d11_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Modes of Frog Reproduction<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">BBC Worldwide Americas, Inc.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Asexual reproduction is relatively easy to achieve because it involves only a single animal. Sexual reproduction is much more complex because the partners often have to find each other and precisely coordinate their reproductive behavior. In most cases, each partner is either male or female, but in some animals—such as earthworms, slugs, and snails–each one is a hermaphrodite, an animal that has both male and female organs. Hermaphrodites usually fertilize each other, with both partners producing young (<i>see </i>Hermaphroditism).</span><br /><img src="http://farm4.static.flickr.com/3036/2770296837_22b4234f0e_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Western Grebe Courtship<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">During the spring, western grebes perform spectacular courtship dances. In the “rushing” display, the mating pair swim side-by-side with their wings held back, their long necks arched, and their yellow beaks angled upward. They swim so quickly that their bodies are pushed up out of the water and they appear to run across the surface. After courtship the male and female build a floating nest out of plant material.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">BBC Worldwide Americas, Inc.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Most aquatic animals shed their eggs and sperm into the water, where external fertilization takes place. In corals and many other sessile species, the moment of spawning is often triggered by the tides, maximizing the chances that the egg and sperm will meet. In a minority of marine animals, fertilization is internal, meaning that the male mates with the female, inserting his sperm into her body. For this to work, the male needs special adaptations to make the transfer. Male sharks and rays use special claspers that are attached to their pelvic fins, while barnacles, which are often hermaphrodites, use a threadlike penis that can be almost as long as their bodies.</span><br /><img src="http://farm4.static.flickr.com/3290/2771144214_13ba5d8e76_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Internal Fertilization<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Terrestrial vertebrates clasp each other tightly during copulation, the act by which the male deposits his sperm into the female’s reproductive tract. In the giant Galápagos tortoises pictured here, mating may take hours.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Tui De Roy/Oxford Scientific Films<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">On land, external fertilization is rare because egg and sperm cells cannot survive for long in the open. As a result, almost all land animals must mate to trigger internal fertilization in order to reproduce. Different groups of animals have evolved a wide variety of mechanisms to make sure that males and females manage to locate suitable partners. Some female insects emit chemicals called pheromones, which guide males towards them, while others use sound signals or biochemically produced light (<i>see </i>Bioluminescence). In birds, elaborate plumage and courtship displays help to attract females towards the males (<i>see </i>Animal Courtship and Mating).</span><br /><img src="http://farm4.static.flickr.com/3158/2771144402_23b802c35c_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Honey Bee From Egg to Adult<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The queen honey bee may lay 1500 eggs in a single day. Worker bees feed the wormlike larva constantly—as many as 1300 times a day—after it hatches, sealing the cell when the grub has grown to fill it. The larva pupates in about 12 days, and the adult bee chews through the wax cap of its cell approximately three weeks after the eggs were first laid. Newly emerged adults perform various maintenance tasks until they are ready to begin foraging outside the hive.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The males of many insects and virtually all mammals use a penis to transfer sperm to the female, who harbors the eggs, in a process known as copulation. The penis ensures that sperm is transferred successfully without being carried away by wind, water, or other environmental elements. Most birds and reptiles mate using a cloaca, a single opening located on the lower abdomen. During mating, these animals align their cloacas for transfer of sperm. Some birds, such as bald eagles, can perform this feat in mid-air. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Once a female has mated, egg development can proceed in two different ways. In oviparous species, which include the majority of vertebrates except mammals, and also most insects, the fertilized eggs are laid and develop outside the mother’s body. In viviparous animals, which include nearly all mammals together with some reptiles and sharks, the young develop inside the mother and are born live.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Most animals that are born live look similar to their parents, although they are not fully developed. By contrast, many egg-laying invertebrates look completely different from their parents when they hatch and often live in a completely different way. Known as larvae, these young change shapes as they grow up, during a process called metamorphosis. Larvae are also found in some fish and most amphibians.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">C<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Mating Systems<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Animals that reproduce sexually have evolved a wide variety of different systems for maximizing the number of young that can be raised. In the simplest system, each female is partnered by a male, and the partnership lasts for life. In more complex systems, the fittest adults have many partners while others have none at all.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In polygynous breeding systems, successful males mate with more than one female. Polygyny is common in birds, particularly in species where the males establish breeding territories that provide access to food. A male with a good territory may attract several mates, while one with an inferior territory may attract few or none. Polygyny can also be seen in some mammals and is taken to extremes in species such as elephant seals. The largest and most powerful male elephant seals, weighing up to four times as much as the females, clash viciously for dominance on a breeding beach. A successful male can assemble a harem of over twenty females, but weaker males are excluded from breeding altogether.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In polyandrous breeding systems, one female mates with several males. This kind of breeding system is rare and usually occurs in species where the males take on the work of raising the young. An example of a polyandrous bird is the North American spotted sandpiper. In this species, females compete for males. A single female can lay up to five sets, or clutches, of eggs, and each clutch is incubated by a different partner.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The most specialized mating systems of all occur in animals that form permanent family groups. In social insects, which include many bees and wasps and all ants and termites, each group or colony is founded by a single female or queen. The queen is the only individual in the colony to reproduce. Her offspring, which can number more than a million, forage for food, maintain the nest, and care for the young.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">D<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Parental Care</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3062/2771144586_dfb11f5e31_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Killer Whale Family<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Showing the characteristic contrasting white patches above the eyes and under the jaws, a male and female killer whale, <i>Orcinus orca,</i> swim protectively on either side of their baby. Killer whales maintain close ties to the social structure of their natal pods, or groups, for life. To prevent inbreeding, however, the whales typically seek mates outside of their original pod.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">David E Myers/Tony Stone Images<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">With the exception of birds, the majority of egg-laying animals play no part in helping their young to survive. A large proportion of their young die, and to offset this, they often produce a huge number of eggs. A housefly, for example, can lay over a thousand eggs in the course of its life, while a female cod can lay 3 million.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Most amphibians and reptiles lay smaller clutches of eggs, and some of them remain with their eggs and guard them until they hatch. Birds lay smaller clutches still, and the parents incubate the eggs, or keep them warm until they hatch, and continue to care for their young once they have hatched. Most ground-nesting species protect their young and lead them to food, but typical tree-nesting birds provide their young with both food and shelter until they are able to fend for themselves. Without this parental care, the young birds would have no hope of survival.</span><br /><img src="http://farm4.static.flickr.com/3186/2771144770_186a43bf50_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">American Redstart Feeding Young<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">A female American redstart turns toward her offspring, which begs for food with its gaping mouth.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Ralph A. Reinhold/Animals Animals<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Parental care is equally important in mammals, which provide food for their young in the form of milk. Raising a family in this way creates a close link between the mother and her young. This method also allows the young to learn important patterns of behavior by watching their mother at work. In small rodents, this learning period lasts for just a few days, but in larger mammals, it can last for more than a year.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">VIII<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">STRATEGIES FOR SURVIVAL</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3014/2771145080_475fd7eb53_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Animals in Extremes<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Discovery Enterprises, LLC<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In the living world, resources such as food and space are limited. As a result, survival is a constant struggle. Through evolution, animals have developed a range of adaptations that give them the best chances of success.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The most obvious of these adaptations are physical ones that affect the shape or structure of an animal’s body. Equally important, although often less conspicuous, are adaptations that affect behavior and body processes. Together, these different adaptations allow each species to pursue a distinctive way of life.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Physical Adaptations</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3128/2771145434_88180625bc_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Tulip-Tree Beauty<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The tulip-tree beauty is a large moth that feeds on the foliage of the tulip tree as a caterpillar. Found from southern Canada to Florida, the moths often have banded coloration that camouflages them against tree bark. <o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">John R. MacGregor/Peter Arnold, Inc.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The need to eat exposes animals to the danger of being attacked and eaten themselves. To avoid this fate, all animals have physical adaptations that enable them to escape being attacked or to survive an attack once it is underway.</span><br /><img src="http://farm4.static.flickr.com/3284/2771145664_d08446502a_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Turtle Skeleton<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The turtle or tortoise body is encased in a shell made up of a series of bony plates covered with a horny shield. The vertebrae and ribs are fused to the inside of this shell, which gives it additional support and strength. It is impossible for turtles or tortoises to crawl out of their shells. Turtles have a relatively flattened shell and are aquatic, while tortoises have a dome-shaped shell and are terrestrial.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Dorling Kindersley<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The simplest form of defense is a rapid escape, which calls for keen senses and well-developed systems for movement. Many plant-eating mammals depend on this strategy for survival and must maintain a constant lookout for danger. A less-demanding survival strategy, found in many small animals such as insects, involves deception. These animals use camouflage to blend in with their backgrounds, or they mimic inedible objects such as twigs or bird droppings. If a predator does come too close, they still have the option of making a dash for safety.</span><br /><img src="http://farm4.static.flickr.com/3026/2770298587_d53f065952_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Regal Horned Lizard<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The well-camouflaged regal horned lizard, <i>Phrynosoma solare,</i> requires so many ants a day to sustain it that it almost always is found near an anthill. Regal horned lizards usually fare poorly in captivity, where quantities of ants are often insufficient. It remains motionless if approached, but if picked up, it may attempt to disconcert its attacker by puffing up its body and squirting blood, sometimes as far as a few feet, from a reserve behind its eyes. The regal horned lizard is the largest of the American species of horned lizards and can be recognized by the four large horns on the back of its head.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">M.P.L. Fogden/Oxford Scientific Films<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">A more sophisticated form of mimicry occurs in animals that resemble species that are poisonous. This is common in insects, and it also occurs in some snakes. Poisonous insects, such as bees and wasps, are often brightly colored to warn other animals that they are best left alone. By adopting these colors and developing similar body shapes, non-poisonous insects benefit from the same protection. The physical adaptations involved can be elaborate. The hornet clearwing moth, for example, is yellow and brown like a stinging hornet. On its first flight, it loses most of its wing scales, resulting in transparent wings that make the resemblance even more convincing.</span><br /><img src="http://farm4.static.flickr.com/3153/2771145934_7eb7e8eb18_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Snowshoe Hare in Summer and Winter<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The snowshoe hare uses camouflage to hide from predators. The summer coat of the snowshoe hare provides excellent camouflage among the grasses and shrubs of its summer habitat, while the white winter coat blends in perfectly with the snowy forest.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Judd Cooney/Oxford Scientific Films<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">An alternative defense, seen in a wide range of animals, uses armor or spines to fend off an attack. Animal armor includes hard shells, overlapping scales, and in the case of armadillos, bands of hardened plates connected by areas of softer skin. If they are threatened, many of these animals can shut their bodies away inside their armor, making them difficult to attack. The disadvantage of this defense is that the animal cannot escape. If its armor is broken open, death is almost certain.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Behavioral Adaptations</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3230/2771146020_0d1bc5f0c6_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Egyptian Vulture<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">This Egyptian vulture holds a stone in its beak in preparation for smashing an ostrich egg. Egyptian vultures are unusual among birds because they use stones as tools for obtaining food.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Roy Toft/Tom Stack and Associates<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In simple animals, behavior is governed almost entirely by instinct, meaning that it is pre-programmed by an animal’s genes. In more complex animals, instinctive behavior is often modified by learning, producing more-flexible responses to the outside world.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Many forms of behavior help animals to survive severe environmental conditions. Two examples are hibernation, which enables animals to survive cold and food shortages in winter; and estivation, which allows animals to survive drought and heat in summer. True hibernators, such as bats and some rodents, become completely inactive during winter, and their body temperature falls close to freezing. While in this state, they survive entirely on food reserves stored in their bodies. Estivating animals, which include land snails and some amphibians, seal themselves up when conditions become dry and only become active again when it rains. Between these two extremes, many other animals show less drastic patterns of behavior that are triggered by cold or heat. Winter wrens, for example, often crowd together for sleep when temperatures fall below freezing. On warmer nights, they sleep on their own.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Special forms of behavior also help animals to find food, to avoid being eaten, and to protect their young. One of the most advanced forms of this behavior is the use of tools. Several kinds of animals, particularly primates and birds, pick up implements such as twigs and stones and use them to get at food. More rarely, some tool-using animals seek out a particular object and then shape it so that it can be used. Woodpecker finches probe for insect grubs by making tools from cactus spines, and chimpanzees sometimes dig for termites using specially prepared twigs.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Defensive behavior is exhibited by individual animals and also by animal groups. Group defense is common in herding mammals, particularly in species such as the musk-ox, which form a protective ring around their calves when threatened by wolves. It can also be seen in swallows, starlings, and other songbirds, which instinctively mob hawks and other birds of prey. By grouping together to harass their enemies, they reduce the chances that they or their young will be singled out and attacked.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Individual defensive behavior is often based on threatening gestures that make an animal look larger or more dangerous than it actually is. Sometimes it involves some highly specialized forms of deception. One of the most remarkable is playing dead. Seen in animals such as the Virginia opossum and some snakes, this last-ditch defense is effective against predators that habitually hunt moving prey but leave dead animals alone. After the predator has inspected the “dead” animal and moved on, the prey comes back to life and makes its escape.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">IX<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">ORIGINS OF ANIMALS</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3111/2770298931_596828a77f_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Purple and Yellow Tube Sponge<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The purple and yellow tube sponge displays one of the many different body forms typical of sponges. Sponges, considered to be the most primitive of the multicellular animals, are represented in the fossil record back to the Cambrian Period, at least 600 million years ago. The interior body cavities of sponges provide shelter for a variety of small crabs, sea stars, and other marine invertebrates.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Joe Dorsey/Oxford Scientific Films<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Most biologists agree that animals evolved from simpler single-celled organisms. Exactly how this happened is unclear, because few fossils have been left to record the sequence of events. Faced with this lack of fossil evidence, researchers have attempted to piece together animal origins by examining the single-celled organisms alive today.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Modern single-celled organisms are classified into two kingdoms: the prokaryotes and protists. Prokaryotes, which include bacteria, are very simple organisms, and lack many of the features seen in animal cells. Protists, on the other hand, are more complex, and their cells contain all the specialized structures, or organelles, found in the cells of animals. One protist group, the choanoflagellates or collar flagellates, contains organisms that bear a striking resemblance to cells that are found in sponges. Most choanoflagellates live on their own, but significantly, some form permanent groups or colonies.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">This tendency to form colonies is widely believed to have been an important stepping stone on the path to animal life. The next step in evolution would have involved a transition from colonies of independent cells to colonies containing specialized cells that were dependent on each other for survival. Once this development had occurred, such colonies would have effectively become single organisms. Increasing specialization among groups of cells could then have created tissues, triggering the long and complex evolution of animal bodies.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">This conjectural sequence of events probably occurred along several parallel paths. One path led to the sponges, which retain a collection of primitive features that sets them apart from all animals. Another path led to two major subdivisions of the animal kingdom: the protostomes, which include arthropods, annelid worms, mollusks, and cnidarians; and the deuterostomes, which include echinoderms and chordates. Protostomes and deuterostomes differ fundamentally in the way they develop as embryos, strongly suggesting that they split from each other a long time ago.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Animal life first appeared perhaps a billion years ago, but for a long time after this, the fossil record remains almost blank. Fossils exist that seem to show burrows and other indirect evidence for animal life, but the first direct evidence of animals themselves appears about 650 million years ago, toward the end of the Precambrian period. At this time, the animal kingdom stood on the threshold of a great explosion in diversity (<i>see </i>Biodiversity). By the end of the Cambrian Period, 150 million years later, all of the main types of animal life existing today had become established.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Moving onto Land<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">When the first animals evolved, dry land was probably devoid of any kind of life, except possibly bacteria. Without terrestrial plants, land-based animals would have had nothing to eat. But when plants took up life on land over 400 million years ago, that situation changed, and animals evolved that could make use of this new source of food. The first land animals included primitive wingless insects and probably a range of soft-bodied invertebrates that have not left fossil remains. The first vertebrates to move onto land were the amphibians, which appeared about 370 million years ago.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">For all animals, life on land involved meeting some major challenges. Foremost among these were the need to conserve water and the need to extract oxygen from the air. Another problem concerned the effects of gravity. Water buoys up living things, but air, which is 750 times less dense than water, generates almost no buoyancy at all. To function effectively on land, animals needed support.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In soft-bodied land animals such as earthworms, this support is provided by a hydrostatic skeleton, which works by internal pressure. The animal’s body fluids press out against its skin, giving the animal its shape. In insects and other arthropods, support is provided by the exoskeleton (external skeleton), while in vertebrates it is provided by bones. Exoskeletons can play a double role by helping animals to conserve water, but they have one important disadvantage: unlike an internal bony skeleton, their weight increases very rapidly as they get bigger, eventually making them too heavy to move. This explains why insects have all remained relatively small, while some vertebrates have reached very large sizes.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Speciation and Extinction</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3201/2771146400_ae8c99b6ae_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Galápagos Finches<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The fourteen species of finch that inhabit the Galápagos Islands are believed to have evolved from a single species resembling the blue-black grassquit, <i>Volatinia jacarina,</i> abundant in Latin America and the Pacific coast of South America. The ancestral finch, with its short, stout, conical bill specialized for crushing seeds, probably migrated from the mainland to the Galápagos Islands. Its descendants, free to exploit the resources they would otherwise share with warblers, woodpeckers, and other birds, adapted to the available range of habitats (tree, cactus, or ground) and food (seeds, cactus, fruit, or insects). The size and shape of their bills reflect these specializations, an example of adaptive radiation.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Like other living things, animals evolve by adapting to and exploiting their surroundings. In the billion-year history of animal life, this process has created vast numbers of new species, each capable of using resources in a slightly different way. Some of these species are alive today, but these are a minority; an even greater number are extinct, having lost the struggle for survival.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Speciation, the birth of new species, usually occurs when a group of living things becomes isolated from others of their kind (<i>see </i>Species and Speciation). Once this has occurred, the members of the group follow their own evolutionary path and adapt in ways that make them increasingly distinct. After a long period—typically thousands of years—their unique features mean that they can no longer breed with their former relatives. At this point, a new species comes into being.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In animals, this isolation can come about in several different ways. The simplest form, geographical isolation, occurs when members of an original species become separated by a physical barrier. One example of such a barrier is the open sea, which isolates animals that have been accidentally stranded on remote islands. As the new arrivals adapt to their adopted home, they become more and more distinct from their mainland relatives. Sometimes the result is a burst of adaptive radiation, which produces a number of different species. In the Hawaiian Islands, for example, 22 species of honeycreepers have evolved from a single pioneering species of finch-like bird.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Another type of isolation is thought to occur where there is no physical separation. In this case, differences in behavior, such as mate selection, may sometimes help to split a single species into distinct groups. If the differences persist for a long enough time, new species are created.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The fate of a new species depends very much on the environment in which it evolved. If the environment is stable and no new competitors appear on the scene, an animal species may change very little in hundreds of thousands of years. But if the environment changes rapidly and competitors arrive from outside, the struggle for survival is much more intense. In these conditions, either a species changes, or it eventually becomes extinct.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">During the history of animal life, on at least five occasions, sudden environmental change has triggered simultaneous extinction on a massive scale. One of these mass extinctions occurred at the end of the Cretaceous Period, about 65 million years ago, killing all dinosaurs and perhaps two-thirds of marine species. An even greater mass extinction took place at the end of the Permian Period, about 200 million years ago. Many biologists believe that we are at present living in a sixth period of mass extinction, this time triggered by human beings.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">X<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">ANIMALS IN THE BALANCE OF NATURE<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Compared to plants, animals make up only a small part of the total mass of living matter on earth. Despite this, they play an important part in shaping and maintaining natural environments.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Many habitats are directly influenced by the way animals live. Grasslands, for example, exist partly because grasses and grazing animals have evolved a close partnership, which prevents other plants from taking hold. Tropical forests also owe their existence to animals, because most of their trees rely on animals to distribute their pollen and seeds. Soil is partly the result of animal activity, because earthworms and other invertebrates help to break down dead remains and recycle the nutrients that they contain. Without its animal life, the soil would soon become compacted and infertile.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">By preying on each other, animals also help to keep their own numbers in check. This prevents abrupt population peaks and crashes and helps to give living systems a built-in stability. On a global scale, animals also influence some of the nutrient cycles on which almost all life depends. They distribute essential mineral elements in their waste, and they help to replenish the atmosphere’s carbon dioxide when they breathe. This carbon dioxide is then used by plants as they grow.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Animals and People</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3058/2771146570_ed98425eaf_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">African Elephant Killed by Poachers<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Elephant populations are on the brink of extinction due to poachers who kill elephants for their ivory tusks. An international ban on ivory trade, instituted in 1989 by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), has diminished the illicit ivory trade and reduced the killing. Over 120 countries support the ban.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Wolfgang Bayer/Bruce Coleman, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Until relatively recently in human history, people existed as nomadic hunter-gatherers. They used animals primarily as a source of food and also for raw materials that could be used for making tools and clothes. By today’s standards, hunter-gatherers were equipped with rudimentary weapons, but they still had a major impact on the numbers of some species. Many scientists believe, for example, that humans were involved in a cluster of extinctions that occurred about 12,000 years ago in North America. In less than a millennium, two-thirds of the continent’s large mammal species disappeared.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">This simple relationship between people and animals changed with domestication, which also began about 12,000 years ago. Instead of being actively hunted, domesticated animals were slowly brought under human control. Some were kept for food or for clothing, others for muscle power, and some simply for companionship.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The first animal to be domesticated was almost certainly the dog, which was bred from wolves. It was followed by species such as the cat, horse, camel, llama, and aurochs (a species of wild cattle), and also by the Asian jungle fowl, which is the ancestor of today’s chickens. Through selective breeding, each of these animals has been turned into forms that are particularly suitable for human use. Today, many domesticated animals, including chickens, vastly outnumber their wild counterparts. In some cases, such as the horse, the original wild species has died out altogether.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Over the centuries, many domesticated animals have been introduced into different parts of the world only to escape and establish themselves in the wild. Together with stowaway pests such as rats, these feral animals have often had a highly damaging effect on native wildlife. Cats, for example, have inflicted great damage on Australia’s smaller marsupials, and feral pigs and goats continue to be serious problems for the native wildlife of the Galápagos Islands.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Despite the growth of domestication, humans continue to hunt some wild animals. Some forms of hunting are carried out mainly for sport, but others provide food or animal products. Until recently, one of the most significant of these forms of hunting was whaling, which reduced many whale stocks to the brink of extinction. Today, highly efficient sea fishing threatens some species of fish with the same fate (<i>see </i>Fisheries).</span><br /><img src="http://farm4.static.flickr.com/3128/2770299779_95fccb0a85_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Endangered Nēnē Goose<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Rats and mongooses introduced in the Hawaiian Islands have found an easy meal in the nēnē goose, one of the many bird species native only to Hawaii. Through captive breeding programs, the population of this endangered bird had rebounded to more than 1,000 by the early 2000s, but today the birds are all genetically similar, creating inbreeding that harms their chances of survival.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">James L. Amos/Corbis<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Since the beginning of agriculture, the human population has increased by more than two thousand times. To provide the land needed for growing food and housing people, large areas of Earth’s landscapes have been completely transformed. Forests have been cut down, wetlands drained, and deserts irrigated, reducing these natural habitats to a fraction of their former extent.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Some species of animals have managed to adapt to these changes. A few, such as the brown rat, raccoon, and house sparrow, have benefited by exploiting the new opportunities that have opened up and have successfully taken up life on farms, or in towns and cities. But most animals have specialized ways of life that make them dependent on a particular kind of habitat. With the destruction of their habitats, their number inevitably declines.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">During the last century or so, animals have also had to face additional threats from human activities. Foremost among these are environmental pollution and the increasing demand for resources, such as timber and fresh water. For some animals, the combination of these changes has proved so damaging that their numbers are now below the level needed to guarantee survival.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Across the world, efforts are currently under way to address this urgent problem (<i>see </i>Endangered Species). In the most extreme cases, gravely threatened animals can be helped by taking them into captivity and then releasing them once breeding programs have increased their number. One species that was restored in this way is the Hawaiian mountain goose or nēnē. In the 1950s, its population had been reduced to about 25 birds. Captive breeding has since helped the population increase, although the nēnē remains on the endangered list.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">While captive breeding is a useful emergency measure, it cannot assure the long-term survival of a species. Today animal protection focuses primarily on the preservation of entire habitats, an approach that maintains the necessary links between the different species the habitats support. With the continued growth in the world’s human population, habitat preservation will require a sustained reduction in our use of the world’s resources to minimize our impact on the natural world.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 15pt;"><span style="font-size: 12pt; font-family: "Times New Roman","serif";"><br />Contributed By:<br />David Burnie<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif";">Microsoft ® Encarta ® 2007.</span></b><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif";"> © 1993-2006 Microsoft Corporation. All rights reserved.<o:p></o:p></span></p> <p class="MsoNormal"><o:p> </o:p></p>ghozian karamihttp://www.blogger.com/profile/13214011599962806335noreply@blogger.com0tag:blogger.com,1999:blog-192751622867664710.post-38333773083754267522009-01-02T16:32:00.000-08:002009-01-02T16:33:54.403-08:00Anthropology<p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 24pt; font-family: "MS Reference Serif","serif";">Anthropology<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">I<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">INTRODUCTION<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Anthropology, the study of all aspects of human life and culture. Anthropology examines such topics as how people live, what they think, what they produce, and how they interact with their environments. Anthropologists try to understand the full range of human diversity as well as what all people share in common.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Anthropologists ask such basic questions as: When, where, and how did humans evolve? How do people adapt to different environments? How have societies developed and changed from the ancient past to the present? Answers to these questions can help us understand what it means to be human. They can also help us to learn ways to meet the present-day needs of people all over the world and to plan how we might live in the future.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">II<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">KEY CONCEPTS<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Much of the work of anthropologists is based on three key concepts: society, culture, and evolution. Together, these concepts constitute the primary ways in which anthropologists describe, explain, and understand human life.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Society and Culture<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Two interrelated anthropological concepts, society and culture, are crucial to understanding what makes humans unique. In its general sense, a society consists of any group of interacting animals, such as a herd of bison. But human societies often include millions or billions of people who share a common culture. Culture refers to the ways of life learned and shared by people in social groups. Culture differs from the simpler, inborn types of thinking and behavior that govern the lives of many animals. The people in a human society generally share common cultural patterns, so anthropologists may refer to particular societies as cultures, making the two terms somewhat interchangeable.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Culture is fundamentally tied to people’s ability to use language and other symbolic forms of representation, such as art, to create and communicate complex thoughts. Thus, many anthropologists study people’s languages and other forms of communication. Symbolic representation allows people to pass a great amount of knowledge from generation to generation. People use symbols to give meaning to everything around them, every thought, and every kind of human interaction.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Evolution</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3223/2771146978_98d0b8fd9a_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Tree of Human Evolution<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Fossil evidence indicates that the first humans evolved from ape ancestors at least 6 million years ago. Many species of humans followed, but only some left descendants on the branch leading to <i>Homo sapiens.</i> In this slide show, white skulls represent species that lived during the time period indicated; gray skulls represent extinct human species.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Most anthropologists also believe that an understanding of human evolution explains much about people’s biology and culture<i>.</i> Biological evolution is the natural process by which new and more complex organisms develop over time. Some anthropologists study how the earliest humans evolved from ancestral primates<i>,</i> a broader classification group that includes humans, monkeys, and apes. They also study how humans evolved, both biologically and culturally, over the past several million years to the present.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Humans have changed little biologically for the past 100,000 years. On the other hand, today’s worldwide culture, characterized by the rapid movement of people and ideas throughout the world, is only a few hundred years old. Today’s global-scale culture differs vastly from that of the <i>small-scale societies</i> (nonindustrialized societies, with small populations) in which our ancestors lived for hundreds of thousands of years. Understanding these kinds of societies and their cultures can help us make more sense of how people cope with life in today’s culturally diverse and complex world.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">III<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">FIELDS OF ANTHROPOLOGY<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Because anthropology is a very broad field of study, anthropologists focus on particular areas of interest. In the United States, anthropologists generally specialize in one of four subfields: cultural anthropology, linguistic anthropology, archaeology, and physical anthropology. Each of the subfields requires special training and involves different research techniques. Anthropology departments in colleges and universities in the United States usually teach courses covering all of these subfields.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In many other countries it is common for the subfields to be found in their own academic departments and to be known by different names. For example, in Britain and other parts of Europe, what Americans call cultural anthropology is commonly called social anthropology or ethnology. Also in Europe, archaeology and the field of linguistics (including what American anthropologists study as linguistic anthropology) are often considered as fields distinct from anthropology.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Cultural Anthropology<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Cultural anthropology involves the study of people living in present-day societies and their cultures. Cultural anthropologists study such topics as how people make their living, how people interact with each other, what beliefs people hold, and what institutions organize people in a society. Cultural anthropologists often live for months or years with the people they study. This is called fieldwork. Some must learn new, and sometimes unwritten languages, and this may require extra training in linguistics (the study of the sounds and grammar of languages). Cultural anthropologists commonly write book-length (and sometimes shorter) accounts of their fieldwork, known as ethnographies.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Linguistic Anthropology<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Linguistic anthropology focuses on how people use language in particular cultures. Those who practice this form of anthropology have a substantial amount of training in linguistics. Linguistic anthropologists often work with people who have unwritten (purely spoken, or oral) languages or with languages that very few people speak. Linguistic anthropological work may involve developing a way to write a formerly unwritten language. Cultures often use these written versions to teach their children the language and thus keep it in use. Some linguistic anthropologists specialize in reconstructing <i>dead languages</i> (languages no longer in use) and their connections to living languages, a study known as <i>historical linguistics.</i><o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">C<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Archaeology<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Archaeology focuses on the study of past, rather than living, human societies and culture. Most archaeologists study <i>artifacts</i> (the remains of items made by past humans, such as tools, pottery, and buildings) and human <i>fossils</i> (preserved bones). They also examine past environments to understand how natural forces, such as climate and available food, shaped the development of human culture. Some archaeologists study cultures that existed before the development of writing, a time known as prehistory<i>. </i>The archaeological study of periods of human evolution up to the first development of agriculture, about 10,000 years ago, is also called <i>paleoanthropology.</i> Other archaeologists study more recent cultures by examining both their material remains and written documents, a practice known as <i>historical archaeology.</i><o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">D<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Physical Anthropology</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3120/2770300239_3fd7506541_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Forensic Anthropology<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Forensic anthropologists specialize in the analysis of human corpses or remains for legal investigations. In this photo, a forensics team working for the International Criminal Tribunal for the Former Yugoslavia examine human remains on a hillside near Srebrenica in northeastern Bosnia. Forensic analysis helps investigators determine how large numbers of civilians died in the Yugoslav Wars of Succession (1991-1995), information needed to convict those responsible for the killings.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Corbis<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Physical anthropology, also known as biological anthropology, concentrates on the connections between human biology and culture. Some physical anthropologists, like some archaeologists, study human evolution. But physical anthropologists focus on the evolution of human anatomy and physiology, rather than culture. Areas of particular interest include the evolution of the brain, especially the areas of the brain associated with speech and complex thought; of the vocal apparatus necessary for speech; of upright posture; and of hands capable of making and using tools. Physical anthropologists work from the belief that humans are primates. <i>Primatology,</i> the study of the behavior and physiology of nonhuman primates, is a specialized area of interest within physical anthropology. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Some physical anthropologists specialize in forensic science, the study of scientific evidence for legal cases. Forensic anthropologists, with their knowledge of human anatomy, sometimes get called upon by law enforcement officials to identify the sex, age, or ancestry of human remains found at crime scenes or uncovered by excavations. Forensic anthropologists also have exhumed mass graves in cases of genocide, the crime of mass murder usually associated with wars. In some cases, anthropologists have provided evidence used in war crimes trials to convict guilty parties.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">IV<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">ANTHROPOLOGY AND OTHER SOCIAL SCIENCES<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Anthropology shares certain interests and subjects of study with other fields of social science, especially sociology, psychology, and history, but also economics and political science. Anthropology also differs from these fields in many ways.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Like sociology, anthropology involves the study of human society and culture. But anthropology began as the study of small-scale tribal societies, large-scale chiefdoms, and ancient civilizations, and later moved to include global-scale societies. Sociology, on the other hand, has always emphasized the study of modern and urbanized societies. Anthropology involves the comparison of different societies in order to understand the scope of human cultural diversity. Sociology, on the other hand, frequently examines universal patterns of human behavior.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Anthropology also examines certain aspects of human psychology. Anthropology studies how people become <i>enculturated</i>—shaped by their culture as they grow up in a particular society. Through enculturation, people develop culturally accepted ideas of what behavior is normal or abnormal and of how the world works. Anthropology examines how people’s patterns of thought and behavior are shaped by culture and how those patterns vary from society to society. By contrast, psychology generally focuses on the universal characteristics of human thought and behavior, and studies these characteristics in individual people.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The study of history is also a part of anthropology. In its formal sense, the term <i>history</i> refers only to periods of time after the invention of writing. Anthropologists often study historical documents to learn more about the past of living peoples. Historical archaeologists, who specialize in the study of historical cultures, also study written documents. But all anthropologists primarily study people, their societies, and their cultures. Historians, on the other hand, primarily study written records of the past—from which they cannot learn about human societies that had or have no writing. <i>See also </i>History and Historiography.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In addition, anthropology examines some topics also studied in economics and political science. But anthropologists focus on how aspects of economics and politics relate to other aspects of culture, such as important rituals. Anthropologists who specialize in the study of systems of exchange in small-scale societies may refer to themselves as <i>economic anthropologists.</i><o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">V<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">UNDERSTANDING HUMAN DIVERSITY<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Anthropologists have particular ways of approaching their studies. They compare differences among human societies to get an appreciation of cultural diversity. They also study the full breadth of human existence, past and present. In addition, anthropologists try to appreciate all peoples and their cultures and to discourage judgments of cultural superiority or inferiority.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Making Comparisons<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Most anthropological studies involve making comparisons. Only through comparison can anthropologists learn about the uniqueness of particular cultures as well as the characteristics that people in all cultures share.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">For example, comparison has helped anthropologists learn about the variety of ways in which people classify their kinship relations. People of European descent, as well as various Eskimo and Inuit groups, regard all children of their parents’ siblings as “cousins.” But in many other cultures, people may regard some of those same relations as the equivalent of a European or Eskimo “brother” or “sister.” <i>See also </i>Kinship and Descent.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Anthropologists also study how culture has evolved, and continues to evolve, by comparing cultural traits among different groups of people, both past and living. Patterns of similarity and increasing complexity over time can be seen in such cultural traits as forms of language or types of tools. These patterns indicate when and where cultural innovation has occurred and how ideas and people have moved around the world.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">A linguistic anthropologist, for instance, might trace the development and spread of new words or forms of grammar through history. A cultural anthropologist might look for the same kinds of trends and changes in the organization of families in societies of different scale or economic system. Archaeologists, as well, often study trends of styles in artifacts, such as types of pottery. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">By comparing humans with other animals, and particularly other primates, anthropologists can learn about the uniqueness of humans as a species. For instance, unlike other primates, humans commonly use language; use fire; adorn themselves with clothing, jewelry, or body markings; manufacture and decorate objects; and have beliefs about the supernatural.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Comparison also reveals what humans and nonhuman primates have in common. Most primates, including humans, share many biological characteristics, such as relatively large brains, grasping hands, acute vision and depth perception, and teeth designed to eat a variety of foods. Many primates, particularly our closest biological relatives, the chimpanzees, are highly intelligent and social animals like people. Anthropologists believe that many of the characteristics shared by humans and nonhuman primates, but not found in other animals, were probably also shared by our earliest ancestors.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Some physical anthropologists study human genetics, the science of biological heredity. By comparing genetic differences among contemporary human populations, anthropologists try to understand when various populations branched off from a common ancestor, and how each population has adapted to its environment (<i>see </i>Race).<b> </b>For instance, anthropological research suggests that highly pigmented, or dark, skin evolved in the tropics as a protection against intense sunlight. Lighter, unpigmented skin most likely evolved in temperate climates to absorb more light, which is crucial for the body’s ability to make vitamin D.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Comparative genetic research has also shown that despite genetic differences, all humans are extremely closely related. Such research suggests that all humans probably share a common ancestor who lived as recently (in evolutionary terms) as 150,000 to 200,000 years ago.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">A cross-cultural perspective allows anthropologists to step back and view human cultural and biological development with relative detachment. As recently as the late 19th century, sociologists and early anthropologists believed that cultural development meant progress—a series of improvements in human life marked by inventions and discoveries. However, as anthropologists studied more cultures, their research suggested that cultural developments are not always advantageous, but that every cultural group lives in a way that works well for many of its people.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">For example, anthropological research has revealed how the technology of food production changed over the past 15,000 years. All people once made their living by hunting and foraging using tools of stone, wood, and bone. Subsequently, some societies moved to gardening and herding, then to plow agriculture using metal tools, and then to industrial factory production using machinery powered by internal combustion engines.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Many people think of the evolution of food production as a story of progress and improvement. But archaeological evidence shows that the first development of agriculture, as early as 9000 <span style="text-transform: uppercase;">bc</span> in the Middle East, may have hurt people's health. These early farmers, who settled in villages, became dependent on a very limited diet of harvested crops as opposed to the varied and nutritious diet available to them as nomadic foragers.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Examining Many Perspectives<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Because anthropology examines human culture from so many perspectives, anthropologists commonly characterize their discipline as <i>holistic,</i> meaning all-encompassing. The holistic approach of anthropological research can provide insight into complex contemporary problems.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Studies of the connections among human ecology, biology, and culture in small-scale societies have given anthropologists insights on large-scale, even worldwide, problems. Anthropologists have studied how small-scale hunter-gatherer, gardening, and farming societies manage to make a living without destroying species of plants or animals, or ruining the soil or water. Their findings may provide new approaches to urgent global environmental problems, such as deforestation and the loss of biological diversity. Anthropologists have learned, for instance, about gardening methods that allow patches of forest to grow back after land has been used for planting and harvesting crops.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Studies of small-scale societies have also provided much information about the importance of various species of plant and animal life to human survival. For instance, anthropologists with knowledge of entomology (the study of insects) have learned how people in small-scale societies have developed food production techniques that allow them to grow healthy crops without artificial fertilizers or pesticides. These techniques benefit insect species that help fertilize plants and help eliminate unwanted animal pests.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Physical anthropologists, along with physicians and other researchers, have also conducted health and nutritional surveys on many relatively self-sufficient societies. For instance, they have analyzed the health of peoples living throughout the Amazon rain forest. This research has consistently shown that people native to the Amazon typically are in excellent physical condition and eat a varied and nutritious diet.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Anthropological studies of hunter-gatherers, such as the San people of the Kalahari Desert, has revealed that they enjoy great amounts of leisure time, despite their need to provide themselves daily with food, shelter, and other basic necessities. Anthropologists have made similar findings in studies of people in other small-scale societies. Such people appear to have far more leisure time than do most people living in urban, industrialized societies.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Anthropological research has also shown that the key to people’s well-being in most small-scale societies centers on their relationship with their environments. For instance, anthropologists trained in botany and linguistics have found that individuals living in many small groups throughout the Amazon use hundreds of rain forest plants for medicine, food, and cosmetics. These societies have long maintained a successful way of life, satisfying their needs according to what the forest can sustainably provide.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Drawing on their knowledge of small-scale societies, anthropologists also now study large-scale urban societies in an attempt to understand the long-term significance and potential impacts of cultural change. Paleoanthropological research has shown that all people lived in small-scale societies for about 99 percent of human existence. With their holistic perspective on cultural evolution and diversity, anthropologists question the ability of rapidly growing urban, industrialized societies to manage the growth of human populations and the potential overuse of natural resources.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">C<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Avoiding Cultural Bias<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">An anthropologist tries to understand other cultures from the perspective of an insider—that is, as someone living within the culture. This technique, known as <i>cultural relativism,</i> helps anthropologists to understand why people in different cultures live as they do. Anthropologists work from the assumption that a culture is effective and adaptive for the people who live in it. In other words, a culture structures and gives meaning to the lives of its members and allows them to work and prosper.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Assuming the insider’s perspective presents a challenge, because most people, including anthropologists, harbor some ethnocentrism, the belief that their own culture makes the most sense or is superior. Ethnocentrism somewhat resembles and sometimes occurs with racism, the belief that some groups of people are genetically superior to others. Ethnocentrism and racism make it difficult to view other people and cultures objectively, according to their own merits. By trying to break the barriers of culturally and racially bound perspectives, anthropologists aim to reduce ethnocentrism and racism and the misunderstandings that they cause.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Anthropological research gives a view of human physical and cultural development that challenges many people’s common beliefs. For example, research by physical anthropologists demonstrates conclusively that humans do not fall into sharply defined races. Although many people have tried to identify the characteristics of pure human races, anthropologists have shown that all human populations contain variability and that all people differ from each other very little genetically. In addition, the most easily observed physical variations—in skin color, facial features, and body form—are only a miniscule portion of the almost endless variety of differences that make every person unique.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">VI<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">RESEARCH METHODS<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Anthropologists use both objective (scientific) and subjective (interpretive) methods in their research. As scientists, anthropologists systematically collect information to answer specific research questions. They also document their work so that other researchers can duplicate it. But many anthropologists also conduct informal kinds of research, including impromptu discussions with and observations of the peoples they study. Some of the more common types of anthropological research methods include (1) immersion in a culture, (2) analysis of how people interact with their environment, (3) linguistic analysis, (4) archaeological analysis, and (5) analysis of human biology.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Cultural Immersion</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3036/2771147428_2cbbb60bf5_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Bronislaw Malinowski<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Bronislaw Malinowski, a Polish-born British anthropologist, established methods of modern cultural anthropological research in his study of the people of the Trobriand Islands, near Papua New Guinea. An actor recites an excerpt from Malinowski’s 1922 book about these people, <i>Argonauts of the Western Pacific.</i><o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">(p) 1998 Microsoft Corporation. All rights reserved./Hulton-Deutsch Collection/Corbis<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Researchers trained in cultural anthropology employ a variety of methods when they study other cultures. Traditionally, however, much anthropological research involves long-term, direct observation of and participation in the life of another culture. This practice, known as <i>participant observation,</i> gives anthropologists a chance to get an insider’s view of how and why other people do what they do.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Polish-born British anthropologist Bronislaw Malinowski was the first anthropologist to document a detailed method of participant observation. Malinowski spent two years living with the people of the Trobriand Islands, part of Papua New Guinea, between 1915 and 1918. He learned the Trobriand language and explored the people’s religion, magic, gardening, trade, and social organization. He later published a series of books describing all aspects of Trobriand life. Malinowski's work became a model of research methods for generations of anthropologists.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Just as Malinowski did, most anthropologists today learn local languages to help them gain an insider’s view of a culture. Anthropologists commonly collect information by informally asking questions of the people with whom they live.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Often anthropologists will find individuals within the society being studied who are especially knowledgeable and who are willing to become so-called informants. Informants typically enjoy talking with a sympathetic outsider who wishes to interpret and record their culture. Informants and anthropologists may also form teams in which the informants work as anthropologists. While informants often provide much useful information, anthropologists also have to take into account the biases that people typically have in explaining their own cultures.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In some cases, anthropologists may use interviews to record extensive life histories of individuals with whom they have good relationships. Older people usually volunteer to tell their life stories, often because they have seen many changes since their youth and enjoy telling of past experiences and lessons learned. Such stories can provide valuable insights on how cultures change.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Anthropologists also commonly construct genealogies (diagrams of kinship relations) and maps to show how the people in communities are related to one another, how people organize themselves in groups, and how people and groups interact with each other. These research tools can provide a way for anthropologists to see cultural patterns and complexities of daily life that would otherwise be difficult to discern or comprehend.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Human Ecology<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Many anthropologists combine cultural research with studies of the environments in which people live. <i>Human ecology</i> examines how people interact with their natural environments, such as to make a living. Anthropologists may collect large amounts of data about features of a culture’s environment, such as types of plants and animals, the chemical and nutritional properties of medicines and foods, and climate patterns. This information can provide explanations for some characteristics of a people’s culture.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">For instance, in the 1960s American anthropologist Roy Rappaport analyzed the ecological significance of a ritual cycle of peace and warfare among the Tsembaga people of Papua New Guinea. Rappaport found that the Tsembaga and neighboring groups would maintain peace for periods of between 12 and 20 years. During these periods, the people would grow sweet potato gardens and raise pigs. The people would also guard areas of land they had previously gardened but which were now unused and believed to be occupied by ancestor spirits. When the presence of too many pigs rooting up gardens and eating sweet potato crops became a nuisance, the Tsembaga would feast on the pigs, perform a ritual to remove spirit ancestors from old gardens, and then lift the ban on warfare. The lifting of the ban allowed the Tsembaga to capture abandoned lands from other groups. This regulation of warfare coincided with the amount of time it took for abandoned gardens to regain their fertility, and so made good ecological sense.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">C<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Linguistic Analysis<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Linguistic anthropologists, as well as many cultural anthropologists, use a variety of methods to analyze the details of a people’s language. The practice of <i>phonology,</i> for example, involves precisely documenting the sound properties of spoken words. Many linguistic anthropologists also practice <i>orthography,</i> the technique of creating written versions of spoken languages. In addition, most study the properties of grammar in languages, looking for the rules that guide how people communicate their thoughts through strings of words.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Language reveals much about a people’s culture. Anthropologists have studied such topics as how different languages assign gender to words, shape the ways in which people perceive the natural and supernatural worlds, and create or reinforce divisions of rank and status within societies.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">For instance, many of the peoples native to North America conceive of time as a continual cycle of renewal, a concept quite different from the European belief that time only moves forward in a progression from the past to the future. Linguists have found that many Native American languages, such as that of the Hopi of the North American Southwest, include grammatical constructions for saying that something exists in a state of “becoming,” even though it does not yet actually exist. English and other European languages cannot as easily express such an idea, nor can most Europeans or Americans of European descent truly understand it.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">D<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Archaeological Analysis<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Archaeologists use specialized research methods and tools for the careful excavation and recording of the buried remains of past cultures. Remote sensing involves the use of airplane photography and radar systems to find buried sites of past human cultures. Rigorous methods of excavation allow archaeologists to map the precise locations of remains for later analysis. <i>Seriation</i>, the practice of determining relative age relationships among different types of artifacts based on their shapes and styles, helps archaeologists learn how past cultures changed and evolved. Archaeologists also use a variety of dating methods involving chemical and other types of scientific analysis to reveal the age of buried objects up to millions of years old.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In addition, some archaeologists have training in cultural anthropology, and they may use cultural research to help them interpret what they find buried in the ground. For example, people in many small-scale societies continued to make tools of stone into the 20th century, and some still know how. By watching these people make their tools, archaeologists have learned how to interpret patterns of chipped pieces of stone buried in the ground.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">E<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Physical Anthropological Research<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Physical anthropologists often rely on rigorous medical scientific methods for at least part of their research, in addition to more general observational methods. All physical anthropologists have detailed knowledge of human skeletal anatomy. Paleoanthropologists and forensic anthropologists can construct extremely detailed descriptions of people’s lives from only measurements of bones and teeth. These researchers typically analyze the chemical or cellular composition of bones and teeth, patterns of wear or injury, and placement in or on the ground. Such analyses can reveal information about the sex, age, work habits, and diet of a person who died long ago.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Some physical anthropologists specialize in epidemiology, the study of disease and health among large groups of people. In addition to studying diseases themselves, physical anthropologists focus on cultural causes and preventions of disease. They may study such specific medical topics as nutrition and gastrointestinal function, human reproduction, or the effects of drugs on brain and body function. For instance, physical anthropologists working in San Francisco, California, studied how the beliefs and practices of homosexual and bisexual men factored into the spread of the AIDS (acquired immunodeficiency syndrome) virus in the 1980s. This information helped in the design of effective health education programs to reduce the spread of the disease.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Physical anthropologists studying human genetics use sophisticated laboratory techniques to analyze human chromosomes and DNA (deoxyribonucleic acid), the structures through which people inherit traits from their parents. With these techniques, researchers have identified human populations that have genetic predispositions to specific diseases, such as types of cancer. This knowledge has promoted increased focus on the use of preventive measures among people with higher risk for disease.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">VII<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">DOCUMENTING AND PRESENTING RESEARCH<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Whatever kind of work they do, anthropologists share an interest in making the findings of anthropological research available as widely as possible. Many anthropologists work as professors in colleges and universities. In addition to teaching, they publish results of their research in scholarly books and journals. Others write popular books and magazine articles, produce films, lecture to nonacademic audiences, or work in museums organizing exhibits and maintaining collections.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Academic anthropologists often present their work in a highly technical style, narrowly focused for specialists in the particular subfields of anthropology. Historically, anthropologists conducted field research in order to produce an ethnography, a book or long article that describes many aspects of a particular culture.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Early ethnographies attempted to describe entire cultures. For example, in 1946 American anthropologists Clyde Kluckhohn and Dorothea Leighton published a study on the culture of the Navajo (also spelled Navaho), Native Americans of the Southwestern United States. The book, called <i>The Navajo,</i> covered a wide variety of topics about the Navajo, including their prehistory, history, economic activities, physique, clothing, housing, health, kinship, religious life, language, worldview, and relations with outsiders.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Ethnographies also sometimes focus on a single aspect of a culture. Bronislaw Malinowski's ethnography <i>Argonauts of the Western Pacific</i> (1922) dealt primarily with the interisland trading system of the Trobriand Islanders. Malinowski demonstrated, in great detail, how the ritual exchange of items such as jewelry, food, clothing, and weapons among trading partners was central to the entire culture.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Some ethnographies written between the 1920s and the 1960s discussed the history of a culture and described how it changed over time. But many classic anthropological texts of this period were written in a timeless <i>ethnographic present,</i> describing a culture as though it had always existed in the same way, and always would. This style represented a trend in anthropology known as functionalism, in which anthropologists analyzed cultures as if all the parts of a culture fit and worked neatly together. The functionalist model of cultural integrity portrayed cultures as being stable and unchanging.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Later anthropologists became more concerned with the dynamics of culture change. It became clear by the 1960s that the world and all its cultures were changing in dramatic ways. Contemporary ethnographies often focus on change, especially changes brought about by global cultural contact, urbanization, and people’s increasing exposure to and dependence on mass-produced goods, services, and images (as from films or advertisements).<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">A contemporary anthropologist may write an ethnography from the perspective of a single individual within a culture. Others may write stories or poems. Many try to write using the voices of people they study, and some encourage informants to write their own ethnographies. Anthropologists always give copies of their books or articles to the people they study.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">VIII<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">ETHICAL CONCERNS<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Often, the people that anthropologists study have strong feelings about how they are portrayed to the rest of the world. Professional anthropologists must therefore exercise great care in how they conduct and present their work. Anthropological research also has the potential to disrupt a people’s way of life and bring problems into their societies. Anthropologists try to avoid introducing new ideas, technologies, or even food items into the societies they study, because to do so can make people want things that cannot be readily obtained.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Anthropologists also have ethical obligations to those who fund their research activities as well as to students and the interested public who may want to learn from their work. As a basic rule, anthropologists only conduct research openly, honestly, and with the approval of the people they study. In the United States, federally funded projects and research conducted through a public university might face a formal review procedure to make sure that the rights and safety of human subjects are protected.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Today, anthropologists are also obliged to share their research results with the people who helped produce it and to acknowledge the assistance those people give. Anthropologists do not normally pay for specific information, but they may compensate some of the people they study for their time and effort put in as field assistants or informants.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In rare cases a researcher might decide not to work with a particularly isolated and self-sufficient group because to do so might unavoidably introduce disease and open the way for exploitation by other outsiders. Small, self-sufficient societies may have difficulty defending themselves against more powerful groups. For example, information from anthropological work can familiarize governments and businesses with small-scale societies living in remote regions. This information can convince state and business interests to negotiate with the people of such societies about using their land for such projects as road or dam building, mining, or large-scale farming. These so-called development projects can cause great hardships for people who live off the land.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Anthropologists must practice particularly great care if they work directly for governmental or commercial agencies whose political or economic interests could conflict with the interests of the people being studied. For example, in the 1970s and 1980s the Brazilian government hired anthropologists to pacify people who lived in the rain forest and who were being forcibly relocated to make way for the Trans-Amazon Highway. While some anthropologists considered this work unethical, others felt they could help negotiate with the government to minimize damage to the peoples living in the highway’s future path.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Most anthropologists take a position of cultural relativism when making decisions on issues of ethics and rights. This position calls for respect for all cultural differences and opposes culture change imposed on one society by another. Anthropologists know that people derive their individual identity and sense of dignity from their own cultures. This ethical stance reflects the 1948 United Nations Universal Declaration of Human Rights and the United Nations Declaration on the Rights of Indigenous Peoples (drafted in 1994), both of which recognize cultural practices as basic human rights.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">This does not mean, however, that anthropologists believe all cultural practices are necessarily good. Extreme relativism, which anthropologists avoid, could condone such acts as the Holocaust or other instances of mass <i>ethnocide</i> (the killing of people of a particular ethnic group). Many cultures may foster practices that clearly harm some individuals. Such practices include infanticide (the killing of infants), the burning of people thought to be witches, and the surgical modification of women’s sexual organs (known as female genital mutilation). Anthropologists might speak out against such practices, but generally they believe that change should come from within a culture and not be imposed from outside it.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Archaeologists have other ethical concerns to consider. Archaeological excavations may unearth sensitive or sacred remains of past cultures with living descendants. Such remains might include the bones of dead ancestors or ancient religious offerings.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Archaeologists respect the claims of cultural groups to ownership of their ancestors’ cultural and physical remains, and work to prevent unauthorized removal of such materials by commercial collectors. They also commonly hand over most or all of their finds to the rightful owners or to museums of the countries in which excavations took place. Sometimes, however, an archaeologist may argue that certain excavated materials have such great scientific importance that they should be analyzed before being returned or reburied.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">IX<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">HISTORY OF ANTHROPOLOGY<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "Times New Roman","serif"; display: none;"><o:p> </o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Origins<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Anthropology traces its roots to ancient Greek historical and philosophical writings about human nature and the organization of human society. Anthropologists generally regard Herodotus, a Greek historian who lived in the 400s <span style="text-transform: uppercase;">bc</span>, as the first thinker to write widely on concepts that would later become central to anthropology. In the book <i>History</i>, Herodotus described the cultures of various peoples of the Persian Empire, which the Greeks conquered during the first half of the 400s <span style="text-transform: uppercase;">bc</span>. He referred to Greece as the dominant culture of the West and Persia as the dominant culture of the East. This type of division, between white people of European descent and other peoples, established the mode that most anthropological writing would later adopt.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The Arab historian Ibn Khaldun, who lived in the 14th century <span style="text-transform: uppercase;">ad,</span> was another early writer of ideas relevant to anthropology. Khaldun examined the environmental, sociological, psychological, and economic factors that affected the development and the rise and fall of civilizations. Both Khaldun and Herodotus produced remarkably objective, analytic, ethnographic descriptions of the diverse cultures in the Mediterranean world, but they also often used secondhand information.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">During the Middle Ages (5th to 15th centuries <span style="text-transform: uppercase;">ad</span>) biblical scholars dominated European thinking on questions of human origins and cultural development. They treated these questions as issues of religious belief and promoted the idea that human existence and all of human diversity were the creations of God.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Beginning in the 15th century, European explorers looking for wealth in new lands provided vivid descriptions of the exotic cultures they encountered on their journeys in Asia, Africa, and what are now the Americas. But these explorers did not respect or know the languages of the peoples with whom they came in contact, and they made brief, unsystematic observations.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The European Age of Enlightenment of the 17th and 18th centuries marked the rise of scientific and rational philosophical thought. Enlightenment thinkers, such as Scottish-born David Hume, John Locke of England, and Jean-Jacques Rousseau of France, wrote a number of humanistic works on the nature of humankind. They based their work on philosophical reason rather than religious authority and asked important anthropological questions. Rousseau, for instance, wrote on the moral qualities of “primitive” societies and about human inequality. But most writers of the Enlightenment also lacked firsthand experience with non-Western cultures.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Imperialism and Increased Contact with Other Cultures</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3173/2771147912_95731df44c_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Origins of Anthropology<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The modern study of anthropology had its origins in the European exploration and colonization of lands in the Americas, Asia, Africa, and the Pacific. European contacts with vastly different peoples sparked an interest in understanding and explaining human diversity, the goals of anthropology.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Collection Viollet/Liaison Agency<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">With the rise of imperialism (political and economic control over foreign lands) in the 18th and 19th centuries, Europeans came into increasing contact with other peoples around the world, prompting new interest in the study of culture. Imperialist nations of Western Europe—such as Belgium, the Netherlands, Portugal, Spain, France, and England—extended their political and economic control to regions in the Pacific, the Americas, Asia, and Africa.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The increasing dominance of global commerce, capitalist (profit-driven) economies, and industrialization in late-18th-century Europe led to vast cultural changes and social upheavals throughout the world. European industries and the wealthy, elite classes of people who owned them looked to exotic foreign lands for sources of labor and goods for manufacturing. In addition, poorer Europeans, many of whom were displaced from their land by industrialization, tried to build new lives abroad. Several European countries took over the administration of foreign regions as colonies (<i>see </i>Colonialism and Colonies). <i>See also </i>Capitalism.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Europeans suddenly had a flood of new information about the foreign peoples encountered in colonial frontiers. The colonizing nations of Europe also wanted scientific explanations and justifications for their global dominance. In response to these developments, and out of an interest in new and strange cultures, the first amateur anthropologists formed societies in many Western European countries in the early 19th century. These societies eventually spawned professional anthropology.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Anthropological societies devoted themselves to scientifically studying the cultures of colonized and unexplored territories. Researchers filled ethnological and archaeological museums with collections obtained from the new empires of Europe by explorers, missionaries, and colonial administrators. Physicians and zoologists, acting as novice physical anthropologists, measured the skulls of people from various cultures and wrote detailed descriptions of the people’s physical features.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Toward the end of the 19th century anthropologists began to take academic positions in colleges and universities. Anthropological associations also became advocates for anthropologists to work in professional positions. They promoted anthropological knowledge for its political, commercial, and humanitarian value.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">C<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The Beginnings of Modern Anthropology<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In the 19th century modern anthropology came into being along with the development and scientific acceptance of theories of biological and cultural evolution. In the early 19th century, a number of scientific observations, especially of unearthed bones and other remains, such as stone tools, indicated that humanity’s past had covered a much greater span of time than that indicated by the Bible (<i>see </i>Creationism).<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In 1836 Danish archaeologist Christian Thomsen proposed that three long ages of technology had preceded the present era in Europe. He called these the Stone Age, Bronze Age, and Iron Age. Thomsen's concept of technological ages fit well with the views of Scottish geologist Sir Charles Lyell, who proposed that the earth was much older than previously believed and had changed through many gradual stages.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">C</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">1<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Evolutionary Theory</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3090/2771148224_2434e3a111_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Caricature of Charles Darwin<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">When Charles Darwin published <i>The Descent of Man</i> in 1871, he challenged the fundamental beliefs of most people by asserting that humans and apes had evolved from a common ancestor. Many critics of Darwin misunderstood his theory to mean that people had descended directly from apes. This caricature of Charles Darwin as an ape appeared in the <i>London Sketch Book</i> in 1874.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Mary Evans Picture Library/Science Source/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In 1859 British naturalist Charles Darwin published his influential book <i>On the Origin of Species</i>. In this book, he argued that animal and plant species had changed, or evolved, through time under the influence of a process that he called natural selection. Natural selection, Darwin said, acted on variations within species, so that some variants survived and reproduced, and others perished. In this way, new species slowly evolved even as others continued to exist. Darwin’s theory was later supported by studies of genetic inheritance conducted in the 1850s and 1860s by Austrian monk Gregor Mendel. Evolutionary theory conflicted with established religious doctrine that all species had been determined at the creation of the world and had not changed since.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">English social philosopher Herbert Spencer applied a theory of progressive evolution to human societies in the middle 1800s. He likened societies to biological organisms, each of which adapted to survive or else perished. Spencer later coined the phrase 'survival of the fittest' to describe this process. Theories of social evolution such as Spencer’s seemed to offer an explanation for the apparent success of European nations as so-called advanced civilizations.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">C</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">2<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Anthropological Evolutionary Theories</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3046/2770301615_aab9dd64e6_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Edward Tylor<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Sir Edward Burnett Tylor was a pioneer of cultural anthropology in Britain. Tylor gave one of the first anthropological definitions of culture in his book <i>Primitive Culture</i> (1871). Here an actor recites Tylor’s definition of culture.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">(p) 1998 Microsoft Corporation. All rights reserved./The Image Works<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">During the late 1800s many anthropologists promoted their own models of social and biological evolution. Their writings portrayed people of European descent as biologically and culturally superior to all other peoples. The most influential anthropological presentation of this viewpoint appeared in <i>Ancient Society</i>, published in 1877 by American anthropologist Lewis Henry Morgan.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Morgan argued that European civilization was the pinnacle of human evolutionary progress, representing humanity’s highest biological, moral, and technological achievement. According to Morgan, human societies had evolved to civilization through earlier conditions, or stages, which he called Savagery and Barbarism. Morgan believed these stages occurred over many thousands of years and compared them to geological ages. But Morgan attributed cultural evolution to moral and mental improvements, which he proposed were, in turn, related to improvements in the ways that people produced food and to increases in brain size.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Morgan also examined the material basis of cultural development. He believed that under Savagery and Barbarism people owned property communally, as groups. Civilizations and political states, he said, developed together with the private ownership of property. States thus protected people’s rights to own property. Morgan's theories coincided with and influenced those of German political theorists Friedrich Engels and Karl Marx. Engels and Marx, using a model like Morgan’s, predicted the demise of state-supported capitalism. They saw communism, a new political and economic system based on the ideals of communality, as the next evolutionary stage for human society.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Like Morgan, Sir Edward Tylor, a founder of British anthropology, also promoted the theories of cultural evolution in the late 1800s. Tylor attempted to describe the development of particular kinds of customs and beliefs found across many cultures. For example, he proposed a sequence of stages for the evolution of religion—from animism (the belief in spirits), through polytheism (the belief in many gods), to monotheism (the belief in one god).<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In 1871 Tylor also wrote a still widely quoted definition of culture, describing it as “that complex whole that includes knowledge, belief, art, morals, law, custom and any other capabilities and habits acquired by man as a member of a society.” This definition formed the basis for the modern anthropological concept of culture.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">C</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">3<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Cultural Evolution, Colonialism, and Social Darwinism<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The colonial nations of Europe used ethnocentric theories of cultural evolution to justify the expansion of their empires. Writings based on such theories described conquered peoples as “backward” and therefore unfit for survival unless colonists “civilized” them to live and act as Europeans did. This application of evolutionary theory to control social and political policy became known as social Darwinism<i>.</i><o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Theories of cultural evolution in the 19th century took no account of the successes of small-scale societies that had developed long-term adaptations to particular environments. Nor did they recognize any shortcomings of European civilization, such as high rates of poverty and crime.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Furthermore, while many proponents of cultural evolution suggested that the people in small-scale societies were biologically inferior to people of European descent, no evidence actually supported this position. But not all anthropologists believed in this type of cultural evolution. Many actually rejected all evolutionary theory because others misused and abused it.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">D<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">New Directions in Theory and Research<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Anthropology emerged as a serious professional and scientific discipline beginning in the 1920s. The focus and practice of anthropological research developed in different ways in the United States and Europe.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">D</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">1<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The Influence of Boas</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3212/2770301887_db66a980c8_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Franz Boas<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">German-American anthropologist Franz Boas, a professor at Columbia University in New York City for 37 years, helped pioneer modern anthropology. He advocated the theories that there is no pure race and that no race is superior to any other.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Corbis<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In the 1920s and 1930s anthropology assumed its present form as a four-field academic profession in the United States under the influence of German-born American anthropologist Franz Boas. Boas wanted anthropology to be a well-respected science. He was interested in all areas of anthropological research and had done highly regarded fieldwork in all areas except archaeology. As a professor at Columbia University in New York City from 1899 until his retirement in 1937, he helped define the discipline and trained many of the most prominent American anthropologists of the 20th century. Many of his students—including Alfred Kroeber, Ruth Benedict, and Margaret Mead—went on to establish anthropology departments at universities throughout the country.</span><br /><img src="http://farm4.static.flickr.com/3050/2770302299_22c82733ed_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Margaret Mead<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">American anthropologist Margaret Mead spent many years studying how culture influences individual personality. Mead lived among the Samoan people during 1925 and 1926 to observe their way of life and the types of personalities common in their cultural group. Her 1928 book, <i>Coming of Age in Samoa,</i> provoked a great debate among sociocultural anthropologists regarding the proper method and interpretation of field research. Mead’s approach to studying groups of people, which focused on the individual people and groups with whom she lived, earned her much criticism from anthropologists who believed that research must rely more directly on statistical research and the incorporation of cross-cultural and testable hypotheses.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Courtesy of Gordon Skene Sound Collection. All rights reserved./UPI/THE BETTMANN ARCHIVE<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Boas stressed the importance of anthropologists conducting original fieldwork to get firsthand experiences with the cultures they wished to describe. He also opposed racist and ethnocentric evolutionary theories. Based on his own studies, including his measurement of the heads of people from many cultures, Boas argued that genetic differences among human populations could not explain cultural variation.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Boas urged anthropologists to do detailed research on particular cultures and their histories, rather than attempt to construct grand evolutionary stages for all of humankind in the tradition of Morgan and Tylor. Boas’s theoretical approach became known as <i>historical particularism,</i> and it forms the basis for the fundamental anthropological concept of cultural relativism.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">D</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">2<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Functionalism</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3258/2770302411_b5e71b58da_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Émile Durkheim<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Émile Durkheim, one of the fathers of sociology, utilized scientific methods to approach the study of society and social groups. His work influenced the school of anthropology known as functionalism. Durkheim believed that individuals should be considered within the context of the society in which they live.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">THE BETTMANN ARCHIVE<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Many other anthropologists working in Boas’s time, mostly in Europe, based their research on the theories of 19th-century French sociologist Émile Durkheim. Like Sir Edward Tylor, Durkheim was interested in religions across cultures. But he was not interested in the evolution of religion. Durkheim instead proposed that religious beliefs and rituals functioned to integrate people in groups and to maintain the smooth functioning of societies.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Durkheim’s ideas were expanded upon by Bronislaw Malinowski and A. R. Radcliffe-Brown, two major figures in the development of modern British anthropology beginning in the 1920s and 1930s. Their approach to understanding culture was known as <i>structural</i> <i>functionalism, </i>or simply <i>functionalism.</i><o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">A typical functionalist study analyzed how cultural institutions kept a society in working order. For example, many studies examined rites of passage, such as initiation ceremonies. Through a series of such ceremonies, groups of children of the same age would be initiated into new roles and take on new responsibilities as they grew into adults. According to functionalists, any unique characteristics of the rites of passage of a particular society had to do with how initiation ceremonies worked in the function of that society.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Functionalists based their approach to doing fieldwork on their theories. They lived for long periods with the people they studied, carefully recording even very small details about a people’s culture and social life. The resulting ethnographies portrayed all aspects of culture and social life as interdependent parts of a complex model. Functionalist research methods became the blueprint for much anthropological research throughout the 20th century.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">During the first half of the 20th century, many anthropologists conducted functionalist ethnographic studies in the service of colonial governments. This research allowed colonial administrators to predict what would happen to an entire society in response to particular colonial policies. Administrators might want to know, for instance, what would happen if they imposed taxes on households or on individuals.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">D</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">3<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Structuralism</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3007/2770302577_0ae71cb11f_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Claude Lévi-Strauss<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">French anthropologist Claude Lévi-Strauss based his understanding of culture on studies of people’s languages and recurring patterns of thought and behavior. His cultural theories are associated with the anthropological movement known as structuralism.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Keystone Pressedienst GmbH<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In the 1950s French anthropologist Claude Lévi-Strauss developed an anthropological theory and analytic method known as structuralism. He was influenced by the theories of Durkheim and one of Durkheim’s collaborators, French anthropologist Marcel Mauss. Lévi-Strauss proposed that many common cultural patterns—such as those found in myth, ritual, and language—are rooted in basic structures of the mind.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">He wrote, for instance, about the universal tendency of the human mind to sort things into sets of opposing concepts, such as day and night, black and white, or male and female. Lévi-Strauss believed such basic conceptual patterns became elaborated through culture. For example, many societies divide themselves into contrasting but complementary groups, known as <i>moieties</i> (from the French word for “half”). Each moiety traces its descent through one line to a common ancestor. In addition to many shared ritual functions, moieties create a system for controlling sex and marriage. A person from one moiety may only marry or have sexual relations with a person from the other moiety.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">D</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">4<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Cultural Materialism and Cultural Ecology<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In the 1960s, American anthropologists such as Julian Steward, Roy Rappaport, and Marvin Harris began to study how culture and social institutions relate to a people’s technology, economy, and natural environment. All of these factors together define a people’s <i>patterns of subsistence</i>—how they feed, clothe, shelter, and otherwise provide for themselves.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Economic and ecological approaches to understanding culture and societies are known as <i>cultural materialism</i> or <i>cultural ecology.</i> Harris, for instance, analyzed the religious practice in India of regarding cows as sacred. He suggested that this religious practice developed as a cultural response to the value of cows as work animals for farming and other essential tasks and as a source of dung, which is dried as fuel.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">D</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">5<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Symbolic Anthropology<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In the 1970s many anthropologists, including American ethnologist Clifford Geertz and British ethnologist Victor Turner, moved away from ecological and economic explanations of people’s cultures. Instead, these anthropologists looked for the meanings of particular cultural symbols and rituals within cultures themselves, an approach known as <i>symbolic anthropology.</i><o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Symbolic anthropological studies often focus on one particularly important ritual or symbol<i> </i>within a society. Anthropologists using this approach attempt to demonstrate how this one symbol or ritual shapes or reflects an entire culture. Geertz, for example, attempted to show how the culture of the people of Bali, Indonesia, could be understood by examining the important Balinese ritual of staging and betting on cockfights.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">X<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">ANTHROPOLOGY TODAY<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">By the early 1990s anthropology had become a very diverse field with numerous areas of specialization. For example, the American Anthropological Association, one of the discipline’s most important professional organizations in the United States, includes sections focused on such specific topics as agriculture, consciousness, education, the environment, feminism, film and photography, museums, nutrition, politics and law, psychology, urban issues, and work. Other groups focus on geographic areas, including Africa, Europe, Latin America, the Middle East, and North America. Specialization within anthropology has become so important that many academic departments have begun questioning the need to teach about the original four subfields.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">New research agendas have also emerged, and several new trends in world culture have dramatically changed anthropology. Independent, self-sufficient cultures—the focus of traditional anthropology—have virtually disappeared. In addition, the world faces increasing problems of poverty, violence, and environmental degradation. In response to these trends, many anthropologists have shifted their attention to studying urban culture and the workings of global culture. Much new research examines the dynamics of global commerce and the international exchange of ideas, beliefs, and cultural practices.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Beginning in the 1980s a series of new ideas, collectively called postmodernism, also raised questions about some of anthropology’s fundamental methods and objectives. As a result, some anthropologists have moved into a new area of research sometimes known as <i>cultural studies.</i> Others have continued to use more traditional anthropological research methods to solve problems associated with cross-cultural conflicts. This type of work is known as <i>applied anthropology.</i><o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Postmodernism and Cultural Studies<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Postmodernism describes the philosophy of examining the nature of meaning and knowing, although academics in many fields have debated over its precise definition. Postmodernists question the validity of the faith in science and rationalism that originated during the Enlightenment and that became associated with the philosophy known as modernism. They also question whether anthropology is, or should be, a science. Because all knowledge is necessarily shaped by culture, they argue, anthropologists cannot be objective in their research.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In response to this argument, some anthropologists have turned to simply studying and writing about the effects of the influence of culture on their own perspectives, and on the perspectives of all people. While much of this work is still done in anthropology departments, it has also become a distinct area of research known as <i>cultural studies.</i> Some see cultural studies as a new discipline, separate from anthropology. Others regard it as the newest phase of anthropological theory.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Critics of traditional anthropology view it as a form of colonialism and exploitation. This notion has gained ground as anthropologists have studied the history of their own discipline and reexamined the relationship between the development of anthropology and colonialism. Moreover, traditional anthropology has always been dominated by the ideas, research, and writing of white Europeans and Americans. This, too, is changing, as increasing numbers of people from diverse cultural backgrounds are working in anthropology and cultural studies.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Researchers working in cultural studies have also redefined culture. They tend to view culture as something that people continually negotiate over with each other, rather than as something they share. This view makes sense to a generation of anthropologists who grew up in the 1960s in the United States and Europe. During that time, young people challenged the cultural traditions of their parents and questioned such important problems as racism, sexism, and the violence of modern warfare. They also began to view some of the world’s worst problems—such as ethnic violence, poverty, and environmental destruction—as legacies of the colonial era that also gave rise to anthropology.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Many researchers in cultural studies have worked to <i>deconstruct</i> (take apart to analyze and critique) traditional ethnographies and other types of anthropological research. Their analyses demonstrate that a good deal of this older research might have misrepresented or negatively affected the cultures described. The practice of critiquing early anthropological work requires no special anthropological training or fieldwork. Thus, the field of cultural studies includes people schooled in such diverse topics as literature, gender studies, sociology, and history.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Some anthropologists have reacted against the antiscience critiques of postmodernism. They reject the position that scientific research cannot teach us anything about the nature of the world or humanity. But critiques of traditional anthropological practices may improve the quality of anthropological work by making researchers even more conscious about the methods they use.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Applied Anthropology</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3136/2770302805_794f372f53_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">World Congress of Indigenous Peoples<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">In 1992 indigenous peoples from around the world gathered in the town of Kari-Oca outside of Rio de Janeiro, Brazil, at the World Congress of Indigenous Peoples. They drafted documents and signed petitions stating their shared views on respect for land and natural resources, world economic development, and the rights of indigenous cultural groups to determine their own futures.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Antonio Ribeiro/Liaison Agency<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Since the 1960s, anthropologists have increasingly applied their special research skills and cross-cultural insights to try to solve important world problems. <i>Applied anthropology </i>involves helping cultural groups, organizations, businesses, and governments solve a wide range of problems.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Applied anthropology developed with the end of colonialism. Many colonies gained their independence within two decades after the end of World War II in 1945. International political and economic agencies began employing anthropologists to promote the development of new forms of industrial and agricultural production in these newly independent countries. This work, known as <i>development anthropology,</i> often involved helping small, self-sufficient societies adjust to the changes brought by development projects.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Many small societies of indigenous peoples who were threatened by development projects began to organize themselves collectively. The term <i>indigenous peoples</i> refers to those who have inhabited and made their living directly off the same land for hundreds or thousands of years. By the 1970s, indigenous groups had begun to come together in order to defend their rights to land and natural resources.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In response, many anthropologists shifted from being advocates for development to providing support for indigenous groups. People who were once the subjects of anthropological study now hire anthropologists to work for them. For example, Native American tribes and nations have employed archaeologists, linguistic anthropologists, and cultural anthropologists to help them document and protect their cultural heritage. Some Native Americans have also become anthropologists themselves to help their own tribal groups.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Archaeological analysis can help support people’s claims to land and natural resources by demonstrating that their ancient ancestors lived, hunted, fished, or buried their dead in a particular place. Cultural anthropologists and archaeologists may also provide testimony in legal cases to defend the integrity of indigenous groups. Linguistic anthropologists can prepare teaching materials and texts for previously unwritten languages. These materials can help teach children to continue to speak their native languages in the face of cultural change.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Anthropologists have also become increasingly interested in examining and trying to lessen the causes and consequences of injustice, violence, and poverty wherever it occurs. For instance, physical anthropologists have supported international human rights organizations by helping to excavate and identify the remains of the victims of political and ethnic mass killings. They have also helped to identify the perpetrators of such killings in a number of countries, including Argentina, Chile, El Salvador, Guatemala, Rwanda, and the former Yugoslavia.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Governments in many parts of the world support the business of large agricultural companies that convert subsistence farmers into wageworkers to produce crops for export. Cultural anthropologists and physical anthropologists specializing in nutrition and health have gathered evidence showing that these changes have led to increased rates of poverty, malnutrition, and infant mortality. In the United States, anthropologists have examined the human impacts of factory closings and wage reductions as companies have shifted their operations overseas (<i>see </i>Multinational Corporation). Anthropologists hope the results of this research will convince governments and businesses to consider the potential negative effects of their actions.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">As commerce and cross-cultural exchange create a new global-scale culture, anthropologists hope to learn how social power and decision making are organized around the world. They want to ensure that people remain free to live according to unique cultural beliefs and practices, safe from the control of powerful commercial and political interests.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 15pt;"><span style="font-size: 12pt; font-family: "Times New Roman","serif";"><br />Contributed By:<br />John H. Bodley<o:p></o:p></span></p> <b><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif";">Microsoft ® Encarta ® 2007.</span></b><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif";"> © 1993-2006 Microsoft Corporation. All rights reserved.</span>ghozian karamihttp://www.blogger.com/profile/13214011599962806335noreply@blogger.com0tag:blogger.com,1999:blog-192751622867664710.post-70903110359263895972009-01-02T16:27:00.000-08:002009-01-02T16:31:21.656-08:00Astronomy<p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 24pt; font-family: "MS Reference Serif","serif";">Astronomy<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">I<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">INTRODUCTION</span></p></td></tr></tbody></table><br /><img style="width: 226px; height: 301px;" src="http://farm4.static.flickr.com/3156/2771150216_0f6a479e13.jpg?v=0"><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Horsehead Nebula<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The Horsehead Nebula, located over 1,000 light-years away in the constellation Orion, is an enormous interstellar cloud of gas and dust. This dark nebula is visible from Earth only because it blocks light emanating from young stars located behind the nebula.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Canada-France-Hawaii Telescope/J.-C.Cuillandre/Coelum/2001<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Astronomy, study of the universe and the celestial bodies, gas, and dust within it. Astronomy includes observations and theories about the solar system, the stars, the galaxies, and the general structure of space. Astronomy also includes cosmology, the study of the universe and its past and future. People who study astronomy are called astronomers, and they use a wide variety of methods to perform their research. These methods usually involve ideas of physics, so most astronomers are also astrophysicists, and the terms <i>astronomer</i> and <i>astrophysicist</i> are basically identical. Some areas of astronomy also use techniques of chemistry, geology, and biology.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Astronomy is the oldest science, dating back thousands of years to when primitive people noticed objects in the sky overhead and watched the way the objects moved. In ancient Egypt, the first appearance of certain stars each year marked the onset of the seasonal flood, an important event for agriculture. In 17th-century England, astronomy provided methods of keeping track of time that were especially useful for accurate navigation. Astronomy has a long tradition of practical results, such as our current understanding of the stars, day and night, the seasons, and the phases of the Moon. Much of today's research in astronomy does not address immediate practical problems. Instead, it involves basic research to satisfy our curiosity about the universe and the objects in it. One day such knowledge may well be of practical use to humans. <i>See also </i>History of Astronomy.<o:p></o:p></span></p>ghozian karamihttp://www.blogger.com/profile/13214011599962806335noreply@blogger.com0tag:blogger.com,1999:blog-192751622867664710.post-58114488461042790382009-01-02T16:26:00.000-08:002009-01-02T16:27:44.387-08:00Automobile<p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 24pt; font-family: "MS Reference Serif","serif";">Automobile<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">I<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">INTRODUCTION</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3267/2771157918_7b377640a2.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Automobile Systems<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Automobiles are powered and controlled by a complicated interrelationship between several systems. This diagram shows the parts of a car with a gas engine and manual transmission (the air filter and carburetor have been removed to show the parts beneath but usually appear in the space above the intake manifold). The major systems of the automobile are the power plant, the power train, the running gear, and the control system. Each of these major categories include a number of subsystems, as shown here. The power plant includes the engine, fuel, electrical, exhaust, lubrication, and coolant systems. The power train includes the transmission and drive systems, including the clutch, differential, and drive shaft. Suspension, stabilizers, wheels, and tires are all part of the running gear, or support system. Steering and brake systems are the major components of the control system, by which the driver directs the car.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Automobile, self-propelled vehicle used primarily on public roads but adaptable to other surfaces. Automobiles changed the world during the 20th century, particularly in the United States and other industrialized nations. From the growth of suburbs to the development of elaborate road and highway systems, the so-called horseless carriage has forever altered the modern landscape. The manufacture, sale, and servicing of automobiles have become key elements of industrial economies. But along with greater mobility and job creation, the automobile has brought noise and air pollution, and automobile accidents rank among the leading causes of death and injury throughout the world. But for better or worse, the 1900s can be called the Age of the Automobile, and cars will no doubt continue to shape our culture and economy well into the 21st century.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Automobiles are classified by size, style, number of doors, and intended use. The typical automobile, also called a car, auto, motorcar, and passenger car, has four wheels and can carry up to six people, including a driver. Larger vehicles designed to carry more passengers are called vans, minivans, omnibuses, or buses. Those used to carry cargo are called pickups or trucks, depending on their size and design. Minivans are van-style vehicles built on a passenger car frame that can usually carry up to eight passengers. Sport-utility vehicles, also known as SUVs, are more rugged than passenger cars and are designed for driving in mud or snow. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Auto manufacturing plants in 40 countries produced a total of 63.9 million vehicles, including 42.8 million passenger cars, in 2004, according to Ward’s Auto, an auto industry analyst. About 16.2 million vehicles, including 6.3 million passenger cars, were produced in North America in 2004. For information on the business of making cars, <i>see </i>Automobile Industry.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The automobile is built around an engine. Various systems supply the engine with fuel, cool it during operation, lubricate its moving parts, and remove exhaust gases it creates. The engine produces mechanical power that is transmitted to the automobile’s wheels through a drivetrain, which includes a transmission, one or more driveshafts, a differential gear, and axles. Suspension systems, which include springs and shock absorbers, cushion the ride and help protect the vehicle from being damaged by bumps, heavy loads, and other stresses. Wheels and tires support the vehicle on the roadway and, when rotated by powered axles, propel the vehicle forward or backward. Steering and braking systems provide control over direction and speed. An electrical system starts and operates the engine, monitors and controls many aspects of the vehicle’s operation, and powers such components as headlights and radios. Safety features such as bumpers, air bags, and seat belts help protect occupants in an accident.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">II<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">POWER SYSTEM<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Gasoline internal-combustion engines power most automobiles, but some engines use diesel fuel, electricity, natural gas, solar energy, or fuels derived from methanol (wood alcohol) and ethanol (grain alcohol).<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Most gasoline engines work in the following way: Turning the ignition key operates a switch that sends electricity from a battery to a starter motor. The starter motor turns a disk known as a flywheel, which in turn causes the engine’s crankshaft to revolve. The rotating crankshaft causes pistons, which are solid cylinders that fit snugly inside the engine’s hollow cylinders, to move up and down. Fuel-injection systems or, in older cars, a carburetor deliver fuel vapor from the gas tank to the engine cylinders.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The pistons compress the vapor inside the cylinders. An electric current flows through a spark plug to ignite the vapor. The fuel mixture explodes, or combusts, creating hot expanding gases that push the pistons down the cylinders and cause the crankshaft to rotate. The crankshaft is now rotating via the up-and-down motion of the pistons, permitting the starter motor to disengage from the flywheel.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Engine<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The basic components of an internal-combustion engine are the engine block, cylinder head, cylinders, pistons, valves, crankshaft, and camshaft. The lower part of the engine, called the engine block, houses the cylinders, pistons, and crankshaft. The components of other engine systems bolt or attach to the engine block. The block is manufactured with internal passageways for lubricants and coolant. Engine blocks are made of cast iron or aluminum alloy and formed with a set of round cylinders.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The upper part of the engine is the cylinder head. Bolted to the top of the block, it seals the tops of the cylinders. Pistons compress air and fuel against the cylinder head prior to ignition. The top of the piston forms the floor of the combustion chamber. A rod connects the bottom of the piston to the crankshaft. Lubricated bearings enable both ends of the connecting rod to pivot, transferring the piston’s vertical motion into the crankshaft’s rotational force, or torque. The pistons’ motion rotates the crankshaft at speeds ranging from about 600 to thousands of revolutions per minute (rpm), depending on how much fuel is delivered to the cylinders.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Fuel vapor enters and exhaust gases leave the combustion chamber through openings in the cylinder head controlled by valves. The typical engine valve is a metal shaft with a disk at one end fitted to block the opening. The other end of the shaft is mechanically linked to a camshaft, a round rod with odd-shaped lobes located inside the engine block or in the cylinder head. Inlet valves open to allow fuel to enter the combustion chambers. Outlet valves open to let exhaust gases out.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">A gear wheel, belt, or chain links the camshaft to the crankshaft. When the crankshaft forces the camshaft to turn, lobes on the camshaft cause valves to open and close at precise moments in the engine’s cycle. When fuel vapor ignites, the intake and outlet valves close tightly to direct the force of the explosion downward on the piston.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Engine Types<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The blocks in most internal-combustion engines are in-line designs or V designs. In-line designs are arranged so that the cylinders stand upright in a single line over the crankshaft. In a V design, two rows of cylinders are set at an angle to form a V. At the bottom of the V is the crankshaft. In-line configurations of six or eight cylinders require long engine compartments found more often in trucks than in cars. The V design allows the same number of cylinders to fit into a shorter, although wider, space. Another engine design that fits into shorter, shallower spaces is a horizontally opposed, or flat, arrangement in which the crankshaft lies between two rows of cylinders.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Engines become more powerful, and use more fuel, as the size and number of cylinders increase. Most modern vehicles in the United States have 4-, 6-, or 8-cylinder engines, but car engines have been designed with 1, 2, 3, 5, 12, and more cylinders.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Diesel engines, common in large trucks or buses, are similar to gasoline internal-combustion engines, but they have a different ignition system. Diesels compress air inside the cylinders with greater force than a gasoline engine does, producing temperatures hot enough to ignite the diesel fuel on contact. Some cars have rotary engines, also known as Wankel engines, which have one or more elliptical chambers in which triangular-shaped rotors, instead of pistons, rotate.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Electric motors have been used to power automobiles since the late 1800s. Electric power supplied by batteries runs the motor, which rotates a driveshaft, the shaft that transmits engine power to the axles. Commercial electric car models for specialized purposes were available in the 1980s. General Motors Corporation introduced a mass-production all-electric car in the mid-1990s.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Automobiles that combine two or more types of engines are called hybrids. A typical hybrid is an electric motor with batteries that are recharged by a generator run by a small gas- or diesel-powered engine. These hybrids are known as hybrid electric vehicles (HEVs). By relying more on electricity and less on fuel combustion, HEVs have higher fuel efficiency and emit fewer pollutants. Several automakers have experimented with hybrids. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In 1997 Toyota Motor Corporation became the first to mass-produce a hybrid vehicle, the Prius. It became available in Japan in 1997 and in North America in 2000. The first hybrid available for sale in North America, the Honda Insight, was offered by Honda Motor Co., Ltd., in 1999. Honda later introduced a hybrid version of the Honda Civic. In August 2004 the Ford Motor Company became the first U.S. automaker to release a hybrid vehicle when it began production of the Ford Escape Hybrid, the first hybrid sport- utility vehicle (SUV). The Escape Hybrid was released for the 2005 model year.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">C<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Fuel Supply</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3115/2770311317_4d147ec02f.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Fuel-Injection System<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The fuel-injection system replaces the carburetor in most new vehicles to provide a more efficient fuel delivery system. Electronic sensors respond to varying engine speeds and driving conditions by changing the ratio of fuel to air. The sensors send a fine mist of fuel from the fuel supply through a fuel-injection nozzle into a combustion chamber, where it is mixed with air. The mixture of fuel and air triggers ignition.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The internal-combustion engine is powered by the burning of a precise mixture of liquefied fuel and air in the cylinders’ combustion chambers. Fuel is stored in a tank until it is needed, then pumped to a carburetor or, in newer cars, to a fuel-injection system.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The carburetor controls the mixture of gas and air that travels to the engine. It mixes fuel with air at the head of a pipe, called the intake manifold, leading to the cylinders. A vacuum created by the downward strokes of pistons draws air through the carburetor and intake manifold. Inside the carburetor, the airflow transforms drops of fuel into a fine mist, or vapor. The intake manifold delivers the fuel vapor to the cylinders, where it is ignited.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">All new cars produced today are equipped with fuel injection systems instead of carburetors. Fuel injectors spray carefully calibrated bursts of fuel mist into cylinders either at or near openings to the combustion chambers. Since the exact quantity of gas needed is injected into the cylinders, fuel injection is more precise, easier to adjust, and more consistent than a carburetor, delivering better efficiency, gas mileage, engine responsiveness, and pollution control. Fuel-injection systems vary widely, but most are operated or managed electronically.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">High-performance automobiles are often fitted with air-compressing equipment that increases an engine’s output. By increasing the air and fuel flow to the engine, these features produce greater horsepower. Superchargers are compressors powered by the crankshaft. Turbochargers are turbine-powered compressors run by pressurized exhaust gas.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">D<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Exhaust System<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The exhaust system carries exhaust gases from the engine’s combustion chamber to the atmosphere and reduces, or muffles, engine noise. Exhaust gases leave the engine in a pipe, traveling through a catalytic converter and a muffler before exiting through the tailpipe.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Chemical reactions inside the catalytic converter change most of the hazardous hydrocarbons and carbon monoxide produced by the engine into water vapor and carbon dioxide.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The conventional muffler is an enclosed metal tube packed with sound-deadening material. Most conventional mufflers are round or oval-shaped with an inlet and outlet pipe at either end. Some contain partitions to help reduce engine noise.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Car manufacturers are experimenting with an electronic muffler, which uses sensors to monitor the sound waves of the exhaust noise. The sound wave data are sent to a computer that controls speakers near the tailpipe. The system generates sound waves 180 degrees out of phase with the engine noise. The sound waves from the electronic muffler collide with the exhaust sound waves and they cancel each other out, leaving only low-level heat to emerge from the tailpipe.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">E<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Cooling and Heating System<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Combustion inside an engine produces temperatures high enough to melt cast iron. A cooling system conducts this heat away from the engine’s cylinders and radiates it into the air.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In most automobiles, a liquid coolant circulates through the engine. A pump sends the coolant from the engine to a radiator, which transfers heat from the coolant to the air. In early engines, the coolant was water. In most automobiles today, the coolant is a chemical solution called antifreeze that has a higher boiling point and lower freezing point than water, making it effective in temperature extremes. Some engines are air cooled, that is, they are designed so a flow of air can reach metal fins that conduct heat away from the cylinders.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">A second, smaller radiator is fitted to all modern cars. This unit uses engine heat to warm the interior of the passenger compartment and supply heat to the windshield defroster. <o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">III<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">DRIVETRAIN<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The rotational force of the engine’s crankshaft turns other shafts and gears that eventually cause the drive wheels to rotate. The various components that link the crankshaft to the drive wheels make up the drivetrain. The major parts of the drivetrain include the transmission, one or more driveshafts, differential gears, and axles.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Transmission</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3013/2770311551_9051d7fea8.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Automatic Transmission System<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The automatic transmission is one of the key components of an automobile. Located just behind the engine, the transmission changes the speed and power ratios between the engine and the driving wheels of a vehicle.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The transmission, also known as the gearbox, transfers power from the engine to the driveshaft. As the engine’s crankshaft rotates, combinations of transmission gears pass the energy along to a driveshaft. The driveshaft causes axles to rotate and turn the wheels. By using gears of different sizes, a transmission alters the rotational speed and torque of the engine passed along to the driveshaft. Higher gears permit the car to travel faster, while low gears provide more power for starting a car from a standstill and for climbing hills.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The transmission usually is located just behind the engine, although some automobiles were designed with a transmission mounted on the rear axle. There are three basic transmission types: manual, automatic, and continuously variable.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">A manual transmission has a gearbox from which the driver selects specific gears depending on road speed and engine load. Gears are selected with a shift lever located on the floor next to the driver or on the steering column. The driver presses on the clutch to disengage the transmission from the engine to permit a change of gears. The clutch disk attaches to the transmission’s input shaft. It presses against a circular plate attached to the engine’s flywheel. When the driver presses down on the clutch pedal to shift gears, a mechanical lever called a clutch fork and a device called a throwout bearing separate the two disks. Releasing the clutch pedal presses the two disks together, transferring torque from the engine to the transmission.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">An automatic transmission selects gears itself according to road conditions and the amount of load on the engine. Instead of a manual clutch, automatic transmissions use a hydraulic torque converter to transfer engine power to the transmission.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Instead of making distinct changes from one gear to the next, a continuously variable transmission uses belts and pulleys to smoothly slide the gear ratio up or down. Continuously variable transmissions appeared on machinery during the 19th century and on a few small-engine automobiles as early as 1900. The transmission keeps the engine running at its most efficient speed by more precisely matching the gear ratio to the situation. Commercial applications have been limited to small engines. <o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Front- and Rear-Wheel Drive</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3032/2771158782_0dd0629952.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Differential<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The gears of a differential allow a car's powered wheels to rotate at different speeds as the car turns around corners. The car's drive shaft rotates the crown wheel, which in turn rotates the half shafts leading to the wheels. When the car is traveling straight ahead, the planet pinions do not spin, so the crown wheel rotates both wheels at the same rate. When the car turns a corner, however, the planet pinions spin in opposite directions, allowing one wheel to slip behind and forcing the other wheel to turn faster.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Depending on the vehicle’s design, engine power is transmitted by the transmission to the front wheels, the rear wheels, or to all four wheels. The wheels receiving power are called drive wheels: They propel the vehicle forward or backward. Most automobiles either are front-wheel or rear-wheel drive. In some vehicles, four-wheel drive is an option the driver selects for certain road conditions; others feature full-time, all-wheel drive.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The differential is a gear assembly in an axle that enables each powered wheel to turn at different speeds when the vehicle makes a turn. The driveshaft connects the transmission’s output shaft to a differential gear in the axle. Universal joints at both ends of the driveshaft allow it to rotate as the axles move up and down over the road surface.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In rear-wheel drive, the driveshaft runs under the car to a differential gear at the rear axle. In front-wheel drive, the differential is on the front axle and the connections to the transmission are much shorter. Four-wheel-drive vehicles have drive shafts and differentials for both axles.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">IV<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">SUPPORT SYSTEMS<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Automobiles would deliver jolting rides, especially on unpaved roads, without a system of shock absorbers and other devices to protect the auto body and passenger compartment from severe bumps and bounces.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Suspension System<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The suspension system, part of the undercarriage of an automobile, contains springs that move up and down to absorb bumps and vibrations. In one type of suspension system, a long tube, or strut, has a shock absorber built into its center section. Shock absorbers control, or dampen, the sudden loading and unloading of suspension springs to reduce wheel bounce and the shock transferred from the road wheels to the body. One shock absorber is installed at each wheel. Modern shock absorbers have a telescoping design and use oil, gas, and air, or a combination to absorb energy.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Luxury sedans generally have a soft suspension for comfortable riding. Sports cars and sport-utility vehicles have firmer suspensions to improve cornering ability and control over rough terrain.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Older automobiles were equipped with one-piece front axles attached to the frame with semielliptic leaf springs, much like the arrangement on horse-drawn buggies. Front wheels on modern cars roll independently of each other on half-shafts instead of on a common axle. Each wheel has its own axle and suspension supports, so the shock of one wheel hitting a bump is not transferred across a common axle to the other wheel or the rest of the car. Many rear-axle suspensions for automobiles and heavier vehicles use rigid axles with coil or leaf springs. However, advanced passenger cars, luxury sedans, and sports cars feature independent rear-wheel suspension systems.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Active suspensions are computer-controlled adjustments of the downward force of each wheel as the vehicle corners or rides over uneven terrain. Sensors, a pump, and hydraulic cylinders, all monitored and controlled by computer, enable the vehicle to lean into corners and compensate for the dips and dives that accompany emergency stops and rapid acceleration.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Wheels and Tires<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Wheels support the vehicle’s weight and transfer torque to the tires from the drivetrain and braking systems. Automobile wheels generally are made of steel or aluminum. Aluminum wheels are lighter, more impact absorbent, and more expensive.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Pneumatic (air-filled) rubber tires, first patented in 1845, fit on the outside rims of the wheels. Tires help smooth out the ride and provide the automobile’s only contact with the road, so traction and strength are primary requirements. Tire treads come in several varieties to match driving conditions.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">V<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">CONTROL SYSTEMS<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">A driver controls the automobile’s motion by keeping the wheels pointed in the desired direction, and by stopping or slowing the speed at which the wheels rotate. These controls are made possible by the steering and braking systems. In addition, the driver controls the vehicle’s speed with the transmission and the gas pedal, which adjusts the amount of fuel fed to the engine.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Steering<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Automobiles are steered by turning the front wheels, although a few automobile types have all-wheel steering. Most steering systems link the front wheels together by means of a tie-rod. The tie-rod insures that the turning of one wheel is matched by a corresponding turn in the other.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">When a driver turns the steering wheel, the mechanical action rotates a steering shaft inside the steering column. Depending on the steering mechanism, gears or other devices convert the rotating motion of the steering wheel into a horizontal force that turns the wheels.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Manual steering relies only on the force exerted by the driver to turn the wheels. Conventional power steering uses hydraulic pressure, operated by the pressure or movement of a liquid, to augment that force, requiring less effort by the driver. Electric power steering uses an electric motor instead of hydraulic pressure.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Brakes</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3250/2771159026_87a8784e11.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Disc and Drum Brakes<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Disc and drum brakes create friction to slow the wheels of a motor vehicle. When a driver presses on the brake pedal of a vehicle, brake lines filled with fluid transmit the force to the brakes. In a disc brake, the fluid pushes the brake pads in the caliper against the rotor, slowing the wheel. In a drum brake, the fluid pushes small pistons in the brake cylinder against the hinged brake shoes. The shoes pivot outward and press against a drum attached to the wheel to slow the wheel.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Brakes enable the driver to slow or stop the moving vehicle. The first automobile brakes were much like those on horse-drawn wagons. By pulling a lever, the driver pressed a block of wood, leather, or metal, known as the shoe, against the wheel rims. With sufficient pressure, friction between the wheel and the brake shoe caused the vehicle to slow down or stop. Another method was to use a lever to clamp a strap or brake shoes tightly around the driveshaft.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">A brake system with shoes that pressed against the inside of a drum fitted to the wheel, called drum brakes, appeared in 1903. Since the drum and wheel rotate together, friction applied by the shoes inside the drum slowed or stopped the wheel. Cotton and leather shoe coverings, or linings, were replaced by asbestos after 1908, greatly extending the life of the brake mechanism. Hydraulically assisted braking was introduced in the 1920s. Disk brakes, in which friction pads clamp down on both sides of a disk attached to the axle, were in use by the 1950s.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">An antilock braking system (ABS) uses a computer, sensors, and a hydraulic pump to stop the automobile’s forward motion without locking the wheels and putting the vehicle into a skid. Introduced in the 1980s, ABS helps the driver maintain better control over the car during emergency stops and while braking on slippery surfaces.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Automobiles are also equipped with a hand-operated brake used for emergencies and to securely park the car, especially on uneven terrain. Pulling on a lever or pushing down on a foot pedal sets the brake.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">VI<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">ELECTRICAL SYSTEM<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The automobile depends on electricity for fuel ignition, headlights, turn signals, horn, radio, windshield wipers, and other accessories. A battery and an alternator supply electricity. The battery stores electricity for starting the car. The alternator generates electric current while the engine is running, recharging the battery and powering the rest of the car’s electrical needs.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Early automotive electrical systems ran on 6 volts, but 12 volts became standard after World War II (1939-1945) to operate the growing number of electrical accessories. Eventually, 24- or 48-volt systems may become the standard as more computers and electronics are built into automobiles.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Ignition System</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3128/2770312405_62928eeb27.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Ignition System<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The ignition system delivers voltage to ignite the fuel in the automotive vehicle. When the ignition switch is turned on, low-voltage electric current flows from the battery to the coil, which converts the current to high-voltage. The current then flows to the distributor, which delivers it to each of the spark plugs. The spark plugs send an igniting spark to the fuel/air mixture in the combustion chambers.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The ignition system supplies high-voltage current to spark plugs to ignite fuel vapor in the cylinders. There are many variations, but all gasoline-engine ignition systems draw electric current from the battery, significantly increase the current’s voltage, then deliver it to spark plugs that project into the combustion chambers. An electric arc between two electrodes at the bottom of the spark plug ignites the fuel vapor.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In older vehicles, a distributor, which is an electrical switching device, routes high-voltage current to the spark plugs. The distributor’s housing contains a switch called the breaker points. A rotating shaft in the distributor causes the switch to open and close, interrupting the supply of low-voltage current to a transformer called a coil. The coil uses electromagnetic induction (<i>see </i>Electricity: <i>Electromagnetism</i>) to convert interruptions of the 12-volt current into surges of 20,000 volts or more. This high-voltage current passes back to the distributor, which mechanically routes it through wires to spark plugs, producing a spark that ignites the gas vapor in the cylinders. A condenser absorbs excess current and protects the breaker points from damage by the high-voltage surge. The distributor and other devices control the timing of the spark-plug discharges.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In modern ignition systems, the distributor, coil, points, and condenser have been replaced by solid-state electronics controlled by a computer. A computer controls the ignition system and adjusts it to provide maximum efficiency in a variety of driving conditions.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">VII<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">SAFETY FEATURES<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Manufacturers continue to build lighter vehicles with improved structural rigidity and ability to protect the driver and passengers during collisions.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Bumpers evolved as rails or bars to protect the front and rear of the car’s body from damage in minor collisions. Over the years, bumpers became stylish and, in some cases, not strong enough to survive minor collisions without expensive repairs. Eventually, government regulations required bumpers designed to withstand low-speed collisions with less damage. Some bumpers can withstand 4-km/h (2.5-mph) collisions with no damage, while others can withstand 8-km/h (5-mph) collisions with no damage.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Modern vehicles feature crumple zones, portions of the automobile designed to absorb forces that otherwise would be transmitted to the passenger compartment. Passenger compartments on many vehicles also have reinforced roll bar structures in the roof, in case the vehicle overturns, and protective beams in the doors to help protect passengers from side impacts.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Seat belt and upper-body restraints that relax to permit comfort but tighten automatically during an impact are now common. Some car models are equipped with shoulder-restraint belts that slide into position automatically when the car’s doors close.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">An air bag is a high-speed inflation device hidden in the hub of the steering wheel or in the dash on the passenger’s side. Some automobiles have side-impact air bags, located in doors or seats. At impact, the bag inflates almost instantaneously. The inflated bag creates a cushion between the occupant and the vehicle’s interior. Air bags first appeared in the mid-1970s, available as an optional accessory. Today they are installed on all new passenger cars sold in the United States.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Air bags inflate with great force, which occasionally endangers a child or infant passenger. Some newer automobile models are equipped with switches to disable the passenger-side air bags when a child or infant is traveling in the passenger seat. Automakers continue to research ways to make air-bag systems less dangerous for frail and small passengers, yet effective in collisions.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">VIII<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">HISTORY</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3206/2771159382_764201bdb6.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Horseless Carriage<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The original horseless carriage was introduced in 1893 by brothers Charles and Frank Duryea. It was America’s first internal-combustion motor car, and it was followed by Henry Ford’s first experimental car that same year.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">THE BETTMANN ARCHIVE<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The history of the automobile actually began about 4,000 years ago when the first wheel was used for transportation in India. In the early 15th century the Portuguese arrived in China and the interaction of the two cultures led to a variety of new technologies, including the creation of a wheel that turned under its own power. By the 1600s small steam-powered engine models had been developed, but it was another century before a full-sized engine-powered vehicle was created.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In 1769 French Army officer Captain Nicolas-Joseph Cugnot built what has been called the first automobile. Cugnot’s three-wheeled, steam-powered vehicle carried four persons. Designed to move artillery pieces, it had a top speed of a little more than 3.2 km/h (2 mph) and had to stop every 20 minutes to build up a fresh head of steam.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">As early as 1801 successful but very heavy steam automobiles were introduced in England. Laws barred them from public roads and forced their owners to run them like trains on private tracks. In 1802 a steam-powered coach designed by British engineer Richard Trevithick journeyed more than 160 km (100 mi) from Cornwall to London. Steam power caught the attention of other vehicle builders. In 1804 American inventor Oliver Evans built a steam-powered vehicle in Chicago, Illinois. French engineer Onésiphore Pecqueur built one in 1828.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">British inventor Walter Handcock built a series of steam carriages in the mid-1830s that were used for the first omnibus service in London. By the mid-1800s England had an extensive network of steam coach lines. Horse-drawn stagecoach companies and the new railroad companies pressured the British Parliament to approve heavy tolls on steam-powered road vehicles. The tolls quickly drove the steam coach operators out of business.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">During the early 20th century steam cars were popular in the United States. Most famous was the Stanley Steamer, built by American twin brothers Freelan and Francis Stanley. A Stanley Steamer established a world land speed record in 1906 of 205.44 km/h (121.573 mph). Manufacturers produced about 125 models of steam-powered automobiles, including the Stanley, until 1932. <o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Internal-Combustion Engine<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Development of lighter steam cars during the 19th century coincided with major developments in engines that ran on gasoline or other fuels. Because the newer engines burned fuel in cylinders inside the engine, they were called internal-combustion engines.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In 1860 French inventor Jean-Joseph-Étienne Lenoir patented a one-cylinder engine that used kerosene for fuel. Two years later, a vehicle powered by Lenoir’s engine reached a top speed of about 6.4 km/h (about 4 mph). In 1864 Austrian inventor Siegfried Marcus built and drove a carriage propelled by a two-cylinder gasoline engine. American George Brayton patented an internal-combustion engine that was displayed at the 1876 Centennial Exhibition in Philadelphia, Pennsylvania.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In 1876 German engineer Nikolaus August Otto built a four-stroke gas engine, the most direct ancestor to today’s automobile engines. In a four-stroke engine the pistons move down to draw fuel vapor into the cylinder during stroke one; in stroke two, the pistons move up to compress the vapor; in stroke three the vapor explodes and the hot gases push the pistons down the cylinders; and in stroke four the pistons move up to push exhaust gases out of the cylinders. Engines with two or more cylinders are designed so combustion occurs in one cylinder after the other instead of in all at once. Two-stroke engines accomplish the same steps, but less efficiently and with more exhaust emissions.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Automobile manufacturing began in earnest in Europe by the late 1880s. German engineer Gottlieb Daimler and German inventor Wilhelm Maybach mounted a gasoline-powered engine onto a bicycle, creating a motorcycle, in 1885. In 1887 they manufactured their first car, which included a steering tiller and a four-speed gearbox. Another German engineer, Karl Benz, produced his first gasoline car in 1886. In 1890 Daimler and Maybach started a successful car manufacturing company, The Daimler Motor Company, which eventually merged with Benz’s manufacturing firm in 1926 to create Daimler-Benz. The joint company makes cars today under the Mercedes-Benz nameplate (<i>see </i>DaimlerChrysler AG).<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In France, a company called Panhard-Levassor began making cars in 1894 using Daimler’s patents. Instead of installing the engine under the seats, as other car designers had done, the company introduced the design of a front-mounted engine under the hood. Panhard-Levassor also introduced a clutch and gears, and separate construction of the chassis, or underlying structure of the car, and the car body. The company’s first model was a gasoline-powered buggy steered by a tiller.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">French bicycle manufacturer Armand Peugeot saw the Panhard-Levassor car and designed an automobile using a similar Daimler engine. In 1891 this first Peugeot automobile paced a 1,046-km (650-mi) professional bicycle race between Paris and Brest. Other French automobile manufacturers opened shop in the late 1800s, including Renault. In Italy, Fiat (Fabbrica Italiana Automobili di Torino) began building cars in 1899.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">American automobile builders were not far behind. Brothers Charles Edgar Duryea and James Frank Duryea built several gas-powered vehicles between 1893 and 1895. The first Duryea, a one-cylinder, four-horsepower model, looked much like a Panhard-Levassor model. In 1893 American industrialist Henry Ford built an internal-combustion engine from plans he saw in a magazine. In 1896 he used an engine to power a vehicle mounted on bicycle wheels and steered by a tiller. <o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Early Electric Cars<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">For a few decades in the 1800s, electric engines enjoyed great popularity because they were quiet and ran at slow speeds that were less likely to scare horses and people. By 1899 an electric car designed and driven by Belgian inventor Camille Jenatzy set a record of 105.8810 km/h (65.79 mph).<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Early electric cars featured a large bank of storage batteries under the hood. Heavy cables connected the batteries to a motor between the front and rear axles. Most electric cars had top speeds of 48 km/h (30 mph), but could go only 80 km (50 mi) before their batteries needed recharging. Electric automobiles were manufactured in quantity in the United States until 1930.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">IX<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">AUTOMOBILES IN THE 20TH CENTURY<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">For many years after the introduction of automobiles, three kinds of power sources were in common use: steam engines, gasoline engines, and electric motors. In 1900 more than 2,300 automobiles were registered in New York City; Boston, Massachusetts; and Chicago, Illinois. Of these, 1,170 were steam cars, 800 were electric cars, and only 400 were gasoline cars. Gasoline-powered engines eventually became the nearly universal choice for automobiles because they allowed longer trips and faster speeds than engines powered by steam or electricity.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">But development of gasoline cars in the early 1900s was hindered in the United States by legal battles over a patent obtained by New York lawyer George B. Selden. Selden saw a gasoline engine at the Philadelphia Centennial Exposition in 1876. He then designed a similar one and obtained a broad patent that for many years was interpreted to apply to all gasoline engines for automobiles. Although Selden did not manufacture engines or automobiles, he collected royalties from those who did.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Henry Ford believed Selden’s patent was invalid. Selden sued when Ford refused to pay royalties for Ford-manufactured engines. After eight years of court battles, the courts ruled in 1911 that Selden’s patent applied only to two-stroke engines. Ford and most other manufacturers were using four-stroke engines, so Selden could not charge them royalties.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Improvements in the operating and riding qualities of gasoline automobiles developed quickly after 1900. The 1902 Locomobile was the first American car with a four-cylinder, water-cooled, front-mounted gasoline engine, very similar in design to most cars today. Built-in baggage compartments appeared in 1906, along with weather resistant tops and side curtains. An electric self-starter was introduced in 1911 to replace the hand crank used to start the engine turning. Electric headlights were introduced at about the same time.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Most automobiles at the turn of the 20th century appeared more or less like horseless carriages. In 1906 gasoline-powered cars were produced that had a style all their own. In these new models, a hood covered the front-mounted engine. Two kerosene or acetylene lamps mounted to the front served as headlights. Cars had fenders that covered the wheels and step-up platforms called running boards, which helped passengers get in and out of the vehicle. The passenger compartment was behind the engine. Although drivers of horse-drawn vehicles usually sat on the right, automotive steering wheels were on the left in the United States.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In 1903 Henry Ford incorporated the Ford Motor Company, which introduced its first automobile, the Model A, in that same year. It closely resembled the 1903 Cadillac, which was hardly surprising since Ford had designed cars the previous year for the Cadillac Motor Car Company. Ford’s company rolled out new car models each year, and each model was named with a letter of the alphabet. By 1907, when models R and S appeared, Ford’s share of the domestic automobile market had soared to 35 percent.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Ford’s famous Model T debuted in 1908 but was called a 1909 Ford. Ford built 17,771 Model T’s and offered nine body styles. Popularly known as the Tin Lizzy, the Model T became one of the biggest-selling automobiles of all time. Ford sold more than 15 million before stopping production of the model in 1927. The innovative assembly-line method used by the company to build its cars was widely adopted in the automobile industry.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">By 1920 more than 8 million Americans owned cars. Major reasons for the surge in automobile ownership were Ford’s Model T, the assembly-line method of building it, and the affordability of cars for the ordinary wage earner.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Improvements in engine-powered cars during the 1920s contributed to their popularity: synchromesh transmissions for easier gear shifting; four-wheel hydraulic brake systems; improved carburetors; shatterproof glass; balloon tires; heaters; and mechanically operated windshield wipers.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">From 1930 to 1937, automobile engines and bodies became large and luxurious. Many 12- and 16-cylinder cars were built. Independent front suspension, which made the big cars more comfortable, appeared in 1933. Also introduced during the 1930s were stronger, more reliable braking systems, and higher-compression engines, which developed more horsepower. Mercedes introduced the world’s first diesel car in 1936. Automobiles on both sides of the Atlantic were styled with gracious proportions, long hoods, and pontoon-shaped fenders. Creative artistry merged with industrial design to produce appealing, aerodynamic automobiles.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Some of the first vehicles to fully incorporate the fender into the bodywork came along just after World War II, but the majority of designs still had separate fenders with pontoon shapes holding headlight assemblies. Three companies, Ford, Nash, and Hudson Motor Car Company, offered postwar designs that merged fenders into the bodywork. The 1949 Ford was a landmark in this respect, and its new styling was so well accepted the car continued in production virtually unchanged for three years, selling more than 3 million. During the 1940s, sealed-beam headlights, tubeless tires, and the automatic transmission were introduced.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Two schools of styling emerged in the 1950s, one on each side of the Atlantic. The Europeans continued to produce small, light cars weighing less than 1,300 kg (2,800 lb). European sports cars of that era featured hand-fashioned aluminum bodies over a steel chassis and framework.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In America, automobile designers borrowed features for their cars that were normally found on aircraft and ships, including tailfins and portholes. Automobiles were produced that had more space, more power, and smoother riding capability. Introduction of power steering and power brakes made bigger cars easier to handle. The Buick Motor Car Company, Olds Motor Vehicle Company (Oldsmobile), Cadillac Automobile Company, and Ford all built enormous cars, some weighing as much as 2,495 kg (5,500 lb).<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The first import by German manufacturer Volkswagen AG, advertised as the Beetle, arrived in the United States in 1949. Only two were sold that year, but American consumers soon began buying the Beetle and other small imports by the thousands. That prompted a downsizing of some American-made vehicles. The first American car called a compact was the Nash Rambler. Introduced in 1950, it did not attract buyers on a large scale until 1958. More compacts, smaller in overall size than a standard car but with virtually the same interior body dimensions, emerged from the factories of many major manufacturers. The first Japanese imports, 16 compact trucks, arrived in the United States in 1956.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In the 1950s new automotive features were introduced, including air conditioning and electrically operated car windows and seat adjusters. Manufacturers changed from the 6-volt to the 12-volt ignition system, which gave better engine performance and more reliable operation of the growing number of electrical accessories.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">By 1960 sales of foreign and domestic compacts accounted for about one-third of all passenger cars sold in the United States. American cars were built smaller, but with increased engine size and horsepower. Heating and ventilating systems became standard equipment on even the least expensive models. Automatic transmissions, power brakes, and power steering became widespread. Styling sometimes prevailed over practicality—some cars were built in which the engines had to be lifted to allow simple service operations, like changing the spark plugs. Back seats were designed with no legroom.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In the 1970s American manufacturers continued to offer smaller, lighter models in addition to the bigger sedans that led their product lines, but Japanese and European compacts continued to sell well. Catalytic converters were introduced to help reduce exhaust emissions.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">During this period, the auto industry was hurt by the energy crisis, created when the Organization of Petroleum Exporting Countries (OPEC), a cartel of oil-producing countries, cut back on sales to other countries. The price of crude oil skyrocketed, driving up the price of gasoline. Large cars were getting as little as 8 miles per gallon (mpg), while imported compacts were getting as much as 35 mpg. More buyers chose the smaller, more fuel-efficient imports.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Digital speedometers and electronic prompts to service parts of the vehicle appeared in the 1980s. Japanese manufacturers opened plants in the United States. At the same time, sporty cars and family minivans surged in popularity.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Advances in automobile technology in the 1980s included better engine control and the use of innovative types of fuel. In 1981 Bayerische Motoren Werke AG (BMW) introduced an on-board computer to monitor engine performance. A solar-powered vehicle, SunRaycer, traveled 3,000 km (1,864 mi) in Australia in six days.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">X<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">NEW TECHNOLOGIES<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "Times New Roman","serif"; display: none;"><o:p> </o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Antipollution Strategies<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Pollution-control laws adopted at the beginning of the 1990s in some of the United States and in Europe called for automobiles that produced better gas mileage with lower emissions. The California Air Resources Board required companies with the largest market shares to begin selling vehicles that were pollution free—in other words, electric. In 1996 General Motors became the first to begin selling an all-electric car, the EV1, to California buyers. The all-electric cars introduced so far have been limited by low range, long recharges, and weak consumer interest. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Engines that run on hydrogen have been tested. Hydrogen combustion produces only a trace of harmful emissions, no carbon dioxide, and a water-vapor by-product. However, technical problems related to the gas’s density and flammability remain to be solved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Diesel engines burn fuel more efficiently, and produce fewer pollutants, but they are noisy. Popular in trucks and heavy vehicles, diesel engines are only a small portion of the automobile market. A redesigned, quieter diesel engine introduced by Volkswagen in 1996 may pave the way for more diesels, and less pollution, in passenger cars.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Hybrid-Electric Vehicles (HEVs)<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">While some developers searched for additional alternatives, others investigated ways to combine electricity with liquid fuels to produce low-emissions power systems. The hybrid-electric vehicle (HEV) uses both an electric motor or motors and a gasoline or diesel engine that charges the batteries in order to extend the distance that the vehicle can travel without having to recharge the batteries. An HEV at a stoplight typically sits silent, burning no fuel and making no pollution, if the batteries are sufficiently charged. If driven slowly, as in heavy traffic, the vehicle might move only on electric power. Only when more power is demanded for acceleration or to move a heavy load, does the gasoline or diesel engine come into play. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Two automobiles with such hybrid engines, the Toyota Prius and the Honda Insight, became available in the late 1990s. The Prius hit automobile showrooms in Japan in 1997, selling 30,000 models in its first two years of production. The Prius became available for sale in North America in 2000. The Honda Insight debuted in North America in late 1999. Both vehicles promised to double the fuel efficiency of conventional gasoline-powered cars while significantly reducing toxic emissions. The Ford Motor Company introduced the first U.S.-made hybrid when it began production for the Ford Escape Hybrid in August 2004. The 2005 model year Escape was also the first hybrid in the sport-utility vehicle (SUV) category. Electric Car.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">C<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Computers and Navigation Devices<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Computer control of automobile systems increased dramatically during the 1990s. The central processing unit (CPU) in modern engines manages overall engine performance. Microprocessors regulating other systems share data with the CPU. Computers manage fuel and air mixture ratios, ignition timing, and exhaust-emission levels. They adjust the antilock braking and traction control systems. In many models, computers also control the air conditioning and heating, the sound system, and the information displayed in the vehicle’s dashboard.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Expanded use of computer technology, development of stronger and lighter materials, and research on pollution control will produce better, “smarter” automobiles. In the 1980s the notion that a car would “talk” to its driver was science fiction; by the 1990s it had become reality.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Onboard navigation was one of the new automotive technologies in the 1990s. By using the satellite-aided global positioning system (GPS), a computer in the automobile can pinpoint the vehicle’s location within a few meters. The onboard navigation system uses an electronic compass, digitized maps, and a display screen showing where the vehicle is relative to the destination the driver wants to reach. After being told the destination, the computer locates it and directs the driver to it, offering alternative routes if needed.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Some cars now come equipped with GPS locator beacons, enabling a GPS system operator to locate the vehicle, map its location, and if necessary, direct repair or emergency workers to the scene.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Cars equipped with computers and cellular telephones can link to the Internet to obtain constantly updated traffic reports, weather information, route directions, and other data. Future built-in computer systems may be used to automatically obtain business information over the Internet and manage personal affairs while the vehicle’s owner is driving.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">D<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Other Improvements<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">During the 1980s and 1990s, manufacturers trimmed 450 kg (1,000 lb) from the weight of the typical car by making cars smaller. Less weight, coupled with more efficient engines, doubled the gas mileage obtained by the average new car between 1974 and 1995. Further reductions in vehicle size are not practical, so the emphasis has shifted to using lighter materials, such as plastics, aluminum alloys, and carbon composites, in the engine and the rest of the vehicle.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Looking ahead, engineers are devising ways to reduce driver errors and poor driving habits. Systems already exist in some locales to prevent intoxicated drivers from starting their vehicles. The technology may be expanded to new vehicles. Anticollision systems with sensors and warning signals are being developed. In some, the car’s brakes automatically slow the vehicle if it is following another vehicle too closely. New infrared sensors or radar systems may warn drivers when another vehicle is in their “blind spot.”<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Catalytic converters work only when they are warm, so most of the pollution they emit occurs in the first few minutes of operation. Engineers are working on ways to keep the converters warm for longer periods between drives, or heat the converters more rapidly.</span><br /><img src="http://farm4.static.flickr.com/3063/2770313147_a0ac14a8e5.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Gas-Electric Hybrids<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The Toyota Prius, <i>top</i>, a four-seat hybrid electric vehicle (HEV), was the first HEV to be marketed when Toyota introduced it in Japan in 1997. The Honda Insight, <i>bottom</i>, a two-seat HEV, followed in 1999 when it was sold in both Japan and the United States. The Prius had its U.S. debut in 2000.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Marty Lederhandler and Kim D. Johnson/AP Wide World Photos, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 15pt;"><span style="font-size: 12pt; font-family: "Times New Roman","serif";"><br />Contributed By:<br />David Fetherston<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif";">Microsoft ® Encarta ® 2007.</span></b><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif";"> © 1993-2006 Microsoft Corporation. All rights reserved.<o:p></o:p></span></p> <p class="MsoNormal"><o:p> </o:p></p>ghozian karamihttp://www.blogger.com/profile/13214011599962806335noreply@blogger.com0tag:blogger.com,1999:blog-192751622867664710.post-19939377578113463522009-01-02T16:22:00.000-08:002009-01-02T16:25:32.096-08:00Badminton<p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 24pt; font-family: "MS Reference Serif","serif";">Badminton<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">I<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">INTRODUCTION</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3217/2770313331_5f66cb7eae.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Olympic Badminton Match<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Badminton is a racket sport played with a <i>shuttlecock,</i> a cork ball fitted with stabilizing feathers. Badminton was first played as an Olympic medal sport at the 1992 Games in Barcelona, Spain. Seen here is a match from the men’s doubles competition.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Pool J.O. Barcelone/Liaison Agency<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Badminton, game for two or four players using lightweight rackets and a shuttlecock<i>,</i> a cork ball fitted with stabilizing feathers. Players hit the shuttlecock back and forth over a net, trying to keep it from hitting the ground. Some people play badminton outdoors on a level grassy area or beach. However, tournament-level badminton is played indoors on a specially marked court.</span><br /><img src="http://farm4.static.flickr.com/3041/2770313481_e0028cdd75.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Shuttlecock<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The shuttlecock used in tournament badminton is typically 2.5 in (6.4 cm) long, 0.2 oz (5.7 g) in weight, and made of 16 goosefeathers inserted into a cork base. The shuttlecock is designed so that it will spin in flight and the players will hit the cork end rather than the feathers.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Badminton’s governing body, the International Badminton Federation (IBF), has about 140 member nations. The IBF estimates that about 200 million people play the game worldwide and that more than 1,000 players participate in international competition. Badminton’s growth accelerated after the game’s debut as a medal sport during the 1992 Summer Olympic Games. China, Denmark, Indonesia, Japan, Malaysia, and South Korea are just a few of the countries where badminton is popular.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">II<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">PLAYING AREA</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3097/2771160592_7765dc70a3.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Badminton Court<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">A badminton court resembles a tennis court in shape and markings, but it has smaller dimensions.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">International rules state that an indoor badminton court must be rectangular, with white lines marked on a level wooden floor or on a special mat that is rolled onto a level playing surface. A singles court is 44 ft (13.41 m) long and 17 ft (5.18 m) wide. For doubles, alleys 1 ft 6 in (0.46 m) wide along the two longer sides of the court come into play, making the court 20 ft (6.10 m) wide. Because many shots fly high into the air, there must be clearance of at least 30 ft (9.14 m) above the court. A net stretched across the middle of the court has a top edge set to a height of 5 ft (1.52 m) at the center and 5 ft 1 in (1.55 m) at the posts.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">III<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">EQUIPMENT<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Badminton rackets weigh between 3.5 and 5 oz (99 and 141 g) and consist of a leather or terrycloth handle; a long, thin shaft; and a stringed area called the head<i>.</i> Official rules limit the total length of a racket to 26.75 in (67.95 cm). The head of a racket measures 11 in (28 cm) in length and 8.6 in (21.8 cm) in width and is strung with synthetic nylon or gut at between 25 and 35 lb (11.3 and 15.9 kg) of tension. Early rackets were made of wood, but badminton rackets are now commonly made of aluminum, boron, graphite, and titanium.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Tournament-quality shuttlecocks, also called shuttles or birdies, weigh 0.2 oz (5.7 gm) and consist of 16 goose feathers that protrude from one side of a ball-shaped cork base. Most shuttles used by casual players are plastic and have synthetic feathers. Both types of shuttles are 2.5 in (6.4 cm) long. When the shuttlecock is in the air, its aerodynamics cause it to spin so that when players hit it, they almost always strike the cork, not the feathers.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">IV<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">SERVICE AND PLAY<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Play begins with a serve from a service area on the right-hand side of the court to a receiver in a diagonally opposite service area across the net. To serve, the server stands behind the service line and strikes the cork base of the shuttle in an underhand motion. The receiver must then return the shuttle before it hits the ground, and the players hit the shuttle back and forth until one side fails to return it.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Play ends when the shuttle hits the ground on one side of the court or when one player makes a fault, or error, such as hitting the shuttle into the net or out of bounds. Specific faults for servers include striking the feathers of the shuttle first or serving overhand. The receiver can be faulted for not being within the service court, for not having both feet on the floor when receiving, and for moving before the serve is made.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">During play, faults include hitting the shuttle into the roof or lights, hitting it through the net, double-hitting or slinging a shot, touching the net, playing a shot by reaching over the net, and allowing the shuttle to hit the player’s body. Unsportsmanlike conduct—such as intentionally distracting an opponent—will also earn a player a fault.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">V<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">SCORING AND OFFICIALS<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Points are scored when the opponent fails to return the shuttle, hits it out of bounds, or earns a fault. Points only count for the server (or serving side in doubles), so keeping the service privilege is an important part of the game. If the server loses a rally or makes a fault, the service privilege passes to the opponent. In doubles, this immediate loss of service occurs only at the start of the game. After this first loss of service, each team receives two chances to hold serve. When the first teammate loses serve, the partner serves. If the partner loses serve, the opposing team takes over. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In men’s singles, men’s doubles, women’s doubles, and mixed doubles, the first side to score 15 points is the winner. Women’s singles games are played to 11 points. If the score is tied at 14-14 (or 10-10 in women’s singles) a system called <i>setting </i>settles the outcome. The first side that reached 14 (or 10) elects either to <i>play through,</i> meaning that the next side to win a point wins the game, or to <i>set</i> the game to three additional points, meaning that the first side to reach 17 points (or 13 in women’s singles) wins the game. Each badminton match is a best-of-three-games contest. Average matches last about 45 minutes, but professional matches can last more than 2 hours.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Badminton tournaments involve a number of officials. A referee supervises the tournament organization while an umpire controls each match. Aided by a service judge, the umpire keeps score and rules on faults during play. Up to ten line judges rule on whether particular shots have landed in or out of the court.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">VI<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">SKILLS AND STROKES<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Badminton requires speed, strength, power, agility, and nerve. Players must move quickly from side to side and back and forth, and stamina is important.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">There are six key badminton strokes: the serve, drive, net shot, smash, lift (or lob), and clear<i>.</i> To hit these strokes, players use either a forehand or a backhand grip, depending on court positioning. On the forehand the forefinger acts as a lever and creates power and direction for the stroke. For the backhand the thumb creates this power and direction while placed along the back of the handle.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Many players aim the serve toward the centerline of the opposite service box. This technique limits the angle of the opponent’s return shot. Sometimes players use long, high serves to force opponents to the back of the court. Players also make specialty serves, such as flick<i> </i>serves that barely clear the net or drive serves that are hit down the sideline of the service area, to catch opponents out of position.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Once play has started, players tend to hit straight, low-flying shots called drives. When the shuttle remains close to the center of the court, net shots can be a good option. Net shots can be hard-hit or delicate. They are aimed at the front area of the opponent’s court, forcing the opponent to play the shot close to the net.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">If the opponent manages to return a net shot, the return must be hit high to clear the net. This gives the player a chance for a smash—the deadliest attacking stroke in badminton. A smash is hit to the floor so forcefully that the opponent has no chance to return the shuttle before it hits the ground. The hardest smash has been recorded at more than 200 mph (320 km/h).<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Players also use two looping strokes that knock the shuttle high and deep. The lift, or lob, is an offensive stroke made from the middle or front of the court. This shot sends the shuttle in a high arc above the opponent’s reach, forcing the opponent to the back of the court. The clear is a similar stroke, but it is used for defensive purposes when players find themselves out of position. The high arc gives players time to return to the middle of the court and to prepare for another rally.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">VII<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">COMPETITION<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Many badminton enthusiasts play in clubs or at local and regional levels. Top players compete in the World Grand Prix series, an international circuit of tournaments sanctioned by the IBF. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The world championships are badminton’s biggest event and are held every two years. The tournament features five competitions: men’s and women’s singles, men’s and women’s doubles, and mixed doubles. The world championships are always preceded the previous week at the same venue by the Sudirman Cup world mixed team championships, where contests between nations are decided by five matches: men’s and women’s singles, men’s and women’s doubles, and mixed doubles.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Two of badminton’s most exciting events are the men’s Thomas Cup and the women’s Uber Cup. These world team championships, which take place every two years side by side at the same time and at the same venue, have continental qualifying rounds. Contests are staged in a round-robin format with knockout finals at both the qualifying stages in February and the grand finals in May. Thomas Cup and Uber Cup contests consist of three singles and two doubles matches.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Other major events are the European championships, held every two years, and the Olympic Games and the Commonwealth Games, both held every four years.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The IBF, located in Cheltenham, England, regulates all these events and is the sport’s governing body. Representatives from Canada, Denmark, England, France, Ireland, The Netherlands, New Zealand, Scotland, and Wales founded the organization in 1934. Today the IBF has about 140 member nations.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">VIII<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">HISTORY<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Badminton traces its beginnings to a game played thousands of years ago in Asia. The modern form of the sport was refined in Britain, but it is popular in countries all over the world.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Beginnings<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Badminton evolved from a Chinese game of the 5th century <span style="text-transform: uppercase;">bc</span> called <i>ti jian zi</i> that involved kicking the shuttle. A later version of the sport was played in ancient Greece and India with rackets rather than with feet. A similar game called shuttlecock, or <i>jeu de volant,</i> appeared in Europe during the 1600s.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">British army officers brought a revised version of the game back to Britain from India in the mid-19th century. In 1873 the duke of Beaufort introduced the game to royalty at his country estate, Badminton House, and the sport became known as badminton. Four years later the Bath Badminton Club was founded. The version played by its members forms the basis for today’s game.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Growth in Popularity<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Badminton soon spread beyond Britain to the rest of Europe and to countries throughout the world. It became especially popular in Asia and North America. The only major change through the years was in playing equipment, as lightweight rackets made of aluminum, boron, graphite, and titanium gradually replaced wooden models.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">During and after World War II (1939-1945), American badminton players came to prominence in international play. In the 1940s David Freeman was recognized as the world’s best player. He won seven United States singles titles (1939-1942, 1947, 1948, 1953) and the All-England singles title (1949). He remained unbeaten in singles competition from the age of 19 until he retired at age 33. American-born player Judy Devlin Hashman dominated the women’s game during the 1950s and 1960s; she became a naturalized citizen of Britain in 1970. England’s Gillian Gilks dominated women’s singles, women’s doubles, and mixed doubles play during the early 1970s.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Badminton’s first world championships were held in 1977. Denmark’s Flemming Delfs and Lene Koppen won the men’s and women’s singles titles, respectively. Since then, East Asian nations—primarily China and Indonesia—have dominated professional badminton. In both countries, badminton is as popular as basketball is in the United States or soccer is in Britain. Spectators at matches typically sing, chant, and cheer for their favorite players or teams.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">C<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Recent Developments<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Individuals from China and Indonesia have won numerous world championship titles. Men’s singles world champions include Rudy Hartono (1980) of Indonesia and Yang Yang (1987, 1989), Zhao Jianhua (1991), and Sun Jun (1999) of China. Women’s world champions include Indonesia’s Susi Susanti (1993) and China’s Ye Zhaoying (1995, 1997). <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The most noted doubles player is South Korean men’s star Park Joo Bong, who won an Olympic gold medal in men’s doubles in 1992 and a silver medal in mixed doubles in 1996. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Denmark is also a badminton powerhouse, with players such as 1996 men’s Olympic gold medalist Poul-Erik Hoyer-Larsen, 1997 men’s world champion Peter Rasmussen, and 1999 women’s world champion Camilla Martin.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 15pt;"><span style="font-size: 12pt; font-family: "Times New Roman","serif";"><br />Contributed By:<br />William Kings<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif";">Microsoft ® Encarta ® 2007.</span></b><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif";"> © 1993-2006 Microsoft Corporation. All rights reserved.<o:p></o:p></span></p> <p class="MsoNormal"><o:p> </o:p></p>ghozian karamihttp://www.blogger.com/profile/13214011599962806335noreply@blogger.com0tag:blogger.com,1999:blog-192751622867664710.post-31346942211311982162009-01-02T16:20:00.000-08:002009-01-02T16:22:13.656-08:00All about cell<p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 24pt; font-family: "MS Reference Serif","serif";">Cell (biology)<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">I<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">INTRODUCTION</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3277/2770313819_72ee0366d4.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Paramecium<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The paramecium is a single-celled organism that propels itself by minute, hairlike projections called cilia. Cilia also create currents that sweep food particles toward the paramecium’s gullet for ingestion.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">M.I. Walker/Science Source/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Cell (biology), basic unit of life. Cells are the smallest structures capable of basic life processes, such as taking in nutrients, expelling waste, and reproducing. All living things are composed of cells. Some microscopic organisms, such as bacteria and protozoa, are unicellular, meaning they consist of a single cell. Plants, animals, and fungi are multicellular; that is, they are composed of a great many cells working in concert. But whether it makes up an entire bacterium or is just one of trillions in a human being, the cell is a marvel of design and efficiency. Cells carry out thousands of biochemical reactions each minute and reproduce new cells that perpetuate life.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Cells vary considerably in size. The smallest cell, a type of bacterium known as a mycoplasma, measures 0.0001 mm (0.000004 in) in diameter; 10,000 mycoplasmas in a row are only as wide as the diameter of a human hair. Among the largest cells are the nerve cells that run down a giraffe’s neck; these cells can exceed 3 m (9.7 ft) in length. Human cells also display a variety of sizes, from small red blood cells that measure 0.00076 mm (0.00003 in) to liver cells that may be ten times larger. About 10,000 average-sized human cells can fit on the head of a pin.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Along with their differences in size, cells present an array of shapes. Some, such as the bacterium <i>Escherichia coli</i>, resemble rods. The paramecium, a type of protozoan, is slipper shaped; and the amoeba, another protozoan, has an irregular form that changes shape as it moves around. Plant cells typically resemble boxes or cubes. In humans, the outermost layers of skin cells are flat, while muscle cells are long and thin. Some nerve cells, with their elongated, tentacle-like extensions, suggest an octopus.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In multicellular organisms, shape is typically tailored to the cell’s job. For example, flat skin cells pack tightly into a layer that protects the underlying tissues from invasion by bacteria. Long, thin muscle cells contract readily to move bones. The numerous extensions from a nerve cell enable it to connect to several other nerve cells in order to send and receive messages rapidly and efficiently.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">By itself, each cell is a model of independence and self-containment. Like some miniature, walled city in perpetual rush hour, the cell constantly bustles with traffic, shuttling essential molecules from place to place to carry out the business of living. Despite their individuality, however, cells also display a remarkable ability to join, communicate, and coordinate with other cells. The human body, for example, consists of an estimated 20 to 30 trillion<i> </i>cells. Dozens of different kinds of cells are organized into specialized groups called tissues. Tendons and bones, for example, are composed of connective tissue, whereas skin and mucous membranes are built from epithelial tissue. Different tissue types are assembled into organs, which are structures specialized to perform particular functions. Examples of organs include the heart, stomach, and brain. Organs, in turn, are organized into systems such as the circulatory, digestive, or nervous systems. All together, these assembled organ systems form the human body.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The components of cells are molecules, nonliving structures formed by the union of atoms. Small molecules serve as building blocks for larger molecules. Proteins, nucleic acids, carbohydrates, and lipids, which include fats and oils, are the four major molecules that underlie cell structure and also participate in cell functions. For example, a tightly organized arrangement of lipids, proteins, and protein-sugar compounds forms the plasma membrane, or outer boundary, of certain cells. The organelles, membrane-bound compartments in cells, are built largely from proteins. Biochemical reactions in cells are guided by enzymes, specialized proteins that speed up chemical reactions. The nucleic acid deoxyribonucleic acid (DNA) contains the hereditary information for cells, and another nucleic acid, ribonucleic acid(RNA), works with DNA to build the thousands of proteins the cell needs.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">II<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">CELL STRUCTURE<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Cells fall into one of two categories: prokaryotic or eukaryotic (<i>see </i>Prokaryote). In a prokaryotic cell, found only in bacteria and archaebacteria, all the components, including the DNA, mingle freely in the cell’s interior, a single compartment. Eukaryotic cells, which make up plants, animals, fungi, and all other life forms, contain numerous compartments, or organelles, within each cell. The DNA in eukaryotic cells is enclosed in a special organelle called the nucleus, which serves as the cell’s command center and information library. The term <i>prokaryote</i> comes from Greek words that mean “before nucleus” or “prenucleus,” while <i>eukaryote</i> means “true nucleus.”<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Prokaryotic Cells</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3173/2771160900_bef1412e6f.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Anatomy of a Simple Bacterium<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Bacteria cells typically are surrounded by a rigid, protective cell wall. The cell membrane, also called the plasma membrane, regulates passage of materials into and out of the cytoplasm, the semi-fluid that fills the cell. The DNA, located in the nucleoid region, contains the genetic information for the cell. Ribosomes carry out protein synthesis. Many baceteria contain a pilus (plural pili), a structure that extends out of the cell to transfer DNA to another bacterium. The flagellum, found in numerous species, is used for locomotion. Some bacteria contain a plasmid, a small chromososme with extra genes. Others have a capsule, a sticky substance external to the cell wall that protects bacteria from attack by white blood cells. Mesosomes were formerly thought to be structures with unknown functions, but now are know to be artifacts created when cells are prepared for viewing with electron microscopes.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Prokaryotic cells are among the tiniest of all cells, ranging in size from 0.0001 to 0.003 mm (0.000004 to 0.0001 in) in diameter. About a hundred typical prokaryotic cells lined up in a row would match the thickness of a book page. These cells, which can be rodlike, spherical, or spiral in shape, are surrounded by a protective cell wall. Like most cells, prokaryotic cells live in a watery environment, whether it is soil moisture, a pond, or the fluid surrounding cells in the human body. Tiny pores in the cell wall enable water and the substances dissolved in it, such as oxygen, to flow into the cell; these pores also allow wastes to flow out.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Pushed up against the inner surface of the prokaryotic cell wall is a thin membrane called the plasma membrane. The plasma membrane, composed of two layers of flexible lipid molecules and interspersed with durable proteins, is both supple and strong. Unlike the cell wall, whose open pores allow the unregulated traffic of materials in and out of the cell, the plasma membrane is selectively permeable, meaning it allows only certain substances to pass through. Thus, the plasma membrane actively separates the cell’s contents from its surrounding fluids.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">While small molecules such as water, oxygen, and carbon dioxide diffuse freely across the plasma membrane, the passage of many larger molecules, including amino acids (the building blocks of proteins) and sugars, is carefully regulated. Specialized transport proteins accomplish this task. The transport proteins span the plasma membrane, forming an intricate system of pumps and channels through which traffic is conducted. Some substances swirling in the fluid around the cell can enter it only if they bind to and are escorted in by specific transport proteins. In this way, the cell fine-tunes its internal environment.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The plasma membrane encloses the cytoplasm, the semifluid that fills the cell. Composed of about 65 percent water, the cytoplasm is packed with up to a billion molecules per cell, a rich storehouse that includes enzymes and dissolved nutrients, such as sugars and amino acids. The water provides a favorable environment for the thousands of biochemical reactions that take place in the cell.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Within the cytoplasm of all prokaryotes is deoxyribonucleic acid (DNA), a complex molecule in the form of a double helix, a shape similar to a spiral staircase. The DNA is about 1,000 times the length of the cell, and to fit inside, it repeatedly twists and folds to form a compact structure called a chromosome. The chromosome in prokaryotes is circular, and is located in a region of the cell called the nucleoid. Often, smaller chromosomes called plasmids are located in the cytoplasm. The DNA is divided into units called genes, just like a long train is divided into separate cars. Depending on the species, the DNA contains several hundred or even thousands of genes. Typically, one gene contains coded instructions for building all or part of a single protein. Enzymes, which are specialized proteins, determine virtually all the biochemical reactions that support and sustain the cell.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Also immersed in the cytoplasm are the only organelles in prokaryotic cells—tiny bead-like structures called ribosomes. These are the cell’s protein factories. Following the instructions encoded in the DNA, ribosomes churn out proteins by the hundreds every minute, providing needed enzymes, the replacements for worn-out transport proteins, or other proteins required by the cell.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">While relatively simple in construction, prokaryotic cells display extremely complex activity. They have a greater range of biochemical reactions than those found in their larger relatives, the eukaryotic cells. The extraordinary biochemical diversity of prokaryotic cells is manifested in the wide-ranging lifestyles of the archaebacteria and the bacteria, whose habitats include polar ice, deserts, and hydrothermal vents—deep regions of the ocean under great pressure where hot water geysers erupt from cracks in the ocean floor.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Eukaryotic Animal Cells</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3203/2770314111_cd9d7b4770.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Animal Cell<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">An animal cell typically contains several types of membrane-bound organs, or <i>organelles</i>. The nucleus directs activities of the cell and carries genetic information from generation to generation. The mitochondria generate energy for the cell. Proteins are manufactured by ribosomes, which are bound to the rough endoplasmic reticulum or float free in the cytoplasm. The Golgi apparatus modifies, packages, and distributes proteins while lysosomes store enzymes for digesting food. The entire cell is wrapped in a lipid membrane that selectively permits materials to pass in and out of the cytoplasm.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Eukaryotic cells are typically about ten times larger than prokaryotic cells. In animal cells, the plasma membrane, rather than a cell wall, forms the cell’s outer boundary. With a design similar to the plasma membrane of prokaryotic cells, it separates the cell from its surroundings and regulates the traffic across the membrane.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The eukaryotic cell cytoplasm is similar to that of the prokaryote cell except for one major difference: Eukaryotic cells house a nucleus and numerous other membrane-enclosed organelles. Like separate rooms of a house, these organelles enable specialized functions to be carried out efficiently. The building of proteins and lipids, for example, takes place in separate organelles where specialized enzymes geared for each job are located.</span><br /><img src="http://farm4.static.flickr.com/3170/2771161240_b2719d3480.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Plasma Membrane<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The plasma membrane that surrounds eukaryotic cells is a dynamic structure composed of two layers of phospholipid molecules interspersed with cholesterol and proteins. Phospholipids are composed of a hydrophilic, or water-loving, head and two tails, which are hydrophobic, or water-hating. The two phospholipid layers face each other in the membrane, with the heads directed outward and the tails pointing inward. The water-attracting heads anchor the membrane to the cytoplasm, the watery fluid inside the cell, and also to the water surrounding the cell. The water-hating tails block large water-soluble molecules from passing through the membrane while permitting fat-soluble molecules, including medications such as tranquilizers and sleeping pills, to freely cross the membrane. Proteins embedded in the plasma membrane carry out a variety of functions, including transport of large water soluble molecules such as sugars and certain amino acids. Glycoproteins, proteins bonded to carbohydrates, serve in part to identify the cell as belonging to a unique organism, enabling the immune system to detect foreign cells, such as invading bacteria, which carry different glycoproteins. Cholesterol molecules in the plasma membrane act as stabilizers that limit the movement of the two slippery phospholipids layers, which slide back and forth in the membrane. Tiny gaps in the membrane enable small molecules such as oxygen (upper right) to diffuse readily into and out of the cell. Since cells constantly use up oxygen, decreasing its concentration within the cell, the higher concentration of oxygen outside the cell causes a net flow of oxygen into the cell. The steady stream of oxygen into the cell enables it to carry out aerobic respiration continually, a process that provides the cell with the energy needed to carry out its functions.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The nucleus is the largest organelle in an animal cell. It contains numerous strands of DNA, the length of each strand being many times the diameter of the cell. Unlike the circular prokaryotic DNA, long sections of eukaryotic DNA pack into the nucleus by wrapping around proteins. As a cell begins to divide, each DNA strand folds over onto itself several times, forming a rod-shaped chromosome. <o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The nucleus is surrounded by a double-layered membrane that protects the DNA from potentially damaging chemical reactions that occur in the cytoplasm. Messages pass between the cytoplasm and the nucleus through nuclear pores, which are holes in the membrane of the nucleus. In each nuclear pore, molecular signals flash back and forth as often as ten times per second. For example, a signal to activate a specific gene comes in to the nucleus and instructions for production of the necessary protein go out to the cytoplasm.</span><br /><img src="http://farm4.static.flickr.com/3248/2770314393_292901f0e6.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Nucleus of a Cell<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The nucleus, present in eukaryotic cells, is a discrete structure containing chromosomes, which hold the genetic information for the cell. Separated from the cytoplasm of the cell by a double-layered membrane called the nuclear envelope, the nucleus contains a cellular material called nucleoplasm. Nuclear pores, present around the circumference of the nuclear membrane, allow the exchange of cellular materials between the nucleoplasm and the cytoplasm.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Don W. Fawcett/Science Source/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Attached to the nuclear membrane is an elongated membranous sac called the endoplasmic reticulum. This organelle tunnels through the cytoplasm, folding back and forth on itself to form a series of membranous stacks. Endoplasmic reticulum takes two forms: rough and smooth. Rough endoplasmic reticulum (RER) is so called because it appears bumpy under a microscope. The bumps are actually thousands of ribosomes attached to the membrane’s surface. The ribosomes in eukaryotic cells have the same function as those in prokaryotic cells—protein synthesis—but they differ slightly in structure. Eukaryote ribosomes bound to the endoplasmic reticulum help assemble proteins that typically are exported from the cell. The ribosomes work with other molecules to link amino acids to partially completed proteins. These incomplete proteins then travel to the inner chamber of the endoplasmic reticulum, where chemical modifications, such as the addition of a sugar, are carried out. Chemical modifications of lipids are also carried out in the endoplasmic reticulum.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The endoplasmic reticulum and its bound ribosomes are particularly dense in cells that produce many proteins for export, such as the white blood cells of the immune system, which produce and secrete antibodies. Some ribosomes that manufacture proteins are not attached to the endoplasmic reticulum. These so-called free ribosomes are dispersed in the cytoplasm and typically make proteins—many of them enzymes—that remain in the cell.</span><br /><img src="http://farm4.static.flickr.com/3011/2770314595_1e7aeeedd5.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Golgi Apparatus<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The Golgi apparatus, a minute cellular inclusion in the cytoplasm, is a series of smooth, stacked membranous sacs. The Golgi apparatus modifies proteins after they are produced by the ribosomes.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">David M. Phillips/The Pop. Council/Science Source/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The second form of endoplasmic reticulum, the smooth endoplasmic reticulum (SER), lacks ribosomes and has an even surface. Within the winding channels of the smooth endoplasmic reticulum are the enzymes needed for the construction of molecules such as carbohydrates and lipids. The smooth endoplasmic reticulum is prominent in liver cells, where it also serves to detoxify substances such as alcohol, drugs, and other poisons.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Proteins are transported from free and bound ribosomes to the Golgi apparatus, an organelle that resembles a stack of deflated balloons. It is packed with enzymes that complete the processing of proteins. These enzymes add sulfur or phosphorus atoms to certain regions of the protein, for example, or chop off tiny pieces from the ends of the proteins. The completed protein then leaves the Golgi apparatus for its final destination inside or outside the cell. During its assembly on the ribosome, each protein has acquired a group of from 4 to 100 amino acids called a signal. The signal works as a molecular shipping label to direct the protein to its proper location.</span><br /><img src="http://farm4.static.flickr.com/3088/2771161888_80260fb9e6.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Cytoskeleton<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The cytoskeleton, a network of protein fibers, crisscrosses the cytoplasm of eukaryotic cells, providing shape and mechanical support. The cytoskeleton also functions as a monorail to transport substances around the cell. A cell such as an amoeba changes shape by dismantling parts of the cytoskeleton and reassembling them in other locations.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Don Fawcett/Science Source/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Lysosomes are small, often spherical organelles that function as the cell’s recycling center and garbage disposal. Powerful digestive enzymes concentrated in the lysosome break down worn-out organelles and ship their building blocks to the cytoplasm where they are used to construct new organelles. Lysosomes also dismantle and recycle proteins, lipids, and other molecules.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The mitochondria are the powerhouses of the cell. Within these long, slender organelles, which can appear oval or bean shaped under the electron microscope, enzymes convert the sugar glucose and other nutrients into adenosine triphosphate (ATP). This molecule, in turn, serves as an energy battery for countless cellular processes, including the shuttling of substances across the plasma membrane, the building and transport of proteins and lipids, the recycling of molecules and organelles, and the dividing of cells. Muscle and liver cells are particularly active and require dozens and sometimes up to a hundred mitochondria per cell to meet their energy needs. Mitochondria are unusual in that they contain their own DNA in the form of a prokaryote-like circular chromosome; have their own ribosomes, which resemble prokaryotic ribosomes; and divide independently of the cell.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Unlike the tiny prokaryotic cell, the relatively large eukaryotic cell requires structural support. The cytoskeleton, a dynamic network of protein tubes, filaments, and fibers, crisscrosses the cytoplasm, anchoring the organelles in place and providing shape and structure to the cell. Many components of the cytoskeleton are assembled and disassembled by the cell as needed. During cell division, for example, a special structure called a spindle is built to move chromosomes around. After cell division, the spindle, no longer needed, is dismantled. Some components of the cytoskeleton serve as microscopic tracks along which proteins and other molecules travel like miniature trains. Recent research suggests that the cytoskeleton also may be a mechanical communication structure that converses with the nucleus to help organize events in the cell.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">C<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Eukaryotic Plant Cells</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3011/2771162044_00d62b0048.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Plant Cell<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Plant cells contain a variety of membrane-bound structures called organelles. These include a nucleus that carries genetic material; mitochondria that generate energy; ribosomes that manufacture proteins; smooth endoplasmic reticulum that manufactures lipids used for making membranes and storing energy; and a thin lipid membrane that surrounds the cell. Plant cells also contain chloroplasts that capture energy from sunlight and a single fluid-filled vacuole that stores compounds and helps in plant growth. Plant cells are surrounded by a rigid cell wall that protects the cell and maintains its shape.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Plant cells have all the components of animal cells and boast several added features, including chloroplasts, a central vacuole, and a cell wall. Chloroplasts convert light energy—typically from the Sun—into the sugar glucose, a form of chemical energy, in a process known as photosynthesis. Chloroplasts, like mitochondria, possess a circular chromosome and prokaryote-like ribosomes, which manufacture the proteins that the chloroplasts typically need. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The central vacuole of a mature plant cell typically takes up most of the room in the cell. The vacuole, a membranous bag, crowds the cytoplasm and organelles to the edges of the cell. The central vacuole stores water, salts, sugars, proteins, and other nutrients. In addition, it stores the blue, red, and purple pigments that give certain flowers their colors. The central vacuole also contains plant wastes that taste bitter to certain insects, thus discouraging the insects from feasting on the plant.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In plant cells, a sturdy cell wall surrounds and protects the plasma membrane. Its pores enable materials to pass freely into and out of the cell. The strength of the wall also enables a cell to absorb water into the central vacuole and swell without bursting. The resulting pressure in the cells provides plants with rigidity and support for stems, leaves, and flowers. Without sufficient water pressure, the cells collapse and the plant wilts.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">III<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">CELL FUNCTIONS<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">To stay alive, cells must be able to carry out a variety of functions. Some cells must be able to move, and most cells must be able to divide. All cells must maintain the right concentration of chemicals in their cytoplasm, ingest food and use it for energy, recycle molecules, expel wastes, and construct proteins. Cells must also be able to respond to changes in their environment.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Movement</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3058/2771162160_fcb6dcefd9.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Plant Cell<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Plant cells contain a variety of membrane-bound structures called organelles. These include a nucleus that carries genetic material; mitochondria that generate energy; ribosomes that manufacture proteins; smooth endoplasmic reticulum that manufactures lipids used for making membranes and storing energy; and a thin lipid membrane that surrounds the cell. Plant cells also contain chloroplasts that capture energy from sunlight and a single fluid-filled vacuole that stores compounds and helps in plant growth. Plant cells are surrounded by a rigid cell wall that protects the cell and maintains its shape.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Plant cells have all the components of animal cells and boast several added features, including chloroplasts, a central vacuole, and a cell wall. Chloroplasts convert light energy—typically from the Sun—into the sugar glucose, a form of chemical energy, in a process known as photosynthesis. Chloroplasts, like mitochondria, possess a circular chromosome and prokaryote-like ribosomes, which manufacture the proteins that the chloroplasts typically need. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The central vacuole of a mature plant cell typically takes up most of the room in the cell. The vacuole, a membranous bag, crowds the cytoplasm and organelles to the edges of the cell. The central vacuole stores water, salts, sugars, proteins, and other nutrients. In addition, it stores the blue, red, and purple pigments that give certain flowers their colors. The central vacuole also contains plant wastes that taste bitter to certain insects, thus discouraging the insects from feasting on the plant.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In plant cells, a sturdy cell wall surrounds and protects the plasma membrane. Its pores enable materials to pass freely into and out of the cell. The strength of the wall also enables a cell to absorb water into the central vacuole and swell without bursting. The resulting pressure in the cells provides plants with rigidity and support for stems, leaves, and flowers. Without sufficient water pressure, the cells collapse and the plant wilts.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">III<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">CELL FUNCTIONS<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">To stay alive, cells must be able to carry out a variety of functions. Some cells must be able to move, and most cells must be able to divide. All cells must maintain the right concentration of chemicals in their cytoplasm, ingest food and use it for energy, recycle molecules, expel wastes, and construct proteins. Cells must also be able to respond to changes in their environment.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Movement</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3089/2770315335_92ca596eb5.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Euglena, Showing Whiplike Flagellum<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The euglena is a single-celled alga with two or several flagella (depending on the species) located at one end for locomotion. Other algae, vertebrate sperm cells, and some protozoans and bacteria possess a single flagellum for movement.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Biophoto Associates/Science Source/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Movement in eukaryotes is also accomplished with cilia, short, hairlike proteins built by centrioles, which are barrel-shaped structures located in the cytoplasm that assemble and break down protein filaments. Typically, thousands of cilia extend through the plasma membrane and cover the surface of the cell, giving it a dense, hairy appearance. By beating its cilia as if they were oars, an organism such as the paramecium propels itself through its watery environment. In cells that do not move, cilia are used for other purposes. In the respiratory tract of humans, for example, millions of ciliated cells prevent inhaled dust, smog, and microorganisms from entering the lungs by sweeping them up on a current of mucus into the throat, where they are swallowed. Eukaryotic flagella and cilia are formed from basal bodies, small protein structures located just inside the plasma membrane. Basal bodies also help to anchor flagella and cilia.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Still other eukaryotic cells, such as amoebas and white blood cells, move by amoeboid motion, or crawling. They extrude their cytoplasm to form temporary pseudopodia, or false feet, which actually are placed in front of the cell, rather like extended arms. They then drag the trailing end of their cytoplasm up to the pseudopodia. A cell using amoeboid motion would lose a race to a euglena or paramecium. But while it is slow, amoeboid motion is strong enough to move cells against a current, enabling water-dwelling organisms to pursue and devour prey, for example, or white blood cells roaming the blood stream to stalk and engulf a bacterium or virus.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Nutrition</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3044/2770315475_be3feddd38.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Euglena, Showing Whiplike Flagellum<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The euglena is a single-celled alga with two or several flagella (depending on the species) located at one end for locomotion. Other algae, vertebrate sperm cells, and some protozoans and bacteria possess a single flagellum for movement.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Biophoto Associates/Science Source/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Movement in eukaryotes is also accomplished with cilia, short, hairlike proteins built by centrioles, which are barrel-shaped structures located in the cytoplasm that assemble and break down protein filaments. Typically, thousands of cilia extend through the plasma membrane and cover the surface of the cell, giving it a dense, hairy appearance. By beating its cilia as if they were oars, an organism such as the paramecium propels itself through its watery environment. In cells that do not move, cilia are used for other purposes. In the respiratory tract of humans, for example, millions of ciliated cells prevent inhaled dust, smog, and microorganisms from entering the lungs by sweeping them up on a current of mucus into the throat, where they are swallowed. Eukaryotic flagella and cilia are formed from basal bodies, small protein structures located just inside the plasma membrane. Basal bodies also help to anchor flagella and cilia.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Still other eukaryotic cells, such as amoebas and white blood cells, move by amoeboid motion, or crawling. They extrude their cytoplasm to form temporary pseudopodia, or false feet, which actually are placed in front of the cell, rather like extended arms. They then drag the trailing end of their cytoplasm up to the pseudopodia. A cell using amoeboid motion would lose a race to a euglena or paramecium. But while it is slow, amoeboid motion is strong enough to move cells against a current, enabling water-dwelling organisms to pursue and devour prey, for example, or white blood cells roaming the blood stream to stalk and engulf a bacterium or virus.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Nutrition</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3228/2770315627_d724eece9d.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Mitochondria<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Mitochondria, minute sausage-shaped structures found in the clear cytoplasm of the cell, are responsible for energy production. Mitochondria contain enzymes that help convert food material into adenosine triphosphate (ATP), which can be used directly by the cell as an energy source. Mitochondria tend to be concentrated near cellular structures that require large inputs of energy, such as the flagellum, which is responsible for movement in sperm cells and single-celled plants and animals.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Don Fawcett-Keith Porter/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Cells require energy for a variety of functions, including moving, building up and breaking down molecules, and transporting substances across the plasma membrane. Nutrients contains energy, but cells must convert the energy locked in nutrients to another form—specifically, the ATP molecule, the cell’s energy battery—before it is useful. In single-celled eukaryotic organisms, such as the paramecium, and in multicellular eukaryotic organisms, such as plants, animals, and fungi, mitochondria are responsible for this task. The interior of each mitochondrion consists of an inner membrane that is folded into a mazelike arrangement of separate compartments called cristae. Within the cristae, enzymes form an assembly line where the energy in glucose and other energy-rich nutrients is harnessed to build ATP; thousands of ATP molecules are constructed each second in a typical cell. In most eukaryotic cells, this process requires oxygen and is known as aerobic respiration.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Some prokaryotic organisms also carry out aerobic respiration. They lack mitochondria, however, and carry out aerobic respiration in the cytoplasm with the help of enzymes sequestered there. Many prokaryote species live in environments where there is little or no oxygen, environments such as mud, stagnant ponds, or within the intestines of animals. Some of these organisms produce ATP without oxygen in a process known as anaerobic respiration, where sulfur or other substances take the place of oxygen. Still other prokaryotes, and yeast, a single-celled eukaryote, build ATP without oxygen in a process known as fermentation.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Almost all organisms rely on the sugar glucose to produce ATP. Glucose is made by the process of photosynthesis, in which light energy is transformed to the chemical energy of glucose. Animals and fungi cannot carry out photosynthesis and depend on plants and other photosynthetic organisms for this task. In plants, as we have seen, photosynthesis takes place in organelles called chloroplasts. Chloroplasts contain numerous internal compartments called thylakoids where enzymes aid in the energy conversion process. A single leaf cell contains 40 to 50 chloroplasts. With sufficient sunlight, one large tree is capable of producing upwards of two tons of sugar in a single day. Photosynthesis in prokaryotic organisms—typically aquatic bacteria—is carried out with enzymes clustered in plasma membrane folds called chromatophores. Aquatic bacteria produce the food consumed by tiny organisms living in ponds, rivers, lakes, and seas.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">D<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Protein Synthesis</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3121/2770315811_2463b46ab6.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Ribosomes<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">On the surface of the rough endoplasmic reticulum are numerous small, dark structures called ribosomes. Ribosomes, which are also found floating free in the cytoplasm, are the sites of protein synthesis.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Don W. Fawcett/Science Source/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">A typical cell must have on hand about 30,000 proteins at any one time. Many of these proteins are enzymes needed to construct the major molecules used by cells—carbohydrates, lipids, proteins, and nucleic acids—or to aid in the breakdown of such molecules after they have worn out. Other proteins are part of the cell’s structure—the plasma membrane and ribosomes, for example. In animals, proteins also function as hormones and antibodies, and they function like delivery trucks to transport other molecules around the body. Hemoglobin, for example, is a protein that transports oxygen in red blood cells. The cell’s demand for proteins never ceases.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Before a protein can be made, however, the molecular directions to build it must be extracted from one or more genes. In humans, for example, one gene holds the information for the protein insulin, the hormone that cells need to import glucose from the bloodstream, while at least two genes hold the information for collagen, the protein that imparts strength to skin, tendons, and ligaments. The process of building proteins begins when enzymes, in response to a signal from the cell, bind to the gene that carries the code for the required protein, or part of the protein. The enzymes transfer the code to a new molecule called messenger RNA, which carries the code from the nucleus to the cytoplasm. This enables the original genetic code to remain safe in the nucleus, with messenger RNA delivering small bits and pieces of information from the DNA to the cytoplasm as needed. Depending on the cell type, hundreds or even thousands of molecules of messenger RNA are produced each minute.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Once in the cytoplasm, the messenger RNA molecule links up with a ribosome. The ribosome moves along the messenger RNA like a monorail car along a track, stimulating another form of RNA—transfer RNA—to gather and link the necessary amino acids, pooled in the cytoplasm, to form the specific protein, or section of protein. The protein is modified as necessary by the endoplasmic reticulum and Golgi apparatus before embarking on its mission. Cells teem with activity as they forge the numerous, diverse proteins that are indispensable for life. For a more detailed discussion about protein synthesis, <i>see </i>Genetics: The Genetic Code.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">E<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Cell Division</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3224/2770315897_f35481c050.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">First Cell Divisions<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">As a fertilized egg goes through its first divisions, the daughter cells become progressively smaller. When there are a hundred or more cells, they form a hollow ball of cells, called a blastula, surrounding a fluid-filled cavity. Later divisions produce three layers of cells—endoderm (inner), mesoderm (middle), and ectoderm (outer)—from which the principal features of the animal will differentiate.<o:p></o:p></span></p> <span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">BBC Worldwide Americas, Inc.</span><br /><img src="http://farm4.static.flickr.com/3192/2771162926_550ffedb46.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Mitosis<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Most cells divide at some time during their life cycle, and some divide dozens of times before they die. Organisms rely on cell division for reproduction, growth, and repair and replacement of damaged or worn out cells. Three types of cell division occur: binary fission, mitosis, and meiosis. Binary fission, the method used by prokaryotes, produces two identical cells from one cell. The more complex process of mitosis, which also produces two genetically identical cells from a single cell, is used by many unicellular eukaryotic organisms for reproduction. Multicellular organisms use mitosis for growth, cell repair, and cell replacement. In the human body, for example, an estimated 25 million mitotic cell divisions occur every second in order to replace cells that have completed their normal life cycles. Cells of the liver, intestine, and skin may be replaced every few days. Recent research indicates that even brain cells, once thought to be incapable of mitosis, undergo cell division in the part of the brain associated with memory.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The type of cell division required for sexual reproduction is meiosis. Sexually reproducing organisms include seaweeds, fungi, plants, and animals—including, of course, human beings. Meiosis differs from mitosis in that cell division begins with a cell that has a full complement of chromosomes and ends with gamete cells, such as sperm and eggs, that have only half the complement of chromosomes. When a sperm and egg unite during fertilization, the cell resulting from the union, called a zygote, contains the full number of chromosomes.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">IV<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">ORIGIN OF CELLS</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3234/2770316191_d873c1baf3.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Fossilized Trilobites<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Scientists study fossils to trace the evolution of life from simple cells to more complex organisms. Shown here are fossils of trilobites, primitive arthropods that once dominated the seas but became extinct about 250 million years ago.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">James L. Amos/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The story of how cells evolved remains an open and actively investigated question in science (<i>see </i>Life). The combined expertise of physicists, geologists, chemists, and evolutionary biologists has been required to shed light on the evolution of cells from the nonliving matter of early Earth. The planet formed about 4.5 billion years ago, and for millions of years, violent volcanic eruptions blasted substances such as carbon dioxide, nitrogen, water, and other small molecules into the air. These small molecules, bombarded by ultraviolet radiation and lightning from intense storms, collided to form the stable chemical bonds of larger molecules, such as amino acids and nucleotides—the building blocks of proteins and nucleic acids. Experiments indicate that these larger molecules form spontaneously under laboratory conditions that simulate the probable early environment of Earth.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Scientists speculate that rain may have carried these molecules into lakes to create a primordial soup—a breeding ground for the assembly of proteins, the nucleic acid RNA, and lipids. Some scientists postulate that these more complex molecules formed in hydrothermal vents rather than in lakes. Other scientists propose that these key substances may have reached Earth on meteorites from outer space. Regardless of the origin or environment, however, scientists do agree that proteins, nucleic acids, and lipids provided the raw materials for the first cells. In the laboratory, scientists have observed lipid molecules joining to form spheres that resemble a cell’s plasma membrane. As a result of these observations, scientists postulate that millions of years of molecular collisions resulted in lipid spheres enclosing RNA, the simplest molecule capable of self-replication. These primitive aggregations would have been the ancestors of the first prokaryotic cells.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Fossil studies indicate that cyanobacteria, bacteria capable of photosynthesis, were among the earliest bacteria to evolve, an estimated 3.4 billion to 3.5 billion years ago. In the environment of the early Earth, there was no oxygen, and cyanobacteria probably used fermentation to produce ATP. Over the eons, cyanobacteria performed photosynthesis, which produces oxygen as a byproduct; the result was the gradual accumulation of oxygen in the atmosphere. The presence of oxygen set the stage for the evolution of bacteria that used oxygen in aerobic respiration, a more efficient ATP-producing process than fermentation. Some molecular studies of the evolution of genes in archaebacteria suggest that these organisms may have evolved in the hot waters of hydrothermal vents or hot springs slightly earlier than cyanobacteria, around 3.5 billion years ago. Like cyanobacteria, archaebacteria probably relied on fermentation to synthesize ATP.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Eukaryotic cells may have evolved from primitive prokaryotes about 2 billion years ago. One hypothesis suggests that some prokaryotic cells lost their cell walls, permitting the cell’s plasma membrane to expand and fold. These folds, ultimately, may have given rise to separate compartments within the cell—the forerunners of the nucleus and other organelles now found in eukaryotic cells. Another key hypothesis is known as endosymbiosis. Molecular studies of the bacteria-like DNA and ribosomes in mitochondria and chloroplasts indicate that mitochondrion and chloroplast ancestors were once free-living bacteria. Scientists propose that these free-living bacteria were engulfed and maintained by other prokaryotic cells for their ability to produce ATP efficiently and to provide a steady supply of glucose. Over generations, eukaryotic cells complete with mitochondria—the ancestors of animals—or with both mitochondria and chloroplasts—the ancestors of plants—evolved (<i>see </i>Evolution).<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">V<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">THE DISCOVERY AND STUDY OF CELLS</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3111/2770316301_e761306fc7.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Hooke’s Microscope<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">English scientist Robert Hooke built this microscope in the 17th century and used it to conduct pioneering research. He discovered the cell structure of plants by observing a thin slice of cork under his microscope.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Cecil Fox/Science Source/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The first observations of cells were made in 1665 by English scientist Robert Hooke, who used a crude microscope of his own invention to examine a variety of objects, including a thin piece of cork. Noting the rows of tiny boxes that made up the dead wood’s tissue, Hooke coined the term <i>cell</i> because the boxes reminded him of the small cells occupied by monks in a monastery. While Hooke was the first to observe and describe cells, he did not comprehend their significance. At about the same time, the Dutch maker of microscopes Antoni van Leeuwenhoek pioneered the invention of one of the best microscopes of the time. Using his invention, Leeuwenhoek was the first to observe, draw, and describe a variety of living organisms, including bacteria gliding in saliva, one-celled organisms cavorting in pond water, and sperm swimming in semen. Two centuries passed, however, before scientists grasped the true importance of cells.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Modern ideas about cells appeared in the 1800s, when improved light microscopes enabled scientists to observe more details of cells. Working together, German botanist Matthias Jakob Schleiden and German zoologist Theodor Schwann recognized the fundamental similarities between plant and animal cells. In 1839 they proposed the revolutionary idea that all living things are made up of cells. Their theory gave rise to modern biology: a whole new way of seeing and investigating the natural world.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">By the late 1800s, as light microscopes improved still further, scientists were able to observe chromosomes within the cell. Their research was aided by new techniques for staining parts of the cell, which made possible the first detailed observations of cell division, including observations of the differences between mitosis and meiosis in the 1880s. In the first few decades of the 20th century, many scientists focused on the behavior of chromosomes during cell division. At that time, it was generally held that mitochondria transmitted the hereditary information. By 1920, however, scientists determined that chromosomes carry genes and that genes transmit hereditary information from generation to generation.</span><br /><img src="http://farm4.static.flickr.com/3033/2770316377_f38eabecba.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Antoni van Leeuwenhoek<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Although lacking basic scientific training, Antoni van Leeuwenhoek is credited with inventing the precursor to the modern microscope. Leeuwenhoek was the first to document the structure of red blood corpuscles and the nature of the circulatory system. In addition to describing animalcules (protozoans and bacteria), Leeuwenhoek also accurately described the life cycles of many types of insects.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Culver Pictures<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">During the same period, scientists began to understand some of the chemical processes in cells. In the 1920s, the ultracentrifuge was developed. The ultracentrifuge is an instrument that spins cells or other substances in test tubes at high speeds, which causes the heavier parts of the substance to fall to the bottom of the test tube. This instrument enabled scientists to separate the relatively abundant and heavy mitochondria from the rest of the cell and study their chemical reactions. By the late 1940s, scientists were able to explain the role of mitochondria in the cell. Using refined techniques with the ultracentrifuge, scientists subsequently isolated the smaller organelles and gained an understanding of their functions.</span><br /><img src="http://farm4.static.flickr.com/3060/2771163532_ec25f9233e.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Francis Crick and James Watson<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The deoxyribonucleic acid (DNA) molecule is the genetic blueprint for each cell and ultimately the blueprint that determines every characteristic of a living organism. In 1953 American biochemist James Watson, <i>left,</i> and British biophysicist Francis Crick, <i>right,</i> described the structure of the DNA molecule as a double helix, somewhat like a spiral staircase with many individual steps. Their work was aided by X-ray diffraction pictures of the DNA molecule taken by British biophysicist Maurice Wilkins and British physical chemist Rosalind Franklin. In 1962 Crick, Watson, and Wilkins received the Nobel Prize for their pioneering work on the structure of the DNA molecule.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">While some scientists were studying the functions of cells, others were examining details of their structure. They were aided by a crucial technological development in the 1940s: the invention of the electron microscope, which uses high-energy electrons instead of light waves to view specimens. New generations of electron microscopes have provided resolution, or the differentiation of separate objects, thousands of times more powerful than that available in light microscopes. This powerful resolution revealed organelles such as the endoplasmic reticulum, lysosomes, the Golgi apparatus, and the cytoskeleton. The scientific fields of cell structure and function continue to complement each other as scientists explore the enormous complexity of cells.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The discovery of the structure of DNA in 1953 by American biochemist James D. Watson and British biophysicist Francis Crick ushered in the era of molecular biology. Today, investigation inside the world of cells—of genes and proteins at the molecular level—constitutes one of the largest and fastest moving areas in all of science. One particularly active field in recent years has been the investigation of cell signaling, the process by which molecular messages find their way into the cell via a series of complex protein pathways in the cell.</span><br /><img src="http://farm4.static.flickr.com/3284/2770316685_50ff275e4c.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Scanning Electron Microscope<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">This scanning electron microscope (SEM) at the University of California, Berkeley is located to the left with the computer images of the specimen on the computer screens to the right. Although a SEM cannot resolve objects as small as a transmission electron microscope, the images produced by the SEM are more useful for seeing the three-dimensional aspect of the surface structure of small objects.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Lawrence Migdale/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Another busy area in cell biology concerns programmed cell death, or apoptosis. Millions of times per second in the human body, cells commit suicide as an essential part of the normal cycle of cellular replacement. This also seems to be a check against disease: When mutations build up within a cell, the cell will usually self-destruct. If this fails to occur, the cell may divide and give rise to mutated daughter cells, which continue to divide and spread, gradually forming a growth called a tumor. This unregulated growth by rogue cells can be benign, or harmless, or cancerous, which may threaten healthy tissue. The study of apoptosis is one avenue that scientists explore in an effort to understand how cells become cancerous.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Scientists are also discovering exciting aspects of the physical forces within cells. Cells employ a form of architecture called tensegrity, which enables them to withstand battering by a variety of mechanical stresses, such as the pressure of blood flowing around cells or the movement of organelles within the cell. Tensegrity stabilizes cells by evenly distributing mechanical stresses to the cytoskeleton and other cell components. Tensegrity also may explain how a change in the cytoskeleton, where certain enzymes are anchored, initiates biochemical reactions within the cell, and can even influence the action of genes. The mechanical rules of tensegrity may also account for the assembly of molecules into the first cells. Such new insights—made some 300 years after the tiny universe of cells was first glimpsed—show that cells continue to yield fascinating new worlds of discovery.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 15pt;"><span style="font-size: 12pt; font-family: "Times New Roman","serif";"><br />Contributed By:<br />Christopher King<o:p></o:p></span></p> <b><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif";">Microsoft ® Encarta ® 2007.</span></b><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif";"> © 1993-2006 Microsoft Corporation. All rights reserved.</span>ghozian karamihttp://www.blogger.com/profile/13214011599962806335noreply@blogger.com0tag:blogger.com,1999:blog-192751622867664710.post-40185140385585359152009-01-02T16:19:00.000-08:002009-01-02T16:20:09.687-08:00All about coal<p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 24pt; font-family: "MS Reference Serif","serif";">Coal<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">I<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">INTRODUCTION</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3076/2770316893_1a63e5fc42.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Coal Miners<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">A coal train leaves a mine in Scranton, Pennsylvania, in 1919. United States President William Howard Taft created a federal Bureau of Mines with the objective of reducing mine accidents and fatalities.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">CORBIS-BETTMANN<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Coal, a combustible organic rock composed primarily of carbon, hydrogen, and oxygen. Coal is burned to produce energy and is used to manufacture steel. It is also an important source of chemicals used to make medicine, fertilizers, pesticides, and other products. Coal comes from ancient plants buried over millions of years in Earth’s crust, its outermost layer. Coal, petroleum, natural gas, and oil shale are all known as fossil fuels because they come from the remains of ancient life buried deep in the crust.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Coal is rich in hydrocarbons (compounds made up of the elements hydrogen and carbon). All life forms contain hydrocarbons, and in general, material that contains hydrocarbons is called organic material. Coal originally formed from ancient plants that died, decomposed, and were buried under layers of sediment during the Carboniferous Period, about 360 million to 290 million years ago. As more and more layers of sediment formed over this decomposed plant material, the overburden exerted increasing heat and weight on the organic matter. Over millions of years, these physical conditions caused coal to form from the carbon, hydrogen, oxygen, nitrogen, sulfur, and inorganic mineral compounds in the plant matter. The coal formed in layers known as seams.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Plant matter changes into coal in stages. In each successive stage, higher pressure and heat from the accumulating overburden increase the carbon content of the plant matter and drive out more of its moisture content. Scientists classify coal according to its <i>fixed carbon content</i>, or the amount of carbon the coal produces when heated under controlled conditions. Higher grades of coal have a higher fixed carbon content.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">II<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">MODERN USES OF COAL<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Eighty-six percent of the coal used in the United States is burned by electric power plants to produce electricity. When burned, coal generates energy in the form of heat. In a power plant that uses coal as fuel, this heat converts water into steam, which is pressurized to spin the shaft of a turbine. This spinning shaft drives a generator that converts the mechanical energy of the rotation into electric power (<i>see </i>Electric Motors and Generators; Steam Engine).<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Coal is also used in the steel industry. The steel industry uses coal by first heating it and converting it into coke, a hard substance consisting of nearly pure carbon. The coke is combined with iron ore and limestone. Then the mixture is heated to produce iron (<i>see </i>Iron and Steel Industry). Other industries use different coal gases given off during the coke-forming process to make fertilizers, solvents, medicine, pesticides, and other products.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Fuel companies convert coal into easily transportable gas or liquid fuels (<i>see </i>Synthetic Fuels). Coal-based vapor fuels are produced through the process of <i>gasification. </i>Gasification may be accomplished either at the site of the coalmine or in processing plants. In processing plants, the coal is heated in the presence of steam and oxygen to produce <i>synthesis gas</i>, a mixture of carbon monoxide, hydrogen, and methane used directly as fuel or refined into cleaner-burning gas.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">On-site gasification is accomplished by controlled, incomplete burning of an underground coal bed while adding air and steam. To do this, workers ignite the coal bed, pump air and steam underground into the burning coal, and then pump the resulting gases from the ground. Once the gases are withdrawn, they may be burned to produce heat or generate electricity. Or they may be used in synthetic gases to produce chemicals or to help create liquid fuels.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><i><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Liquefaction</span></i><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;"> processes convert coal into a liquid fuel that has a composition similar to that of crude petroleum. Coal can be liquefied either by direct or indirect processes. However, because coal is a hydrogen-deficient hydrocarbon, any process used to convert coal to liquid or other alternative fuels must add hydrogen. Four general methods are used for liquefaction: (1) pyrolysis and hydrocarbonization, in which coal is heated in the absence of air or in a stream of hydrogen; (2) solvent extraction, in which coal hydrocarbons are selectively dissolved and hydrogen is added to produce the desired liquids; (3) catalytic liquefaction, in which hydrogenation takes place in the presence of a catalyst; and (4) indirect liquefaction, in which carbon monoxide and hydrogen are combined in the presence of a catalyst. <o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">III<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">COAL FORMATION</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3041/2771164094_f9ebeab437.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">How Coal Forms<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The coal we find today formed from generations of plants that died in ancient tropical swamps and accumulated on the swamp bottoms. The plant material first formed a compact organic material called peat. As layers of sediment gradually accumulated over the peat, the pressure and heat exerted by the thickening layers gradually drove out the moisture and increased the carbon content of the peat, forming coal.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Coal is a sedimentary rock formed from plants that flourished millions of years ago when tropical swamps covered large areas of the world. Lush vegetation, such as early club mosses, horsetails, and enormous ferns, thrived in these swamps. Generations of this vegetation died and settled to the swamp bottom, and over time the organic material lost oxygen and hydrogen, leaving the material with a high percentage of carbon. Layers of mud and sand accumulated over the decomposed plant matter, compressing and hardening the organic material as the sediments deepened. Over millions of years, deepening sediment layers, known as overburden, exerted tremendous heat and pressure on the underlying plant matter, which eventually became coal.</span><br /><img src="http://farm4.static.flickr.com/3109/2770317287_3656c6a647.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Cutting Peat<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">A worker cuts peat from lush peatland in Ireland. Peat is the first stage in the transformation of vegetation into coal. For hundreds of years, people have cut, dried, and burned it for heating and cooking. This compact, dark-brown material contains about one third less heating value than coal.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Farrell Grenan/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Before decayed plant material forms coal, the plant material forms a dark brown, compact organic material known as peat. Although peat will burn when dried, it has a low carbon and high moisture content relative to coal. Most of coal’s heating value comes from carbon, whereas inorganic materials, such as moisture and minerals, detract from its heating value. For this reason, peat is a less efficient fuel source than coal. Over time, as layers of sediment accumulate over the peat, this organic material forms lignite, the lowest grade of coal. As the thickening geologic overburden gradually drives moisture from the coal and increases its fixed carbon content, coal evolves from lignite into successively higher-graded coals: subbituminous coal, bituminous coal, and anthracite. Anthracite, the highest rank of coal, has nearly twice the heating value of lignite (<i>see </i>Heat).<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Coal formation began during the Carboniferous Period (known as the <i>first coal age</i>), which spanned 360 million to 290 million years ago. Coal formation continued throughout the Permian, Triassic, Jurassic, Cretaceous, and Tertiary Periods (known collectively as the <i>second coal age</i>), which spanned 290 million to 1.6 million years ago. Coals formed during the first coal age are older, so they are generally located deeper in Earth’s crust. The greater heat and pressures at these depths produce higher-grade coals such as anthracite and bituminous coals. Conversely, coals formed during the second coal age under less intense heat and pressure are generally located at shallower depths. Consequently, these coals tend to be lower-grade subbituminous and lignite coals.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">IV<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">COMPONENTS OF COAL<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Coal contains organic (carbon-containing) compounds transformed from ancient plant material. The original plant material was composed of cellulose, the reinforcing material in plant cell walls; lignin, the substance that cements plant cells together; tannins, a class of compounds in leaves and stems; and other organic compounds, such as fats and waxes. In addition to carbon, these organic compounds contain hydrogen, oxygen, nitrogen, and sulfur. After a plant dies and begins to decay on a swamp bottom, hydrogen and oxygen (and smaller amounts of other elements) gradually dissociate from the plant matter, increasing its relative carbon content.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Coal also contains inorganic components, known as <i>ash</i>. Ash includes minerals such as pyrite and marcasite formed from metals that accumulated in the living tissues of the ancient plants. Quartz, clay, and other minerals are also added to coal deposits by wind and groundwater. Ash lowers the fixed carbon content of coal, decreasing its heating value.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">V<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">COAL DEPOSITS AND RESERVES</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3204/2771164508_5ee488c90a.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Coal Production and Consumption<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">A comparison of the top ten coal-producing countries and the top ten coal-consuming countries shows that China is both the leading producer and the leading consumer of coal. Coal is burned in power plants to produce electricity and in steel mills to make coke for the production of steel.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Although coal deposits exist in nearly every region of the world, commercially significant coal resources occur only in Europe, Asia, Australia, and North America. Commercially significant coal deposits occur in sedimentary rock basins, typically sandwiched as layers called beds or seams between layers of sandstone and shale.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">When experts develop estimates of the world’s coal supply, they distinguish between coal <i>reserves</i> and <i>resources</i>. Reserves are coal deposits that can be mined profitably with existing technology—that is, with current equipment and methods. Resources are an estimate of the world’s total coal deposits, regardless of whether the deposits are commercially accessible. Exploration geologists have found and mapped the world’s most extensive coal beds. At the beginning of 2001, global coal reserves were estimated at 984.2 billion metric tons, in which 1 metric ton equals 1,016 kg (2,240 lb). These reserves occurred in the following regions by order of importance: the Asia Pacific, including Australia, 29.7 percent; North America, 26.1 percent; Russia and the countries of the former Union of Soviet Socialist Republics (USSR), 23.4 percent; Europe, excluding the former USSR, 12.4 percent; Africa and the Middle East, 6.2 percent; and South and Central America, 2.2 percent. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Coal deposits in the United Kingdom, which led the world in coal production until the 20th century, extend throughout parts of England, Wales, and southern Scotland. Coalfields in western Europe underlie the Saar and Ruhr valleys in Germany, the Alsace region of France, and areas of Belgium. Coalfields in central Europe extend throughout parts of Poland, the Czech Republic, and Hungary. The most extensive and valuable coalfield in eastern Europe is the Donets Basin, between the Dnieper and Don rivers (in parts of Russia and Ukraine). Large coal deposits in Russia are being mined in the Kuznetsk Basin in southern Siberia. Coalfields underlying northwestern China are among the largest in the world. Mining of these fields began in the 20th century.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">United States coal reserves are located in six major regions, three of which produce the majority of domestically mined coal. The most productive region in the United States is the Appalachian Basin, covering parts of Pennsylvania, West Virginia, Kentucky, Tennessee, Ohio, and Alabama. Large quantities of coal have also been produced by both the Illinois Basin—extending through Illinois, Indiana, and Kentucky—and the Western Interior Region—extending through Missouri, Kansas, and Oklahoma. Other commercially important U.S. coal regions include the Powder River Basin, underlying parts of Montana and Wyoming; the Green River Basin in Wyoming; the Uinta Basin, covering areas of Utah and Colorado; and the San Juan Basin, underlying parts of Utah, New Mexico and Colorado.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In 2002 estimates of total U.S. coal reserves were approximately 246 billion metric tons. At the beginning of the 21st century production amounted to about 980 million metric tons each year.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">VI<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">COAL MINING<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Coal mining is the removal of coal from the ground. The mining method employed to extract the coal depends on the following criteria: (1) seam thickness, (2) the overburden thickness, (3) the ease of removal of the overburden, (4) the ease with which a shaft can be sunk to reach the coal seam, (5) the amount of coal extracted relative to the amount that cannot be removed, and (6) the market demand for the coal.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The two types of mining methods are surface mining and underground mining. In surface mining the layers of rock or soil overlying a coal seam are first removed after which the coal is extracted from the exposed seam. In underground mining, a shaft is dug to reach the coal seam. Currently, underground mining accounts for approximately 60 percent of the world recovery of coal.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Surface Mining</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3150/2771164654_16c74ae79e.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Giant Coal Bucket<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Strip miners often use extremely large buckets to level or move land. The buckets have sharp, slanted teeth on the front edge and are dragged along the surface of the ground by powerful machines. This bucket, used in the Big Muskie coal mine in Ohio, is the size of a small house.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">UPI/THE BETTMANN ARCHIVE<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Surface mining is used to reach coal reserves that are too shallow to be reached by other mining methods. Types of surface mining include open-pit mining, drift mining, slope mining, contour mining, and auger mining.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">A</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">1<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Open-pit Mining<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In open-pit mining, or strip mining, earth-moving equipment is used to remove the rocky overburden and then huge mechanical shovels scoop coal up from the underlying deposit. The modern coal industry has developed some of the largest industrial equipment ever made, including shovels capable of<i> </i>holding 290 metric tons of coal.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">To reach the coal, bulldozers clear the vegetation and soil. Depending on the hardness and depth of the exposed sedimentary rocks, these rocky layers may be shattered with explosives. To do this, workers drill <i>blast holes</i> into the overlying sedimentary rock, fill these holes with explosives, and then blast the overburden to fracture the rock. Once the broken rock is removed, coal is shoveled from the underlying deposit into giant earth-moving trucks for transport.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">A</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">2<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Drift Mining<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Drift mining is used when a horizontal seam of coal emerges at the surface on the side of a hill or mountain, and the opening into the mine can be made directly into the coal seam. This type of mining is generally the easiest and most economical type because excavation through rock is not necessary. If coal is available in this manner, it is likely to be mined.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">A</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">3<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Slope Mining<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Slope mining occurs when an inclined opening is used to tap the coal seam (or seams). A slope mine may follow the coal seam if the seam is inclined and exposed to the surface, or the slope may be driven through rock strata overlying the coal to reach a seam. Coal transportation from a slope mine can be accomplished by conveyor or by track haulage (using a trolley locomotive if the grade is not severe) or by pulling mine cars up the slope using an electric hoist and steel rope if the grade is steep. The most common practice is to use a belt conveyor.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">A</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">4<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Contour Mining<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Contour mining occurs on hilly or mountainous terrain, where workers use excavation equipment to cut into the hillside along its contour to remove the overlying rock and then mine the coal. The depth to which workers must cut into the hillside depends on factors such as hill slope and coal bed thickness. <o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">A</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">5<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Auger Mining<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Auger mining is frequently employed in open-pit mines where the thickness of the overburden is too great for open-pit mining to be cost-effective. Open-pit mining would require the lengthy and costly removal of the overburden, whereas auger mining is more efficient because it cuts through the overburden and removes the coal as it drills. In this technique, the miners drill a series of horizontal holes into the coal bed with a large auger (drill) powered by a diesel or gasoline engine. These augers are typically about 60 m (200 ft) long and 0.6 to 2.1 m (2 to 7 ft) in diameter. As these enormous drills bore into the coal seam, they discharge coal like a wood drill producing wood shavings. Additional auger lengths are added as the cutting head of the auger penetrates farther into the coal. Penetration continues until the cutting head drifts into the top or bottom of the coal seam, into a previous hole, or until the maximum torque (energy required to twist an object) of the auger is reached.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">A</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">6<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Satellite Aids to Surface Mining<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In the late 1990s some coal mining enterprises used technologies such as the global positioning system (GPS) to help guide the positioning of mining equipment. Satellites operated by the United States Air Force Space Command and leased to companies for commercial use track the position of mining equipment against a map of a mine’s topography. This map uses colors to distinguish soil that should be excavated, soil that should remain in place, and areas that should be filled in. The equipment driver observes this visual information on a monitor while operating the equipment. Some coal mining enterprises have used GPS to increase mining efficiency up to 30 percent. <o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Underground Mining</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3163/2770317881_709638aecb.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Big Pit Mining Museum, Blaenafon<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Coal mining was once the main industry of the Rhondda Valley in Great Britain. The Big Pit ("Pwll Mawr") coal mine ceased production in 1980 but its buildings and machinery were preserved and converted into a museum of mining. Visitors descend into the mine via the 90-m (300-ft) lift shaft to walk through underground roadways, air doors, stables (for pit ponies), and engine houses constructed by past generations of miners.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Spectrum Colour Library<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Underground, or deep, mining occurs when coal is extracted from a seam without removal of the overlying strata. Miners build a shaft mine that enters the earth through a vertical opening and descends from the surface to the coal seam. In the mine, the coal is extracted from the seam by various methods, including conventional mining, continuous mining, longwall mining, and room-and-pillar mining. <o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">B</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">1<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Conventional Mining<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Conventional mining, also called cyclic mining, involves a sequence of operations that proceed in the following order: (1) supporting the roof, (2) ventilation, (3) cutting, (4) drilling, (5) blasting, (6) coal removal, and (7) loading. First, miners make the roof above the seam safe and stable by timbering or by roof bolting, processes intended to prevent the roof from collapsing. At the same time, they create ventilation openings so that dangerous gases can escape and fresh air can reach the miners. Then one or more slots—a few centimeters wide and extending for several meters into the coal—are cut along the face of the coal seam, also known as the wall face, by a large, mobile cutting machine. The cut, or slot, provides easy access to the face and facilitates the breaking up of the coal, which is usually blasted from the seam by explosives known as permissible explosives. This type of explosive produces an almost flame-free explosion and markedly reduces the amount of noxious fumes in comparison with conventional explosives. The coal may then be transported by rubber-tired electric vehicles (shuttle cars) or by chain (or belt) conveyor systems.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">B</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">2<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Continuous Mining<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Continuous mining involves the use of a single machine known as a continuous miner that breaks the coal mechanically and loads it for transport. This mobile machine has a series of metal-studded rotating drums that gouge coal from the face of the coal seam. One continuous miner can mechanically break apart about 1.8 metric tons of coal per hour. Roof support is then installed, ventilation is advanced, and the coalface is ready for the next cycle. The method used to transport the coal requires the installation of mobile belt conveyors.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">B</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">3<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Longwall Mining<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The longwall mining system uses a remote-controlled self-advancing roof in which large blocks of coal are completely extracted in a continuous operation. Hydraulic or self-advancing jacks, known as chocks, support the roof at the immediate face as the coal is removed. As the face advances, the roof is allowed to collapse behind the remote-controlled, roof-building machinery. Miners then remove the fallen coal. Coal recovery is comparable to that attainable with the conventional or continuous mining systems. <o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">B</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">4<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Room-and-Pillar Mining<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Room-and-pillar mining is a means of developing a coalface and, at the same time, retaining supports for the roof. With this technique, rooms are developed from large, parallel tunnels driven into the solid coal, and the intervening pillars of coal are used to support the roof. The percentage of coal recovered from a seam depends on the number and size of protective pillars of coal thought necessary to support the roof safely. Workers may remove some coal pillars just before closing the mine.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">VII<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">COAL MINING SAFETY<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Coalmines are hazardous operations. In the 20th century, more than 100,000 miners died working in coalmines. Many accidents were caused by the mine structure failing through roof collapse or <i>rock bursts</i> (coal pillars exploding from the weight of excessive overburden). Other dangers that miners face include toxic or explosive gases released as the coal is mined, dangerous coal dust, and fires. Fires result when flammable gases trapped in the coal, such as methane, are released during mining operations and accidentally ignited.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Provision of adequate ventilation is an essential safety feature of underground coal mining. Not all of this ventilation is required to enable miners to work in comfort. Most of it is required to dilute the harmful gases, frequently termed damps, produced during mining operations.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Mine Failure<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In room-and-pillar mines deep underground, the extreme weight of the overlying rock can break the pillars down, either gradually or in a violent collapse. If the mine roof or floor consists of softer material such as clay, the massive weight of the overburden can slowly push the pillars into the floor or ceiling, endangering the stability of the mine. When the mine roof and floor consist of particularly hard rock, massive overhead weight can overload the pillars, sometimes causing a spontaneous collapse or rock burst.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Gases<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Because coal and natural gas form by similar natural processes, methane (a principal component of natural gas) is often trapped inside coal deposits. Gases trapped in deeper coal beds have a harder time escaping. Consequently, high-grade coals, which are typically buried deeper than low-grade coals, often contain more methane in the pores and fractures of the deposit. As coalminers saw or blast into a coal deposit, they can release these methane pockets, which may explode spontaneously, often with deadly results. Miners use a technique called <i>methane drainage</i> to reduce dangerous releases of methane. Before mining machinery cuts into the wall face, holes are drilled into the coal and methane is drawn out and piped to the surface.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Coalminers also risk being exposed to other deadly gases, including carbon monoxide, a poisonous by-product of partially burned coal. Carbon monoxide is deadly in quantities as little as 1 percent. It is especially prevalent in underground mines after a methane explosion. In the early 1800s, after a gas explosion, coalminers used canaries to test for carbon monoxide. If the canary died, the miners increased ventilation in the mine to remove the carbon monoxide. The miners then conducted the same test with another canary and repeated the process until a bird survived. Miners also tested for carbon monoxide and methane with a small flame. If the flame’s size increased, methane was present in the air; if the flame went out, carbon monoxide was present.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Other dangerous gases locked inside coal deposits include hydrogen sulfide, a poisonous, colorless gas with an odor of rotten eggs, and carbon dioxide, a colorless, odorless gas. To prevent injury from inhaling these gases, underground coalmines must be sufficiently ventilated. To do this fresh air is continuously pumped through ventilation holes to push out or dilute dangerous gases and provide air for miners to breathe.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">C<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Coal Dust<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">As coal is blasted, shredded, and hauled in a mine, large amounts of coal and silica dust are produced. Coal dust is extremely flammable, and if ignited it can be more violently explosive than methane. Miners can reduce the buildup of coal dust by injecting pressurized water into coal beds before the coal is blasted or cut, by spraying water at all points where dust is likely to be formed, and by installing dust extraction units at strategic points.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Miners who inhale coal dust over a prolonged period can damage their lung tissue. Often, these miners develop spots, lumps, or fibrous growths in their lungs, a condition known as black lung disease, a type of pneumoconiosis. Furthermore, black lung disease can develop into other, often fatal illnesses, including heart disease, emphysema, and cancer. To protect miners from black lung, many mines are equipped with coal-dust filtering units. Miners who operate drilling, cutting, or loading machinery should wear masks at all times.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">D<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Fires<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Coalmine fires can be triggered during routine mining operations. For example, sparks generated by mining equipment can ignite explosive gases, coal dust, and even the coal bed itself. Because coal beds provide an almost inexhaustible fuel source, once a coal seam is ignited, it can be extremely difficult to extinguish. The intense heat generated by burning coal can rupture the overlying rock strata, sometimes causing the roof to collapse. Uncontrollable fires in some coal deposits have continued burning for years, posing a danger to local communities.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Regulations to prevent and control mine fires have been enacted in the United States and other countries. The U.S. regulations require mining companies to install fire-fighting equipment and automatic fire-suppression systems in mines. Internal-combustion engines, which power mining machinery, such as trucks, shuttles, tractors, and scoops, reach high temperatures that can pose a fire hazard. As a result, this equipment must be designed and operated according to the guidelines of the U.S. Mine Safety and Health Administration. <o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">VIII<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">POSTMINING PROCESSES<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Once the coal has been mined, it must be prepared for commercial use and then either stored or transported.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Coal Preparation<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">As-mined<i> </i>coal, also known as run-of-mine coal, often contains unwanted impurities such as rock and dirt and comes in a mixture of different-sized fragments. Thus, another sequence of processes is necessary to make the coal consistent in quality and suitable for selling. These processes are called coal preparation or coal cleaning. Effective preparation of coal prior to combustion improves the homogeneity of the coal supplied, reduces transport costs, improves the burning efficiency, and produces fewer pollutants.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Coal preparation is the stage in coal production when the run-of-mine coal is processed into a range of clean, graded, and uniform coal products suitable for the commercial market, mostly power plants. In some cases, the run-of-mine coal is of such quality that it meets the user’s specifications without the need for preparation, in which case the coal would merely be crushed and put through a large sievelike device to deliver the specified product.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">A number of physical separation technologies are used in cleaning and preparing coal. After the raw run-of-mine coal is crushed, it is separated into various-sized fragments for optimum treatment. Larger material— lumps of coal about 10 to 150 mm (0.4 to 6 in) in length—is usually treated using a technology known as dense-medium separation. The dense medium is usually a liquid with a density just slightly greater than that of the coal. The coal can then be separated from other impurities, such as rock, by being floated in a tank containing the high-density liquid, which is usually a suspension of finely ground magnetite. Because the coal is lighter, it floats and is separated off, while heavier rock and other impurities sink and are removed as waste. Any magnetite mixed with the coal is separated using water sprays and is then recovered, using magnetic drums, and recycled.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The smaller-sized fragments are treated in a variety of ways. In the froth flotation method, coal particles are removed in a froth produced by blowing air into a water bath containing a chemical <i>reagent</i> (substance that takes part in a chemical reaction with another substance). The bubbles attract the coal but not the waste and are skimmed off to recover the smaller-sized fragments. After treatment, the smaller-sized fragments are screened and either dewatered or dried, and then recombined before going through final sampling and quality control procedures. Recombination also enables customers to selectively purchase different grades of coal. More expensive, higher quality supplies can be carefully mixed with lower quality coals to produce an average blend suited to the needs of commercial customers, such as power plants. <o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">A</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">1<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Transport and Storage<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Once the coal has been extracted, it is moved from the mine to the power plant or other place of use or it is stored. Over short distances coal is usually transported by conveyor or truck. For long distances trains, barges, ships, or pipelines are used. Preventive measures are taken at every stage during transport and storage to reduce potential environmental impacts. Dust can be controlled by using water sprays, compacting the coal, and enclosing the stockpiles. Sealed systems can be used to move the coal from the stockpiles to the combustion plant. Well-designed coal-storage facilities can limit the problem of contaminated water run-off. All water is carefully treated before reuse or disposal.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">IX<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">ENVIRONMENTAL ISSUES<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Because significant volumes of earth must be displaced to mine coal, coalmines and the resulting rock waste can harm the environment. Furthermore, burning coal releases environmentally harmful chemical compounds into the air.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Mining and Mining Waste</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3293/2770318351_b6f6f03112.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Coal Strip Mine<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">This excavated area, which borders farmland, has been strip mined for coal. Unless the strip mine is filled and revegetated, surface water runoff from the mined area can flush sediments and sulfur-bearing compounds (acid drainage) into nearby streams and rivers, endangering plant and wildlife communities.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Charles E. Rotkin/Corbis<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Surface mining has resulted in a great deal of damage to the landscape. Many surface mines have removed acres of vegetation and altered topographic features, such as hills and valleys, leaving soil exposed for erosion. Longwall mining, which allows the mine to collapse, results in widespread land subsidence, or sinking. Coal and rock waste, often dumped indiscriminately during surface and underground mining processes, weathers rapidly, producing <i>acid drainage</i>. Acid drainage contains sulfur-bearing compounds that combine with oxygen in water vapor to form sulfuric acid. In addition, weathering of coalmine waste can produce alkaline compounds, heavy metals, and sediments. Acid drainage, alkaline compounds, heavy metals, and sediment leached from mine waste into groundwater or washed away by rainwater can pollute streams, rivers, and lakes. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Today, enterprises in many countries must secure government permits before mining for coal. In the United States, mining companies must submit plans detailing proposed methods for blasting, road construction, land reclamation, and waste disposal. New land reclamation methods, driven by stringent laws and regulations, require coal mining companies to restore strip-mined landscapes to nearly premined conditions.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Burning Coal<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The burning of coal produces environmentally harmful emissions. Some gases produced from burning coal, such as carbon dioxide, are known as greenhouse gases because they trap the Earth’s heat like the roof of a greenhouse and may contribute to global warming. Other emissions from coal combustion can lead to air and water pollution.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">B</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">1<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Greenhouse Effect<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Earth absorbs much of the heat energy radiated from the Sun. The planet then reradiates this heat back into the atmosphere. Carbon dioxide and some other gases that are naturally present in the atmosphere prevent much of the heat from escaping back into space, maintaining Earth at a temperature that can support life. These gases are known as greenhouse gases because they trap the Sun’s heat in much the same way as the glass roof of a botanical greenhouse (<i>see </i>Greenhouse Effect). However, the immense quantity of fossil fuels burned during the world’s rapid industrialization over the last 200 years has raised levels of carbon dioxide in the atmosphere by about 28 percent. This dramatic increase in atmospheric carbon dioxide, coupled with continuing depletion of the world’s forests, which absorb carbon dioxide, has led many scientists to predict a heating of the atmosphere on a global scale. Such a global warming could disrupt weather patterns, cause the polar ice caps to melt, and possibly lead to other environmental problems.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Today, many industrial countries are working to reduce emissions of greenhouse gases.<i> </i>One proposal is to establish a system requiring companies that create greenhouse gases to pay to emit carbon dioxide above a specified level. This payment could take several forms, including (1) purchasing the rights to pollute from a company with carbon dioxide emissions below the specified level; (2) purchasing forests, which absorb carbon dioxide, and keeping them from being developed; or (3) paying to upgrade a plant in a developing country, thus lowering that plant’s carbon dioxide emissions.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">B</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">2<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Acid Rain</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3115/2770318649_34757450f4.jpg?v=0" /><br /><br /><img src="http://farm4.static.flickr.com/3249/2770318817_42ac588f6c.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Anatomy of an Air Scrubber<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">A venturi air scrubber removes polluting particles from gas emissions by spraying a scrubber liquid directly into the emissions. The scrubber liquid surrounds the dirty particles, which are carried with the gas emissions into the separator cylinder. As the gas cycles upward through the cylinder, the liquid-covered particles drop from the gas into the contaminated liquid reservoir.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The U.S. Clean Air Act, implemented in 1970 and revised in 1970 and 1990, is the federal law regulating air pollution in the United States. This legislation has significantly reduced emissions of sulfur oxides, known as <i>acid gases </i>(<i>see </i>Air Pollution). For example, the Clean Air Act requires facilities such as coal-burning power plants to burn low-sulfur coal. High-grade coals (coals with a higher heating value) generally contain more sulfur than low-grade coals such as lignite and subbituminous coal. Therefore, certain processes have been developed to remove sulfur-bearing compounds from high-grade coal prior to burning. The Clean Air Act also requires use of pollution-trapping equipment such as <i>air scrubbers</i> (devices installed inside plant smokestacks to remove sulfur dioxide from coal emissions). In addition, revisions to the Clean Air Act in 1990 established a system that allows coal-burning power plants to buy and sell sulfur emission permits with one another. This system tries to establish a financial incentive to lower sulfur emissions by rewarding power plants that reduce emissions below federal levels. Power plants that cut their sulfur emissions below the permitted levels can sell permits to burn coal to companies that exceed federal levels. Companies that reduce emissions reap financial rewards while polluters must pay an extra cost to pollute.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">B</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">3<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Fly Ash<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The burning of coal releases ashes known as fly ash into the atmosphere. Fly ash contains toxic metals such as arsenic and cadmium. In the United States the Clean Air Act requires that fly ash be removed from coal emissions. As a result, antipollution devices such as air scrubbers, baghouses, and electrostatic precipitators<i> </i>are used to trap these pollutants. Baghouses work like giant vacuum cleaners, drawing coal emissions through giant fabric bags that trap the fly ash inside. Electrostatic precipitators use <i>discharge electrodes</i> (electrically charged parts of an electric circuit) to trap ash particles. In an electrostatic precipitator the electrodes are located between long, positively charged collection plates. As the fly ash passes between these collection plates, the discharge electrodes give each particle a negative charge. These negatively charged particles are then attracted to and held by the positively charged collection plates.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">X<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">CLEAN COAL TECHNOLOGY<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Since 1986 the United States government and private industry have been working together to develop cleaner and more efficient ways to harness the energy in coal. This joint effort, known as the Clean Coal Technology Demonstration Program, includes several technologies, such as fluidized bed coal combustion, furnace sorbent injection, and advanced flue-gas desulfurization.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Fluidized bed coal combustion burns coal in a limestone bed that transfers heat to water, generating steam. This steam is pressurized and used to turn a turbine shaft, which subsequently drives an electric generator. The limestone absorbs sulfur dioxide emitted by the coal, thus reducing the amount of acid gases released during combustion.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">A process called furnace sorbent injection<i> </i>removes acid gas from coal emissions at less cost than expensive scrubbers. A <i>sorbent</i> is a highly absorbent material, such as powdered limestone. It is injected into furnaces, where the powdered limestone reacts with the acid gases emitted by the burning coal. The used powder is siphoned away through the furnace outtake and is captured (with fly ash) in a baghouse or electrostatic precipitator.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">A process called advanced flue-gas desulfurization<i> </i>also removes acid gas from burning coal without expensive scrubbers. Emissions from burning coal are piped into a container called an absorber, where the acid gases react with an absorbing solution (such as a mixture of lime, water, and oxygen). This reaction forms gypsum, a soft white mineral valuable as an ingredient in cement.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">XI<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">HISTORY OF COAL USE<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Early humans used wood, straw, and dried dung for fuel. One of the earliest known references to coal was made by Greek philosopher and scientist Aristotle, who referred to charcoallike rock found in Thrace (a region on the northeastern shore of the Aegean Sea) and in northeastern Italy. Although authentic records are unavailable, historians believe coal was first used commercially in China. Reports indicate the Fu-shun mine in northeastern China provided coal for smelting copper and for casting coins around 1000 <span style="text-transform: uppercase;">bc</span>.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Coal cinders found among Roman ruins in England suggest that the Romans harnessed energy from coal before <span style="text-transform: uppercase;">ad</span> 400. The written records of the monk Reinier of Liège from the early 13th century describe workers mining black earth in Europe. Blacksmiths used this black earth as fuel for metalworking. Other historical records contain numerous references to coal mining in England, in Scotland, and in continental Europe throughout the 13th century. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In the early 18th century the demand for coal escalated when English iron founders John Wilkinson and Abraham Darby used coal, in the form of coke, to manufacture iron. An almost constant demand for coal was created by metallurgical and engineering developments, most notably the invention of the coal-burning steam engine by Scottish mechanical engineer James Watt in 1769.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Until the American Revolution (1775-1783), most of the coal consumed by the American colonies was imported from England or Nova Scotia. Wartime shortages and the need to manufacture munitions spurred the formation of small American coal-mining companies that mined Virginia’s Appalachian bituminous field and other deposits. By the early 1830s U.S. mining companies had emerged throughout the Appalachian region and along the Ohio, Illinois, and Mississippi rivers. The construction of the first practical locomotive in 1804 in England by British engineer Richard Trevithick sparked a tremendous demand for coal. The growth of the railroad industry and the subsequent rise of the steel industry in the 1800s spurred enormous growth in the coal industry in the United States and Europe.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The widespread use of petroleum as a fuel before, during, and after World War I (1914-1918) eventually reduced the demand for coal. The change from coal to oil as fuel in warships (particularly in the United States and British navies) in the early 1900s, the switch in the railway industry to diesel-electric locomotive engines in the 1940s and 1950s, and increasing use of natural gas as a heating fuel all contributed to a decline in coal production. In the 1980s and 1990s, petroleum continued to supplant coal in industry and was increasingly used in oil-fired power plants. Still, electric utilities continued to burn large amounts of coal to produce electricity. <o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 15pt;"><span style="font-size: 12pt; font-family: "Times New Roman","serif";"><br />Contributed By:<br />James Speight<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif";">Microsoft ® Encarta ® 2007.</span></b><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif";"> © 1993-2006 Microsoft Corporation. All rights reserved.<o:p></o:p></span></p> <p class="MsoNormal"><o:p> </o:p></p>ghozian karamihttp://www.blogger.com/profile/13214011599962806335noreply@blogger.com2tag:blogger.com,1999:blog-192751622867664710.post-11344348154710537222009-01-02T16:17:00.000-08:002009-01-02T16:18:36.416-08:00Computer<p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:24;" >Computer<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >I<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >INTRODUCTION</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3158/2771166082_d2301f288e.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Babbage's Difference Engine<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Considered by many to be a direct forerunner of the modern computer, the Difference Engine was able to compute mathematical tables. This woodcut shows a small portion of the ingenious machine, which was designed by Charles Babbage in the 1820s. Although the device did not have a memory, Babbage’s later idea for the Analytical Engine would have been a true, programmable computer if the technology of his time had been able to build it.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >THE BETTMANN ARCHIVE<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Computer, machine that performs tasks, such as calculations or electronic communication, under the control of a set of instructions called a program. Programs usually reside within the computer and are retrieved and processed by the computer’s electronics. The program results are stored or routed to output devices, such as video display monitors or printers. Computers perform a wide variety of activities reliably, accurately, and quickly.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >II<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >USES OF COMPUTERS<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >People use computers in many ways. In business, computers track inventories with bar codes and scanners, check the credit status of customers, and transfer funds electronically. In homes, tiny computers embedded in the electronic circuitry of most appliances control the indoor temperature, operate home security systems, tell the time, and turn videocassette recorders (VCRs) on and off. Computers in automobiles regulate the flow of fuel, thereby increasing gas mileage, and are used in anti-theft systems. Computers also entertain, creating digitized sound on stereo systems or computer-animated features from a digitally encoded laser disc. Computer programs, or applications, exist to aid every level of education, from programs that teach simple addition or sentence construction to programs that teach advanced calculus. Educators use computers to track grades and communicate with students; with computer-controlled projection units, they can add graphics, sound, and animation to their communications (<i>see </i>Computer-Aided Instruction). Computers are used extensively in scientific research to solve mathematical problems, investigate complicated data, or model systems that are too costly or impractical to build, such as testing the air flow around the next generation of aircraft. The military employs computers in sophisticated communications to encode and unscramble messages, and to keep track of personnel and supplies.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >III<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >HOW COMPUTERS WORK</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3138/2770319263_c931ec0491.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Computer System<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >A typical computer system consists of a central processing unit (CPU), input devices, storage devices, and output devices. The CPU consists of an arithmetic/logic unit, registers, control section, and internal bus. The arithmetic/logic unit carries out arithmetical and logical operations. The registers store data and keep track of operations. The control unit regulates and controls various operations. The internal bus connects the units of the CPU with each other and with external components of the system. For most computers, the principal input device is a keyboard. Storage devices include external floppy disc drives and internal memory boards. Output devices that display data include monitors and printers.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >The physical computer and its components are known as hardware. Computer hardware includes the memory that stores data and program instructions; the central processing unit (CPU) that carries out program instructions; the input devices, such as a keyboard or mouse, that allow the user to communicate with the computer; the output devices, such as printers and video display monitors, that enable the computer to present information to the user; and <i>buses</i> (hardware lines or wires) that connect these and other computer components. The programs that run the computer are called software. Software generally is designed to perform a particular type of task—for example, to control the arm of a robot to weld a car’s body, to write a letter, to display and modify a photograph, or to direct the general operation of the computer.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >The Operating System<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >When a computer is turned on it searches for instructions in its memory. These instructions tell the computer how to start up. Usually, one of the first sets of these instructions is a special program called the operating system, which is the software that makes the computer work. It prompts the user (or other machines) for input and commands, reports the results of these commands and other operations, stores and manages data, and controls the sequence of the software and hardware actions. When the user requests that a program run, the operating system loads the program in the computer’s memory and runs the program. Popular operating systems, such as Microsoft Windows and the Macintosh system (Mac OS), have graphical user interfaces (GUIs)—that use tiny pictures, or icons, to represent various files and commands. To access these files or commands, the user clicks the mouse on the icon or presses a combination of keys on the keyboard. Some operating systems allow the user to carry out these tasks via voice, touch, or other input methods.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >Computer Memory</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3115/2771166656_c340a2e93b.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Inside a Computer Hard Drive<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >The inside of a computer hard disk drive consists of four main components. The round disk platter is usually made of aluminum, glass, or ceramic and is coated with a magnetic media that contains all the data stored on the hard drive. The yellow armlike device that extends over the disk platter is known as the head arm and is the device that reads the information off of the disk platter. The head arm is attached to the head actuator, which controls the head arm. Not shown is the chassis which encases and holds all the hard disk drive components.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >FOTO-WERBUNG/Phototake NYC<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >To process information electronically, data are stored in a computer in the form of binary digits, or bits, each having two possible representations (0 or 1). If a second bit is added to a single bit of information, the number of representations is doubled, resulting in four possible combinations: 00, 01, 10, or 11. A third bit added to this two-bit representation again doubles the number of combinations, resulting in eight possibilities: 000, 001, 010, 011, 100, 101, 110, or 111. Each time a bit is added, the number of possible patterns is doubled. Eight bits is called a byte; a byte has 256 possible combinations of 0s and 1s. <i>See also </i>Expanded Memory; Extended Memory.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >A byte is a useful quantity in which to store information because it provides enough possible patterns to represent the entire alphabet, in lower and upper cases, as well as numeric digits, punctuation marks, and several character-sized graphics symbols, including non-English characters such as </span><span style=";font-family:Symbol;font-size:9;color:black;" >p</span><span style=";font-family:";font-size:9;color:black;" >. A byte also can be interpreted as a pattern that represents a number between 0 and 255. A kilobyte—1,024 bytes—can store about 1,000 characters; a megabyte can store about 1 million characters; a gigabyte can store about 1 billion characters; and a terabyte can store about 1 trillion characters. Computer programmers usually decide how a given byte should be interpreted—that is, as a single character, a character within a string of text, a single number, or part of a larger number. Numbers can represent anything from chemical bonds to dollar figures to colors to sounds.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >The physical memory of a computer is either random access memory (RAM), which can be read or changed by the user or computer, or read-only memory (ROM), which can be read by the computer but not altered in any way. One way to store memory is within the circuitry of the computer, usually in tiny computer chips that hold millions of bytes of information. The memory within these computer chips is RAM. Memory also can be stored outside the circuitry of the computer on external storage devices, such as magnetic floppy disks, which can store about 2 megabytes of information; hard drives, which can store gigabytes of information; compact discs (CDs), which can store up to 680 megabytes of information; and digital video discs (DVDs), which can store 8.5 gigabytes of information. A single CD can store nearly as much information as several hundred floppy disks, and some DVDs can hold more than 12 times as much data as a CD.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >C<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >The Bus<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >The bus enables the components in a computer, such as the CPU and the memory circuits, to communicate as program instructions are being carried out. The bus is usually a flat cable with numerous parallel wires. Each wire can carry one bit, so the bus can transmit many bits along the cable at the same time. For example, a 16-bit bus, with 16 parallel wires, allows the simultaneous transmission of 16 bits (2 bytes) of information from one component to another. Early computer designs utilized a single or very few buses. Modern designs typically use many buses, some of them specialized to carry particular forms of data, such as graphics.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >D<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >Input Devices</span></p></td></tr></tbody></table><img src="http://farm4.static.flickr.com/3210/2771166948_c85b37eb1e.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Light Pen<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Light pens are electronic pointers that allow users to modify designs on-screen. The hand-held pointer contains sensors that send signals to the computer whenever light is recorded. The computer’s screen is not lit up all at once, but traced row-by-row by an electron beam sixty times every second. Because of this, the computer is able to determine the pen’s position by noting exactly when the pen detects the electron beam passing its tip. Light pens are often used in computer-aided design and computer-aided manufacture (CAD and CAM) technology because of the flexibility they provide. Here, an engineer uses a light pen to modify a technical drawing on a computer display screen.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Gary Guisinger/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Input devices, such as a keyboard or mouse, permit the computer user to communicate with the computer. Other input devices include a joystick, a rodlike device often used by people who play computer games; a scanner, which converts images such as photographs into digital images that the computer can manipulate; a touch panel, which senses the placement of a user’s finger and can be used to execute commands or access files; and a microphone, used to input sounds such as the human voice which can activate computer commands in conjunction with voice recognition software. “Tablet” computers are being developed that will allow users to interact with their screens using a penlike device.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >E<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >The Central Processing Unit <o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Information from an input device or from the computer’s memory is communicated via the bus to the central processing unit (CPU), which is the part of the computer that translates commands and runs programs. The CPU is a microprocessor chip—that is, a single piece of silicon containing millions of tiny, microscopically wired electrical components. Information is stored in a CPU memory location called a register. Registers can be thought of as the CPU’s tiny scratchpad, temporarily storing instructions or data. When a program is running, one special register called the program counter keeps track of which program instruction comes next by maintaining the memory location of the next program instruction to be executed. The CPU’s control unit coordinates and times the CPU’s functions, and it uses the program counter to locate and retrieve the next instruction from memory.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >In a typical sequence, the CPU locates the next instruction in the appropriate memory device. The instruction then travels along the bus from the computer’s memory to the CPU, where it is stored in a special instruction register. Meanwhile, the program counter changes—usually increasing a small amount—so that it contains the location of the instruction that will be executed next. The current instruction is analyzed by a decoder, which determines what the instruction will do. Any data the instruction needs are retrieved via the bus and placed in the CPU’s registers. The CPU executes the instruction, and the results are stored in another register or copied to specific memory locations via a bus. This entire sequence of steps is called an instruction cycle. Frequently, several instructions may be in process simultaneously, each at a different stage in its instruction cycle. This is called pipeline processing.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >F<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >Output Devices<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Once the CPU has executed the program instruction, the program may request that the information be communicated to an output device, such as a video display monitor or a flat liquid crystal display. Other output devices are printers, overhead projectors, videocassette recorders (VCRs), and speakers. <i>See also </i>Input/Output Devices.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >IV<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >PROGRAMMING LANGUAGES</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3107/2770320131_ba4afffac3.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Application of Programming Languages<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Programming languages allow people to communicate with computers. Once a job has been identified, the programmer must translate, or code, it into a list of instructions that the computer will understand. A computer program for a given task may be written in several different languages. Depending on the task, a programmer will generally pick the language that will involve the least complicated program. It may also be important to the programmer to pick a language that is flexible and widely compatible if the program will have a range of applications. These examples are programs written to average a list of numbers. Both C and BASIC are commonly used programming languages. The machine interpretation shows how a computer would process and execute the commands from the programs.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Programming languages contain the series of commands that create software. A CPU has a limited set of instructions known as machine code that it is capable of understanding. The CPU can understand only this language. All other programming languages must be converted to machine code for them to be understood. Computer programmers, however, prefer to use other computer languages that use words or other commands because they are easier to use. These other languages are slower because the language must be translated first so that the computer can understand it. The translation can lead to code that may be less efficient to run than code written directly in the machine’s language.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >Machine Language<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Computer programs that can be run by a computer’s operating system are called executables. An executable program is a sequence of extremely simple instructions known as machine code. These instructions are specific to the individual computer’s CPU and associated hardware; for example, Intel Pentium and Power PC microprocessor chips each have different machine languages and require different sets of codes to perform the same task. Machine code instructions are few in number (roughly 20 to 200, depending on the computer and the CPU). Typical instructions are for copying data from a memory location or for adding the contents of two memory locations (usually registers in the CPU). Complex tasks require a sequence of these simple instructions. Machine code instructions are binary—that is, sequences of bits (0s and 1s). Because these sequences are long strings of 0s and 1s and are usually not easy to understand, computer instructions usually are not written in machine code. Instead, computer programmers write code in languages known as an assembly language or a high-level language.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >Assembly Language<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Assembly language uses easy-to-remember commands that are more understandable to programmers than machine-language commands. Each machine language instruction has an equivalent command in assembly language. For example, in one Intel assembly language, the statement “MOV A, B” instructs the computer to copy data from location A to location B. The same instruction in machine code is a string of 16 0s and 1s. Once an assembly-language program is written, it is converted to a machine-language program by another program called an assembler. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Assembly language is fast and powerful because of its correspondence with machine language. It is still difficult to use, however, because assembly-language instructions are a series of abstract codes and each instruction carries out a relatively simple task. In addition, different CPUs use different machine languages and therefore require different programs and different assembly languages. Assembly language is sometimes inserted into a high-level language program to carry out specific hardware tasks or to speed up parts of the high-level program that are executed frequently.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >C<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >High-Level Languages<o:p></o:p></span></p> </td> </tr> </tbody></table> <span style=";font-family:";font-size:9;color:black;" >High-level languages were developed because of the difficulty of programming using assembly languages. High-level languages are easier to use than machine and assembly languages because their commands are closer to natural human language. In addition, these languages are not CPU-specific. Instead, they contain general commands that work on different CPUs. For example, a programmer writing in the high-level C++ programming language who wants to display a greeting need include only the following command:<br /><br /><b>cout << ‘Hello, Encarta User!’ <<></b></span><b><br /><img src="http://farm4.static.flickr.com/3272/2770320311_5ebabe360a.jpg?v=0" /><br /></b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><b><span style=";font-family:";font-size:8;" >Grace Hopper<o:p></o:p></span></b></b></p><b> </b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" ><b>A pioneer in data processing, Grace Hopper received credit for creating the first compiler in 1952. Hopper helped to develop two computer languages and to make computers attractive to businesses. One of the most prominent women in the computer industry, Hopper died in 1992.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" ><b>UPI/THE BETTMANN ARCHIVE<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>This command directs the computer’s CPU to display the greeting, and it will work no matter what type of CPU the computer uses. When this statement is executed, the text that appears between the quotes will be displayed. Although the “cout” and “endl” parts of the above statement appear cryptic, programmers quickly become accustomed to their meanings. For example, “cout” sends the greeting message to the “standard output” (usually the computer user’s screen) and “endl” is how to tell the computer (when using the C++ language) to go to a new line after it outputs the message. Like assembly-language instructions, high-level languages also must be translated. This is the task of a special program called a compiler. A compiler turns a high-level program into a CPU-specific machine language. For example, a programmer may write a program in a high-level language such as C++ or Java and then prepare it for different machines, such as a Sun Microsystems work station or a personal computer (PC), using compilers designed for those machines. This simplifies the programmer’s task and makes the software more portable to different users and machines.<o:p></o:p></b></span></p><b> </b><table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >V<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >FLOW-MATIC<o:p></o:p></span></p> </td> </tr> </tbody></table><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>American naval officer and mathematician Grace Murray Hopper helped develop the first commercially available high-level software language, FLOW-MATIC, in 1957. Hopper is credited for inventing the term bug, which indicates a computer malfunction; in 1945 she discovered a hardware failure in the Mark II computer caused by a moth trapped between its mechanical relays. She documented the event in her laboratory notebook, and the term eventually came to represent any computer error, including one based strictly on incorrect instructions in software. Hopper taped the moth into her notebook and wrote, “First actual case of a bug being found.”<o:p></o:p></b></span></p><b> </b><table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >VI<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >FORTRAN<o:p></o:p></span></p> </td> </tr> </tbody></table><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>From 1954 to 1958 American computer scientist John Backus of International Business Machines, Inc. (IBM) developed Fortran, an acronym for <i>For</i>mula <i>Trans</i>lation. It became a standard programming language because it could process mathematical formulas. Fortran and its variations are still in use today, especially in physics.<o:p></o:p></b></span></p><b> </b><table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >VII<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >BASIC<o:p></o:p></span></p> </td> </tr> </tbody></table><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b> Hungarian-American mathematician John Kemeny and American mathematician Thomas Kurtz at Dartmouth College in Hanover, New Hampshire, developed BASIC (<i>B</i>eginner’s <i>A</i>ll-purpose <i>S</i>ymbolic <i>I</i>nstruction <i>C</i>ode) in 1964. The language was easier to learn than its predecessors and became popular due to its friendly, interactive nature and its inclusion on early personal computers. Unlike languages that require all their instructions to be translated into machine code first, BASIC is turned into machine language line by line as the program runs. BASIC commands typify high-level languages because of their simplicity and their closeness to natural human language. For example, a program that divides a number in half can be written as<br /><br /><b>10 INPUT “ENTER A NUMBER,” X<br />20 Y=X/2<br />30 PRINT “HALF OF THAT NUMBER IS,” Y</b><br /><br />The numbers that precede each line are chosen by the programmer to indicate the sequence of the commands. The first line prints “ENTER A NUMBER” on the computer screen followed by a question mark to prompt the user to type in the number labeled “X.” In the next line, that number is divided by two and stored as “Y.” In the third line, the result of the operation is displayed on the computer screen. Even though BASIC is rarely used today, this simple program demonstrates how data are stored and manipulated in most high-level programming languages.<o:p></o:p></b></span></p><b> </b><table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >VIII<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >OTHER HIGH-LEVEL LANGUAGES<o:p></o:p></span></p> </td> </tr> </tbody></table><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>Other high-level languages in use today include C, C++, Ada, Pascal, LISP, Prolog, COBOL, Visual Basic, and Java. Some languages, such as the “markup languages” known as HTML, XML, and their variants, are intended to display data, graphics, and media selections, especially for users of the World Wide Web. Markup languages are often not considered programming languages, but they have become increasingly sophisticated.<o:p></o:p></b></span></p><b> </b><table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >Object-Oriented Programming Languages<o:p></o:p></span></p> </td> </tr> </tbody></table><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>Object-oriented programming (OOP) languages, such as C++ and Java, are based on traditional high-level languages, but they enable a programmer to think in terms of collections of cooperating objects instead of lists of commands. Objects, such as a circle, have properties such as the radius of the circle and the command that draws it on the computer screen. Classes of objects can inherit features from other classes of objects. For example, a class defining squares can inherit features such as right angles from a class defining rectangles. This set of programming classes simplifies the programmer’s task, resulting in more “reusable” computer code. Reusable code allows a programmer to use code that has already been designed, written, and tested. This makes the programmer’s task easier, and it results in more reliable and efficient programs.<o:p></o:p></b></span></p><b> </b><table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >IX<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >TYPES OF COMPUTERS<o:p></o:p></span></p> </td> </tr> </tbody></table><b> </b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;" ><o:p><b> </b></o:p></span></p><b> </b><table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >Digital and Analog<o:p></o:p></span></p> </td> </tr> </tbody></table><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>Computers can be either digital or analog. Virtually all modern computers are digital. Digital refers to the processes in computers that manipulate binary numbers (0s or 1s), which represent switches that are turned on or off by electrical current. A bit can have the value 0 or the value 1, but nothing in between 0 and 1. Analog refers to circuits or numerical values that have a continuous range. Both 0 and 1 can be represented by analog computers, but so can 0.5, 1.5, or a number like </b></span><span style=";font-family:Symbol;font-size:9;color:black;" ><b>p</b></span><span style=";font-family:";font-size:9;color:black;" ><b> (approximately 3.14). <o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>A desk lamp can serve as an example of the difference between analog and digital. If the lamp has a simple on/off switch, then the lamp system is digital, because the lamp either produces light at a given moment or it does not. If a dimmer replaces the on/off switch, then the lamp is analog, because the amount of light can vary continuously from on to off and all intensities in between.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>Analog computer systems were the first type to be produced. A popular analog computer used in the 20th century was the slide rule. To perform calculations with a slide rule, the user slides a narrow, gauged wooden strip inside a rulerlike holder. Because the sliding is continuous and there is no mechanism to stop at any exact values, the slide rule is analog. New interest has been shown recently in analog computers, particularly in areas such as neural networks. These are specialized computer designs that attempt to mimic neurons of the brain. They can be built to respond to continuous electrical signals. Most modern computers, however, are digital machines whose components have a finite number of states—for example, the 0 or 1, or on or off bits. These bits can be combined to denote information such as numbers, letters, graphics, sound, and program instructions.<o:p></o:p></b></span></p><b> </b><table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >Range of Computer Ability</span></p></td></tr></tbody></table><b><br /><img src="http://farm4.static.flickr.com/3188/2771167444_1b7076412b.jpg?v=0" /><br /></b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><b><span style=";font-family:";font-size:8;" >Handheld Computer<o:p></o:p></span></b></b></p><b> </b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" ><b>The handheld computing device attests to the remarkable miniaturization of computer hardware. The early computers of the 1940s were so large that they filled entire rooms. Techonological innovations, such as the integrated circuit in 1959 and the microprocessor in 1971, shrank computers’ central processing units to the size of tiny silicon chips. Handheld computers are sometimes called personal digital assistants (PDAs).<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" ><b>James Leynse/Corbis<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>Computers exist in a wide range of sizes and power. The smallest are embedded within the circuitry of appliances, such as televisions and wristwatches. These computers are typically preprogrammed for a specific task, such as tuning to a particular television frequency, delivering doses of medicine, or keeping accurate time. They generally are “hard-wired”—that is, their programs are represented as circuits that cannot be reprogrammed.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>Programmable computers vary enormously in their computational power, speed, memory, and physical size. Some small computers can be held in one hand and are called personal digital assistants (PDAs). They are used as notepads, scheduling systems, and address books; if equipped with a cellular phone, they can connect to worldwide computer networks to exchange information regardless of location. Hand-held game devices are also examples of small computers.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>Portable laptop and notebook computers and desktop PCs are typically used in businesses and at home to communicate on computer networks, for word processing, to track finances, and for entertainment. They have large amounts of internal memory to store hundreds of programs and documents. They are equipped with a keyboard; a mouse, trackball, or other pointing device; and a video display monitor or liquid crystal display (LCD) to display information. Laptop and notebook computers usually have hardware and software similar to PCs, but they are more compact and have flat, lightweight LCDs instead of television-like video display monitors. Most sources consider the terms “laptop” and “notebook” synonymous.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>Workstations are similar to personal computers but have greater memory and more extensive mathematical abilities, and they are connected to other workstations or personal computers to exchange data. They are typically found in scientific, industrial, and business environments—especially financial ones, such as stock exchanges—that require complex and fast computations.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>Mainframe computers have more memory, speed, and capabilities than workstations and are usually shared by multiple users through a series of interconnected computers. They control businesses and industrial facilities and are used for scientific research. The most powerful mainframe computers, called supercomputers, process complex and time-consuming calculations, such as those used to create weather predictions. Large businesses, scientific institutions, and the military use them. Some supercomputers have many sets of CPUs. These computers break a task into small pieces, and each CPU processes a portion of the task to increase overall speed and efficiency. Such computers are called parallel processors. As computers have increased in sophistication, the boundaries between the various types have become less rigid. The performance of various tasks and types of computing have also moved from one type of computer to another. For example, networked PCs can work together on a given task in a version of parallel processing known as distributed computing.<o:p></o:p></b></span></p><b> </b><table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >X<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >NETWORKS<o:p></o:p></span></p> </td> </tr> </tbody></table><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>Computers can communicate with other computers through a series of connections and associated hardware called a network. The advantage of a network is that data can be exchanged rapidly, and software and hardware resources, such as hard-disk space or printers, can be shared. Networks also allow remote use of a computer by a user who cannot physically access the computer.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>One type of network, a local area network (LAN), consists of several PCs or workstations connected to a special computer called a server, often within the same building or office complex. The server stores and manages programs and data. A server often contains all of a networked group’s data and enables LAN workstations or PCs to be set up without large storage capabilities. In this scenario, each PC may have “local” memory (for example, a hard drive) specific to itself, but the bulk of storage resides on the server. This reduces the cost of the workstation or PC because less expensive computers can be purchased, and it simplifies the maintenance of software because the software resides only on the server rather than on each individual workstation or PC.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>Mainframe computers and supercomputers commonly are networked. They may be connected to PCs, workstations, or terminals that have no computational abilities of their own. These “dumb” terminals are used only to enter data into, or receive output from, the central computer.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>Wide area networks (WANs) are networks that span large geographical areas. Computers can connect to these networks to use facilities in another city or country. For example, a person in Los Angeles can browse through the computerized archives of the Library of Congress in Washington, D.C. The largest WAN is the Internet, a global consortium of networks linked by common communication programs and <i>protocols</i> (a set of established standards that enable computers to communicate with each other). The Internet is a mammoth resource of data, programs, and utilities. American computer scientist Vinton Cerf was largely responsible for creating the Internet in 1973 as part of the United States Department of Defense Advanced Research Projects Agency (DARPA). In 1984 the development of Internet technology was turned over to private, government, and scientific agencies. The World Wide Web, developed in the 1980s by British physicist Timothy Berners-Lee, is a system of information resources accessed primarily through the Internet. Users can obtain a variety of information in the form of text, graphics, sounds, or video. These data are extensively cross-indexed, enabling users to browse (transfer their attention from one information site to another) via buttons, highlighted text, or sophisticated searching software known as search engines.<o:p></o:p></b></span></p><b> </b><table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >XI<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >HISTORY<o:p></o:p></span></p> </td> </tr> </tbody></table><b> </b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;" ><o:p><b> </b></o:p></span></p><b> </b><table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >Beginnings<o:p></o:p></span></p> </td> </tr> </tbody></table><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>The history of computing began with an analog machine. In 1623 German scientist Wilhelm Schikard invented a machine that used 11 complete and 6 incomplete sprocketed wheels that could add, and with the aid of logarithm tables, multiply and divide.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>French philosopher, mathematician, and physicist Blaise Pascal invented a machine in 1642 that added and subtracted, automatically carrying and borrowing digits from column to column. Pascal built 50 copies of his machine, but most served as curiosities in parlors of the wealthy. Seventeenth-century German mathematician Gottfried Leibniz designed a special gearing system to enable multiplication on Pascal’s machine.<o:p></o:p></b></span></p><b> </b><table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >First Punch Cards</span></p></td></tr></tbody></table><b><br /><img src="http://farm4.static.flickr.com/3074/2771167548_18a3eacef1.jpg?v=0" /><br /></b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><b><span style=";font-family:";font-size:8;" >Computer Card Key Punch<o:p></o:p></span></b></b></p><b> </b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" ><b>The IBM 010 punch was one of the first devices designed to perforate cards. A hole or the lack of a hole in a card represented information that could be read by early computers. Modern optical storage devices, such as CD-ROMs, use microscopic pits instead of punched paper holes to store information.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" ><b>THE BETTMANN ARCHIVE/Corbis<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>In the early 19th century French inventor Joseph-Marie Jacquard devised a specialized type of computer: a silk loom. Jacquard’s loom used punched cards to program patterns that helped the loom create woven fabrics. Although Jacquard was rewarded and admired by French emperor Napoleon I for his work, he fled for his life from the city of Lyon pursued by weavers who feared their jobs were in jeopardy due to Jacquard’s invention. The loom prevailed, however: When Jacquard died, more than 30,000 of his looms existed in Lyon. The looms are still used today, especially in the manufacture of fine furniture fabrics.<o:p></o:p></b></span></p><b> </b><table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >C<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >Precursor to Modern Computer<o:p></o:p></span></p> </td> </tr> </tbody></table><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>Another early mechanical computer was the Difference Engine, designed in the early 1820s by British mathematician and scientist Charles Babbage. Although never completed by Babbage, the Difference Engine was intended to be a machine with a 20-decimal capacity that could solve mathematical problems. Babbage also made plans for another machine, the Analytical Engine, considered the mechanical precursor of the modern computer. The Analytical Engine was designed to perform all arithmetic operations efficiently; however, Babbage’s lack of political skills kept him from obtaining the approval and funds to build it. <o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>Augusta Ada Byron, countess of Lovelace, was a personal friend and student of Babbage. She was the daughter of the famous poet Lord Byron and one of only a few woman mathematicians of her time. She prepared extensive notes concerning Babbage’s ideas and the Analytical Engine. Lovelace’s conceptual programs for the machine led to the naming of a programming language (Ada) in her honor. Although the Analytical Engine was never built, its key concepts, such as the capacity to store instructions, the use of punched cards as a primitive memory, and the ability to print, can be found in many modern computers.<o:p></o:p></b></span></p><b> </b><table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >XII<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >DEVELOPMENTS IN THE 20TH CENTURY<o:p></o:p></span></p> </td> </tr> </tbody></table><b> </b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;" ><o:p><b> </b></o:p></span></p><b> </b><table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >Early Electronic Calculators<o:p></o:p></span></p> </td> </tr> </tbody></table><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>Herman Hollerith, an American inventor, used an idea similar to Jacquard’s loom when he combined the use of punched cards with devices that created and electronically read the cards. Hollerith’s tabulator was used for the 1890 U.S. census, and it made the computational time three to four times shorter than the time previously needed for hand counts. Hollerith’s Tabulating Machine Company eventually merged with two companies to form the Computing-Tabulating-Recording Company. In 1924 the company changed its name to International Business Machines (IBM).<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>In 1936 British mathematician Alan Turing proposed the idea of a machine that could process equations without human direction. The machine (now known as a Turing machine) resembled an automatic typewriter that used symbols for math and logic instead of letters. Turing intended the device to be a “universal machine” that could be used to duplicate or represent the function of any other existing machine. Turing’s machine was the theoretical precursor to the modern digital computer. The Turing machine model is still used by modern computational theorists.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>In the 1930s American mathematician Howard Aiken developed the Mark I calculating machine, which was built by IBM. This electronic calculating machine used relays and electromagnetic components to replace mechanical components. In later machines, Aiken used vacuum tubes and <i>solid state transistors</i> (tiny electrical switches) to manipulate the binary numbers. Aiken also introduced computers to universities by establishing the first computer science program at Harvard University in Cambridge, Massachusetts. Aiken obsessively mistrusted the concept of storing a program within the computer, insisting that the integrity of the machine could be maintained only through a strict separation of program instructions from data. His computer had to read instructions from punched cards, which could be stored away from the computer. He also urged the National Bureau of Standards not to support the development of computers, insisting that there would never be a need for more than five or six of them nationwide.<o:p></o:p></b></span></p><b> </b><table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >EDVAC, ENIAC, and UNIVAC</span></p></td></tr></tbody></table><b><br /><img src="http://farm4.static.flickr.com/3215/2770320725_d343a05a0e.jpg?v=0" /><br /></b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><b><span style=";font-family:";font-size:8;" >ENIAC<o:p></o:p></span></b></b></p><b> </b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" ><b>ENIAC (Electronic Numerical Integrator And Computer) was the first fully electronic digital computer. First introduced at the University of Pennsylvania in 1946, it remained in service until 1955. ENIAC contained 18,000 vacuum tubes and required manual rewiring to be programmed.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" ><b>UPI/THE BETTMANN ARCHIVE/Corbis<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>At the Institute for Advanced Study in Princeton, New Jersey, Hungarian-American mathematician John von Neumann developed one of the first computers used to solve problems in mathematics, meteorology, economics, and hydrodynamics. Von Neumann's 1945 design for the Electronic Discrete Variable Automatic Computer (EDVAC)—in stark contrast to the designs of Aiken, his contemporary—was the first electronic computer design to incorporate a program stored entirely within its memory. This machine led to several others, some with clever names like ILLIAC, JOHNNIAC, and MANIAC.<o:p></o:p></b></span></p><b> <span style=";font-family:";font-size:9;color:black;" >American physicist John Mauchly proposed the electronic digital computer called ENIAC, the Electronic Numerical Integrator And Computer. He helped build it along with American engineer John Presper Eckert, Jr., at the Moore School of Engineering at the University of Pennsylvania in Philadelphia. ENIAC was operational in 1945 and introduced to the public in 1946. It is regarded as the first successful, general digital computer. It occupied 167 sq m (1,800 sq ft), weighed more than 27,000 kg (60,000 lb), and contained more than 18,000 vacuum tubes. Roughly 2,000 of the computer’s vacuum tubes were replaced each month by a team of six technicians. Many of ENIAC’s first tasks were for military purposes, such as calculating ballistic firing tables and designing atomic weapons. Since ENIAC was initially not a stored program machine, it had to be reprogrammed for each task.</span><br /><img src="http://farm4.static.flickr.com/3078/2770320873_6110ab66ca.jpg?v=0" /><br /></b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><b><span style=";font-family:";font-size:8;" >UNIVAC Computer System<o:p></o:p></span></b></b></p><b> </b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" ><b>The first commercially available electronic computer, UNIVAC I, was also the first computer to handle both numeric and textual information. Designed by John Presper Eckert, Jr., and John Mauchly, whose corporation subsequently passed to Remington Rand, the implementation of the machine marked the beginning of the computer era. Here, a UNIVAC computer is shown in action. The central computer is in the background, and in the foreground is the supervisory control panel. Remington Rand delivered the first UNIVAC machine to the U.S. Bureau of Census in 1951.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" ><b>THE BETTMANN ARCHIVE<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>Eckert and Mauchly eventually formed their own company, which was then bought by the Rand Corporation. They produced the Universal Automatic Computer (UNIVAC), which was used for a broader variety of commercial applications. The first UNIVAC was delivered to the United States Census Bureau in 1951. By 1957, there were 46 UNIVACs in use.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>Between 1937 and 1939, while teaching at Iowa State College, American physicist John Vincent Atanasoff built a prototype computing device called the Atanasoff-Berry Computer, or ABC, with the help of his assistant, Clifford Berry. Atanasoff developed the concepts that were later used in the design of the ENIAC. Atanasoff’s device was the first computer to separate data processing from memory, but it is not clear whether a functional version was ever built. Atanasoff did not receive credit for his contributions until 1973, when a lawsuit regarding the patent on ENIAC was settled. <o:p></o:p></b></span></p><b> </b><table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >XIII<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >THE TRANSISTOR AND INTEGRATED CIRCUITS TRANSFORM COMPUTING</span></p></td></tr></tbody></table><b><br /><img src="http://farm4.static.flickr.com/3164/2771168050_9281abba3e.jpg?v=0" /><br /></b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><b><span style=";font-family:";font-size:8;" >Circuit Board and Transistors<o:p></o:p></span></b></b></p><b> </b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" ><b>A close-up on a smoke detector’s circuit board reveals its components, which include transistors, resistors, capacitors, diodes, and inductors. Rounded silver containers house the transistors that make the circuit work. Transistors are capable of serving many functions, such as amplifier, switch, and oscillator. Each transistor consists of a small piece of silicon that has been “doped,” or treated with impurity atoms, to create n-type and p-type semiconductors. Invented in 1940, transistors are a fundamental component in nearly all modern electronic devices.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" ><b>H. Schneebeli/Science Source/Photo Researchers, Inc.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>In 1948, at Bell Telephone Laboratories, American physicists Walter Houser Brattain, John Bardeen, and William Bradford Shockley developed the transistor, a device that can act as an electric switch. The transistor had a tremendous impact on computer design, replacing costly, energy-inefficient, and unreliable vacuum tubes.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>In the late 1960s integrated circuits (tiny transistors and other electrical components arranged on a single chip of silicon) replaced individual transistors in computers. Integrated circuits resulted from the simultaneous, independent work of Jack Kilby at Texas Instruments and Robert Noyce of the Fairchild Semiconductor Corporation in the late 1950s. As integrated circuits became miniaturized, more components could be designed into a single computer circuit. In the 1970s refinements in integrated circuit technology led to the development of the modern microprocessor, integrated circuits that contained thousands of transistors. Modern microprocessors can contain more than 40 million transistors.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>Manufacturers used integrated circuit technology to build smaller and cheaper computers. The first of these so-called personal computers (PCs)—the Altair 8800—appeared in 1975, sold by Micro Instrumentation Telemetry Systems (MITS). The Altair used an 8-bit Intel 8080 microprocessor, had 256 bytes of RAM, received input through switches on the front panel, and displayed output on rows of light-emitting diodes (LEDs). Refinements in the PC continued with the inclusion of video displays, better storage devices, and CPUs with more computational abilities. Graphical user interfaces were first designed by the Xerox Corporation, then later used successfully by Apple Computer, Inc.. Today the development of sophisticated operating systems such as Windows, the Mac OS, and Linux enables computer users to run programs and manipulate data in ways that were unimaginable in the mid-20th century.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>Several researchers claim the “record” for the largest single calculation ever performed. One large single calculation was accomplished by physicists at IBM in 1995. They solved one million trillion mathematical subproblems by continuously running 448 computers for two years. Their analysis demonstrated the existence of a previously hypothetical subatomic particle called a glueball. Japan, Italy, and the United States are collaborating to develop new supercomputers that will run these types of calculations 100 times faster.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>In 1996 IBM challenged Garry Kasparov, the reigning world chess champion, to a chess match with a supercomputer called Deep Blue. The computer had the ability to compute more than 100 million chess positions per second. In a 1997 rematch Deep Blue defeated Kasparov, becoming the first computer to win a match against a reigning world chess champion with regulation time controls. Many experts predict these types of parallel processing machines will soon surpass human chess playing ability, and some speculate that massive calculating power will one day replace intelligence. Deep Blue serves as a prototype for future computers that will be required to solve complex problems. At issue, however, is whether a computer can be developed with the ability to learn to solve problems on its own, rather than one programmed to solve a specific set of tasks.<o:p></o:p></b></span></p><b> </b><table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >XIV<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >THE FUTURE OF COMPUTERS</span></p></td></tr></tbody></table><b><img src="http://farm4.static.flickr.com/3147/2770321327_99ab1f519c.jpg?v=0" /><br /></b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><b><span style=";font-family:";font-size:8;" >Deep Blue and Garry Kasparov<o:p></o:p></span></b></b></p><b> </b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" ><b>Deep Blue, the screen of which is seen here as the computer plays chess against Garry Kasparov in 1997, is an IBM supercomputer that uses scalable parallel processing to solve complex problems. Deep Blue uses 256 processors working together to calculate between 50 and 100 billion chess moves in under three minutes. Real world applications of computers like Deep Blue include forecasting the weather, drug and genetics research, designing clean-up plans for toxic waste, and powering web servers on the Internet.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" ><b>Elderfield/Liaison Agency<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>In 1965 semiconductor pioneer Gordon Moore predicted that the number of transistors contained on a computer chip would double every year. This is now known as Moore’s Law, and it has proven to be somewhat accurate. The number of transistors and the computational speed of microprocessors currently doubles approximately every 18 months. Components continue to shrink in size and are becoming faster, cheaper, and more versatile.<o:p></o:p></b></span></p><b> <span style=";font-family:";font-size:9;color:black;" >With their increasing power and versatility, computers simplify day-to-day life. Unfortunately, as computer use becomes more widespread, so do the opportunities for misuse. Computer hackers—people who illegally gain access to computer systems—often violate privacy and can tamper with or destroy records. Programs called viruses or worms can replicate and spread from computer to computer, erasing information or causing malfunctions. Other individuals have used computers to electronically embezzle funds and alter credit histories (<i>see </i>Computer Security). New ethical issues also have arisen, such as how to regulate material on the Internet and the World Wide Web. Long-standing issues, such as privacy and freedom of expression, are being reexamined in light of the digital revolution. Individuals, companies, and governments are working to solve these problems through informed conversation, compromise, better computer security, and regulatory legislation.</span><br /><img src="http://farm4.static.flickr.com/3081/2770321477_f42f96b605.jpg?v=0" /><br /></b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><b><span style=";font-family:";font-size:8;" >Microminiaturization<o:p></o:p></span></b></b></p><b> </b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" ><b>This integrated circuit, an F-100 microprocessor, is only 0.6 cm square and is small enough to pass through the eye of a needle.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" ><b>A. Sternberg/Ferranti Elec./Science Source/Photo Researchers, Inc.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>Computers will become more advanced and they will also become easier to use. Improved speech recognition will make the operation of a computer easier. Virtual reality, the technology of interacting with a computer using all of the human senses, will also contribute to better human and computer interfaces. Standards for virtual-reality program languages—for example, Virtual Reality Modeling language (VRML)—are currently in use or are being developed for the World Wide Web.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>Other, exotic models of computation are being developed, including biological computing that uses living organisms, molecular computing that uses molecules with particular properties, and computing that uses deoxyribonucleic acid (DNA), the basic unit of heredity, to store data and carry out operations. These are examples of possible future computational platforms that, so far, are limited in abilities or are strictly theoretical. Scientists investigate them because of the physical limitations of miniaturizing circuits embedded in silicon. There are also limitations related to heat generated by even the tiniest of transistors.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>Intriguing breakthroughs occurred in the area of quantum computing in the late 1990s. Quantum computers under development use components of a chloroform molecule (a combination of chlorine and hydrogen atoms) and a variation of a medical procedure called magnetic resonance imaging (MRI) to compute at a molecular level. Scientists use a branch of physics called quantum mechanics, which describes the behavior of subatomic particles (particles that make up atoms), as the basis for quantum computing. Quantum computers may one day be thousands to millions of times faster than current computers, because they take advantage of the laws that govern the behavior of subatomic particles. These laws allow quantum computers to examine all possible answers to a query simultaneously. Future uses of quantum computers could include code breaking (<i>see </i>cryptography) and large database queries. Theorists of chemistry, computer science, mathematics, and physics are now working to determine the possibilities and limitations of quantum computing.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" ><b>Communications between computer users and networks will benefit from new technologies such as broadband communication systems that can carry significantly more data faster or more conveniently to and from the vast interconnected databases that continue to grow in number and type.<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 15pt;"><span style=";font-family:";font-size:12;" ><b><br />Contributed By:<br />Timothy Law Snyder<o:p></o:p></b></span></p><b> </b><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><b><span style=";font-family:";font-size:9;" >Microsoft ® Encarta ® 2007.</span></b><span style=";font-family:";font-size:9;" > © 1993-2006 Microsoft Corporation. All rights reserved.<o:p></o:p></span></b></p><b> </b><p class="MsoNormal"><o:p><b> </b></o:p></p><b><br /><span style=";font-family:";font-size:9;color:black;" ></span><br /></b>ghozian karamihttp://www.blogger.com/profile/13214011599962806335noreply@blogger.com0tag:blogger.com,1999:blog-192751622867664710.post-22398556092276159862009-01-02T16:13:00.000-08:002009-01-02T16:14:45.957-08:00All about Dog<p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:24;">Dog<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;">I<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;">INTRODUCTION</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3011/2770321733_754202387b.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;">Domestic Dogs<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;">The domestic dog, <i>Canis lupus familiaris,</i> believed to be a direct descendant of the wolf, <i>Canis lupus,</i> has been selectively bred into hundreds of different breeds.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;">Yoav Levy/Phototake NYC/Courtesy of Hollywood Edge. All rights reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">Dog, mammal generally considered to be the first domesticated animal. This trusted work partner and beloved pet learned to live with humans more than 14,000 years ago. A direct descendant of the wolves that once roamed Europe, Asia, and North America, the domestic dog belongs to the dog family, which includes wolves, coyotes, foxes, and jackals. Dog ancestry has been traced to small, civet-like mammals, called miacis, which had short legs and a long body and lived approximately 40 million years ago.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">The evolving relationship between the domestic dog and humans has been documented in fossil evidence, artifacts, and records left by earlier civilizations. Prehistoric dog skeletal remains, excavated from sites in Denmark, England, Germany, Japan, and China, indicate the early coexistence of dogs with people. An ancient Persian cemetery, dating to the 5th century <span style="text-transform: uppercase;">bc</span>, contained thousands of dog skeletons. Their formal burial and the positioning of the dog remains reveal the esteem in which the ancient Persians held their dogs. The relationship shared by dogs and humans also is evident in cave drawings, early pottery, and Asian ivory carvings that depict dogs. A statue of Anubis, the half dog, half jackal Egyptian god, was discovered inside King Tutankhamen’s tomb, constructed in about 1330 <span style="text-transform: uppercase;">bc</span>.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">Literary references to the dog include those found in the Bible and in the Greek classic the <i>Odyssey </i>by Homer. In 1576 an English physician and dog fancier, John Caius, wrote a detailed text on dog breeds, <i>Of English Dogges</i>. Dogs are featured in tapestries that were created in the Middle Ages (5th century to 15th century), and in the work of many artists, including 17th- and 18th-century European painters Peter Paul Rubens and Thomas Gainsborough.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">Although it is not known how humans and dogs first learned to coexist, people soon discovered the many ways dogs could enrich their lives. Dogs have been used to hunt for food, herd animals, guard livestock and property, destroy rats and other vermin, pull carts and sleds, perform rescues, and apprehend lawbreakers. They have been used during wartime as sentinels and message carriers. Today trained dogs are used to alert deaf people to common household sounds, such as the ringing telephone or doorbell; guide the blind; or retrieve objects for quadriplegics. Perhaps the most common of the many roles served by the domestic dog, however, is that of companion. As animals with strong social tendencies, dogs typically crave close contact with their owners. And people tend to form loving bonds with dogs. This companionship often helps to ease the pain and isolation of the elderly or people whose physical or mental health requires long-term convalescence or institutionalization.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;">II<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;">PHYSICAL CHARACTERISTICS</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3146/2770321939_9e1e290960.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;">Dog Skeleton<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;">A dog’s skeleton enhances agility and endurance. The strong front legs bear more than 60 percent of the animal’s weight, yet still permit flexibility and nimbleness. The hind legs, attached to massive muscles, enable powerful acceleration and help to maintain running speed.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">Domestic dogs vary widely in appearance, particularly in size. The Shih Tzu, for example, is 20 to 28 cm (8 to 11 in) in length and weighs 4 to 7 kg (9 to 15 lb). The Irish wolfhound is at the other end of the scale, measuring about 71 to 94 cm (about 28 to 37 in) at the shoulder and weighing up to about 61 kg (about 135 lb). Coat color, length, texture, and pattern also vary greatly. The muzzle may appear shortened, as in the Pekingese, or elongated, as in the Doberman pinscher. Limbs are relatively short in the basset hound and dachshund, but long in the greyhound. Ear shape and carriage also vary, but these characteristics may be influenced by a dog owner’s decision to crop, or cut, the ears to make them stand up. Some dogs, notably the chow chow, even have a naturally blue-black tongue.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">Despite these differences, all breeds of the domestic dog are essentially identical in anatomy. The skeleton of the domestic dog has an average of 321 bones, with variation reflecting differences in the number of bones in the tail and the presence of a dewclaw, an extra digit on the paw that not all breeds have. The rib cage consists of 13 pairs of ribs; the spine has 7 cervical vertebrae, 13 thoracic vertebrae, 7 lumbar vertebrae, and 3 sacral vertebrae. Rear paws have four complete digits and front paws have four or five digits. Most puppies have 28 temporary teeth, which are replaced with 42 permanent teeth at about six months of age.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">Some breed differences evolved to help dogs survive in their native environment or occupation. For example, dogs that lived and worked outdoors, such as the Komondor of Hungary, needed a thick, weather-resistant coat to protect them from the elements and, perhaps, the biting teeth of predatory animals. Similarly, the Labrador retriever developed an oily coat, webbed feet, and a rudder-like tail to help it perform better in recovering downed waterfowl.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">Just as distinct physical characteristics became trademarks in some breeds, unusual sensory abilities characterize others. Most dogs are able to detect scents and hear high-pitched sounds that are beyond human perception, but some breeds have especially acute sensory skills. The bloodhound, for instance, can follow a four-day-old track using its highly developed sense of smell. Other breeds with a keen sense of smell include the German shepherd, golden retriever, beagle, and Newfoundland. These dogs have been trained for such varied duties as detecting hidden drugs, explosives, termites, and even a decomposing body immersed in deep water.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;">III<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;">REPRODUCTION, BIRTH, AND THE YOUNG<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">Dogs generally reach sexual maturity at about six months of age, with small breeds often maturing earlier than large breeds. Female dogs, or bitches, become sexually receptive to mating during a period called estrus (also called season or heat), which occurs about twice a year for 6 to 12 days. After a gestation period of about 63 days, an average litter of three to six puppies is born.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">Blind and unable to stand, newborn puppies are helpless and spend 90 percent of their time sleeping and 10 percent nursing. Becoming chilled is the greatest danger facing a healthy newborn puppy because its immature circulatory system cannot sustain an adequate body temperature. For this reason, newborn puppies tend to stay close to their mother or cuddle together for warmth. Mothers clean, nurse, and defend their pups until they can live on their own, but fathers do not involve themselves in the care of the young.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;">IV<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;">DOG BREEDS</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3091/2770322069_526a398ae0.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;">Cairn Terrier<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;">Cairn terriers originated on the Isle of Skye, off the coast of Scotland. Skilled and courageous working dogs, old-world cairn terriers would bolt rodents and small mammals from cairns, or piles of rocks. Modern breeders of the dogs attempt to preserve the character of old-world cairn terriers.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;">Dorling Kindersley<o:p></o:p></span></p> <span style=";font-family:";font-size:9;color:black;">Of the more than 300 breeds of dogs that exist worldwide, 150 are recognized by the American Kennel Club (AKC), the primary kennel club in the United States. Since its founding in 1884 the AKC registers purebred dogs—dogs whose parents and ancestors were of the same breed since the breed was first recognized. More than one million such dogs are registered annually. Kennel clubs in other countries, such as the Canadian Kennel Club, the Kennel Club of England, and the Japanese Kennel Club, use their own standards in recognizing dog breeds.</span><br /><img src="http://farm4.static.flickr.com/3104/2771169116_4009889435.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;">Norwegian Elkhound<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;">The Norwegian elkhound is a breed of hunting dog. The breed is characterized by a short, strong body, a broad chest, a thick coat, and a curled tail.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;">Robert and Eunice Pearcy/Animals Animals<o:p></o:p></span></p> <span style=";font-family:";font-size:9;color:black;">The AKC organizes the 150 breeds it recognizes into seven groups (plus a miscellaneous category), based on physical and temperamental characteristics and the purpose for which the breed was originally developed. The club classifies breeds as terrier, working, sporting, hound, herding, toy, and nonsporting.</span><br /><img src="http://farm4.static.flickr.com/3041/2770322339_2a05b17410.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;">Bulldog<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;">The bulldog was originally bred for the sport of bullbaiting; after the sport was banned, the bulldog was bred once again to lose its viciousness. The bulldog is often considered a mascot of the British.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;">Dorling Kindersley<o:p></o:p></span></p> <span style=";font-family:";font-size:9;color:black;">The terriers often have wiry coats and possess a feisty personality, which reflects their original use in catching prey such as foxes, badgers, and rabbits. Working dogs, such as the boxer or Alaskan Malamute, are muscular, even-tempered, and obedient, a necessary quality in dogs that serve as working partners with humans. Many of the sporting dogs, such as pointers and retrievers, are active dogs that respond instinctively when spotting game. Hounds such as the beagle are known for their stamina, acute sense of smell, and baying bark, qualities that are an invaluable aid to hunters and trackers. Other tireless helpers of humans are herding dogs, recognized for their innate ability to drive livestock and keep farm animals from straying. The low-to-the-ground Pembroke or Cardigan Welsh Corgi can drive a herd of cows many times its size. Toy dogs, on the other hand, are known for their diminutive size and function as companionable house pets. The papillon, named for the French word for butterfly because it has ears that resemble butterfly wings, is a happy, friendly dog, suitable for small living spaces. The final dog group, nonsporting , includes a wide variety of purebreds that differ in size, coat, overall appearance, and personality, from the shorthaired spotted dalmatian to the curly-haired poodle.</span><br /><img src="http://farm4.static.flickr.com/3177/2771169340_346f241717.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;">Kuvasz<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;">The kuvasz is a breed of working dog originally bred as guard dogs in Europe. This large breed is characterized by strong muscles and a white coat.<o:p></o:p></span></p> <span style=";font-family:";font-size:8;">Gerard Lacz/Peter Arnold, Inc.</span><br /><img src="http://farm4.static.flickr.com/3155/2770322567_c5aafb1a52.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;">Pug<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;">A pug is a breed of toy dog characterized by a wrinkled forehead and flat, black nose. Its short hair can be solid black or light- colored with black markings on the face and ears.<o:p></o:p></span></p> <span style=";font-family:";font-size:8;">Carolyn A. McKeone/Photo Researchers, Inc.</span><br /><img src="http://farm4.static.flickr.com/3286/2771169602_3cfe77ed11.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;">Groenendael Belgian Sheepdog<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;">Its black color distinguishes the Groenendael variety of Belgian sheepdog from the three other varieties—the Belgian Laekenois, the Belgian Malinois, and the Belgian Tervuren. Although sheepdogs were first developed in the 1200s, the Groenendael breed, also known simply as the Belgian sheepdog, was not created until the late 1800s, when the owner of a café in Groenendael, Belgium, mated two black sheepdogs. The Belgian sheepdog is often used to herd and guard farm livestock.<o:p></o:p></span></p> <span style=";font-family:";font-size:8;">Henry Ausloos/Animals Animals</span><br /><img src="http://farm4.static.flickr.com/3008/2770322749_26c144176d.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;">Cocker Spaniel<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;">The cocker spaniel has long been bred for hunting and may have been named after a primary prey, the woodcock. Hunters valued the dog for its intelligence and trainability. These qualities serve domestic pet owners as well, contributing to the breed’s popularity as a pet.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;">Dorling Kindersley<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;">V<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;">DOG BEHAVIOR<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">Instinctive behaviors of the domestic dog are comparable to those of its wild relatives, the wolf, coyote, fox, and jackal. Unlike trained behaviors, such as being housebroken or responding to human commands, instinctive behaviors are those that dogs do without being taught and include vocalizations, body language, and marking. For example, by four weeks of age, puppies bark, whine, growl, and howl—-just like their wild relatives. Even the African Basenji, known as the barkless dog, yodels when aroused. These sounds, whether elicited in excitement, fear, territoriality, or pain, are one way that dogs communicate with one another and with other animals and people.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">Dogs also communicate through their use of body language. Facial expression, ear posture, tail carriage, <i>hackle</i> (hair on back) display, and body stance signal a dog’s state of fear, excitement, aggression, or submission. Understanding the meaning behind these signals can be important. Signs of potential hostility in a dog include bared teeth, flattened ears, erect tail, stiff legs, and bristling back hair; the dog may also growl or bark. People observing these behaviors should keep their arms at their sides and slowly back away, while firmly saying “no.” When approaching a strange dog, first ask the owner if the dog may be touched. Once given permission, hold the hands low and speak softly. Staring directly at a dog may arouse intimidation or aggression, so eye contact with strange dogs should be avoided.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">Dogs typically mark their territory with urine as part of the social communication between animals in general and among the species. A dog may defend the territory by growling, barking, or assuming aggressive body language.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">In addition to these instinctive behaviors, dogs are capable of learning certain trained behaviors, such as following obedience commands. The domesticated dog is able and willing to learn appropriate behaviors and is highly motivated to please its owner, critical factors that have contributed to the success of the domestic dog as a companion.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;">VI<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;">CARING FOR A DOG<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">The decision to adopt a dog should be made carefully because it is a serious commitment that can last for several years. Small dogs may live 12 or more years, although very large dogs typically have a shorter lifespan, sometimes as brief as 8 years. Before buying a dog, potential owners should examine their lifestyle, living accommodations, and plans for the dog. Other decisions should include who, in the case of a family, will care for the dog and whether the family or individual owner will have enough time, attention, and money to meet the dog’s needs.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">For example, a busy family might not have the necessary time to groom a dog with a thick coat, and some people might be unwilling to keep up with the frequent vacuuming needed with a breed that sheds large amounts of hair. Further, a large dog that requires lots of exercise would not thrive in a small apartment, nor would a tiny dog be safe around very young children, who may be too rough with these dogs. Potential owners also should decide which gender dog they prefer and if it will be used for breeding. Another decision is to determine if the dog will be a show dog, a working dog, or a pet because this will influence which individual to select. Finally, anyone who would like to acquire a dog should be sure to budget for its food; medical expenses, which will cover immunizations, check-ups, and sick visits; and any kennel care required in the owner’s absence.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">Many people prefer a purebred dog so that they can predict how the dog will look and act when fully grown. Most veterinarians and responsible dog fanciers believe that a private breeder with a good track record in producing healthy puppies is the best option for choosing purebreds. To locate a breeder, check the newspaper, visit a dog show, contact a veterinarian or experienced acquaintance, or call a local kennel club or the AKC. Visit several breeders and meet each litter’s <i>dam</i> (mother) and <i>sire</i> (father), if possible. Be prepared to ask, and answer, a lot of questions. Reputable breeders vigorously screen prospective buyers to ensure that their puppies go to good homes. Other potential owners are satisfied with mixed-breed dogs, called mongrels or mutts. Animal shelters and humane societies, veterinarian offices, and classified advertising are all resources for finding a mixed-breed that meets the needs of a potential owner.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">When adopting a puppy, wait until it is at least eight weeks of age before separating it from its mother. Although the various breeds, and dogs in general, have different temperaments, look for a clean puppy that is happy, outgoing, and alert. A puppy that is excessively shy or thin or that has obvious health problems, such as discharge from its eyes or nose, is not a good choice.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">A new puppy should be taken to a veterinarian soon after adoption for a thorough physical examination and to ensure that it is current on vaccinations. All puppies need a series of immunizations to protect them against distemper, a viral disease that causes respiratory symptoms and can affect the nervous system; leptospirosis, a bacterial disease that damages the liver; hepatitis, a viral disease that also targets the liver; parvovirus, which harms the intestinal tract; and parainfluenza, which causes respiratory problems. Immunizations for these five diseases are usually administered in one vaccination. Dogs also need rabies shots to protect them from this virus, which is transmitted in the saliva by the bite of an infected animal and attacks the nervous system. Some owners opt for additional vaccinations against Lyme disease, a bacterial infection that is transmitted by parasitic deer ticks; kennel cough, a respiratory disease caused by the bordatella bacteria; and coronavirus, which targets the intestinal tract.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">Most young puppies harbor roundworms, intestinal parasites that are diagnosed by examining a stool sample. Roundworms rob the puppy of nutrients, resulting in the puppy’s failure to thrive; the parasites are eliminated with several doses of oral medication. Dogs of all ages should follow a drug regimen to protect them from another parasite, heartworm, which damages heart tissue, obstructs blood flow, and often causes death. The veterinarian should also discuss spaying or neutering (making a dog infertile), which are essential in nonbreeding dogs to protect their health and reduce the population of unwanted dogs. This common surgical procedure is usually not done until a pup is six months old.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">Veterinarians recommend that dogs of all ages have a yearly checkup, including vaccination booster shots and screening for external and internal parasites. Since dogs cannot communicate their health problems through words, an annual examination is important for the early detection and treatment of problems. Owners should be aware of signs of possible illness requiring veterinary attention, including changes in appetite and behavior.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">All puppies and dogs have three daily requirements: plenty of fresh drinking water, correct amounts of nutritious food, and adequate exercise for the dog’s age, breed, and temperament. An outdoor dog needs shelter from the elements and plenty of shade during the summer months, and indoor pets must have regular access to the outdoors for elimination. Whatever their living arrangements, all dogs require the loving attention of their owners.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">Grooming considerations vary from breed to breed. Short-coated dogs usually need to be brushed once or twice a week, whereas long-haired dogs may need daily grooming to prevent the coat from matting or tangling. Dogs need only be bathed when dirty, and the shampoo used should be one that will protect the coat’s natural oils. Grooming also includes attending to the dog’s eyes, ears, teeth, anal glands, and nails; details of such care, however, should first be explained by a veterinarian.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;">VII<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;">TRAINING YOUR DOG</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3129/2770323001_a82e3d4567.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;">Dogsledding<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;">Dogs are often used to drive sleds, such as these sled dog teams in Canada’s Northwest Territories.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;">Corbis<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">Training is another vital part of raising a happy and healthy dog. All dogs should be trained to walk on a leash and be housebroken. Some people prefer housebreaking a puppy by training it to urinate and defecate on newspapers, which are laid flat in a small area such as a foyer. The puppy is rewarded each time it voids on the paper; then the newspapered area is gradually reduced and finally eliminated altogether. However, crate training, in which a dog is confined to a crate for limited periods, is more effective because dogs will avoid soiling their own living quarters. Whichever method is chosen, housebreaking should begin as soon as a puppy comes home with its new owner, who should provide the puppy with frequent opportunities to urinate and defecate outside. In general, pups are not completely housebroken until they are at least 12 weeks old.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">Most puppies are ready to begin obedience lessons at six to eight months of age. The first lessons should be relatively brief, about 10 to 15 minutes a day, and gradually increase to 30 minutes, depending on the dog’s level of concentration. Training is best accomplished with lots of praise and a stern “no” for corrections. The trainer should always be consistent in reinforcing good behavior and correcting bad behavior and should never strike a dog. Many trainers use a leash and chain-link collar, known as a choke collar. Despite its name, the collar is never meant to choke a dog, but is used to deliver quick snaps to gain and direct a dog’s attention. This training collar is useful in teaching basic obedience commands, such as <i>sit, stay, heel, come,</i> and <i>down.</i><o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;">VIII<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;">DOG SHOWS</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3038/2771170068_d282b6ea3d.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;">Poodle Clipping<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;">A poodle submits to having its fur trimmed. The clipping of poodles originated as a method of reducing drag while the dog was swimming. Trimming is often a requirement for dogs that are entered in shows.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;">Jerry Cooke/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">In the United States, the AKC sponsors 14,000 competitive dog shows and performance events each year. Dog show judges evaluate a dog’s conformation to its breed standard—an official physical description of the ideal specimen for a particular breed—and compare the dog with other dogs at the show. Most show dogs are competing for points toward their championship. At a large dog show, such as the Westminster Kennel Club show held over two days in New York City each February, a field of thousands of dogs is progressively thinned to a single Best in Show winner.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;">A variety of performance events are held that seek to provide dogs with an opportunity to perform the function for which they were originally bred. For instance, a saluki, a hound dog, may enter a lure coursing event to demonstrate its skill at pursuing swift prey. Small terriers may vocalize and lunge into a tunnel after “quarry” at an earth dog trial. Bloodhounds may follow a scent laid down by handlers at a tracking test. The puli, a herding dog, may gather a flock of sheep at a herding trial. Many performance events offer increasing levels of difficulty that are reflected in a range of titles. Once earned, these titles are entered into a dog’s permanent AKC record. Whether people choose to enter their dogs in formal competition, work with them, or simply enjoy their companionship, all dogs thrive on the bond that is fostered by a caring owner.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 15pt;"><span style=";font-family:";font-size:12;"><br />Contributed By:<br />Elizabeth M. Bodner<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:9;">Microsoft ® Encarta ® 2007.</span></b><span style=";font-family:";font-size:9;"> © 1993-2006 Microsoft Corporation. All rights reserved.<o:p></o:p></span></p> <p class="MsoNormal"><o:p> </o:p></p>ghozian karamihttp://www.blogger.com/profile/13214011599962806335noreply@blogger.com1tag:blogger.com,1999:blog-192751622867664710.post-38242294131474566812008-12-11T07:09:00.000-08:002008-12-11T07:21:09.518-08:00All About Earth<p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 24pt; font-family: "MS Reference Serif","serif";">Earth (planet)<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">I<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">INTRODUCTION</span></p></td></tr></tbody></table><img src="http://farm4.static.flickr.com/3265/2767407807_2d6cd2961d_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Earth<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">An oxygen-rich and protective atmosphere, moderate temperatures, abundant water, and a varied chemical composition enable Earth to support life, the only planet known to harbor life. The planet is composed of rock and metal, which are present in molten form beneath its surface. The Apollo 17 spacecraft took this snapshot in 1972 of the Arabian Peninsula, the African continent, and Antarctica (most of the white area near the bottom).<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">NASA/Science Source/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Earth (planet), one of nine planets in the solar system, the only planet known to harbor life, and the “home” of human beings. From space Earth resembles a big blue marble with swirling white clouds floating above blue oceans. About 71 percent of Earth’s surface is covered by water, which is essential to life. The rest is land, mostly in the form of continents that rise above the oceans.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Earth’s surface is surrounded by a layer of gases known as the atmosphere, which extends upward from the surface, slowly thinning out into space. Below the surface is a hot interior of rocky material and two core layers composed of the metals nickel and iron in solid and liquid form.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Unlike the other planets, Earth has a unique set of characteristics ideally suited to supporting life as we know it. It is neither too hot, like Mercury, the closest planet to the Sun, nor too cold, like distant Mars and the even more distant outer planets—Jupiter, Saturn, Uranus, Neptune, and tiny Pluto. Earth’s atmosphere includes just the right amount of gases that trap heat from the Sun, resulting in a moderate climate suitable for water to exist in liquid form. The atmosphere also helps block radiation from the Sun that would be harmful to life. Earth’s atmosphere distinguishes it from the planet Venus, which is otherwise much like Earth. Venus is about the same size and mass as Earth and is also neither too near nor too far from the Sun. But because Venus has too much heat-trapping carbon dioxide in its atmosphere, its surface is extremely hot—462°C (864°F)—hot enough to melt lead and too hot for life to exist.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Although Earth is the only planet known to have life, scientists do not rule out the possibility that life may once have existed on other planets or their moons, or may exist today in primitive form. Mars, for example, has many features that resemble river channels, indicating that liquid water once flowed on its surface. If so, life may also have evolved there, and evidence for it may one day be found in fossil form. Water still exists on Mars, but it is frozen in polar ice caps, in permafrost, and possibly in rocks below the surface.</span><br /><img src="http://farm4.static.flickr.com/3124/2767407847_8c962cfed0_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Earth from the Moon<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">In the late 1960s, people saw for the first time what Earth looked like from space. This famous photo of Earth was taken by astronauts on the Apollo 8 mission as they orbited the Moon in 1968.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">NASA<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">For thousands of years, human beings could only wonder about Earth and the other observable planets in the solar system. Many early ideas—for example, that the Earth was a sphere and that it traveled around the Sun—were based on brilliant reasoning. However, it was only with the development of the scientific method and scientific instruments, especially in the 18th and 19th centuries, that humans began to gather data that could be used to verify theories about Earth and the rest of the solar system. By studying fossils found in rock layers, for example, scientists realized that the Earth was much older than previously believed. And with the use of telescopes, new planets such as Uranus, Neptune, and Pluto were discovered.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In the second half of the 20th century, more advances in the study of Earth and the solar system occurred due to the development of rockets that could send spacecraft beyond Earth. Human beings were able to study and observe Earth from space with satellites equipped with scientific instruments. Astronauts landed on the Moon and gathered ancient rocks that revealed much about the early solar system. During this remarkable advancement in human history, humans also sent unmanned spacecraft to the other planets and their moons. Spacecraft have now visited all of the planets except Pluto. The study of other planets and moons has provided new insights about Earth, just as the study of the Sun and other stars like it has helped shape new theories about how Earth and the rest of the solar system formed.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">As a result of this recent space exploration, we now know that Earth is one of the most geologically active of all the planets and moons in the solar system. Earth is constantly changing. Over long periods of time land is built up and worn away, oceans are formed and re-formed, and continents move around, break up, and merge.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Life itself contributes to changes on Earth, especially in the way living things can alter Earth’s atmosphere. For example, Earth at one time had the same amount of carbon dioxide in its atmosphere as Venus now has, but early forms of life helped remove this carbon dioxide over millions of years. These life forms also added oxygen to Earth’s atmosphere and made it possible for animal life to evolve on land.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">A variety of scientific fields have broadened our knowledge about Earth, including biogeography, climatology, geology, geophysics, hydrology, meteorology, oceanography, and zoogeography. Collectively, these fields are known as Earth science. By studying Earth’s atmosphere, its surface, and its interior and by studying the Sun and the rest of the solar system, scientists have learned much about how Earth came into existence, how it changed, and why it continues to change.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">II<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">EARTH, THE SOLAR SYSTEM, AND THE GALAXY</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3257/2768255108_52567bf977_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Solar System<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Earth is the third planet from the Sun, after Mercury and Venus. The average distance between Earth and the Sun is 150 million km (93 million mi). Earth and all the other planets in the solar system revolve, or orbit, around the Sun due to the force of gravitation. The Earth travels at a velocity of about 107,000 km/h (about 67,000 mph) as it orbits the Sun. All but one of the planets orbit the Sun in the same plane—that is, if an imaginary line were extended from the center of the Sun to the outer regions of the solar system, the orbital paths of the planets would intersect that line. The exception is Pluto, which has an <i>eccentric</i> (unusual) orbit. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Earth’s orbital path is not quite a perfect circle but instead is slightly <i>elliptical </i>(oval-shaped). For example, at maximum distance Earth is about 152 million km (about 95 million mi) from the Sun; at minimum distance Earth is about 147 million km (about 91 million mi) from the Sun. If Earth orbited the Sun in a perfect circle, it would always be the same distance from the Sun.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The solar system, in turn, is part of the Milky Way Galaxy, a collection of billions of stars bound together by gravity. The Milky Way has armlike discs of stars that spiral out from its center. The solar system is located in one of these spiral arms, known as the Orion arm, which is about two-thirds of the way from the center of the Galaxy. In most parts of the Northern Hemisphere, this disc of stars is visible on a summer night as a dense band of light known as the Milky Way.</span><br /><img src="http://farm4.static.flickr.com/3291/2767408073_e166d2b6b8_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Milky Way Galaxy<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Our own solar system exists within one of the spiral arms of the disk-shaped galaxy called the Milky Way. This false-color image looks toward the center of the Milky Way, located 30,000 light-years away. Bright star clusters are visible along with darker areas of dust and gas.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Morton-Milon/Science Source/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Earth is the fifth largest planet in the solar system. Its diameter, measured around the equator, is 12,756 km (7,926 mi). Earth is not a perfect sphere but is slightly flattened at the poles. Its polar diameter, measured from the North Pole to the South Pole, is somewhat less than the equatorial diameter because of this flattening. Although Earth is the largest of the four planets—Mercury, Venus, Earth, and Mars—that make up the <i>inner solar system</i> (the planets closest to the Sun), it is small compared with the giant planets of the outer solar system—Jupiter, Saturn, Uranus, and Neptune. For example, the largest planet, Jupiter, has a diameter at its equator of 143,000 km (89,000 mi), 11 times greater than that of Earth. A famous atmospheric feature on Jupiter, the Great Red Spot, is so large that three Earths would fit inside it.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Earth has one natural satellite, the Moon. The Moon orbits the Earth, completing one revolution in an elliptical path in 27 days 7 hr 43 min 11.5 sec. The Moon orbits the Earth because of the force of Earth’s gravity. However, the Moon also exerts a gravitational force on the Earth. Evidence for the Moon’s gravitational influence can be seen in the ocean tides. A popular theory suggests that the Moon split off from Earth more than 4 billion years ago when a large meteorite or small planet struck the Earth.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">As Earth revolves around the Sun, it rotates, or spins, on its <i>axis</i>, an imaginary line that runs between the North and South poles. The period of one complete rotation is defined as a day and takes 23 hr 56 min 4.1 sec. The period of one revolution around the Sun is defined as a year, or 365.2422 solar days, or 365 days 5 hr 48 min 46 sec. Earth also moves along with the Milky Way Galaxy as the Galaxy rotates and moves through space. It takes more than 200 million years for the stars in the Milky Way to complete one revolution around the Galaxy’s center.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Earth’s axis of rotation is <i>inclined</i> (tilted) 23.5° relative to its plane of revolution around the Sun. This inclination of the axis creates the seasons and causes the height of the Sun in the sky at noon to increase and decrease as the seasons change. The Northern Hemisphere receives the most energy from the Sun when it is tilted toward the Sun. This orientation corresponds to summer in the Northern Hemisphere and winter in the Southern Hemisphere. The Southern Hemisphere receives maximum energy when it is tilted toward the Sun, corresponding to summer in the Southern Hemisphere and winter in the Northern Hemisphere. Fall and spring occur in between these orientations.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">III<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">EARTH’S ATMOSPHERE<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The atmosphere is a layer of different gases that extends from Earth’s surface to the exosphere, the outer limit of the atmosphere, about 9,600 km (6,000 mi) above the surface. Near Earth’s surface, the atmosphere consists almost entirely of nitrogen (78 percent) and oxygen (21 percent). The remaining 1 percent of atmospheric gases consists of argon (0.9 percent); carbon dioxide (0.03 percent); varying amounts of water vapor; and trace amounts of hydrogen, nitrous oxide, ozone, methane, carbon monoxide, helium, neon, krypton, and xenon.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Layers of the Atmosphere</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3265/2767408187_8281098d01_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Divisions of the Atmosphere<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Without our atmosphere, there would be no life on Earth. A relatively thin envelope, the atmosphere consists of layers of gases that support life and provide protection from harmful radiation.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The layers of the atmosphere are the troposphere, the stratosphere, the mesosphere, the thermosphere, and the exosphere. The troposphere is the layer in which weather occurs and extends from the surface to about 16 km (about 10 mi) above sea level at the equator. Above the troposphere is the stratosphere, which has an upper boundary of about 50 km (about 30 mi) above sea level. The layer from 50 to 90 km (30 to 60 mi) is called the mesosphere. At an altitude of about 90 km, temperatures begin to rise. The layer that begins at this altitude is called the thermosphere because of the high temperatures that can be reached in this layer (about 1200°C, or about 2200°F). The region beyond the thermosphere is called the exosphere. The thermosphere and the exosphere overlap with another region of the atmosphere known as the ionosphere, a layer or layers of ionized air extending from almost 60 km (about 50 mi) above Earth’s surface to altitudes of 1,000 km (600 mi) and more.</span><br /><img src="http://farm4.static.flickr.com/3131/2768255504_2e282fd83f_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Greenhouse Effect<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Earth’s atmosphere and the way it interacts with the oceans and radiation from the Sun are responsible for the planet’s climate and weather. The atmosphere plays a key role in supporting life. Almost all life on Earth uses atmospheric oxygen for energy in a process known as cellular respiration, which is essential to life. The atmosphere also helps moderate Earth’s climate by trapping radiation from the Sun that is reflected from Earth’s surface. Water vapor, carbon dioxide, methane, and nitrous oxide in the atmosphere act as “greenhouse gases.” Like the glass in a greenhouse, they trap infrared, or heat, radiation from the Sun in the lower atmosphere and thereby help warm Earth’s surface. Without this greenhouse effect, heat radiation would escape into space, and Earth would be too cold to support most forms of life.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Other gases in the atmosphere are also essential to life. The trace amount of ozone found in Earth’s stratosphere blocks harmful ultraviolet radiation from the Sun. Without the ozone layer, life as we know it could not survive on land. Earth’s atmosphere is also an important part of a phenomenon known as the water cycle or the hydrologic cycle. <i>See also </i>Atmosphere.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The Atmosphere and the Water Cycle</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3170/2767408335_4044c5ae6b_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Water Cycle<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The water cycle simply means that Earth’s water is continually recycled between the oceans, the atmosphere, and the land. All of the water that exists on Earth today has been used and reused for billions of years. Very little water has been created or lost during this period of time. Water is constantly moving on Earth’s surface and changing back and forth between ice, liquid water, and water vapor. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The water cycle begins when the Sun heats the water in the oceans and causes it to evaporate and enter the atmosphere as water vapor. Some of this water vapor falls as precipitation directly back into the oceans, completing a short cycle. Some of the water vapor, however, reaches land, where it may fall as snow or rain. Melted snow or rain enters rivers or lakes on the land. Due to the force of gravity, the water in the rivers eventually empties back into the oceans. Melted snow or rain also may enter the ground. Groundwater may be stored for hundreds or thousands of years, but it will eventually reach the surface as springs or small pools known as seeps. Even snow that forms glacial ice or becomes part of the polar caps and is kept out of the cycle for thousands of years eventually melts or is warmed by the Sun and turned into water vapor, entering the atmosphere and falling again as precipitation. All water that falls on land eventually returns to the ocean, completing the water cycle.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">IV<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">EARTH’S SURFACE<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Earth’s surface is the outermost layer of the planet. It includes the hydrosphere, the crust, and the biosphere.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Hydrosphere<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The hydrosphere consists of the bodies of water that cover 71 percent of Earth’s surface. The largest of these are the oceans, which contain over 97 percent of all water on Earth. Glaciers and the polar ice caps contain just over 2 percent of Earth’s water in the form of solid ice. Only about 0.6 percent is under the surface as groundwater. Nevertheless, groundwater is 36 times more plentiful than water found in lakes, inland seas, rivers, and in the atmosphere as water vapor. Only 0.017 percent of all the water on Earth is found in lakes and rivers. And a mere 0.001 percent is found in the atmosphere as water vapor. Most of the water in glaciers, lakes, inland seas, rivers, and groundwater is fresh and can be used for drinking and agriculture. Dissolved salts compose about 3.5 percent of the water in the oceans, however, making it unsuitable for drinking or agriculture unless it is treated to remove the salts.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Crust<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The crust consists of the continents, other land areas, and the basins, or floors, of the oceans. The dry land of Earth’s surface is called the continental crust. It is about 15 to 75 km (9 to 47 mi) thick. The oceanic crust is thinner than the continental crust. Its average thickness is 5 to 10 km (3 to 6 mi). The crust has a definite boundary called the Mohorovičić discontinuity, or simply the Moho. The boundary separates the crust from the underlying mantle, which is much thicker and is part of Earth’s interior.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Oceanic crust and continental crust differ in the type of rocks they contain. There are three main types of rocks: igneous, sedimentary, and metamorphic. Igneous rocks form when molten rock, called magma, cools and solidifies. Sedimentary rocks are usually created by the breakdown of igneous rocks. They tend to form in layers as small particles of other rocks or as the mineralized remains of dead animals and plants that have fused together over time. The remains of dead animals and plants occasionally become mineralized in sedimentary rock and are recognizable as fossils. Metamorphic rocks form when sedimentary or igneous rocks are altered by heat and pressure deep underground.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Oceanic crust consists of dark, dense igneous rocks, such as basalt and gabbro. Continental crust consists of lighter-colored, less dense igneous rocks, such as granite and diorite. Continental crust also includes metamorphic rocks and sedimentary rocks.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">C<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Biosphere<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The biosphere includes all the areas of Earth capable of supporting life. The biosphere ranges from about 10 km (about 6 mi) into the atmosphere to the deepest ocean floor. For a long time, scientists believed that all life depended on energy from the Sun and consequently could only exist where sunlight penetrated. In the 1970s, however, scientists discovered various forms of life around hydrothermal vents on the floor of the Pacific Ocean where no sunlight penetrated. They learned that primitive bacteria formed the basis of this living community and that the bacteria derived their energy from a process called chemosynthesis that did not depend on sunlight. Some scientists believe that the biosphere may extend relatively deep into Earth’s crust. They have recovered what they believe are primitive bacteria from deeply drilled holes below the surface.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">D<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Changes to Earth’s Surface<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Earth’s surface has been constantly changing ever since the planet formed. Most of these changes have been gradual, taking place over millions of years. Nevertheless, these gradual changes have resulted in radical modifications, involving the formation, erosion, and re-formation of mountain ranges, the movement of continents, the creation of huge supercontinents, and the breakup of supercontinents into smaller continents.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The weathering and erosion that result from the water cycle are among the principal factors responsible for changes to Earth’s surface. Another principal factor is the movement of Earth’s continents and seafloors and the buildup of mountain ranges due to a phenomenon known as plate tectonics. Heat is the basis for all of these changes. Heat in Earth’s interior is believed to be responsible for continental movement, mountain building, and the creation of new seafloor in ocean basins. Heat from the Sun is responsible for the evaporation of ocean water and the resulting precipitation that causes weathering and erosion. In effect, heat in Earth’s interior helps build up Earth’s surface while heat from the Sun helps wear down the surface.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">D</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">1<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Weathering<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Weathering is the breakdown of rock at and near the surface of Earth. Most rocks originally formed in a hot, high-pressure environment below the surface where there was little exposure to water. Once the rocks reached Earth’s surface, however, they were subjected to temperature changes and exposed to water. When rocks are subjected to these kinds of surface conditions, the minerals they contain tend to change. These changes constitute the process of weathering. There are two types of weathering: physical weathering and chemical weathering.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Physical weathering involves a decrease in the size of rock material. Freezing and thawing of water in rock cavities, for example, splits rock into small pieces because water expands when it freezes. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Chemical weathering involves a chemical change in the composition of rock. For example, feldspar, a common mineral in granite and other rocks, reacts with water to form clay minerals, resulting in a new substance with totally different properties than the parent feldspar. Chemical weathering is of significance to humans because it creates the clay minerals that are important components of soil, the basis of agriculture. Chemical weathering also causes the release of dissolved forms of sodium, calcium, potassium, magnesium, and other chemical elements into surface water and groundwater. These elements are carried by surface water and groundwater to the sea and are the sources of dissolved salts in the sea.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">D</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">2<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Erosion</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3038/2768255844_168e88ca4c_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Glacial Erosion<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Glaciers erode the Earth’s surface through processes such as abrasion, crushing, and fracturing of the material in the glacier’s path. Glaciers move by growing or shrinking, depending on the climate. Moving glaciers erode and transport large quantities of rocks, sand, and other particles along their path. The icy path shown here is a moraine formed by a glacier in Switzerland.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Paolo Koch/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Erosion is the process that removes loose and weathered rock and carries it to a new site. Water, wind, and glacial ice combined with the force of gravity can cause erosion.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Erosion by running water is by far the most common process of erosion. It takes place over a longer period of time than other forms of erosion. When water from rain or melted snow moves downhill, it can carry loose rock or soil with it. Erosion by running water forms the familiar gullies and V-shaped valleys that cut into most landscapes. The force of the running water removes loose particles formed by weathering. In the process, gullies and valleys are lengthened, widened, and deepened. Often, water overflows the banks of the gullies or river channels, resulting in floods. Each new flood carries more material away to increase the size of the valley. Meanwhile, weathering loosens more and more material so the process continues.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Erosion by glacial ice is less common, but it can cause the greatest landscape changes in the shortest amount of time. Glacial ice forms in a region where snow fails to melt in the spring and summer and instead builds up as ice. For major glaciers to form, this lack of snowmelt has to occur for a number of years in areas with high precipitation. As ice accumulates and thickens, it flows as a solid mass. As it flows, it has a tremendous capacity to erode soil and even solid rock. Ice is a major factor in shaping some landscapes, especially mountainous regions. Glacial ice provides much of the spectacular scenery in these regions. Features such as <i>horns</i> (sharp mountain peaks), <i>arêtes</i> (sharp ridges), glacially formed lakes, and U-shaped valleys are all the result of glacial erosion.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Wind is an important cause of erosion only in <i>arid</i> (dry) regions. Wind carries sand and dust, which can scour even solid rock. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Many factors determine the rate and kind of erosion that occurs in a given area. The climate of an area determines the distribution, amount, and kind of precipitation that the area receives and thus the type and rate of weathering. An area with an arid climate erodes differently than an area with a humid climate. The elevation of an area also plays a role by determining the potential energy of running water. The higher the elevation the more energetically water will flow due to the force of gravity. The type of bedrock in an area (sandstone, granite, or shale) can determine the shapes of valleys and slopes, and the depth of streams.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">A landscape’s geologic age—that is, how long current conditions of weathering and erosion have affected the area—determines its overall appearance. Relatively young landscapes tend to be more rugged and angular in appearance. Older landscapes tend to have more rounded slopes and hills. The oldest landscapes tend to be low-lying with broad, open river valleys and low, rounded hills. The overall effect of the wearing down of an area is to level the land; the tendency is toward the reduction of all land surfaces to sea level.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">D</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">3<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Plate Tectonics<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Opposing this tendency toward leveling is a force responsible for raising mountains and plateaus and for creating new landmasses. These changes to Earth’s surface occur in the outermost solid portion of Earth, known as the lithosphere. The lithosphere consists of the crust and another region known as the upper mantle and is approximately 65 to 100 km (40 to 60 mi) thick. Compared with the interior of the Earth, however, this region is relatively thin. The lithosphere is thinner in proportion to the whole Earth than the skin of an apple is to the whole apple. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Scientists believe that the lithosphere is broken into a series of plates, or segments. According to the theory of plate tectonics, these plates move around on Earth’s surface over long periods of time. Tectonics comes from the Greek word, <i>tektonikos</i>, which means “builder.”<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">According to the theory, the lithosphere is divided into large and small plates. The largest plates include the Pacific plate, the North American plate, the Eurasian plate, the Antarctic plate, the Indo-Australian plate, and the African plate. Smaller plates include the Cocos plate, the Nazca plate, the Philippine plate, and the Caribbean plate. Plate sizes vary a great deal. The Cocos plate is 2,000 km (1,000 mi) wide, while the Pacific plate is nearly 14,000 km (nearly 9,000 mi) wide.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">These plates move in three different ways in relation to each other. They pull apart or move away from each other, they collide or move against each other, or they slide past each other as they move sideways. The movement of these plates helps explain many geological events, such as earthquakes and volcanic eruptions as well as mountain building and the formation of the oceans and continents.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">D3</span><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">a</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);"><o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">When Plates Pull Apart</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3245/2767408749_c2b57e5827_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Magma Upwelling<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Mid-ocean ridges occur along boundaries between plates of Earth’s outer shell where new seafloor is created as the plates spread apart. As plates move apart under the ocean, molten rock, or magma, wells up from deep below the surface of the seafloor. Some of the magma that ascends to the seafloor produces enormous volcanic eruptions. The rest solidifies on the edges of the plates as they spread apart, creating new rocky seafloor material.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Archive Photos<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">When the plates pull apart, two types of phenomena occur depending on whether the movement takes place in the oceans or on land. When plates pull apart on land, deep valleys known as rift valleys form. An example of a rift valley is the Great Rift Valley that extends from Syria in the Middle East to Mozambique in Africa. When plates pull apart in the oceans, long, sinuous chains of volcanic mountains called mid-ocean ridges form, and new seafloor is created at the site of these ridges. Rift valleys are also present along the crests of the mid-ocean ridges.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Most scientists believe that gravity and heat from the interior of the Earth cause the plates to move apart and to create new seafloor. According to this explanation, molten rock known as magma rises from Earth’s interior to form hot spots beneath the ocean floor. As two oceanic plates pull apart from each other in the middle of the oceans, a crack, or rupture, appears and forms the mid-ocean ridges. These ridges exist in all the world’s ocean basins and resemble the seams of a baseball. The molten rock rises through these cracks and creates new seafloor.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">D3</span><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">b</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);"><o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">When Plates Collide</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3261/2768256128_93da2e1bfd_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Converging Plates<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The outer layer of the Earth, the lithosphere, is broken into about 20 pieces, called tectonic plates. These plates slowly slide around on the asthenosphere below, periodically colliding with each other.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">When plates collide or push against each other, regions called convergent plate margins form. Along these margins, one plate is usually forced to dive below the other. As that plate dives, it triggers the melting of the surrounding lithosphere and a region just below it known as the asthenosphere. These pockets of molten crust rise behind the margin through the overlying plate, creating curved chains of volcanoes known as arcs. This process is called subduction.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">If one plate consists of oceanic crust and the other consists of continental crust, the denser oceanic crust will dive below the continental crust. If both plates are oceanic crust, then either may be subducted. If both are continental crust, subduction can continue for a while but will eventually end because continental crust is not dense enough to be forced very far into the upper mantle.</span><br /><img src="http://farm4.static.flickr.com/3117/2768256290_7c888e24f8_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Mount Everest<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Mount Everest, the world’s highest mountain at 8,850 m (29,035 ft), is located in the Himalayas. The Himalayas form the highest mountain system in the world, with more than 30 peaks towering 7,600 m (25,000 ft) or more.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Keren Su/Tony Stone Images<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The results of this subduction process are readily visible on a map showing that 80 percent of the world’s volcanoes rim the Pacific Ocean where plates are colliding against each other. The subduction zone created by the collision of two oceanic plates—the Pacific plate and the Philippine plate—can also create a trench. Such a trench resulted in the formation of the deepest point on Earth, the Mariana Trench, which is estimated to be 11,033 m (36,198 ft) below sea level.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">On the other hand, when two continental plates collide, mountain building occurs. The collision of the Indo-Australian plate with the Eurasian plate has produced the Himalayan Mountains. This collision resulted in the highest point of Earth, Mount Everest, which is 8,850 m (29,035 ft) above sea level.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">D3</span><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">c</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);"><o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">When Plates Slide Past Each Other</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3199/2768256472_dd60347534_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">San Andreas Fault, California<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The San Andreas Fault, unlike most faults that stay below the ocean, emerges from the Pacific Ocean and traverses hundreds of miles of land. It runs through California for about 1,000 km (about 600 mi) from Point Arena to the Imperial Valley. The fault marks the boundary between the North American and Pacific tectonic plates; earthquakes are caused by these plates sliding together.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Francois Gohier/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Finally, some of Earth’s plates neither collide nor pull apart but instead slide past each other. These regions are called transform margins. Few volcanoes occur in these areas because neither plate is forced down into Earth’s interior and little melting occurs. Earthquakes, however, are abundant as the two rigid plates slide past each other. The San Andreas Fault in California is a well-known example of a transform margin.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The movement of plates occurs at a slow pace, at an average rate of only 2.5 cm (1 in) per year. But over millions of years this gradual movement results in radical changes. Current plate movement is making the Pacific Ocean and Mediterranean Sea smaller, the Atlantic Ocean larger, and the Himalayan Mountains higher.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">V<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">EARTH’S INTERIOR</span></p></td></tr></tbody></table><br /><img style="width: 466px; height: 275px;" src="http://farm4.static.flickr.com/3017/2767409307_79fc968f94_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Internal Structure of the Earth<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Earth is made up of a series of layers that formed early in the planet’s history, as heavier material gravitated toward the center and lighter material floated to the surface. The dense, solid, inner core of iron is surrounded by a liquid, iron, outer core. The lower mantle consists of molten rock, which is surrounded by partially molten rock in the asthenosphere and solid rock in the upper mantle and crust. Between some of the layers, there are chemical or structural changes that form discontinuities. Lighter elements, such as silicon, aluminum, calcium, potassium, sodium, and oxygen, compose the outer crust.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The interior of Earth plays an important role in plate tectonics. Scientists believe it is also responsible for Earth’s magnetic field. This field is vital to life because it shields the planet’s surface from harmful cosmic rays and from a steady stream of energetic particles from the Sun known as the solar wind.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Composition of the Interior<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Earth’s interior consists of the mantle and the core. The mantle and core make up by far the largest part of Earth’s mass. The distance from the base of the crust to the center of the core is about 6,400 km (about 4,000 mi).<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Scientists have learned about Earth’s interior by studying rocks that formed in the interior and rose to the surface. The study of meteorites, which are believed to be made of the same material that formed the Earth and its interior, has also offered clues about Earth’s interior. Finally, seismic waves generated by earthquakes provide geophysicists with information about the composition of the interior. The sudden movement of rocks during an earthquake causes vibrations that transmit energy through the Earth in the form of waves. The way these waves travel through the interior of Earth reveals the nature of materials inside the planet.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The mantle consists of three parts: the lower part of the lithosphere, the region below it known as the asthenosphere, and the region below the asthenosphere called the lower mantle. The entire mantle extends from the base of the crust to a depth of about 2,900 km (about 1,800 mi). Scientists believe the asthenosphere is made up of mushy plastic-like rock with pockets of molten rock. The term <i>asthenosphere</i> is derived from Greek and means “weak layer.” The asthenosphere’s soft, plastic quality allows plates in the lithosphere above it to shift and slide on top of the asthenosphere. This shifting of the lithosphere’s plates is the source of most tectonic activity. The asthenosphere is also the source of the basaltic magma that makes up much of the oceanic crust and rises through volcanic vents on the ocean floor.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The mantle consists of mostly solid iron-magnesium silicate rock mixed with many other minor components including radioactive elements. However, even this solid rock can flow like a “sticky” liquid when it is subjected to enough heat and pressure. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The core is divided into two parts, the outer core and the inner core. The outer core is about 2,260 km (about 1,404 mi) thick. The outer core is a liquid region composed mostly of iron, with smaller amounts of nickel and sulfur in liquid form. The inner core is about 1,220 km (about 758 mi) thick. The inner core is solid and is composed of iron, nickel, and sulfur in solid form. Because the inner core is surrounded by a liquid region, it can rotate independently. Recent scientific studies indicate that the inner core may actually rotate faster than the rest of the planet, making one full extra spin over a period of 700 to 1,200 years. The inner core and the outer core also contain a small percentage of radioactive material. The existence of radioactive material is one of the sources of heat in Earth’s interior because as radioactive material decays, it gives off heat. Temperatures in the inner core may be as high as 6650°C (12,000°F).<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The Core and Earth’s Magnetism</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3255/2768256746_3a2e9f6bc6_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Earth’s Magnetic Field<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Scientists believe that Earth’s liquid iron core is instrumental in creating a magnetic field that surrounds Earth and shields the planet from harmful cosmic rays and the Sun’s solar wind. The idea that Earth is like a giant magnet was first proposed in 1600 by English physician and natural philosopher William Gilbert. Gilbert proposed the idea to explain why the magnetized needle in a compass points north. According to Gilbert, Earth’s magnetic field creates a magnetic north pole and a magnetic south pole. The magnetic poles do not correspond to the geographic North and South poles, however. Moreover, the magnetic poles wander and are not always in the same place. The north magnetic pole is currently close to Ellef Ringnes Island in the Queen Elizabeth Islands near the boundary of Canada’s Northwest Territories with Nunavut. The south magnetic pole lies just off the coast of Wilkes Land, Antarctica.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Not only do the magnetic poles wander, but they also reverse their polarity—that is, the north magnetic pole becomes the south magnetic pole and vice versa. Magnetic reversals have occurred at least 170 times over the past 100 million years. The reversals occur on average about every 200,000 years and take place gradually over a period of several thousand years. Scientists still do not understand why these magnetic reversals occur but think they may be related to Earth’s rotation and changes in the flow of liquid iron in the outer core.</span><br /><img src="http://farm4.static.flickr.com/3177/2768257032_22c5d54ed0_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Aurora Borealis<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The aurora borealis, commonly known as the northern lights, creates a spectacular light show near Fairbanks, Alaska. Auroras, most frequently seen in the far northern and far southern regions of the globe, are common sights in the Alaskan sky. Luminous displays visible to the naked eye only at night, auroras occur when charged particles from the Sun interact with gases in Earth’s atmosphere.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Jack Finch/Science Source/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Some scientists theorize that the flow of liquid iron in the outer core sets up electrical currents that produce Earth’s magnetic field. Known as the dynamo theory, this theory appears to be the best explanation yet for the origin of the magnetic field. Earth’s magnetic field operates in a region above Earth’s surface known as the magnetosphere. The magnetosphere is shaped somewhat like a teardrop with a long tail that trails away from the Earth due to the force of the solar wind.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Inside the magnetosphere are the Van Allen radiation belts, named for the American physicist James A. Van Allen who discovered them in 1958. The Van Allen belts are regions where charged particles from the Sun and from cosmic rays are trapped and sent into spiral paths along the lines of Earth’s magnetic field. The radiation belts thereby shield Earth’s surface from these highly energetic particles. Occasionally, however, due to extremely strong magnetic fields on the Sun’s surface, which are visible as sunspots, a brief burst of highly energetic particles streams along with the solar wind. Because Earth’s magnetic field lines converge and are closest to the surface at the poles, some of these energetic particles sneak through and interact with Earth’s atmosphere, creating the phenomenon known as an aurora.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">VI<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">EARTH’S PAST<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "Times New Roman","serif"; display: none;"><o:p> </o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Origin of Earth<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Most scientists believe that the Earth, Sun, and all of the other planets and moons in the solar system formed about 4.6 billion years ago from a giant cloud of gas and dust known as the solar nebula. The gas and dust in this solar nebula originated in a star that ended its life in a violent explosion known as a supernova. The solar nebula consisted principally of hydrogen, the lightest element, but the nebula was also seeded with a smaller percentage of heavier elements, such as carbon and oxygen. All of the chemical elements we know were originally made in the star that became a supernova. Our bodies are made of these same chemical elements. Therefore, all of the elements in our solar system, including all of the elements in our bodies, originally came from this star-seeded solar nebula.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Due to the force of gravity tiny clumps of gas and dust began to form in the early solar nebula. As these clumps came together and grew larger, they caused the solar nebula to contract in on itself. The contraction caused the cloud of gas and dust to flatten in the shape of a disc. As the clumps continued to contract, they became very dense and hot. Eventually the atoms of hydrogen became so dense that they began to fuse in the innermost part of the cloud, and these nuclear reactions gave birth to the Sun. The fusion of hydrogen atoms in the Sun is the source of its energy.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Many scientists favor the planetesimal theory for how the Earth and other planets formed out of this solar nebula. This theory helps explain why the inner planets became rocky while the outer planets, except for Pluto, are made up mostly of gases. The theory also explains why all of the planets orbit the Sun in the same plane.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">According to this theory, temperatures decreased with increasing distance from the center of the solar nebula. In the inner region, where Mercury, Venus, Earth, and Mars formed, temperatures were low enough that certain heavier elements, such as iron and the other heavy compounds that make up rock, could condense out—that is, could change from a gas to a solid or liquid. Due to the force of gravity, small clumps of this rocky material eventually came together with the dust in the original solar nebula to form protoplanets or planetesimals (small rocky bodies). These planetesimals collided, broke apart, and re-formed until they became the four inner rocky planets. The inner region, however, was still too hot for other light elements, such as hydrogen and helium, to be retained. These elements could only exist in the outermost part of the disc, where temperatures were lower. As a result two of the outer planets—Jupiter and Saturn—are mostly made of hydrogen and helium, which are also the dominant elements in the atmospheres of Uranus and Neptune.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The Early Earth</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3042/2767409853_5eea7f0e3b_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The Early Earth<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Life originated on Earth about four billion years ago, when oceans dotted with volcanic islands covered most of Earth’s surface and continents were very small. The air was hot and contained almost no breathable oxygen. The Moon was much closer to Earth, and a day was less than 15 hours long. Meteorites fell more frequently, and there was more volcanic activity than there is today.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Within the planetesimal Earth, heavier matter sank to the center and lighter matter rose toward the surface. Most scientists believe that Earth was never truly molten and that this transfer of matter took place in the solid state. Much of the matter that went toward the center contained radioactive material, an important source of Earth’s internal heat. As heavier material moved inward, lighter material moved outward, the planet became layered, and the layers of the core and mantle were formed. This process is called differentiation. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Not long after they formed, more than 4 billion years ago, the Earth and the Moon underwent a period when they were bombarded by meteorites, the rocky debris left over from the formation of the solar system. The impact craters created during this period of heavy bombardment are still visible on the Moon’s surface, which is unchanged. Earth’s craters, however, were long ago erased by weathering, erosion, and mountain building. Because the Moon has no atmosphere, its surface has not been subjected to weathering or erosion. Thus, the evidence of meteorite bombardment remains.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Energy released from the meteorite impacts created extremely high temperatures on Earth that melted the outer part of the planet and created the crust. By 4 billion years ago, both the oceanic and continental crust had formed, and the oldest rocks were created. These rocks are known as the Acasta Gneiss and are found in Canada’s Northwest Territories. Due to the meteorite bombardment, the early Earth was too hot for liquid water to exist and so it was impossible for life to exist.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">C<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Geologic Time</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3014/2767410093_001ce5c19c_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Fossil-bearing Rocks<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Sedimentary rocks, such as this fossil-bearing limestone, can help geologists determine geologic time. Because the bottom layers were deposited first, the oldest fossils are found in the bottom layers of sedimentary rocks. The accumulation of shells or shell fragments and other fossils in limestone provides geologists with a record of the evolution of the animals that used to live in the ancient oceans.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Carolina Biological Supply/Phototake NYC<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Geologists divide the history of the Earth into three eons: the Archean Eon, which lasted from around 4 billion to 2.5 billion years ago; the Proterozoic Eon, which lasted from 2.5 billion to 543 million years ago; and the Phanerozoic Eon, which lasted from 543 million years ago to the present. Each eon is subdivided into different eras. For example, the Phanerozoic Eon includes the Paleozoic Era, the Mesozoic Era, and the Cenozoic Era. In turn, eras are further divided into periods. For example, the Paleozoic Era includes the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian Periods.</span><br /><img src="http://farm4.static.flickr.com/3140/2768257600_4398d530e5_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Geologic Time Scale<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The Archean Eon is subdivided into four eras, the Eoarchean, the Paleoarchean, the Mesoarchean, and the Neoarchean. The beginning of the Archean is generally dated as the age of the oldest terrestrial rocks, which are about 4 billion years old. The Archean Eon ended 2.5 billion years ago when the Proterozoic Eon began. The Proterozoic Eon is subdivided into three eras: the Paleoproterozoic Era, the Mesoproterozoic Era, and the Neoproterozoic Era. The Proterozoic Eon lasted from 2.5 billion years ago to 543 million years ago when the Phanerozoic Eon began. The Phanerozoic Eon is subdivided into three eras: the Paleozoic Era from 543 million to 248 million years ago, the Mesozoic Era from 248 million to 65 million years ago, and the Cenozoic Era from 65 million years ago to the present.</span><br /><img style="width: 365px; height: 215px;" src="http://farm4.static.flickr.com/3202/2768257908_de2212cd66_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Stratigraphic Column<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Fossils preserved in rock strata provide scientists with clues to evolutionary history. This stratigraphic column is based on paleontological evidence and shows the order in which organisms appeared in the fossil-rich Paleozoic era. Each layer represents a particular time frame and shows a representative organism that flourished during that time. Although fossils are rarely found in the idealized and localized fashion shown here, they are often in more or less chronological order. Generally, the oldest fossils appear in lower layers, and the most recent fossils at the top, so that placement may be used as an aid in dating the specimens.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Geologists base these divisions on the study and dating of rock layers or strata, including the fossilized remains of plants and animals found in those layers. Until the late 1800s scientists could only determine the relative ages of rock strata. They knew that in general the top layers of rock were the youngest and formed most recently, while deeper layers of rock were older. The field of stratigraphy shed much light on the relative ages of rock layers.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The study of fossils also enabled geologists to determine the relative ages of different rock layers. The fossil record helped scientists determine how organisms evolved or when they became extinct. By studying rock layers around the world, geologists and paleontologists saw that the remains of certain animal and plant species occurred in the same layers, but were absent or altered in other layers. They soon developed a fossil index that also helped determine the relative ages of rock layers.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Beginning in the 1890s, scientists learned that radioactive elements in rock decay at a known rate. By studying this radioactive decay, they could determine an absolute age for rock layers. This type of dating, known as radiometric dating, confirmed the relative ages determined through stratigraphy and the fossil index and assigned absolute ages to the various strata. As a result scientists were able to assemble Earth’s geologic time scale from the Archean Eon to the present. <i>See also </i>Geologic Time.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">C</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">1<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Precambrian</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3122/2768257976_af9e46d98e_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Cyanobacteria<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Cyanobacteria (formerly blue-green algae) are among the most ancient organisms on earth. These photosynthetic organisms can be single-celled, connected in afilamentous form as shown here, or arranged in simple colonies. Cyanobacteria are capable of enduring a wide variety of environmental conditions ranging from freshwater and marine habitats to snowfields and glaciers. They are capable of surviving and flourishing even at extremely high temperatures.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Peter Parks/Oxford Scientific Films<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The Precambrian is a time span that includes the Archean and Proterozoic eons and began about 4 billion years ago. The Precambrian marks the first formation of continents, the oceans, the atmosphere, and life. The Precambrian represents the oldest chapter in Earth’s history that can still be studied. Very little remains of Earth from the period of 4.6 billion to about 4 billion years ago due to the melting of rock caused by the early period of meteorite bombardment. Rocks dating from the Precambrian, however, have been found in Africa, Antarctica, Australia, Brazil, Canada, and Scandinavia. Some zircon mineral grains deposited in Australian rock layers have been dated to 4.2 billion years.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The Precambrian is also the longest chapter in Earth’s history, spanning a period of about 3.5 billion years. During this timeframe, the atmosphere and the oceans formed from gases that escaped from the hot interior of the planet as a result of widespread volcanic eruptions. The early atmosphere consisted primarily of nitrogen, carbon dioxide, and water vapor. As Earth continued to cool, the water vapor condensed out and fell as precipitation to form the oceans. Some scientists believe that much of Earth’s water vapor originally came from comets containing frozen water that struck Earth during the period of meteorite bombardment. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">By studying 2-billion-year-old rocks found in northwestern Canada, as well as 2.5-billion-year-old rocks in China, scientists have found evidence that plate tectonics began shaping Earth’s surface as early as the middle Precambrian. About a billion years ago, the Earth’s plates were centered around the South Pole and formed a supercontinent called Rodinia. Slowly, pieces of this supercontinent broke away from the central continent and traveled north, forming smaller continents.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Life originated during the Precambrian. The earliest fossil evidence of life consists of prokaryotes, one-celled organisms that lacked a nucleus and reproduced by dividing, a process known as asexual reproduction. Asexual division meant that a prokaryote’s hereditary material was copied unchanged. The first prokaryotes were bacteria known as archaebacteria. Scientists believe they came into existence perhaps as early as 3.8 billion years ago, but certainly by about 3.5 billion years ago, and were anaerobic—that is, they did not require oxygen to produce energy. Free oxygen barely existed in the atmosphere of the early Earth. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Archaebacteria were followed about 3.46 billion years ago by another type of prokaryote known as cyanobacteria or blue-green algae. These cyanobacteria gradually introduced oxygen in the atmosphere as a result of photosynthesis. In shallow tropical waters, cyanobacteria formed mats that grew into humps called stromatolites. Fossilized stromatolites have been found in rocks in the Pilbara region of western Australia that are more than 3.4 billion years old and in rocks of the Gunflint Chert region of northwest Lake Superior that are about 2.1 billion years old.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">For billions of years, life existed only in the simple form of prokaryotes. Prokaryotes were followed by the relatively more advanced eukaryotes, organisms that have a nucleus in their cells and that reproduce by combining or sharing their heredity makeup rather than by simply dividing. Sexual reproduction marked a milestone in life on Earth because it created the possibility of hereditary variation and enabled organisms to adapt more easily to a changing environment. The very latest part of Precambrian time some 560 million to 545 million years ago saw the appearance of an intriguing group of fossil organisms known as the Ediacaran fauna. First discovered in the northern Flinders Range region of Australia in the mid-1940s and subsequently found in many locations throughout the world, these strange fossils appear to be the precursors of many of the fossil groups that were to explode in Earth's oceans in the Paleozoic Era. <i>See also </i>Evolution; Natural Selection.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">C</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">2<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Paleozoic Era</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3211/2767410685_d97ee8bd3e_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The Earliest Animals<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The earliest known animals on Earth were a bizarre collection of life forms that emerged just prior to and during the Cambrian Period, some of which were exquisitely preserved in fossil beds in various parts of the world. Some of the more extraordinary creatures (depicted in this artist's conception) were the formidable predator <i>Anomalocaris</i> (foreground upper right) about to make a meal of <i>Waptia</i>, which it holds in its extended claws. Just below <i>Anomalocaris</i> and slightly to its left is <i>Opabinia</i> using its long, trunklike snout to grasp <i>Burgessochaeta,</i> a bristle worm. The fernlike objects (left and center) are actually animals, as are the primitive sponges (center foreground) that resemble a saguaro cactus. The depictions of these fernlike animals are based on a group of fossils known as the Ediacaran fossils and date from about 550 million years ago.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">D.W. Miller<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">At the start of the Paleozoic Era about 543 million years ago, an enormous expansion in the diversity and complexity of life occurred. This event took place in the Cambrian Period and is called the Cambrian explosion. Nothing like it has happened since. Almost all of the major groups of animals we know today made their first appearance during the Cambrian explosion. Almost all of the different “body plans” found in animals today—that is, the way an animal’s body is designed, with heads, legs, rear ends, claws, tentacles, or antennae—also originated during this period. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Fishes first appeared during the Paleozoic Era, and multicellular plants began growing on the land. Other land animals, such as scorpions, insects, and amphibians, also originated during this time. Just as new forms of life were being created, however, other forms of life were going out of existence. Natural selection meant that some species were able to flourish, while others failed. In fact, mass extinctions of animal and plant species were commonplace. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Most of the early complex life forms of the Cambrian explosion lived in the sea. The creation of warm, shallow seas, along with the buildup of oxygen in the atmosphere, may have aided this explosion of life forms. The shallow seas were created by the breakup of the supercontinent Rodinia. During the Ordovician, Silurian, and Devonian periods, which followed the Cambrian Period and lasted from 490 million to 354 million years ago, some of the continental pieces that had broken off Rodinia collided. These collisions resulted in larger continental masses in equatorial regions and in the Northern Hemisphere. The collisions built a number of mountain ranges, including parts of the Appalachian Mountains in North America and the Caledonian Mountains of northern Europe.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Toward the close of the Paleozoic Era, two large continental masses, Gondwanaland to the south and Laurasia to the north, faced each other across the equator. Their slow but eventful collision during the Permian Period of the Paleozoic Era, which lasted from 290 million to 248 million years ago, assembled the supercontinent Pangaea and resulted in some of the grandest mountains in the history of Earth. These mountains included other parts of the Appalachians and the Ural Mountains of Asia. At the close of the Paleozoic Era, Pangaea represented over 90 percent of all the continental landmasses. Pangaea straddled the equator with a huge mouthlike opening that faced east. This opening was the Tethys Ocean, which closed as India moved northward creating the Himalayas. The last remnants of the Tethys Ocean can be seen in today’s Mediterranean Sea.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The Paleozoic came to an end with a major extinction event, when perhaps as many as 90 percent of all plant and animal species died out. The reason is not known for sure, but many scientists believe that huge volcanic outpourings of lavas in central Siberia, coupled with an asteroid impact, were joint contributing factors.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">C</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">3<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Mesozoic Era</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3264/2768258422_b9f249c124_m.jpg" /><br /><br /><img src="http://farm4.static.flickr.com/3288/2768258650_5dc30528bd_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Extent of Pleistocene Epoch Glaciation<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">During the Pleistocene epoch of the Quaternary Ice Age, glaciers (represented on map in white) covered much of the Earth’s northern hemisphere. Ice Ages consist of glacial periods and warmer interglacial periods. Although the Pleistocene, the Earth’s most recent glacial event, ended 10,000 years ago, many scientists believe that the Earth remains in an interglacial state of the Quaternary Ice Age.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The Cenozoic Era, beginning about 65 million years ago, is the period when mammals became the dominant form of life on land. Human beings first appeared in the later stages of the Cenozoic Era. In short, the modern world as we know it, with its characteristic geographical features and its animals and plants, came into being. All of the continents that we know today took shape during this era.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">A single catastrophic event may have been responsible for this relatively abrupt change from the Age of Reptiles to the Age of Mammals. Most scientists now believe that a huge asteroid or comet struck the Earth at the end of the Mesozoic and the beginning of the Cenozoic eras, causing the extinction of many forms of life, including the dinosaurs. Evidence of this collision came with the discovery of a large impact crater off the coast of Mexico’s Yucatán Peninsula and the worldwide finding of iridium, a metallic element rare on Earth but abundant in meteorites, in rock layers dated from the end of the Cretaceous Period. The extinction of the dinosaurs opened the way for mammals to become the dominant land animals.<o:p></o:p></span></p> <span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The Cenozoic Era is divided into the Tertiary and the Quaternary periods. The Tertiary Period lasted from about 65 million to about 1.8 million years ago. The Quaternary Period began about 1.8 million years ago and continues to the present day. These periods are further subdivided into epochs, such as the Pleistocene, from 1.8 million to 10,000 years ago, and the Holocene, from 10,000 years ago to the present.</span><br /><img src="http://farm4.static.flickr.com/3085/2767411311_de9e648651_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Glaciers<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Discovery Enterprises, LLC<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Early in the Tertiary Period, Pangaea was completely disassembled, and the modern continents were all clearly outlined. India and other continental masses began colliding with southern Asia to form the Himalayas. Africa and a series of smaller microcontinents began colliding with southern Europe to form the Alps. The Tethys Ocean was nearly closed and began to resemble today’s Mediterranean Sea. As the Tethys continued to narrow, the Atlantic continued to open, becoming an ever-wider ocean. Iceland appeared as a new island in later Tertiary time, and its active volcanism today indicates that seafloor spreading is still causing the country to grow. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Late in the Tertiary Period, about 6 million years ago, humans began to evolve in Africa. These early humans began to migrate to other parts of the world between 2 million and 1.7 million years ago.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The Quaternary Period marks the onset of the great ice ages. Many times, perhaps at least once every 100,000 years on average, vast glaciers 3 km (2 mi) thick invaded much of North America, Europe, and parts of Asia. The glaciers eroded considerable amounts of material that stood in their paths, gouging out U-shaped valleys. Anatomically modern human beings, known as <i>Homo sapiens</i>, became the dominant form of life in the Quaternary Period. Most <i>anthropologists</i> (scientists who study human life and culture) believe that anatomically modern humans originated only recently in Earth’s 4.6-billion-year history, within the past 200,000 years. <i>See also </i>Human Evolution.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">VII<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">EARTH’S FUTURE<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">With the rise of human civilization about 8,000 years ago and especially since the Industrial Revolution in the mid-1700s, human beings began to alter the surface, water, and atmosphere of Earth. In doing so, they have become active geological agents, not unlike other forces of change that influence the planet. As a result, Earth’s immediate future depends to a great extent on the behavior of humans. For example, the widespread use of fossil fuels is releasing carbon dioxide and other greenhouse gases into the atmosphere and threatens to warm the planet’s surface. This global warming could melt glaciers and the polar ice caps, which could flood coastlines around the world and many island nations. In effect, the carbon dioxide that was removed from Earth’s early atmosphere by the oceans and by primitive plant and animal life, and subsequently buried as fossilized remains in sedimentary rock, is being released back into the atmosphere and is threatening the existence of living things. <i>See also </i>Global Warming.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Even without human intervention, Earth will continue to change because it is geologically active. Many scientists believe that some of these changes can be predicted. For example, based on studies of the rate that the seafloor is spreading in the Red Sea, some geologists predict that in 200 million years the Red Sea will be the same size as the Atlantic Ocean is today. Other scientists predict that the continent of Asia will break apart millions of years from now, and as it does, Lake Baikal in Siberia will become a vast ocean, separating two landmasses that once made up the Asian continent.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In the far, far distant future, however, scientists believe that Earth will become an uninhabitable planet, scorched by the Sun. Knowing the rate at which nuclear fusion occurs in the Sun and knowing the Sun’s mass, <i>astrophysicists</i> (scientists who study stars) have calculated that the Sun will become brighter and hotter about 3 billion years from now, when it will be hot enough to boil Earth’s oceans away. Based on studies of how other Sun-like stars have evolved, scientists predict that the Sun will become a <i>red giant</i>, a star with a very large, hot atmosphere, about 7 billion years from now. As a red giant the Sun’s outer atmosphere will expand until it engulfs the planet Mercury. The Sun will then be 2,000 times brighter than it is now and so hot it will melt Earth’s rocks. Earth will end its existence as a burnt cinder. <i>See also </i>Sun.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Three billion years is the life span of millions of human generations, however. Perhaps by then, humans will have learned how to journey beyond the solar system to colonize other planets in the Milky Way Galaxy and find another place to call “home.” <o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 15pt;"><span style="font-size: 12pt; font-family: "Times New Roman","serif";"><br /><br />Reviewed By:<br />Alan V. Morgan<o:p></o:p></span></p> <b><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif";">Microsoft ® Encarta ® 2007.</span></b><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif";"> © 1993-2006 Microsoft Corporation. All rights reserved.</span>ghozian karamihttp://www.blogger.com/profile/13214011599962806335noreply@blogger.com0tag:blogger.com,1999:blog-192751622867664710.post-87487974022480068582008-12-11T06:39:00.000-08:002008-12-11T06:53:37.519-08:00Geology<p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 24pt; font-family: "MS Reference Serif","serif";">Geology<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">I<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">INTRODUCTION</span></p></td></tr></tbody></table><img src="http://farm4.static.flickr.com/3219/2767405197_059341a33f_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Cliffs of Normandy<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Composed of the same form of limestone as the White Cliffs of Dover in England, the Cliffs of Normandy are a distinctive landmark on the French coastline. Geological evidence suggests that a land bridge connected the two land masses during the Cretaceous Era. The arches shown here are a result of the action of water on softer sections of the rock.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Alan Carr/Robert Harding Picture Library<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Geology, study of the planet earth, its rocky exterior, its history, and the processes that act upon it. Geology is also referred to as earth science and geoscience. The word geology comes from the Greek <i>geo,</i> “earth,” and <i>logia,</i> “the study of.” Geologists seek to understand how the earth formed and evolved into what it is today, as well as what made the earth capable of supporting life. Geologists study the changes that the earth has undergone as its physical, chemical, and biological systems have interacted during its 4.5 billion year history.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Geology is an important way of understanding the world around us, and it enables scientists to predict how our planet will behave. Scientists and others use geology to understand how geological events and earth’s geological history affect people, for example, in terms of living with natural disasters and using the earth’s natural resources. As the human population grows, more and more people live in areas exposed to natural geologic hazards, such as floods, earthquakes, tsunamis, volcanoes, and landslides. Some geologists use their knowledge to try to understand these natural hazards and forecast potential geologic events, such as volcanic eruptions or earthquakes. They study the history of these events as recorded in rocks and try to determine when the next eruption or earthquake will occur. They also study the geologic record of climate change in order to help predict future changes. As human population grows, geologists’ ability to locate fossil and mineral resources, such as oil, coal, iron, and aluminum, becomes more important. Finding and maintaining a clean water supply, and disposing safely of waste products, requires understanding the earth’s systems through which they cycle.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The field of geology includes subfields that examine all of the earth's systems, from the deep interior core to the outer atmosphere, including the hydrosphere (the waters of the earth) and the biosphere (the living component of earth). Generally, these subfields are divided into the two major categories of physical and historical geology. Geologists also examine events such as asteroid impacts, mass extinctions, and ice ages. Geologic history shows that the processes that shaped the earth are still acting on it and that change is normal.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Many other scientific fields overlap extensively with geology, including oceanography, atmospheric sciences, physics, chemistry, botany, zoology, and microbiology. Geology is also used to study other planets and moons in our solar system. Specialized fields of extraterrestrial geology include lunar geology, the study of earth’s moon, and astrogeology, the study of other rocky bodies in the solar system and beyond. Scientific teams currently studying Mars and the moons of Jupiter include geologists.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">II<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">GUIDING PRINCIPLES OF GEOLOGY<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Geologists use three main principles, or concepts, to study earth and its history. The first concept, called plate tectonics, is the theory that the earth’s surface is made up of separate, rigid plates moving and floating over another, less rigid layer of rock. These plates are made up of the continents and the ocean floor as well as the rigid rock beneath them. The second guiding concept is that many processes that occur on the earth may be described in terms of recycling: the reuse of the same materials in cycles, or repeating series of events. The third principle is called uniformitarianism. Uniformitarianism states that the physical and chemical processes that have acted throughout geologic time are the same processes that are observable today. Because of this, geologists can use their knowledge of what is happening on the earth right now to help explain what happened in the past. <o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Plate Tectonics</span></p></td></tr></tbody></table><br /><br /><img src="http://farm3.static.flickr.com/2144/2768252478_270707a51d_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Plate Tectonics<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Plate tectonics is the unifying theory of geology. It was established in the 1960s, making it one of the most recent revolutions in all of science. The theory describes the lithosphere (the outer rocky layer of the earth) as a collection of rigid plates that move sideways above a less rigid layer called the asthenosphere. The asthenosphere is made up of rock that is under tremendous pressure, which softens it and allows it to move and circulate slowly. Plate tectonics is useful in the field of geology because it can be used to explain a variety of geologic processes, including volcanic activity, earthquakes, and mountain building.<i> See also </i>Earth.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Geologic Cycles<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">A second guiding principle of geology is the principle of recycling materials, or using materials many times. All processes in geology can be viewed as a series of mostly closed cycles, meaning the materials of the cycles are found on earth, and very few materials from outside our world are introduced into these cycles. The energy that drives geologic recycling comes from two sources: the sun and the earth's interior. Two examples of geologic cycles are the rock cycle and the water cycle.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The rock cycle begins as rocks are uplifted, or pushed up by tectonic forces. The exposed rocks erode as a result of surface processes, such as rain and wind. The eroded particles, or sediment, travel by wind or moving water until they are deposited, and the deposited material settles into layers. Additional sediment may bury these layers until heat and pressure metamorphose, or change, the underlying sediment to metamorphic rock. Additional sediment may compact the layers into sedimentary rocks. Rocks can also be subducted (sunk down into the lower layers of the earth) by plate tectonic processes. Buried and subducted rocks may also melt and recrystallize into igneous rocks (<i>see </i>Magma). Metamorphic, sedimentary, and igneous rocks may then be uplifted, starting the rock cycle again.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The water cycle is also known as the hydrologic cycle. Phases of the water cycle are storage, evaporation, precipitation, and runoff. Water is stored in glaciers, polar ice caps, lakes, rivers, oceans, and in the ground. Heat from the sun evaporates water from the earth’s surface and the water then condenses to form clouds. It falls back to the earth as precipitation, either as rain or snow, then runs into the oceans through rivers or underground and begins the cycle again.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">C<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Uniformitarianism<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Uniformitarianism, or actualism, helps geologists use their knowledge of modern processes and events to reconstruct the past. The principle of uniformitarianism depends on the 'uniformity of laws,' which assumes that the laws of physics and chemistry have remained constant. To test uniformity of laws, geologists can examine preserved one-billion-year-old ripples that look very much like ripples on the beach today. If gravity had changed, water and sand would have interacted differently in the past, and the ripple evidence would be different. Also, minerals in three-billion-year-old rocks are the same as minerals forming in rocks today, confirming the uniformity of chemical laws. Uniformitarianism contrasts with, for example, the idea that past events such as floods or earthquakes were caused by divine intervention or supernatural causes. Catastrophism, which calls on major catastrophes to explain earth’s history, is also sometimes contrasted with uniformitarianism. However, uniformitarianism can include past catastrophes.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">III<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">THE GEOLOGIC TIME SCALE</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3186/2767405349_aee53b3f72_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Geologic Time Scale<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Geologists have created a geologic time scale to provide a common vocabulary for talking about past events. The practice of determining when past geologic events occurred is called geochronology. This practice began in the 1700s and has sometimes involved some personal and international disputes that led to differences in terminology. Today the geologic time scale is generally agreed upon and used by scientists around the world, dividing time into eons, eras, periods, and epochs. Every few years, the numerical time scale is refined based on new evidence, and geologists publish an update.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Geologists use several methods to determine geologic time. These methods include physical stratigraphy, or the placement of events in the order of their occurrence, and biostratigraphy, which uses fossils to determine geologic time. Another method geologists use is correlation, which allows geologists to determine whether rocks in different geographic locations are the same age. In radiometric dating, geologists use the rate of decay of certain radioactive elements in minerals to assign numerical ages to the rocks.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The process of determining geologic time includes several steps. Geologists first determine the relative age of rocks—which rocks are older and which are younger. They then may correlate rocks to determine which rocks are the same age. Next, they construct a geologic time scale. Finally, they determine the specific numerical ages of rocks by various dating methods and assign numbers to the time scale.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Relative Time<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Geologists create a relative time scale using rock sequences and the fossils contained within these sequences. The scale they create is based on The Law of Superposition, which states that in a regular series of sedimentary rock strata, or layers, the oldest strata will be at the bottom, and the younger strata will be on top. Danish geologist Nicolaus Steno (also called Niels Stensen) used the idea of uniformity of physical processes. Steno noted that sediment was denser than liquid or air, so it settled until it reached another solid. The newer sediment on the top layer is younger than the layer it settled upon. Since this is what happens in the world today, it should also determine how rock layers formed in the past. Crosscutting relationships are also used to determine the relative age of rocks. For instance, if a thin intrusion of granite, called a dike, cuts through a layer of limestone, the granite must be younger than the limestone.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Biostratigraphy</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3079/2767405477_bbc83f0f43_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Fossil-bearing Rocks<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Sedimentary rocks, such as this fossil-bearing limestone, can help geologists determine geologic time. Because the bottom layers were deposited first, the oldest fossils are found in the bottom layers of sedimentary rocks. The accumulation of shells or shell fragments and other fossils in limestone provides geologists with a record of the evolution of the animals that used to live in the ancient oceans.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Carolina Biological Supply/Phototake NYC<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In the field of biostratigraphy geologists study the placement of fossils to determine geologic time. British surveyor William Smith and French anatomist Georges Cuvier both reasoned that in a series of fossil-bearing rocks, the oldest fossils are at the bottom, with successively younger fossils above. They thus extended Steno's Law of Superposition and recognized that fossils could be used to determine geologic time. This principle is called fossil succession. Smith and Cuvier also noted that unique fossils were characteristic of different layers. Biostratigraphy is most useful for determining geologic time during the Phanerozoic Eon (Greek <i>phaneros,</i> “evident”; <i>zoic</i>, “life”), the time of visible and abundant fossil life that has lasted for about the past 570 million years. Although fossils exist that are as old as three billion years or more, they are not common. Few fossils exist that are useful for determining geologic age from time before about 1 billion years ago, so biostratigraphy is of limited use in older sedimentary rocks.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">C<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Correlation<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Using correlation to determine which rocks are of equal age is important for reconstructing snapshots in geologic history. Correlation may use the physical characteristics of rocks or fossils to determine equivalent age. For example, the limestone at the top of one side of the Grand Canyon can be correlated to the opposite side of the canyon. Also, ash from a volcanic eruption can be correlated over long distances and wide areas. Fossils are the most useful tools for correlation. Since the work of Smith and Cuvier, biostratigraphers have noted that 'like fossils are of like age.” This is the principle of fossil correlation.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">D<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Radiometric Dating<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Another fundamental goal of geochronology is to determine numerical ages of rocks and to assign numbers to the geologic time scale. The primary tool for this task is radiometric dating, in which the decay of radioactive elements is used to date rocks and minerals. Radiometric dating works best on igneous rocks (rocks that crystallized from molten material). It can also be used to date minerals in metamorphic rocks (rocks that formed when parent rock was submitted to intense heat and pressure and metamorphosed into another type of rock). It is of limited use, however, in sedimentary rocks formed by the compaction of layers of sediment. One of the great triumphs of geochronology is that numbers acquired by radiometric dating matched predictions based on superposition and other means of geologic age determination, confirming the assumption of uniformitarianism. Using dated rocks, geologists have been able to assign numbers to the geologic time scale. <i>See also </i>Dating Methods.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">IV<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">GEOLOGIC SPATIAL SCALES</span></p></td></tr></tbody></table><br /><br /><img src="http://farm4.static.flickr.com/3087/2768252784_66671cb662_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Uluru<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Uluru, also called Ayers Rock, is one of the largest monoliths, or rock masses, in the world. Located in Uluru-Kata Tjuta National Park in central Australia, the monolith measures about 3.6 km (2.2 mi) long and 348 m (1,142 ft) high. Rock paintings made thousands of years ago by Aboriginal artists cover the walls of many caves in Uluru.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Art Wolfe/Tony Stone Images<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In order to understand geologic processes and to reconstruct the geologic past, geologists work at different spatial, or size, scales—scales that range from microscopic to planetary. In order to work at these spatial scales, they use a number of tools. At the microscopic level, traditional tools include the petrographic microscope, used to identify minerals and examine rock textures. Modern tools for examining rock chemistry and structure include complex scanning electron microscopes, microprobes that can obtain very small geologic or mineralogic samples, and mass spectrometers (instruments that measure the quantity of atoms, or groups of atoms, in a geologic sample). Geologists can also use lasers and particle accelerators for high-precision work, such as in argon-argon radiometric dating, the use of isotopes of the element argon to date geologic samples.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Some geologic features are very large, and geologists must create detailed maps to observe them completely. Geologists use maps to record basic information, to examine trends, and to understand processes and geologic history. For example, a map may record the locations of historical earthquakes, helping to identify faults. Geologic maps can help geologists understand the history of a mountain belt or locate new mineral deposits. On a planetary scale, geologists can map the earth’s surface using data from orbiting satellites. Geologists also make maps reconstructing a view of the earth at some time in the past; such maps are called paleogeographic maps. Geologists who study Mars map the planet’s surface features with the help of images and information from spacecraft probes sent to Mars.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Traditionally, maps have resulted from fieldwork. In the field, geologists locate exposures of rock, or rock outcrops, and features such as faults, folds, or other geologic structures on a base map or aerial photograph. Mapping has improved through the use of remote sensing techniques, such as radar and infrared mapping from aircraft and satellites, and this in turn has helped geologists better understand the earth. Geologists can now determine latitude and longitude positions on the earth by using the global positioning system of satellites (GPS). Map information can now be stored digitally, as in geographic information systems (GIS). Subsurface, or underground, mapping is becoming more common. This technique uses drilled cores and sound waves sent below the ground to map structures such as faults.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">V<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">FIELDS OF GEOLOGY<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Geologists have found it useful to divide geology into two main fields: physical geology, which examines the nature of the earth in its present state, and historical geology, which examines the changes the earth has undergone throughout time.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Physical Geology</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3145/2768252972_956bf4d4ef_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Eruption of Mount Saint Helens<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The volcano known as Mount Saint Helens, in the southwestern portion of Washington state in the United States, began to erupt on March 27, 1980, after a long period of dormancy. It continued to burble until its first large-scale eruption on May 18, 1980. This violent blast sent clouds of ash and other volcanic debris into the atmosphere and killed 57 people. With the eruption, the mountain’s elevation dropped from 2950 m (9677 ft) to 2550 m (8365 ft).<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Krafft-Explorer/Science Source/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Physical geology can be subdivided into a number of disciplines according to the way geologists study the earth and which physical aspects they study. Fields such as geophysics, geochemistry, mineralogy and petrology, and structural geology apply the sciences of physics and chemistry to study aspects of the earth. Hydrology, geomorphology, and marine geology incorporate the study of water and its effects on weathering into geology, while environmental, economic, and engineering geology apply geologic knowledge and engineering principles to solve practical problems.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">A</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">1<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Geophysics<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In the field of geophysics, geologists apply the concepts of physics to the study of the earth. Geophysics is such a broad field that scientists sometimes consider it a separate field from geology. The largest subdiscipline in geophysics is seismology, the study of the travel of seismic waves through the earth. Seismic waves are generated naturally by earthquakes, or they can be made artificially by explosions from bombs or air guns. Seismologists study earthquakes and construct models of the earth's interior using seismic techniques. Geophysics also includes the study of the physics of materials such as rocks, minerals, and ice within the fields of petrology, mineralogy, and glaciology. Geophysicists study the behavior of the planet’s oceans, atmosphere, and volcanoes. Specialists called volcanologists study the world’s volcanoes and try to predict eruptions by using seismology and other remote sensing techniques, such as satellite imagery. Monitoring active volcanoes is especially important in highly populated areas.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">A</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">2<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Geochemistry<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Geochemistry is the application of chemistry to the study of the earth, its materials, and the cycling of chemicals through its systems. It is essential in numerical dating and in reconstructing past conditions on the earth. Geochemistry is important for tracing the transport of chemicals through the earth’s four component systems: the lithosphere (rocky exterior), the hydrosphere (waters of the earth), the atmosphere (air), and the biosphere (the system of living things). Biogeochemistry is an emerging field that examines the chemical interactions between living and nonliving systems—for example, microorganisms that act in soil formation. Geochemistry has important applications in environmental and economic geology as well as in the fields of mineralogy and petrology.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">A</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">3<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Mineralogy and Petrology</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3271/2768253188_440d6641aa_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Rock Crystals in a Lunar Sample<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">A petrographic microscope is used to make an image of a thin sample of lunar rock. The different colors represent different mineral compositions.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Jan Hinsch/Science Source/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The fields of mineralogy (the study of minerals) and petrology (the study of rocks) are closely related because rocks are made of minerals. Mineralogists and petrologists study the origin, occurrence, structure, and history of rocks or minerals. They attempt to understand the physical, chemical, and less commonly, biological conditions under which geologic materials form. Mineralogy is important for understanding natural materials and is also used in the materials engineering field, such as in ceramics. Petrology focuses on two of the three rock types: igneous rocks—rocks made from molten material—and metamorphic rocks—those rocks that have been changed by high temperatures or pressures. The third rock type, sedimentary rocks, are the focus of sedimentary geology, commonly classified under historical geology.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">A</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">4<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Structural Geology <o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Structural geology deals with the form, arrangement, and internal structure of rocks, including their history of deformation, such as folding and faulting. Structural geology includes everything from field mapping to the study of microscopic deformation within rocks. Most geologic reconstructions require an understanding of structural geology. The term <i>tectonics</i> is commonly used for large-scale structural geology, such as the study of the history of a mountain belt, or plate tectonics (the study of the crustal plates). Neotectonics is the study of recent faulting and deformation; such studies can reconstruct the history of active faults, and the history can be used in hazard analysis and land-use planning.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">A</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">5<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Hydrology and Geomorphology<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The earth's surface processes are the focus of hydrology and geomorphology. Hydrology is the study of water on the earth's surface, excluding the oceans. Hydrogeology is the study of groundwater (water under the ground) and the geologic processes of surface water. As water is necessary for life, hydrology and hydrogeology are important for economic and environmental reasons, such as maintaining a clean water supply. Geomorphology is the examination of the development of present landforms; geomorphologists attempt to understand the nature and origin of these landforms. They may work from the large scale of mountain belts to the small scale of <i>rill marks </i>(small grooves in sand). Geomorphologists commonly specialize in one of many areas, such as in glacial or periglacial (near glaciers), fluvial (river), hillslope, or coastal processes. Their work is important for a basic understanding of the active surface that humans live on, a surface that is subject to erosion, landslides, floods, and other processes that affect our daily lives.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">A</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">6<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Marine Geology<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Geology specific to the ocean environment is called marine geology. Marine geologists may be specialists in a number of fields, including petrology, sedimentology, stratigraphy, paleontology, geochemistry, geophysics, and volcanology. They may take samples from the ocean while out at sea or make measurements through remote sensing techniques. Drilling platforms and drilling ships allow earth scientists to make more-detailed studies of the history of the oceans and the ocean floor. For example, in 1984 an international team of geoscientists from 20 nations formed the Ocean Drilling Program, an outgrowth of the earlier Deep Sea Drilling Program. This program is designed to set up drilling through the top sedimentary layer and the ocean crust in deep-sea sites around the world. This work has helped the field of paleoceanography (the reconstruction of the history of the oceans, including ancient ocean chemistry, temperature, circulation, and biology). <i>See also </i>Ocean and Oceanography.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">A</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">7<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Environmental, Economic, and Engineering Geology</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3085/2767406867_9854b9bf8f_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Relief Map<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Relief maps are three-dimensional models of the terrain in an area; on them, color and scale are used to indicate geographical features rather than simply to delineate political boundaries. Because of this feature, relief maps are extensively used in engineering and the military. This map shows portions of Alaska and northwestern Canada.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">United States Geological Survey<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The application of geologic knowledge to practical problems is the focus of the fields of environmental, economic, and engineering geology. Environmental geology involves the protection of human health and safety through understanding geological processes. For example, it is critically important to understand the geology of areas where people propose to store nuclear waste products. The study of geologic hazards, such as earthquakes and volcanic eruptions, can also be considered part of environmental geology. Economic geology is the use of geologic knowledge to find and recover materials that can be used profitably by humans, including fuels, ores, and building materials. Because these products are so diverse, economic geologists must be broadly trained; they commonly specialize in a particular aspect of economic geology, such as petroleum geology or mining geology. Engineering geology is the application of engineering principles to geologic problems. Two fields of engineering that use geology extensively are civil engineering and mining engineering. For example, the stability of a building or bridge requires an understanding of both the foundation material (rocks, soil) and the potential for earthquakes in the area. <i>See also </i>Engineering: <i>Geological and Mining Engineering</i>.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Historical Geology<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Historical geology focuses on the study of the evolution of earth and its life through time. Historical geology includes many subfields. Stratigraphy and sedimentary geology are fields that investigate layered rocks and the environments in which they are found. Geochronology is the study of determining the age of rocks, while paleontology is the study of fossils. Other fields, such as paleoceanography, paleoseismology, paleoclimatology, and paleomagnetism, apply geologic knowledge of ancient conditions to learn more about the earth. The Greek prefix <i>paleo</i> is used to identify ancient conditions or periods in time, and commonly means “the reconstruction of the past.”<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">B</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">1<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Stratigraphy</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3007/2768254192_8b4e75e790_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Stratigraphic Column<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Fossils preserved in rock strata provide scientists with clues to evolutionary history. This stratigraphic column is based on paleontological evidence and shows the order in which organisms appeared in the fossil-rich Paleozoic era. Each layer represents a particular time frame and shows a representative organism which flourished during that time. Although fossils are rarely found in the idealized and localized fashion shown here, they are often in more or less chronological order. Generally, the oldest fossils appear in lower layers and the most recent fossils at the top, so that placement may be used as an aid in dating the specimens.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Stratigraphy is the study of the history of the earth's crust, particularly its stratified (layered) rocks. Stratigraphy is concerned with determining age relationships of rocks as well as their distribution in space and time. Rocks may be studied in an outcrop but commonly are studied from drilled cores (samples that have been collected by drilling into the earth). Most of the earth's surface is covered with sediment or layered rocks that record much of geologic history; this is what makes stratigraphy important. It is also important for many economic and environmental reasons. A large portion of the world's fossil fuels, such as oil, gas, and coal, are found in stratified rocks, and much of the world's groundwater is stored in sediments or stratified rocks.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Stratigraphy may be subdivided into a number of fields. Biostratigraphy is the use of fossils for age determination and correlation of rock layers; magnetostratigraphy is the use of magnetic properties in rocks for similar purposes. Newer fields in stratigraphy include chemostratigraphy, seismic stratigraphy, and sequence stratigraphy. Chemostratigraphy uses chemical properties of strata for age determination and correlation as well as for recognizing events in the geologic record. For example, oxygen isotopes (forms of oxygen that contain a different number of neutrons in the nuclei of atoms) may provide evidence of an ancient paleoclimate. Carbon isotopes may identify biologic events, such as extinctions. Rare chemical elements may be concentrated in a <i>marker layer</i> (a distinctive layer that can be correlated over long distances). Seismic stratigraphy is the subsurface study of stratified rocks using seismic reflection techniques. This field has revolutionized stratigraphic studies since the late 1970s and is now used extensively both on land and offshore. Seismic stratigraphy is used for economic reasons, such as finding oil, and for scientific studies. An offshoot of seismic stratigraphy is sequence stratigraphy, which helps geologists reconstruct sea level changes throughout time. The rocks used in sequence stratigraphy are bounded by, or surrounded by, surfaces of erosion called unconformities.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">B</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">2<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Sedimentology</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3175/2768254468_ff2cd511ae_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Folded Rocks of the Dynamic Earth<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">The theory of plate motions explains how mountains are built by forces that shape the earth’s crust. Large pieces of crust on the surface of the earth move laterally. This creates huge compressional forces that may bend or even break rocks. These sedimentary rock layers show an anticlinal fold, in which the layers bend downward from the crest.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">V. Englebert/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Sedimentology, or sedimentary geology, is the study of sediments and sedimentary rocks and the determination of their origin. Sedimentary geology is process oriented, focusing on how sediment was deposited. Sedimentologists are geologists who attempt to interpret past environments based on the observed characteristics, called facies, of sedimentary rocks. Facies analysis uses physical, chemical, and biological characteristics to reconstruct ancient environments. Facies analysis helps sedimentologists determine the features of the layers, such as their geometry, or layer shape; porosity, or how many pores the rocks in the layers have; and permeability, or how permeable the layers are to fluids. This type of analysis is important economically for understanding oil and gas reservoirs as well as groundwater supplies.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">B</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">3<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Geochronology<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The determination of the age of rocks is called geochronology. The fundamental tool of geochronology is radiometric dating (the use of radioactive decay processes as recorded in earth materials to determine the numerical age of rocks). Most radiometric dating techniques are useful in dating igneous and metamorphic rocks and minerals. One type of non-radiometric dating, called <i>strontium isotope dating,</i> measures different forms of the element strontium in sedimentary materials to date the layers. Geologists also have ways to determine the ages of surfaces that have been exposed to the sun and to cosmic rays. These methods are called thermoluminescence dating and cosmogenic isotope dating. Geologists can count the annual layers recorded in tree rings, ice cores, and certain sediments such as those found in lakes, for very precise geochronology. However, this method is only useful for time periods up to tens of thousands of years. Some geoscientists are now using Milankovitch cycles (the record of change in materials caused by variations in the earth's orbit) as a geologic time clock. <i>See also </i>Dating Methods: <i>Radiometric Dating</i>.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">B</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">4<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Paleontology and Paleobiology</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3152/2768254744_d1cd1f7889_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Paleontologist with Seismosaurus Bone<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(48, 71, 109);">Paleontologists often spend hours to uncover a single bone, painstakingly removing the dirt and rock that surrounds it. Here, a paleontologist reattaches a rib bone of a seismosaurus before excavation continues.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="font-size: 8pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(142, 142, 142);">Ray Nelson/Phototake NYC<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Paleontology is the study of ancient or fossil life. Paleobiology is the application of biological principles to the study of ancient life on earth. These fields are fundamental to stratigraphy and are used to reconstruct the history of organisms' evolution and extinction throughout earth history. The oldest fossils are older than 3 billion years, although fossils do not become abundant and diverse until about 500 million years ago. Different fossil organisms are characteristic of different times, and at certain times in earth history, there have been <i>mass extinctions</i> (times when a large proportion of life disappears). Other organisms then replace the extinct forms. The study of fossils is one of the most useful tools for reconstructing geologic history because plants and animals are sensitive to environmental changes, such as changes in the climate, temperature, food sources, or sunlight. Their fossil record reflects the world that existed while they were alive. Paleontology is commonly divided into vertebrate paleontology (the study of organisms with backbones), invertebrate paleontology (the study of organisms without backbones), and micropaleontology (the study of microscopic fossil organisms). Many other subfields of paleontology exist as well. Paleobotanists study fossil plants, and palynologists study fossil pollen. Ichnology is the study of trace fossils—tracks, trails, and burrows left by organisms. Paleoecology attempts to reconstruct the behavior and relationships of ancient organisms.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 16pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(224, 224, 228);">B</span><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">5<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Paleoceanography and Paleoclimatology<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Paleoceanography (the study of ancient oceans) and paleoclimatology (the study of ancient climates) are two subfields that use fossils to help reconstruct ancient conditions. Scientists also study stable isotopes, or different forms, of oxygen to reconstruct ancient temperatures. They use carbon and other chemicals to reconstruct aspects of ancient oceanographic and climatic conditions. Detailed paleoclimatic studies have used cores from ice sheets in Antarctica and Greenland to reconstruct the last 200,000 years. Ocean cores, tree rings, and lake sediments are also useful in paleoclimatology. Geologists hope that by understanding past oceanographic and climatic changes, they can help predict future change.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">VI<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">HISTORY OF GEOLOGY<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Geology originated as a modern scientific discipline in the 18th century, but humans have been collecting systematic knowledge of the earth since at least the Stone Age. In the Stone Age, people made stone tools and pottery, and had to know which materials were useful for these tasks. Between the 4th century and 1st century <span style="text-transform: uppercase;">bc</span>, ancient Greek and Roman philosophers began the task of keeping written records relating to geology. Throughout the medieval and Renaissance periods, people began to study mineralogy and made detailed geologic observations. The 18th and 19th centuries brought widespread study of geology, including the publication of Charles Lyell’s book <i>Principles of Geology</i>, and the National Surveys (expeditions that focused on the collection of geologic and other scientific data). The concept of geologic time was further developed during the 19th century as well. At the end of the 19th century and into the<sup> </sup>20th century, the field of geology expanded even more. During this time, geologists developed the theories of continental drift, plate tectonics, and seafloor spreading.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Ancient Greek and Roman Philosophers<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In western science, the first written records of geological thought come from the Greeks and Romans. In the 1st century <span style="text-transform: uppercase;">bc,</span> for example, Roman architect Vitruvius wrote about building materials such as <i>pozzolana</i>, a volcanic ash that Romans used to make hydraulic cement, which hardened under water. Historian Pliny the Elder, in his encyclopedia, <i>Naturalis Historia</i> (Natural History), summarized Greek and Roman ideas about nature.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Science as an organized system of thought can trace its roots back to the Greek philosopher Aristotle. In the 4th century <span style="text-transform: uppercase;">bc</span> Aristotle developed a philosophical system that explained nature in a methodical way. His system proposed that the world is made of four elements (earth, air, fire, and water), with four qualities (cold, hot, dry, and wet), and four <i>causes</i> (material, efficient, formal, and final). According to Aristotle, elements could change into one another, and the earth was filled with water and air, which could rush about and cause earthquakes. Other philosophers of this era who wrote about earth materials and processes include Aristotle's student Theophrastus, the author of an essay on stones.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Chinese Civilizations<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Chinese civilizations developed ideas about the earth and technologies for studying the earth. For example, in 132 AD the Chinese philosopher Chang Heng invented the earliest known seismoscope. This instrument had a circle of dragons holding balls in their mouths, surrounded by frogs at the base. The balls would drop into the mouths of frogs when an earthquake occurred. Depending on which ball was dropped, the direction of the earthquake could be determined.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">C<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Medieval and Renaissance Periods<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The nature and origin of minerals and rocks interested many ancient writers, and mineralogy may have been the first systematic study to arise in the earth sciences. The Saxon chemist Georgius Agricola wrote <i>De Re Metallica</i> (<i>On the Subject of Metals</i>) following early work by both the Islam natural philosopher Avicenna and the German naturalist Albertus Magnus. <i>De Re Metallica</i> was published in 1556, a year after Agricola’s death. Many consider this book to be the foundation of mineralogy, mining, and metallurgy.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Medieval thought was strongly influenced by Aristotle, but science began to move in a new direction during the Renaissance Period. In the early 1600s, English natural philosopher Francis Bacon reasoned that detailed observations were required to make conclusions. Around this time French philosopher René Descartes argued for a new, rational system of thought. Most natural philosophers, or scientists, in this era studied many aspects of philosophy and science, not focusing on geology alone.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Studies of the earth during this time can be placed in three categories. The first, cosmology, proposed a structure of the earth and its place in the universe. As an example of a cosmology, in the early 1500s Polish astronomer Nicolaus Copernicus proposed that the earth was a satellite in a sun-centered system. The second category, cosmogony, concerned the origin of the earth and the solar system. The Saxon mathematician and natural philosopher Gottfried Wilhelm, Baron von Leibniz, in a cosmogony, described an initially molten earth, with a crust that cooled and broke up, forming mountains and valleys. The third category of study was in the tradition of Francis Bacon, and it involved detailed observations of rocks and related features. English scientist Robert Hooke and Danish anatomist and geologist Nicolaus Steno (Niels Stenson) both made observations in the 17th century of fossils and studied other geologic topics as well. In the 17th century, mineralogy also continued as an important field, both in theory and in practical matters, for example, with the work of German chemist J. J. Becher and Irish natural philosopher Robert Boyle.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">D<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Geology in the 18th and 19th Centuries<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">By the 18th century, geological study began to emerge as a separate field. Italian mining geologist Giovanni Arduino, Prussian chemist and mineralogist Johan Gottlob Lehmann, and Swedish chemist Torbern Bergman all developed ways to categorize the layers of rocks on the earth's surface. The German physician Georg Fuchsel defined the concept of a geologic formation—a distinctly mappable body of rocks. The German scientist Abraham Gottlob Werner called himself a <i>geognost</i> (a knower of the earth). He used these categorizations to develop a theory that the earth's layers had precipitated from a universal ocean. Werner's system was very influential, and his followers were known as Neptunists. This system suggested that even basalt and granite were precipitated from water. Others, such as English naturalists James Hutton and John Playfair, argued that basalt and granite were igneous rocks, solidified from molten materials, such as lava and magma. The group that held this belief became known as Volcanists or Plutonists.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">By the early 19th century, many people were studying geologic topics, although the term <i>geologist</i> was not yet in general use. Scientists, such as Scottish geologist Charles Lyell, and French geologist Louis Constant Prevost, wanted to establish geology as a rational scientific field, like chemistry or physics. They found this goal to be a challenge in two important ways. First, some people wanted to reconcile geology with the account of creation in Genesis (a book of the Old Testament) or wanted to use supernatural explanations for geologic features. Second, others, such as French anatomist Georges Cuvier, used catastrophes to explain much of earth’s history. In response to these two challenges, Lyell proposed a strict form of uniformitarianism, which assumed not only uniformity of laws but also uniformity of rates and conditions. However, assuming the uniformity of rates and conditions was incorrect, because not all processes have had constant rates throughout time. Also, the earth has had different conditions throughout geologic time—that is, the earth as a rocky planet has evolved. Although Lyell was incorrect to assume uniformity of rates and conditions, his well reasoned and very influential three-volume book, <i>Principles of Geology</i>, was published and revised 11 times between 1830 and 1872. Many geologists consider this book to mark the beginning of geology as a professional field.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Although parts of their theories were rejected, Abraham Gottlob Werner and Georges Cuvier made important contributions to stratigraphy and historical geology. Werner's students and followers went about attempting to correlate rocks according to his system, developing the field of physical stratigraphy. Cuvier and his co-worker Alexandre Brongniart, along with English surveyor William Smith, established the principles of biostratigraphy, using fossils to establish the age of rocks and to correlate them from place to place. Later, with these established stratigraphies, geologists used fossils to reconstruct the history of life's evolution on earth.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">E<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Age of Geologic Exploration<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In the late 18th and the 19th centuries, naturalists on voyages of exploration began to make important contributions to geology. Reports by German natural historian Alexander von Humboldt about his travels influenced the worlds of science and art. The English naturalist Charles Darwin, well known for his theory of evolution, began his scientific career on the voyage of the HMS <i>Beagle,</i> where he made many geological observations. American geologist James Dwight Dana sailed with the Wilkes Expedition throughout the Pacific and made observations of volcanic islands and coral reefs. In the 1870s, the HMS <i>Challenger</i> was launched as the first expedition specifically to study the oceans.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Expeditions on land also led to new geologic observations. Countries and states established geological surveys in order to collect information and map geologic resources. For example, in the 1860s and 1870s , , John Wesley Powell, and George Wheeler conducted four surveys of the American West. These surveys led to several new concepts in geology. American geologist described the Basin and Range Province and first recognized laccoliths (round igneous rock intrusions). Reports also came back of spectacular sites such as Yellowstone, Yosemite, and the Grand Canyon, which would later become national parks. Competition between these survey parties finally led the Congress of the United States to establish the U.S. Geological Survey in 1879.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">F<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Geologic Time<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Determining the age of the earth became a renewed scholarly effort in the 19th century. Unlike the Greeks and most eastern philosophers, who considered the earth to be eternal, western philosophers believed that the planet had a definite beginning and must have a measurable age. One way to measure this age was to count generations in the Bible, as the Anglican Archbishop James Ussher did in the 1600s, coming up with a total of about 6000 years. In the 1700s, French natural scientist George Louis Leclerc (Comte de Buffon) tried to measure the age of the earth. He calculated the time it would take the planet to cool based on the cooling rates of iron balls and came up with 75,000 years. During the 18th century, James Hutton argued that processes such as erosion, occurring at observed rates, indicated an earth that was immeasurably old. By the early 19th century, geologists commonly spoke in terms of 'millions of years.' Even religious professors, such as English clergyman and geologist William Buckland, referred to this length of time.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Other means for calculating the age of the earth used in the 19th century included determining how long it would take the sea to become salty and calculating how long it would take for thick piles of sediment to accumulate. Irish physicist William Thomson (Lord Kelvin) returned to Buffon's method and calculated that the earth was no more than 100 million years old. Meanwhile, Charles Darwin and others argued that evolution proceeded slowly enough that it required at least hundreds of millions of years.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">With the discovery of radioactivity in 1896 by French physicist Henri Becquerel, scientists, such as British physicist Ernest Rutherford and American radiochemist Bertram Boltwood, recognized that the ages of minerals and rocks could be determined by radiometric dating. By the early 20th century, Boltwood had dated some rocks to be more than 2 billion years old. During this time, English geologist Arthur Holmes began a long career of refining the dates on the geologic time scale, a practice that continues to this day.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">G<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Theory of Continental Drift<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">In 1910 American geologist Frank B. Taylor proposed that lateral (sideways) motion of continents caused mountain belts to form on their front edges. Building on this idea in 1912, German meteorologist Alfred Wegener proposed a theory that came to be known as Continental Drift: He proposed that the continents had moved and were once part of one, large supercontinent called Pangaea. Wegener was attempting to explain the origin of continents and oceans when he expanded upon Taylor’s idea. His evidence included the shapes of continents, the physics of ocean crust, the distribution of fossils, and paleoclimatology data. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Continental drift helped to explain a major geologic issue of the 19th century: the origin of mountains. Theories commonly called on the cooling and contracting of the earth to form mountain chains. The mountain-building theories of German geologist Leopold von Buch and French geologist Leonce Elie de Beaumont were catastrophic in nature. American geologists James Hall and James Dwight Dana proposed the geosynclinal theory of mountain building—a theory based on the downward bending of the earth’s crust (a geosyncline). Austrian geologist Eduard Suess developed a related theory. Hall, Dana, and Suess believed that continents and ocean basins were ancient, permanent features on earth and that mountain belts formed at their edges.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Most geologists did not accept the theory of continental drift in the 1920s and 1930s. British geologist Arthur Holmes supported continental drift and proposed that convection (a type of heat movement) inside the earth drove continental drift. Others who favored the idea included South African geologist Alex du Toit, who studied geologic evidence for the southern continents of Gondwanaland, part of the hypothetical supercontinent Pangaea. Other scientists, such as British geophysicist Harold Jeffreys, argued that continental drift was physically impossible. Paleontologists, such as American George Gaylord Simpson, said that the distribution of fossils could be explained by other means.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">H<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Theory of Seafloor Spreading<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">After World War II, geophysical evidence began to accumulate that confirmed the lateral motion of continents and indicated the young age of oceanic crust. This evidence led to the theories of seafloor spreading and plate tectonics in the 1960s. American marine geologists Robert S. Dietz and Harry H. Hess proposed the seafloor spreading hypothesis, the concept that the oceanic crust is created as the seafloor spreads apart along midocean ridges. American oceanographers Bruce C. Heezen, Marie Tharp, and others prepared detailed maps of the ocean floors and the mid-Atlantic ridge and rift system, a mountainous chain found throughout the ocean. These maps provided additional evidence that seemed to support the continental drift theory. Further evidence came from paleomagnetism, the record of the orientation of earth's magnetic field recorded in rocks. In the 1950s, British geophysicist S. Keith Runcorn determined that this evidence indicated that the continents had moved relative to the earth’s magnetic poles and to each other. British marine geophysicists Fred J. Vine and Drummond Matthews described the record of changes in the earth’s magnetic field when they discovered “magnetic stripes” formed at spreading centers of the mid-ocean ridges, leading to the Vine-Matthews hypothesis. Magnetic stripes were also independently described by Canadian geophysicist Lawrence Morley and confirmed by American marine geologist Walter Pitman and others. These stripes indicated reversals of the direction of the earth’s magnetic field recorded in rock as new ocean crust was created at mid-ocean ridges. Scientists used paleomagnetism and seafloor spreading to determine that the continents had moved relative to the magnetic poles and to each other.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">I<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Theory of Plate Tectonics<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Canadian geophysicist J. Tuzo Wilson and American geophysicist Jason Morgan, among others, proposed the outline of the theory of plate tectonics in the 1960s. This theory stated that the earth’s lithosphere is made up of several rigid plates. These plates slide and move over a less-rigid layer called the asthenosphere. A plate may be composed entirely of oceanic crust, like the Pacific Plate, or of part ocean crust and part continental crust, like the North American Plate. New ocean crust is generated at ocean ridges (underwater mountain chains formed by the young ocean crust). Older ocean crust sinks down, or subducts, into the earth’s mantle at subduction zones, which are found at the deepest parts of the ocean, called trenches. As the plates move, they collide and form mountains. The plates recycle crust, generate volcanoes, and move past each other along faults. Using satellites, scientists can now measure movement of the continental plates in centimeters per year. Plate boundaries are the sites of most of the earth's earthquakes and the majority of earth's volcanoes. The continents are made of remelted sediments and partially melted oceanic crust, forming a lower density layer that has collected through time. The mechanism that drives the earth’s crustal plates is still not known, but geologists can use plate tectonics to explain most geologic activity. <i>See also </i>Earth.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 18pt; font-family: "MS Reference Sans Serif","sans-serif"; color: rgb(153, 153, 153);">J<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="font-size: 12pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">Earth as a Planetary Body<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif"; color: black;">The full recognition by scientists of earth as a planetary body, combining the fields of solar-system astronomy and geology, is perhaps the latest revolution in the earth sciences. Although scientists have recognized earth as a planet for centuries, space exploration that began in the 1960s created a new view of the earth. Photographs of earth taken from space had a profound effect on how people saw the earth. The exploration of neighboring moons and planets has led to a new understanding of the earth as an evolving planet.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 15pt;"><span style="font-size: 12pt; font-family: "Times New Roman","serif";"><br />Contributed By:<br />Joanne Bourgeois<o:p></o:p></span></p> <b><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif";">Microsoft ® Encarta ® 2007.</span></b><span style="font-size: 9pt; font-family: "MS Reference Sans Serif","sans-serif";"> © 1993-2006 Microsoft Corporation. All rights reserved</span>ghozian karamihttp://www.blogger.com/profile/13214011599962806335noreply@blogger.com0tag:blogger.com,1999:blog-192751622867664710.post-83492679070626337242008-12-11T06:23:00.000-08:002008-12-11T06:30:27.103-08:00Global Warming<p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">GlobalGlobal Warming<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">I<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">INTRODUCTION<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="">Global Warming, increase in the average temperature of the atmosphere, oceans, and landmasses of Earth. The planet has warmed (and cooled) many times during the 4.65 billion years of its history. At present Earth appears to be facing a rapid warming, which most scientists believe results, at least in part, from human activities. The chief cause of this warming is thought to be the burning of fossil fuels, such as coal, oil, and natural gas, which releases into the atmosphere carbon dioxide and other substances known as greenhouse gases. As the atmosphere becomes richer in these gases, it becomes a better insulator, retaining more of the heat provided to the planet by the Sun.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">The average surface temperature of Earth is just below 15°C (59°F). Over the last century, this average has risen by about 0.6 Celsius degree (1 Fahrenheit degree). Scientists predict further warming of 1.4 to 5.8 Celsius degrees (2.5 to 10.4 Fahrenheit degrees) by the year 2100. This temperature rise is expected to melt polar ice caps and glaciers as well as warm the oceans, all of which will expand ocean volume and raise sea level by an estimated 9 to 100 cm (4 to 40 in), flooding some coastal regions and even entire islands. Some regions in warmer climates will receive more rainfall than before, but soils will dry out faster between storms. This soil desiccation may damage food crops, disrupting food supplies in some parts of the world. Plant and animal species will shift their ranges toward the poles or to higher elevations seeking cooler temperatures, and species that cannot do so may become extinct. The potential consequences of global warming are so great that many of the world's leading scientists have called for international cooperation and immediate action to counteract the problem.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">II<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">THE GREENHOUSE EFFECT</span></p></td></tr></tbody></table><br /><br /><img src="http://farm4.static.flickr.com/3245/2767403257_b4943e5ddf_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="">Greenhouse Effect<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <span style="">The energy that lights and warms Earth comes from the Sun. Most of the energy that floods onto our planet is short-wave radiation, including visible light. When this energy strikes the surface of Earth, the energy changes from light to heat and warms Earth. Earth’s surface, in turn, releases some of this heat as long-wave infrared radiation.</span><br /><img src="http://farm4.static.flickr.com/3282/2768251084_58c93931c7_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="">Carbon Cycle<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="">Photosynthesis plays a crucial role in the carbon cycle. Carbon continuously circulates in the earth’s ecosystem. In the atmosphere, it exists as colorless, odorless carbon dioxide gas, which is used by plants in the process of photosynthesis. Animals acquire the carbon stored in plant tissue when they eat and exhale carbon dioxide as a by-product of metabolism. Although some carbon is removed from circulation temporarily as coal, petroleum, fossil fuels, gas, and limestone deposits, cellular respiration and photosynthesis balance to keep the amount of atmospheric carbon relatively stable. Industrialization, however, has contributed additional carbon dioxide to the environment.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">Much of this long-wave infrared radiation makes it all the way back out to space, but a portion remains trapped in Earth’s atmosphere. Certain gases in the atmosphere, including water vapor, carbon dioxide, and methane, provide the trap. Absorbing and reflecting infrared waves radiated by Earth, these gases conserve heat as the glass in a greenhouse does and are thus known as greenhouse gases. As the concentration of these greenhouse gases in the atmosphere increases, more heat energy remains trapped below. All life on Earth relies on this greenhouse effect—without it, the planet would be colder by about 33 Celsius degrees (59 Fahrenheit degrees), and ice would cover Earth from pole to pole. However, a growing excess of greenhouse gases in Earth’s atmosphere threatens to tip the balance in the other direction—toward continual warming.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">III<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">TYPES OF GREENHOUSE GASES<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="">Greenhouse gases occur naturally in the environment and also result from human activities. By far the most abundant greenhouse gas is water vapor, which reaches the atmosphere through evaporation from oceans, lakes, and rivers.<o:p></o:p></span></p> <span style="">Carbon dioxide is the next most abundant greenhouse gas. It flows into the atmosphere from many natural processes, such as volcanic eruptions; the respiration of animals, which breathe in oxygen and exhale carbon dioxide; and the burning or decay of organic matter, such as plants. Carbon dioxide leaves the atmosphere when it is absorbed into ocean water and through the photosynthesis of plants, especially trees. Photosynthesis breaks up carbon dioxide, releasing oxygen into the atmosphere and incorporating the carbon into new plant tissue.</span><br /><img src="http://farm4.static.flickr.com/3133/2767403831_847944b1c5_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="">Industrial Smokestacks<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="">Carbon dioxide, sulfur dioxide, and other types of contaminants pouring from industrial smokestacks contribute largely to the world’s atmospheric pollution. Carbon dioxide contributes significantly to global warming, while sulfur dioxide emissions are the principal cause of acid rain in the northeastern United States.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="">Kim Westerskov/Oxford Scientific Films<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">Humans escalate the amount of carbon dioxide released to the atmosphere when they burn fossil fuels, solid wastes, and wood and wood products to heat buildings, drive vehicles, and generate electricity. At the same time, the number of trees available to absorb carbon dioxide through photosynthesis has been greatly reduced by deforestation, the long-term destruction of forests by indiscriminate cutting of trees for lumber or to clear land for agricultural activities.<o:p></o:p></span></p> <span style="">Ultimately, the oceans and other natural processes absorb excess carbon dioxide in the atmosphere. However, human activities have caused carbon dioxide to be released to the atmosphere at rates much faster than that at which Earth’s natural processes can cycle this gas. In 1750 there were about 281 molecules of carbon dioxide per million molecules of air (abbreviated as parts per million, or ppm). In 2006 two major scientific organizations—the World Meteorological Organization (WMO) and the United States National Oceanic and Atmospheric Administration (NOAA)—reported that levels of carbon dioxide in the atmosphere had hit a record high. Using different measurement techniques, the WMO said carbon dioxide levels had risen to 377 ppm, an annual increase of 1.8 ppm, and the NOAA reported a figure of 381 ppm for a yearly increase of 2.6 ppm. If current predictions prove accurate, by the year 2100 carbon dioxide will reach concentrations of more than 540 to 970 ppm. At the highest estimation, this concentration would be triple the levels prior to the Industrial Revolution, the widespread replacement of human labor by machines that began in Britain in the mid-18th century and soon spread to other parts of Europe and to the United States.</span><br /><img src="http://farm4.static.flickr.com/3212/2768251312_68eed120d4_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="">Photosynthesis<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="">© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">Methane is an even more effective insulator, trapping over 20 times more heat than does the same amount of carbon dioxide. Methane is emitted during the production and transport of coal, natural gas, and oil. Methane also comes from rotting organic waste in landfills, and it is released from certain animals, especially cows, as a byproduct of digestion. Since the beginning of the Industrial Revolution in the mid-1700s, the amount of methane in the atmosphere has more than doubled.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">Nitrous oxide is a powerful insulating gas released primarily by burning fossil fuels and by plowing farm soils. Nitrous oxide traps about 300 times more heat than does the same amount of carbon dioxide. The concentration of nitrous oxide in the atmosphere has increased 17 percent over preindustrial levels.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">In addition, greenhouse gases are produced in many manufacturing processes. Perfluorinated compounds result from the smelting of aluminum. Hydrofluorocarbons form during the manufacture of many products, including the foams used in insulation, furniture, and car seats. Refrigerators built in some developing nations still use chlorofluorocarbons as coolants. In addition to their ability to retain atmospheric heat, some of these synthetic chemicals also destroy Earth’s high-altitude ozone layer, the protective layer of gases that shields Earth from damaging ultraviolet radiation. For most of the 20th century these chemicals have been accumulating in the atmosphere at unprecedented rates. But since 1995, in response to regulations enforced by the Montréal Protocol on Substances that Deplete the Ozone Layer and its amendments, the atmospheric concentrations of many of these gases are either increasing more slowly or decreasing. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">Scientists are growing concerned about other gases produced from manufacturing processes that pose an environmental risk. In 2000 scientists identified a substantial rise in atmospheric concentrations of a newly identified synthetic compound called trifluoromethyl sulfur pentafluoride. Atmospheric concentrations of this gas are rising quickly, and although it still is extremely rare in the atmosphere, scientists are concerned because the gas traps heat more effectively than all other known greenhouse gases. Perhaps more worrisome, scientists have been unable to confirm the industrial source of the gas.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">IV<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">MEASURING GLOBAL WARMING</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3016/2768251416_11348f044b_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="">GOES Weather Satellite<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="">Broadcasters use data from meteorological satellites to predict weather and to broadcast storm warnings when necessary. Satellites such as the Geostationary Operational Environmental Satellite (GOES) collect meteorological and infrared information about the atmosphere and the ocean. A camera on the GOES is continuously pointed at Earth, broadcasting satellite images of cloud patterns both day and night. Here, the GOES-C satellite is being encapsulated inside its payload fairing aboard a Delta rocket.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="">NASA<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">As early as 1896 scientists suggested that burning fossil fuels might change the composition of the atmosphere and that an increase in global average temperature might result. The first part of this hypothesis was confirmed in 1957, when researchers working in the global research program called the International Geophysical Year sampled the atmosphere from the top of the Hawaiian volcano Mauna Loa. Their instruments indicated that carbon dioxide concentration was indeed rising. Since then, the composition of the atmosphere has been carefully tracked. The data collected show undeniably that the concentrations of greenhouse gases in the atmosphere are increasing.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">Scientists have long suspected that the global climate, the long-term average pattern of temperature, was also growing warmer, but they were unable to provide conclusive proof. Temperatures vary widely all the time and from place to place. It takes many years of climate observations to establish a trend. Records going back to the late 1800s did seem to show a warming trend, but these statistics were spotty and untrustworthy. Early weather stations often were located near cities, where temperature measurements were affected by the heat emitted from buildings and vehicles and stored by building materials and pavements. Since 1957, however, data have been gathered from more reliable weather stations, located far away from cities, and from satellites. These data have provided new, more accurate measurements, especially for the 70 percent of the planetary surface that is ocean water (<i>see </i>Satellite, Artificial). These more accurate records indicate that a surface warming trend exists and that, moreover, it has become more pronounced. Looking back from the end of the 20th century, records show that the ten warmest years of the century all occurred after 1980, and the three hottest years occurred after 1990, with 2005 being the warmest year of all.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">Greenhouse gas concentrations are increasing. Temperatures are rising. But does the gas increase necessarily cause the warming, and will these two phenomena continue to occur together? In 1988 the United Nations Environment Program and the World Meteorological Organization established a panel of 200 leading scientists to consider the evidence. In its Third Assessment Report, released in 2001, this Intergovernmental Panel on Climate Change (IPCC) concluded that global air temperature had increased 0.6 Celsius degree (1 Fahrenheit degree) since 1861. The panel agreed that the warming was caused primarily by human activities that add greenhouse gases to the atmosphere. The IPCC predicted in 2001 that the average global temperature would rise by another 1.4 to 5.8 Celsius degrees (2.5 to 10.4 Fahrenheit degrees) by the year 2100. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">The IPCC panel cautioned that even if greenhouse gas concentrations in the atmosphere ceased growing by the year 2100, the climate would continue to warm for a period after that as a result of past emissions. Carbon dioxide remains in the atmosphere for a century or more before nature can dispose of it. If greenhouse gas emissions continue to increase, experts predict that carbon dioxide concentrations in the atmosphere could rise to more than three times preindustrial levels early in the 22nd century, resulting in dramatic climate changes. Large climate changes of the type predicted are not unprecedented; indeed, they have occurred many times in the history of Earth. However, human beings would face this latest climate swing with a huge population at risk.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">V<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">EFFECTS OF GLOBAL WARMING</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3139/2767404277_fd8033f807_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="">Shrinking Greenland Ice Sheet<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="">The Greenland ice sheet underwent extensive surface melting from 1992 to 2002, according to the Arctic Climate Impact Assessment report released in 2004. Tinted areas in these satellite images show the extent of surface melting in 1992 and in 2002. The report warned that the melting of Greenland’s ice sheet and the melting of glaciers in Alaska and Canada are increasingly contributing to a rise in the world’s sea level.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="">Clifford Grabhorn/Courtesy of ACIA 2004<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">Scientists use elaborate computer models of temperature, precipitation patterns, and atmosphere circulation to study global warming. Based on these models, scientists have made several predictions about how global warming will affect weather, sea levels, coastlines, agriculture, wildlife, and human health.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">Weathe</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3084/2768251880_92ef3c7e40_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="">Storm Surge Barrier, The Netherlands<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="">Some experts predict that an increase in global warming will result in unpredictable weather patterns, including storm surges in which wind piles up water in low-lying areas. The curved arms of the New Waterway Storm Surge Barrier in The Netherlands protect Rotterdam and other inland cities from flooding during large storms on the North Sea. Normally, the large, curved arms are retracted to allow ships from the North Sea to travel to ports along the New Waterway. When a dangerous storm is anticipated, the arms are swung out to block off the waterway and prevent large waves from pushing floodwaters inland.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="">ANP-Foto<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">Scientists predict that during global warming, the northern regions of the Northern Hemisphere will heat up more than other areas of the planet, northern and mountain glaciers will shrink, and less ice will float on northern oceans. Regions that now experience light winter snows may receive no snow at all. In temperate mountains, snowlines will be higher and snowpacks will melt earlier. Growing seasons will be longer in some areas. Winter and nighttime temperatures will tend to rise more than summer and daytime ones.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">The warmed world will be generally more humid as a result of more water evaporating from the oceans. Scientists are not sure whether a more humid atmosphere will encourage or discourage further warming. On the one hand, water vapor is a greenhouse gas, and its increased presence should add to the insulating effect. On the other hand, more vapor in the atmosphere will produce more clouds, which reflect sunlight back into space, which should slow the warming process (<i>see </i>Water Cycle). <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">Greater humidity will increase rainfall, on average, about 1 percent for each Fahrenheit degree of warming. (Rainfall over the continents has already increased by about 1 percent in the last 100 years.) Storms are expected to be more frequent and more intense. However, water will also evaporate more rapidly from soil, causing it to dry out faster between rains. Some regions might actually become drier than before. Winds will blow harder and perhaps in different patterns. Hurricanes, which gain their force from the evaporation of water, are likely to be more severe. Against the background of warming, some very cold periods will still occur. Weather patterns are expected to be less predictable and more extreme.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">Sea Levels</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3203/2767404991_0c0fd14321_m.jpg" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="">Flooding in Bangladesh<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="">An increase in global warming will likely result in a rise in sea levels that could threaten many coastal areas around the world. Experts predict that parts of Bangladesh may become completely submerged if sea levels rise.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style="">Express Newspapers/Getty Images<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">As the atmosphere warms, the surface layer of the ocean warms as well, expanding in volume and thus raising sea level. Warming will also melt much glacier ice, especially around Greenland, further swelling the sea. Sea levels worldwide rose 10 to 25 cm (4 to 10 in) during the 20th century, and IPCC scientists predict a further rise of 9 to 88 cm (4 to 35 in) in the 21st century.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">Sea-level changes will complicate life in many coastal regions. A 100-cm (40-in) rise could submerge 6 percent of The Netherlands, 17.5 percent of Bangladesh, and most or all of many islands. Erosion of cliffs, beaches, and dunes will increase. Storm surges, in which winds locally pile up water and raise the sea, will become more frequent and damaging. As the sea invades the mouths of rivers, flooding from runoff will also increase upstream. Wealthier countries will spend huge amounts of money to protect their shorelines, while poor countries may simply evacuate low-lying coastal regions.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">Even a modest rise in sea level will greatly change coastal ecosystems. A 50-cm (20-in) rise will submerge about half of the present coastal wetlands of the United States. New marshes will form in many places, but not where urban areas and developed landscapes block the way. This sea-level rise will cover much of the Florida Everglades.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">C<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">Agriculture<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="">A warmed globe will probably produce as much food as before, but not necessarily in the same places. Southern Canada, for example, may benefit from more rainfall and a longer growing season. At the same time, the semiarid tropical farmlands in some parts of Africa may become further impoverished. Desert farm regions that bring in irrigation water from distant mountains may suffer if the winter snowpack, which functions as a natural reservoir, melts before the peak growing months. Crops and woodlands may also be afflicted by more insects and plant diseases.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">D<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">Animals and Plants<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="">Animals and plants will find it difficult to escape from or adjust to the effects of warming because humans occupy so much land. Under global warming, animals will tend to migrate toward the poles and up mountainsides toward higher elevations, and plants will shift their ranges, seeking new areas as old habitats grow too warm. In many places, however, human development will prevent this shift. Species that find cities or farmlands blocking their way north or south may die out. Some types of forests, unable to propagate toward the poles fast enough, may disappear.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">E<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">Human Health<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="">In a warmer world, scientists predict that more people will get sick or die from heat stress, due less to hotter days than to warmer nights (giving the sufferers less relief). Diseases now found in the tropics, transmitted by mosquitoes and other animal hosts, will widen their range as these animal hosts move into regions formerly too cold for them. Today 45 percent of the world’s people live where they might get bitten by a mosquito carrying the parasite that causes malaria; that percentage may increase to 60 percent if temperatures rise. Other tropical diseases may spread similarly, including dengue fever, yellow fever, and encephalitis. Scientists also predict rising incidence of allergies and respiratory diseases as warmer air grows more charged with pollutants, mold spores, and pollens. <o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">VI<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">DEBATES OVER GLOBAL WARMING<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="">Scientists do not all agree about the nature and impact of global warming. A few observers still question whether temperatures have actually been rising at all. Others acknowledge past change but argue that it is much too early to be making predictions for the future. Such critics may also deny that the evidence for the human contribution to warming is conclusive, arguing that a purely natural cycle may be driving temperatures upward. The same dissenters tend to emphasize the fact that continued warming could have benefits in some regions.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">Scientists who question the global warming trend point to three puzzling differences between the predictions of the global warming models and the actual behavior of the climate. First, the warming trend stopped for three decades in the middle of the 20th century; there was even some cooling before the climb resumed in the 1970s. Second, the total amount of warming during the 20th century was only about half what computer models predicted. Third, the troposphere, the lower region of the atmosphere, did not warm as fast as the models forecast. However, global warming proponents believe that two of the three discrepancies have now been explained. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">The lack of warming at midcentury is now attributed largely to air pollution that spews particulate matter, especially sulfates, into the upper atmosphere. These particulates, also known as aerosols, reflect some incoming sunlight out into space. Continued warming has now overcome this effect, in part because pollution control efforts have made the air cleaner.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">The unexpectedly small amount of total warming since 1900 is now attributed to the oceans absorbing vast amounts of the extra heat. Scientists long suspected that this was happening but lacked the data to prove it. In 2000 the U.S. National Oceanic and Atmospheric Administration (NOAA) offered a new analysis of water temperature readings made by observers around the world over 50 years. Records showed a distinct warming trend: World ocean temperatures in 1998 were higher than the 50-year average by 0.2 Celsius degree (0.3 Fahrenheit degree), a small but very significant amount.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">The third discrepancy is the most puzzling. Satellites detect less warming in the troposphere than the computer models of global climate predict. According to some critics, the atmospheric readings are right, and the higher temperatures recorded at Earth’s surface are not to be trusted. In January 2000 a panel appointed by the National Academy of Sciences to weigh this argument reaffirmed that surface warming could not be doubted. However, the lower-than-predicted troposphere measurements have not been entirely explained.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">VII<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">EFFORTS TO CONTROL GLOBAL WARMING<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="">The total consumption of fossil fuels is increasing by about 1 percent per year. No steps currently being taken or under serious discussion will likely prevent global warming in the near future. The challenge today is managing the probable effects while taking steps to prevent detrimental climate changes in the future. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">Damage can be curbed locally in various ways. Coastlines can be armored with dikes and barriers to block encroachments of the sea. Alternatively, governments can assist coastal populations in moving to higher ground. Some countries, such as the United States, still have the chance to help plant and animal species survive by preserving habitat corridors, strips of relatively undeveloped land running north and south. Species can gradually shift their ranges along these corridors, moving toward cooler habitats.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">There are two major approaches to slowing the buildup of greenhouse gases. The first is to keep carbon dioxide out of the atmosphere by storing the gas or its carbon component somewhere else, a strategy called carbon sequestration. The second major approach is to reduce the production of greenhouse gases.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">Carbon Sequestration<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="">The simplest way to sequester carbon is to preserve trees and to plant more. Trees, especially young and fast-growing ones, soak up a great deal of carbon dioxide, break it down in photosynthesis, and store the carbon in new wood. Worldwide, forests are being cut down at an alarming rate, particularly in the tropics. In many areas, there is little regrowth as land loses fertility or is changed to other uses, such as farming or building housing developments. Reforestation could offset these losses and counter part of the greenhouse buildup.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">Many companies and governments in the United States, Norway, Brazil, Malaysia, Russia, and Australia have initiated reforestation projects. In Guatemala, the AES Corporation, a U.S.-based electrical company, has joined forces with the World Resources Institute and the relief agency CARE to create community woodlots and to teach local residents about tree-farming practices. The trees planted are expected to absorb up to 58 million tons of carbon dioxide over 40 years.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">Carbon dioxide gas can also be sequestered directly. Carbon dioxide has traditionally been injected into oil wells to force more petroleum out of the ground or seafloor. Now it is being injected simply to isolate it underground in oil fields, coal beds, or aquifers. At one natural gas drilling platform off the coast of Norway, carbon dioxide brought to the surface with the natural gas is captured and reinjected into an aquifer from which it cannot escape. The same process can be used to store carbon dioxide released by a power plant, factory, or any large stationary source. Deep ocean waters could also absorb a great deal of carbon dioxide. The feasibility and environmental effects of both these options are now under study by international teams. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">In an encouraging trend, energy use around the world has slowly shifted away from fuels that release a great deal of carbon dioxide toward fuels that release somewhat less of this heat-trapping gas. Wood was the first major source of energy used by humans. With the dawn of the Industrial Revolution in the 18th century, coal became the dominant energy source. By the mid-19th century oil had replaced coal in dominance, fueling the internal combustion engines that were eventually used in automobiles. By the 20th century, natural gas began to be used worldwide for heating and lighting. In this progression, combustion of natural gas releases less carbon dioxide than oil, which in turn releases less of the gas than do either coal or wood.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">Nuclear energy, though controversial for reasons of safety and the high costs of nuclear waste disposal, releases no carbon dioxide at all. Solar power, wind power, and hydrogen fuel cells also emit no greenhouse gases. Someday these alternative energy sources may prove to be practical, low-pollution energy sources, although progress today is slow. <i>See also </i>Energy Supply, World; Wind Energy.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">National and Local Programs<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="">The developed countries are all working to reduce greenhouse emissions. Several European countries impose heavy taxes on energy usage, designed partly to curb such emissions. Norway taxes industries according to the amount of carbon dioxide they emit. In The Netherlands, government and industry have negotiated agreements aimed at increasing energy efficiency, promoting alternative energy sources, and cutting down greenhouse gas output.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">In the United States, the Department of Energy, the Environmental Protection Agency, product manufacturers, local utilities, and retailers have collaborated to implement the Energy Star program. This voluntary program rates appliances for energy use and gives some money back to consumers who buy efficient machines. The Canadian government has established the FleetWise program to cut carbon dioxide emissions from federal vehicles by reducing the number of vehicles it owns and by training drivers to use them more efficiently. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">Many local governments are also working against greenhouse emissions by conserving energy in buildings, modernizing their vehicles, and advising the public. Individuals, too, can take steps. The same choices that reduce other kinds of pollution work against global warming. Every time a consumer buys an energy-efficient appliance; adds insulation to a house; recycles paper, metal, and glass; chooses to live near work; or commutes by public transportation, he or she is fighting global warming.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">C<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style="">International Agreements<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style="">International cooperation is required for the successful reduction of greenhouse gases. In 1992 at the Earth Summit in Rio de Janeiro, Brazil, 150 countries pledged to confront the problem of greenhouse gases and agreed to meet again to translate these good intentions into a binding treaty.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">In 1997 in Japan, 160 nations drafted a much stronger agreement known as the Kyōto Protocol. This treaty, which went into force in February 2005, calls for the 38 industrialized countries that now release the most greenhouse gases to cut their emissions to levels 5 percent below those of 1990. This reduction is to be achieved no later than 2012. Initially, the United States voluntarily accepted a more ambitious target, promising to reduce emissions to 7 percent below 1990 levels; the European Union, which had wanted a much tougher treaty, committed to 8 percent; and Japan, to 6 percent. The remaining 122 nations, mostly developing nations, were not asked to commit to a reduction in gas emissions.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">But in 2001 newly elected U.S. president George W. Bush renounced the treaty, saying that such carbon dioxide reductions in the United States would be too costly. He also objected that developing nations would not be bound by similar carbon dioxide reducing obligations. The Kyōto Protocol could not go into effect unless industrial nations accounting for 55 percent of 1990 greenhouse gas emissions ratified it. That requirement was met in 2004 when the cabinet of Russian president Vladimir Putin approved the treaty, paving the way for it to go into effect in 2005. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">Some critics find the Kyōto Protocol too weak. Even if it were enforced immediately, it would only slightly slow the buildup of greenhouse gases in the atmosphere. Much stronger action would be required later, particularly because the developing nations exempted from the Kyōto rules are expected to produce half the world’s greenhouse gases by 2035. The most influential opponents of the protocol, however, find it too strong. Opposition to the treaty in the United States is spurred by the oil industry, the coal industry, and other enterprises that manufacture or depend on fossil fuels. These opponents claim that the economic costs to carry out the Kyōto Protocol could be as much as $300 billion, due mainly to higher energy prices. Proponents of the Kyōto sanctions believe the costs will prove more modest—$88 billion or less—much of which will be recovered as Americans save money after switching to more efficient appliances, vehicles, and industrial processes.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">Behind the issue of cost lies a larger question: Can an economy grow without increasing its greenhouse gas emissions at the same time? In the past, prosperity and pollution have tended to go together. Can they now be separated, or decoupled, as economists say? In nations with strong environmental policies, economies have continued to grow even as many types of pollution have been reduced. However, limiting the emission of carbon dioxide has proved especially difficult. For example, The Netherlands, a heavily industrialized country that is also an environmental leader, has done very well against most kinds of pollution but has failed to meet its goal of reducing carbon dioxide output.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style="">After 1997 representatives to the Kyōto Protocol met regularly to negotiate a consensus about certain unresolved issues, such as the rules, methods, and penalties that should be enforced in each country to slow greenhouse emissions. The negotiators designed a system in which nations with successful cleanup programs could profit by selling unused pollution rights to other nations. For example, nations that find further improvement difficult, such as The Netherlands, could buy pollution credits on the market, or perhaps earn them by helping reduce greenhouse gas emissions in less developed countries, where more can be achieved at less expense. Russia, in particular, stood to benefit from this system. In 1990 the Russian economy was in a shambles, and its greenhouse gas emissions were huge. Since then Russia has already cut its emissions by more than 5 percent below 1990 levels and is in a position to sell emission credits to other industrialized countries, particularly those in the European Union (EU).<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 15pt;"><span style=""><br />Contributed By:<br />John Hart<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style="">Microsoft ® Encarta ® 2007.</span></b><span style=""> © 1993-2006 Microsoft Corporation. All rights reserved.<o:p></o:p></span></p> <p class="MsoNormal"><o:p> </o:p></p>ghozian karamihttp://www.blogger.com/profile/13214011599962806335noreply@blogger.com0tag:blogger.com,1999:blog-192751622867664710.post-47425313498649736792008-12-11T06:07:00.000-08:002008-12-11T06:12:21.136-08:00Geomorphology<p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:24;" >Geomorphology<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >I<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >INTRODUCTION</span></p></td></tr></tbody></table><br /><img src="http://farm3.static.flickr.com/2133/2771170216_6b3513d624.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Slope Development<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Landforms and landscapes change over time as a result of various dynamic factors. These factors include tectonic movement, weather, erosion, and gravity. At any given moment, a landscape may include one or more of the features shown.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Geomorphology, scientific study of landforms and landscapes. The term usually applies to the origins and dynamic morphology (changing structure and form) of the earth's land surfaces, but it can also include the morphology of the seafloor and the analysis of extraterrestrial terrains. Sometimes included in the field of physical geography, geomorphology is really the geological aspect of the visible landscape. The science has developed in two distinctive ways that must be integrated in order for the whole picture of landscapes to emerge.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >II<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >HISTORICAL GEOMORPHOLOGY<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >One approach to the science of landforms is by means of historical, cyclic geomorphology. The concepts involved were worked out at the turn of the 20th century by the American geologist William Morris Davis, who stated that every landform could be analyzed in terms of structure, process, and stage. The first two are also treated by process geomorphology, discussed below; but the third, by introducing the element of time, is subject to a far greater degree of interpretation. Davis argued that every landform underwent development through a predictable, cyclic sequence: youth, maturity, and old age.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Historical geomorphology relies on various chronological analyses, notably those provided by stratigraphic studies of the last 2 million years, known as the Quaternary period. The relative chronology usually may be worked out by observation of stratigraphic relationships, and the time intervals involved may then be established more precisely by dating methods such as historical records, radiocarbon analysis, tree-ring counting (dendrochronology), and paleomagnetic studies. By applying such methods to stratigraphic data, a quantitative chronology of events is constructed that furnishes a basis for calculating long-term rates of change.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >III<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >PROCESS GEOMORPHOLOGY<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >This second branch of geomorphology analyzes contemporary dynamic processes at work in landscapes. The mechanisms involved—weathering and erosion—combine processes that are in some respects destructive and in others constructive. The bedrock and soil provide the passive material, whereas the climatic regime and crustal dynamics together provide the principal active variables.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >IV<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >UNDERLYING DYNAMICS</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3111/2770323463_6eb7f30f29.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Folded Rocks<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Geomorphologists study the shape of the earth’s surface and the various processes that change the landscape. For example when large pieces of the earth’s crust move laterally, they create huge compressional forces that can bend or even break rocks. Here, the sedimentary rock layers show an anticlinal fold, in which the layers bend downward from the crest.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >V. Englebert/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >In geomorphological processes, gravity is an all-pervading, essentially invariable energy factor; a second variable, energy flow is provided by solar radiation. The latter is expressed either as a direct thermal variable or, indirectly, through the hydrologic cycle, which involves evaporation of water from the ocean, atmospheric transport of water, precipitation as rain or snow, and a return to the ocean by various processes. A third energy factor is heat flow from the earth's interior. Although of a magnitude considerably less than solar energy, this heat flow ultimately is responsible for creating major geological structures such as faults, but rates of change tend to be quite low (usually less than 1 mm per year). Nonetheless, in particular zones—for example, along crustal-plate boundaries (<i>see </i>Plate Tectonics) such as the San Andreas fault—stress may build up until released catastrophically in violent displacements of up to 12 m (40 ft). Locally, heat flow from the interior is concentrated in eruptions of magma (molten rock), which produce a variety of volcanic landforms.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >V<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >WEATHERING AND EROSION</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3168/2770323679_0aca2bb8f3.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Glacial Erosion<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Glaciers, such as this icy formation in Switzerland, erode the land over which they move. Glacial erosion is caused by distinct processes, such as abrasion, crushing, and fracturing of the glacier. Climate changes affect the size of glaciers, and glaciers move by growing or shrinking depending on the climate. Moving glaciers erode and transport large quantities of rocks, sand, and other particles along their path. Glacial erosion processes form features such as hanging valleys, moraines, cirques, horns, and scoured rock faces.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Paolo Koch/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Weathering is often a combination of three processes: the mechanical process, as in the growth of ice or salt crystals or in thermal heating and cooling; the chemical process, as in acid-water solutions that tend to dissolve minerals such as calcite and feldspar; and the biological process, as in the effect of plant roots, which generate both mechanical and chemical energy. Erosion is the dislodging, removal, and transport of material, either in solution or in particle form. The energy to accomplish this may be provided in the form of raindrops, running water, wind, waves, or simply gravity (as in a landslide).<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >An eroding landmass tends to rise to compensate for the removal of the load, but it eventually stabilizes as land relief decreases and stream gradients decline. The resulting surface, almost flat, is called a peneplain. It may be interrupted, here and there, by isolated hills called monadnocks consisting of rocks especially resistant to erosion. The theoretical base level of such a surface—the ultimate grade of streams—is mean sea level. For a peneplain to form and not be destroyed by renewed erosion, sea level must remain stable for millions of years. However, since the end of the Quaternary Ice Age, 10,000 years ago, sea level has risen hundreds of feet.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Human-induced soil erosion is a feature of the present day and of the last few millennia, because clearing land of native vegetation or excessive grazing by domesticated animals exposes the soil to massive erosion. In this way some 3 billion metric tons of particulate material are washed from the surface of the U.S. alone each year. In undisturbed natural settings, on the other hand—notably in low-relief continental interiors—erosion rates are very slow (except in semiarid areas where thunderstorms produce flash floods). In structurally active belts such as in youthful mountains, which as a rule coincide with plate boundaries that recently collided or rifted, erosion rates may be enormous.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Of all the different processes acting on the earth's surface, rain and rivers are the most vigorous erosive agents. By contrast, although wave action on a rocky coast is often impressive, the rate of retreat of the shoreline is generally very slow. Sand dunes in the Sahara are also impressive, but the sand is only a relatively thin veneer; and the moraines left by giant continental glaciers are likewise only superficial scrapings of ancient soils. In general, without human interference, the landscape is stable.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 15pt;"><span style=";font-family:";font-size:12;" ><br />Contributed By:<br />Rhodes W. Fairbridge<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:9;" >Microsoft ® Encarta ® 2007.</span></b><span style=";font-family:";font-size:9;" > © 1993-2006 Microsoft Corporation. All rights reserved.<o:p></o:p></span></p> <p class="MsoNormal"><o:p> </o:p></p>ghozian karamihttp://www.blogger.com/profile/13214011599962806335noreply@blogger.com0tag:blogger.com,1999:blog-192751622867664710.post-61471677829970960352008-12-11T05:33:00.000-08:002008-12-11T06:04:16.498-08:00All about islam<p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:24;" >Islam<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >I<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >INTRODUCTION</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3136/2771170902_d0990e0c91.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >The Qur’an<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >The inscription on buildings of verses from the Qur’an symbolizes the living presence of the holy book in Islamic society. This tower with decorative Qur’anic inscriptions is in Delhi, India.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Gillian Darley/Edifice/Corbis<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Islam, one of the three major world religions, along with Judaism and Christianity, that profess monotheism, or the belief in a single God. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >In the Arabic language, the word <i>Islam</i> means “surrender” or “submission”—submission to the will of God. A follower of Islam is called a <i>Muslim,</i> which in Arabic means “one who surrenders to God.” The Arabic name for God, <i>Allah</i>, refers to the God worshiped by Jews and Christians. Islam’s central teaching is that there is only one all-powerful, all-knowing God, and this God created the universe. This rigorous monotheism, as well as the Islamic teaching that all Muslims are equal before God, provides the basis for a collective sense of loyalty to God that transcends class, race, nationality, and even differences in religious practice. Thus, all Muslims belong to one community, the <i>umma</i>, irrespective of their ethnic or national background.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Within two centuries after its rise in the 7th century, Islam spread from its original home in Arabia into Syria, Egypt, North Africa, and Spain to the west, and into Persia, India, and, by the end of the 10th century, beyond to the east. In the following centuries, Islam also spread into Anatolia and the Balkans to the north, and sub-Saharan Africa to the south. The Muslim community comprises about 1 billion followers on all five continents, and Islam is the fastest-growing religion in the world. The most populous Muslim country is Indonesia, followed by Pakistan and Bangladesh. Beyond the Middle East, large numbers of Muslims live in India, Nigeria, the former republics of the Union of Soviet Socialist Republics (USSR), and China. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >One of the reasons for the growth of the Muslim community has been its openness to new members. Children born to Muslim parents are automatically considered Muslim. At any time, a non-Muslim can convert to Islam by declaring himself or herself to be a Muslim. A person’s declaration of faith is sufficient evidence of conversion to Islam and need not be confirmed by others or by religious authorities.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >II<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >THE TEACHINGS OF MUHAMMAD</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3184/2771171044_53e51866b1.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Mecca, Saudi Arabia<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >The al-Haram Mosque in Mecca, Saudi Arabia, holds the holiest shrine of Islam, the Kaaba. As the birthplace of Islam’s founder, the Prophet Muhammad, Mecca is considered a holy city. It is a pilgrimage point for Muslims worldwide, who are expected to visit the city at least once if they are able to do so.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Mehmet Biber/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Around the year <span style="text-transform: uppercase;">ad</span> 570 Muhammad, the founding prophet of Islam, was born in Mecca, at the time the central city of the Arabian Peninsula. Some 40 years later Muhammad started preaching a new religion, Islam, which constituted a marked break from existing moral and social codes in Arabia. The new religion of Islam taught that there was one God, and that Muhammad was the last in a series of prophets and messengers. Through his messengers God had sent various codes, or systems of laws for living, culminating in the Qur’an (Koran), the holy book of Islam. These messengers were mortal men, and they included among many others Moses, the Hebrew prophet and lawgiver, and Jesus, whom Christians believe to be the son of God rather than a prophet. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Islam also taught that the Christian Bible (which includes the Hebrew Bible as the Old Testament and an additional 27 books referred to as the New Testament), and the Qur'an were all holy books. According to the Qur’an, the two earlier Scriptures had been altered over time from their original forms given by God, while the Qur'an would remain perfect, preserved by God from such distortion. In addition to distinguishing itself from the Hebrew and Christian traditions, the new religion taught that the God of Islam had provided humanity with the means to know good from evil, through the prophets and the Qur’an. Therefore, on the Day of Judgment people will be held accountable for their actions.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Muhammad’s teachings met with severe and hostile opposition, and in the year 622 he left Mecca and sought refuge in the city of Yathrib, as a number of his followers had already done. Upon Muhammad's arrival, the name Yathrib was changed to Medina (meaning “the city”). The date of Muhammad's immigration was later set as the beginning of the 12-month lunar Islamic calendar.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >III<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >THE FIVE PILLARS<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >During the ten years between his arrival in Medina and his death in <span style="text-transform: uppercase;">ad</span> 632, Muhammad laid the foundation for the ideal Islamic state. A core of committed Muslims was established, and a community life was ordered according to the requirements of the new religion. In addition to general moral injunctions, the requirements of the religion came to include a number of institutions that continue to characterize Islamic religious practice today. Foremost among these were the five pillars of Islam, the essential religious duties required of every adult Muslim who is mentally able. The five pillars are each described in some part of the Qur’an and were already practiced during Muhammad's lifetime. They are the profession of faith (<i>shahada</i>), prayer (<i>salat</i>), almsgiving (<i>zakat</i>), fasting (<i>sawm</i>), and pilgrimage (<i>hajj</i>). Although some of these practices had precedents in Jewish, Christian, and other Middle Eastern religious traditions, taken together they distinguish Islamic religious practices from those of other religions. The five pillars are thus the most central rituals of Islam and constitute the core practices of the Islamic faith.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Many polemical descriptions of Islam have focused critically on the Islamic concept of jihad. Jihad, considered the sixth pillar of Islam by some Muslims, has been understood to mean holy war in these descriptions. However, the word in Arabic means 'to struggle' or 'to exhaust one's effort,' in order to please God. Within the faith of Islam, this effort can be individual or collective, and it can apply to leading a virtuous life; helping other Muslims through charity, education, or other means; preaching Islam; and fighting to defend Muslims. Western media of the 20th century continue to focus on the militant interpretations of the concept of jihad, whereas most Muslims do not.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >The Profession of Faith<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >The absolute focus of Islamic piety is Allah, the supreme, all knowing, all-powerful, and above all, all-merciful God. The Arabic word <i>Allah</i> means “the God,” and this God is understood to be the God who brought the world into being and sustains it to its end. By obeying God's commands, human beings express their recognition of and gratitude for the wisdom of creation, and live in harmony with the universe.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >The profession of faith, or witness to faith (shahada), is therefore the prerequisite for membership in the Muslim community. On several occasions during a typical day, and in the saying of daily prayers, a Muslim repeats the profession, 'I bear witness that there is no god but Allah and that Muhammad is his messenger.' There are no formal restrictions on the times and places these words can be repeated. To become a member of the Muslim community, a person has to profess and act upon this belief in the oneness of God and the prophethood of Muhammad. To be a true profession of faith that represents a relationship between the speaker and God, the verbal utterance must express genuine knowledge of its meaning as well as sincere belief. A person’s deeds can be subjected to scrutiny by other Muslims, but a person’s utterance of the profession of faith is sufficient evidence of membership in the Muslim community and cannot be challenged by other members of this community. <o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >The Five Daily Prayers</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3113/2771171188_7b34fd0d15.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Minaret of the Great Mosque at Sāmarrā’<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >This spiral minaret, where the <i>muezzin</i> once called the faithful to prayer, is the only surviving feature of the Great Mosque at Sāmarrā’, Iraq. At the time of its construction (848-852), the Great Mosque at Sāmarrā’ was the largest Islamic mosque in the world.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >SEF/Art Resource, NY<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >The second pillar of Islam is the religious duty to perform five prescribed daily prayers or salat. All adult Muslims are supposed to perform five prayers, preceded by ritual cleansing or purification of the body at different intervals of the day. The Qur’anic references also mention the acts of standing, bowing, and prostrating during prayers and facing a set direction, known as <i>qibla</i>. The Muslims were first required to face Jerusalem during prayer, but already during Muhammad's lifetime they were commanded to face the Kaaba, an ancient shrine in the city of Mecca. The Qur’an also refers to the recitation of parts of the Qur’an as a form of prayer. However, even with its numerous references, the Qur’an alone does not give exact instructions for this central ritual of prayer.<o:p></o:p></span></p> <span style=";font-family:";font-size:9;color:black;" >The most detailed descriptions of the rituals for prayer derive from the example set by the prophet Muhammad and are preserved in later Islamic traditions. Some details of these rituals vary, however all Muslims agree that there are five required daily prayers to be performed at certain times of day: dawn (<i>fajr</i> or <i>subh</i>), noon (<i>zuhr</i>), midafternoon (<i>asr</i>), sunset (<i>maghrib</i>), and evening (<i>isha</i>). The dawn, noon, and sunset prayers do not start exactly at dawn, noon, and sunset; instead, they begin just after, to distinguish the Islamic ritual from earlier practices of worshiping the sun when it rises or sets.</span><br /><img src="http://farm4.static.flickr.com/3002/2771171376_8ca4062fbb.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Layout of a Mosque<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Mosques are laid out in accordance with Muslim prayer. They are generally organized around a courtyard, a reminder of the courtyard of Muhammad’s house, which served as the first mosque. Muslims pray facing the holy city of Mecca, a direction known as the <i>qibla.</i> A <i>mihrab,</i> or prayer niche, indicates the qibla, and the main prayer hall stands on the qibla side. Worshipers, called to prayer by a crier from the minaret, may hear a sermon delivered from the <i>mimbar</i> near the mihrab. A mosque that has a vaulted hall, or <i>eyvan</i> on each side of its courtyard, as this mosque does, is known as a four-eyvan mosque.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >A prayer is made up of a sequence of units called bowings<i> </i>(<i>rak’as</i>). During each of these units, the worshiper stands, bows, kneels, and prostrates while reciting verses from the Qur’an as well as other prayer formulas. With some variations among different Muslim sects, at noon, afternoon, and evening prayers, these units are repeated four times, while during the sunset prayer they are repeated three times, and at dawn only twice. The opening chapter of the Qur’an, al-Fatiha, is repeated in each unit in a prayer sequence. Each prayer concludes with the recitation of the profession of faith followed by the greeting 'may the peace, mercy, and blessings of God be upon you.'<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Wherever Muslims live in substantial numbers throughout the world, the call to prayer, or <i>adhan</i>, is repeated five times a day by a <i>muezzin</i> (crier) from a mosque, the Muslim place of worship. Muslims are encouraged to pray together in mosques, but group prayer is only a religious obligation for the noon prayer on Friday. Women, travelers, sick Muslims, and those attending to the sick are granted license not to attend the Friday congregational prayer, although they may attend if they wish. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >The Friday noon prayer is led by an <i>imam</i>, who is simply a prayer leader; this prayer differs from the usual noon prayers of the other days of the week. As a required part of the ritual at this congregational meeting, two sermons precede the prayer. On other days, Muslims can pray anywhere they wish, either individually or in groups. They must observe the rituals of praying at certain times of day, facing in the direction of Mecca, observing the proper order of prayers, and preparing through symbolic purification. Depending on the situation, this last ritual of ablution requires either total washing of the body or a less elaborate ritual washing of the hands, mouth, face, and feet.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >In addition to the five required daily prayers, Muslims can perform non-obligatory prayers, some of which have fixed ritual formats and are performed before or after each of the five daily prayers. Others are performed at night, either individually or with other Muslims. These additional formal and informal prayers give expression to the primary function of prayer in Islam, which is personal communication with God for the purpose of maintaining the abiding presence of the divine in the personal lives of Muslims. The more formal aspects of prayer also serve to provide a disciplined rhythm that structures the day and fosters a sense of community and shared identity among Muslims.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >C<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >Almsgiving<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >The third pillar of Islam is zakat, or almsgiving. A religious obligation, zakat is considered an expression of devotion to God. It represents the attempt to provide for the poorer sectors of society, and it offers a means for a Muslim to purify his or her wealth and attain salvation. The Qur’an, together with other Islamic traditions, strongly encourages charity and constantly reminds Muslims of their moral obligation to the poor, orphans, and widows; however, it distinguishes between general, voluntary charity (<i>sadaqa</i>) and zakat, the latter being an obligatory charge on the money or produce of Muslims. While the meaning of terms has been open to different interpretations, the Qur’an regularly refers to zakat, identifying specific ways in which this tax can be spent. These specific uses include spending zakat on the poor and the needy, on those who collect and distribute zakat, on those whom Muslims hope to win over and convert to Islam, on travelers, on the ransom of captives, to relieve those who are burdened with debts, and on the cause of God.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >The Qur’an provides less-detailed information about the kinds of things that are subject to the zakat tax or the precise share of income or property that should be paid as zakat. These determinations are provided in the traditions of the prophet Muhammad and have been the subject of elaborate discussions among Muslim legal experts, or jurists. For example, one-fortieth (2.5 percent) of the assets accumulated during the year (including gold, silver, and money) is payable at the end of the year, while one-tenth of the harvest of the land or date trees is payable at harvest time. Cattle, camels, and other domestic animals are subject to a more complex taxation system that depends on the animals in question, their age, the numbers involved, and whether they are freely grazing. Traditional zakat laws do not cover trade, but commercial taxes have been imposed by various Muslim governments throughout history.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >D<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >Fasting</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3203/2770324609_a2b361aef9.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Last Day of Ramadan<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Muslims pray in the upper gallery of a main mosque in the old walled city of Delhi, India. They are celebrating the end of Ramadan, the holy month of fasting as ordained by the Qur’an, the sacred scriptures of Islam.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >REUTERS/CORBIS-BETTMANN<o:p></o:p></span></p> <span style=";font-family:";font-size:9;color:black;" >The fourth pillar of Islam is sawm,<i> </i>or fasting. Clear Qur’anic references to fasting account for the early introduction of this ritual practice. The Qur’an prescribes fasting during the month of Ramadan, the 9th month of the 12-month Islamic lunar year (<i>see </i>Calendar). The month of Ramadan is sacred because the first revelation of the Qur’an is said to have occurred during this month. By tradition the month starts with the sighting of the new moon by at least two Muslims. For the entire month, Muslims must fast from daybreak to sunset by refraining from eating, drinking, and sexual intercourse. Menstruating women, travelers, and sick people are exempted from fasting but have to make up the days they miss at a later date.</span><br /><img src="http://farm4.static.flickr.com/3113/2770324833_d3d52308f5.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Festivities Ending Ramadan<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Members of the Tarabin Bedouin tribe in Egypt prepare food for a three-day festival that marks the end of the Islamic holy month, Ramadan. During Ramadan adult Muslims fast from sunrise to sunset.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Ruth Fremson/AP/Wide World Photos<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >According to various traditional interpretations, the fast introduces physical and spiritual discipline, serves to remind the rich of the misfortunes of the poor, and fosters, through this rigorous act of worship, a sense of solidarity and mutual care among Muslims of all social backgrounds. Thus Muslims usually engage in further acts of worship beyond the ordinary during Ramadan, such as voluntary night prayer, reading sections from the Qur’an, and paying voluntary charity to the poor. Muslims may even choose to wake before daybreak to eat a meal that will sustain them until sunset. After the fasting ends, the holiday of breaking the fast, ‘<i>id al-fitr,</i> begins, lasting for three days.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >At any time of year fasting is also required as a compensation for various offenses and violations of the law. Many Muslims also perform voluntary fasts at various times of the year as acts of devotion and spiritual discipline. However, such additional fasting is not required by Islamic law.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >E<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >Pilgrimage to Mecca</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3182/2771172036_f92b3c20ed.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Pilgrimage to the Kaaba<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Muslims consider the Kaaba—a small sanctuary near the center of the Great Mosque in Mecca— to be the most sacred spot on earth. Muslim legend teaches that the ancient religious patriarchs Abraham and Ishmael built the shrine using foundations first laid by Adam. Muslims all over the world orient themselves toward the Kaaba while praying, and every able Muslim is expected to make a pilgrimage to the Kaaba at least once in his or her lifetime. This picture shows pilgrimage ceremonies, which consist of several days of rituals and festivals during the Islamic month of pilgrimages, Dhu al-Hijja.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Mehmet Biber/Photo Researchers, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >The fifth pillar requires that Muslims who have the physical and financial ability should perform the pilgrimage, or hajj, to Mecca at least once in a lifetime. The ritual of pilgrimage was practiced by Arabs before the rise of Islam and continues from the early days of Islam. The hajj is distinct from other pilgrimages. It must take place during the 12th lunar month of the year, known as <i>Dhu al-Hijja,</i> and it involves a set and detailed sequence of rituals that are practiced over the span of several days. All of the pilgrimage rituals take place in the city of Mecca and its surroundings, and the primary focus of these rituals is a cubical structure called the Kaaba. According to Islamic tradition, the Kaaba, also referred to as the House of God, was built at God's command by the prophet Ibrahim (Abraham of the Hebrew and Christian Bibles) and his son Ismail (<i>see </i>Ishmael).<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >The Qur’an provides detailed descriptions of various parts of the ritual, and it portrays many of these rituals as reenactments of the activities undertaken by Ibrahim and Ismail in the course of building the Kaaba. Set into one corner of the Kaaba is the sacred Black Stone, which according to one Islamic tradition was given to Ibrahim by the angel Gabriel. According to another Islamic tradition this stone was first set in place by Adam.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Once pilgrims arrive in Mecca, ritual purification is performed. Many men shave their heads, and most men and women put on seamless white sheets. This simple and common dress symbolizes the equality of all Muslims before God, a status further reinforced by the prohibition of jewelry, perfumes, sexual intercourse, and hunting. After this ritual purification, Muslims circle the Kaaba seven times, run between al-Safa and al-Marwa, two hills overlooking the Kaaba, seven times, and perform several prayers and invocations. This ritual is a reenactment of the search by Hagar for water to give her son Ismail. <o:p></o:p></span></p> <span style=";font-family:";font-size:9;color:black;" >After these opening rituals, the hajj proper commences on the seventh day and continues for the next three days. Again, it starts with the performance of ritual purification followed by a prayer at the Kaaba mosque. The pilgrims then assemble at Mina, a hill outside Mecca, where they spend the night. The next morning they go to the nearby plain of Arafat, where they stand from noon to sunset and perform a series of prayers and rituals. The pilgrims then head to Muzdalifa, a location halfway between Arafat and Mina, to spend the night. The next morning, the pilgrims head back to Mina, on the way stopping at stone pillars symbolizing Satan, at which they throw seven pebbles.</span><br /><img src="http://farm4.static.flickr.com/3257/2770325287_18ba229234.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Dome of the Rock<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >The oldest extant Islamic structure, the Dome of the Rock stands on the sacred rock in Jerusalem where the Prophet Muhammad is believed to have ascended to heaven. Caliph Abd al-Malik built the mosque during the late 7th century. The mosque’s basic octagonal design encloses a central space topped by a dome. A rich mosaic decoration covers the outer walls.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Israel Ministry of Tourism<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >The final ritual is the slaughter of an animal (sheep, goat, cow, or camel). This is a symbolic reenactment of God's command to Ibrahim to sacrifice his son Ismail, which Ibrahim and Ismail duly accepted and were about to execute when God allowed Ibrahim to slaughter a ram in place of his son. Most of the meat of the slaughtered animals is to be distributed to poor Muslims. The ritual sacrifice ends the hajj<i> </i>and starts the festival of the sacrifice, <i>‘id al-adha. </i>The<i> </i>festivals of breaking fast (‘id al-fitr) at the end of Ramadan and<i> ‘</i>id al-adha<i> </i>are the two major Islamic festivals celebrated by Muslims all over the world.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >During the pilgrimage most Muslims visit Medina, where the tomb of the Prophet is located, before returning to their homes. If the pilgrimage rituals are performed at any time of the year other than the designated time for hajj, the ritual is called <i>umra.</i> Although umra is considered a virtuous act, it does not absolve the person from the obligation of hajj. Most pilgrims perform one or more umras before or after the hajj proper.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Many Muslims pilgrims also travel to Jerusalem, which is the third sacred city for Islam. Muslims believe Muhammad was carried to Jerusalem in a vision. The Dome of the Rock houses the stone from which Muhammad is believed to have ascended to heaven and Allah in a night journey. Some Muslims perform pilgrimages to the Dome of the Rock and to other shrines where revered religious figures are buried. Some of these shrines are important primarily to the local populations, whereas others draw Muslims from distant regions. There are no standard prescribed rituals for these pilgrimages nor are they treated as obligatory acts of worship.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >IV<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >THE MOSQUE</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3246/2770325445_abb00b6da7.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Mosque of Córdoba in Spain<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >This mosque in Córdoba, Spain, was begun in <span style="text-transform: uppercase;">ad</span> 786, while the city was the capital of Moorish Spain. Although the mosque became a Christian cathedral after the Roman Catholics of Spain captured Córdoba in 1236, the building retains its Islamic heritage. The mosque features columns that support horseshoe-shaped arches decorated with stripes of alternating colors. Layered in two tiers, these distinctly Moorish arches convey a light and airy feeling to the interior of the building.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Adam Lubroth/Art Resource, NY<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Of all Muslim institutions, the mosque is the most important place for the public expression of Islamic religiosity and communal identity. A mosque is a physical manifestation of the public presence of Muslims and serves as a point of convergence for Islamic social and intellectual activity. The Arabic word for mosque is <i>masjid</i>, which means a 'place of prostration' before God. Mosques are mentioned in the Qur’an, and the earliest model for a mosque was the residence that the prophet Muhammad built when he moved to Medina. This first mosque was an enclosure marked as a special place of worship. A small part of the mosque was sectioned off to house the Prophet and his family, and the remaining space was left open as a place for Muslims to pray. <o:p></o:p></span></p> <span style=";font-family:";font-size:9;color:black;" >Although later mosques developed into complex architectural structures built in diverse styles, the one requirement of all mosques continues to be based on the earliest model: a designation of space for the purpose of prayer. The early mosque served an equally important function that thousands of mosques continue to serve today: The mosque is a place where Muslims foster a collective identity through prayer and attend to their common concerns. A Muslim city typically has numerous mosques but only a few congregational or Friday mosques where the obligatory Friday noon prayers are performed.</span><br /><img src="http://farm4.static.flickr.com/3083/2770325659_ca630a4fa1.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Mosque in Burkina Faso<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >The Grand Mosque of Bobo-Dioulasso in Burkina Faso is built of mud brick, the local building material. About half the people in Burkina Faso are Muslims.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >J. Hartley/Panos Pictures<o:p></o:p></span></p> <span style=";font-family:";font-size:9;color:black;" >As Islam spread outside Arabia, Islamic architecture was influenced by the various architectural styles of the conquered lands, and both simple and monumental mosques of striking beauty were built in cities of the Islamic world. Despite the borrowings from diverse civilizations, certain common features became characteristic of most mosques and thus serve to distinguish them from the sacred spaces of other religions and cultures.</span><br /><img src="http://farm4.static.flickr.com/3005/2771172750_209f780d0c.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Mosque in Nouakchott<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >A mosque in Nouakchott, the capital of Mauritania. Islam is the state religion of Mauritania and is professed by nearly all Mauritanians.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Christian Sappa/RAPHO<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >The most important characteristic of a mosque is that it should be oriented toward Mecca. One or more niches (<i>mihrab</i>) on one of the walls of the mosque often serve as indicators of this direction, called <i>qibla</i>. When the imam leads the prayers he usually faces one of these niches. Next to the mihrab, a pulpit (<i>minbar</i>) is often provided for the delivery of sermons (<i>khutba</i>). Many mosques also have separate areas for performing ritual ablution, and separate sections for women. In many mosques, several rows of columns are used to mark the way for worshipers to line up behind the imam during prayer. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Mosques usually have one or more <i>minarets,</i> or towers, from which the muezzin calls Muslims to prayer five times a day. In addition to their functional use, these minarets have become distinguishing elements of mosque architecture. In large mosques in particular, minarets have the effect of tempering the enormity and magnificence of the domed structure by conveying to the viewer the elevation of divinity above the pretensions of human grandeur.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Most mosques also have a dome, and the line connecting the center of the dome to the niche is supposed to point toward Mecca. Throughout the world there are many mosques that are not actually directed toward Mecca, but such misalignment is due to inaccurate methods for determining the direction of Mecca and does not imply a disregard for this requirement. The mosque is not a self-contained unit, nor is it a symbolic microcosm of the universe, as are some places of worship in other religions. Rather, the mosque is always built as a connection with Mecca, the ultimate home of Muslim worship that metaphorically forms the center of all mosques. <i>See </i>Islamic Art and Architecture.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >V<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >THE GOD OF ISLAM<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Islamic doctrine emphasizes the oneness, uniqueness, transcendence, and utter otherness of God. As such, God is different from anything that the human senses can perceive or that the human mind can imagine. The God of Islam encompasses all creation, but no mind can fully encompass or grasp him. God, however, is manifest through his creation, and through reflection humankind can easily discern the wisdom and power behind the creation of the world. Because of God’s oneness and his transcendence of human experience and knowledge, Islamic law forbids representations of God, the prophets, and among some Muslims, human beings in general. As a result of this belief, Islamic art came to excel in a variety of decorative patterns including leaf shapes later stylized as arabesques, and Arabic script. In modern times the restrictions on creating images of people have been considerably relaxed, but any attitude of worship toward images and icons is strictly forbidden in Islam.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >Islamic Monotheism</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3114/2770325965_ba23a3e142.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Ardabīl Carpet<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >This carpet was woven for the tomb-mosque of Shah Tahmasp at Ardabīl, Iran, in 1539 and 1540. Carpets like this often had more than 100 knots per sq cm (250 per sq in), so a team of weavers was needed to finish a carpet in a reasonable amount of time. The central design is a medallion shape, a traditional motif for mosque carpets.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Bridgeman Art Library, London/New York<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Before Islam, many Arabs believed in a supreme, all-powerful God responsible for creation; however, they also believed in lesser gods. With the coming of Islam, the Arab concept of God was purged of elements of polytheism and turned into a qualitatively different concept of uncompromising belief in one God, or monotheism. The status of the Arabs before Islam is considered to be one of ignorance of God, or <i>jahiliyya</i>, and Islamic sources insist that Islam brought about a complete break from Arab concepts of God and a radical transformation in Arab belief about God.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Islamic doctrine maintains that Islam’s monotheism continues that of Judaism and Christianity. However, the Qur’an and Islamic traditions stress the distinctions between Islam and later forms of the two other monotheistic religions. According to Islamic belief, both Moses and Jesus, like others before them, were prophets commissioned by God to preach the essential and eternal message of Islam. The legal codes introduced by these two prophets, the Ten Commandments and the Christian Gospels, took different forms than the Qur’an, but according to Islamic understanding, at the level of doctrine they are the same teaching. The recipients of scriptures are called the people of the book or the 'scriptured' people. Like the Jews and the Christians before them, the Muslims became scriptured when God revealed his word to them through a prophet: God revealed the Qur’an to the prophet Muhammad, commanding him to preach it to his people and later to all humanity.<o:p></o:p></span></p> <span style=";font-family:";font-size:9;color:black;" >Although Muslims believe that the original messages of Judaism and Christianity were given by God, they also believe that Jews and Christians eventually distorted them. The self-perceived mission of Islam, therefore, has been to restore what Muslims believe is the original monotheistic teaching and to supplant the older legal codes of the Hebrew and Christian traditions with a newer Islamic code of law that corresponds to the evolving conditions of human societies. Thus, for example, Islamic traditions maintain that Jesus was a prophet whose revealed book was the Christian New Testament, and that later Christians distorted the original scripture and inserted into it the claim that Jesus was the son of God. Or to take another example, Muslims maintain that the strict laws communicated by Moses in the Hebrew Bible were appropriate for their time. Later, however, Jesus introduced a code of behavior that stressed spirituality rather than ritual and law.</span><br /><img src="http://farm4.static.flickr.com/3013/2771173078_69d1cc44f9.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Mosque in Bosnia and Herzegovina<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >The Ottomans conquered most of Bosnia in 1463, and by 1483 controlled most of Herzegovina as well. The two territories, then separated, remained provinces of the Ottoman Empire for the next 400 years. Here, a mosque built by the Ottomans stands near Mostar. Mostar was severely damaged as a result of the civil war that followed Bosnia and Herzegovina’s declaration of independence from Yugoslavia in 1992.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >THE BETTMANN ARCHIVE<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >According to Muslim belief, God sent Muhammad with the last and perfect legal code that balances the spiritual teachings with the law, and thus supplants the Jewish and Christian codes. According to the teachings of Islam, the Islamic code, called Sharia, is the final code, one that will continue to address the needs of humanity in its most developed stages, for all time. The Qur’an mentions 28 pre-Islamic prophets and messengers, and Islamic traditions maintain that God has sent tens of thousands of prophets to various peoples since the beginning of creation. Some of the Qur’anic prophets are familiar from the Hebrew Bible, but others are not mentioned in the Bible and seem to be prophetic figures from pre-Islamic Arabia.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >For the Muslim then, Islamic history unfolds a divine scheme from the beginning of creation to the end of time. Creation itself is the realization of God's will in history. Humans are created to worship God, and human history is punctuated with prophets who guarantee that the world is never devoid of knowledge and proper worship of God. The sending of prophets is itself understood within Islam as an act of mercy. God, the creator and sustainer, never abandons his creations, always providing human beings with the guidance they need for their salvation in this world and a world to come after this one. God is just, and his justice requires informing people, through prophets, of how to act and what to believe before he holds them accountable for their actions and beliefs. However, once people receive the teachings of prophets and messengers, God's justice also means that he will punish those who do wrong or do not believe and will reward those who do right and do believe. Despite the primacy of justice as an essential attribute of God, Muslims believe that God’s most fundamental attribute is mercy.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >Humanity’s Relationship to God</span></p></td></tr></tbody></table><br /><br /><img src="http://farm4.static.flickr.com/3071/2771173290_cf4aa8938b.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Mosque in Tajikistan<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >A majority of Tajikistan’s inhabitants are ethnic Tajiks, who are predominantly Muslim. Under Soviet rule (1921-1991), religion was severely restricted; mosques were closed and religious practice was prohibited outside of state-sanctioned places of worship. Restrictions were eased somewhat in the mid-1980s, but it was not until Tajikistan became independent in 1991 that Muslims were again able to freely practice their religion.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >V. Khristoforov/TASS/SOVFOTO-EASTFOTO<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >According to Islamic belief, in addition to sending prophets, God manifests his mercy in the dedication of all creation to the service of humankind. Islamic traditions maintain that God brought the world into being for the benefit of his creatures. His mercy toward humanity is further manifested in the privileged status God gave to humans. According to the Qur’an and later traditions, God appointed humankind as his vice regents (<i>caliphs</i>) on earth, thus entrusting them with the grave responsibility of fulfilling his scheme for creation. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >The Islamic concept of a privileged position for humanity departs from the early Jewish and Christian interpretations of the fall from Paradise that underlie the Christian doctrine of original sin. In the biblical account, Adam and Eve fall from Paradise as a result of disobeying God’s prohibition, and all of humanity is cast out of Paradise as punishment. Christian theologians developed the doctrine that humankind is born with this sin of their first parents still on their souls, based upon this reading of the story. Christians believe that Jesus Christ came to redeem humans from this original sin so that humankind can return to God at the end of time. In contrast, the Qur’an maintains that after their initial disobedience, Adam and Eve repented and were forgiven by God. Consequently Muslims believe that the descent by Adam and Eve to earth from Paradise was not a fall, but an honor bestowed on them by God. Adam and his progeny were appointed as God's messengers and vice regents, and were entrusted by God with the guardianship of the earth.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >C<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >Angels<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >The nature of humankind’s relationship to God can also be seen clearly by comparing it with that of angels. According to Islamic tradition, angels were created from light. An angel is an immortal being that commits no sins and serves as a guardian, a recorder of deeds, and a link between God and humanity. The angel Gabriel, for example, communicated God's message to the prophet Muhammad. In contrast to humans, angels are incapable of unbelief and always obey God. Some followers of Islam view Satan as an angel who was unusual in his ability to defy God, while others view him as a <i>jinn</i>, or spirit created by God from smokeless fire, who roamed among the angels.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Despite these traits, Islamic doctrine holds that humans are superior to angels. According to Islamic traditions, God entrusted humans and not angels with the guardianship of the earth and commanded the angels to prostrate themselves to Adam. Satan, together with the other angels, questioned God's appointment of fallible humans to the honorable position of viceregency. Being an ardent monotheist, Satan disobeyed God and refused to prostrate himself before anyone but God. For this sin, Satan was doomed to lead human beings astray until the end of the world. According to the Qur’an, God informed the angels that he had endowed humans with a knowledge angels could not acquire.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >D<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >Islamic Theology</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3238/2771173580_7f6a246cf9.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Kazimayn Mosque<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >The gold-domed Kazimayn Mosque, pictured at night, is near Baghdād in Iraq. This famous building, begun in the 11th century and completed in the 19th century, contains the tombs of revered Shia Muslim leaders.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Mehmet Biber/Photo Researchers, Inc.<o:p></o:p></span></p> <span style=";font-family:";font-size:9;color:black;" >For centuries Muslim theologians have debated the subjects of justice and mercy as well as God’s other attributes. Initially, Islamic theology developed in the context of controversial debates with Christians and Jews. As their articulations of the basic doctrines of Islam became more complex, Muslim theologians soon turned to debating different interpretations of the Qur’an among themselves, developing the foundations of Islamic theology.</span><br /><img src="http://farm4.static.flickr.com/3249/2771173754_91d498811f.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Mosque in Vladikavkaz<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >This mosque serves members of the Muslim minority in Vladikavkaz, the capital of the Russian republic of Alania (North Ossetia).<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >SOVFOTO-EASTFOTO<o:p></o:p></span></p> <span style=";font-family:";font-size:9;color:black;" >Recurring debates among Islamic scholars over the nature of God have continued to refine the Islamic concepts of God’s otherness and Islamic monotheism. For example, some theologians interpreted Qur’anic attributions of traits such as hearing and seeing to God metaphorically to avoid comparing God to created beings. Another controversial theological debate focused on the question of free will and predestination. One group of Muslim theologians maintained that because God is just, he creates only good, and therefore only humans can create evil. Otherwise, this group argued, God’s punishment of humans would be unjust because he himself created their evil deeds. This particular view was rejected by other Muslim theologians on the grounds that it limits the scope of God's creation, when the Qur’an clearly states that God is the sole creator of everything that exists in the world.</span><br /><img src="http://farm4.static.flickr.com/3013/2770327041_2c22095558.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Mosque of Muhammad Ali, Cairo<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >The Mosque of Muhammad Ali stands within the walls of the Citadel in Cairo. Built between 1830 and 1857, it is the largest and grandest of the four mosques contained in the Citadel. Cairo has been an Islamic cultural center for more than 1000 years.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Richard Evans<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Another controversial issue was the question of whether the Qur’an was eternal or created in time. Theologians who were devoted to the concept of God's oneness maintained that the Qur’an must have been created in time, or else there would be something as eternal as God. This view was rejected by others because the Qur’an, the ultimate authority in Islam, states in many places and in unambiguous terms that it is the eternal word of God.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Many other theological controversies occupied Muslim thinkers for the first few centuries of Islam, but by the 10th century the views of Islamic theologian al-Ashari and his followers, known as<i> </i>Asharites, prevailed and were adopted by most Muslims. The way this school resolved the question of free will was to argue that no human act could occur if God does not will it, and that God's knowledge encompasses all that was, is, or will be. This view also maintains that it is God's will to create the power in humans to make free choices. God is therefore just to hold humans accountable for their actions. The views of al-Ashari and his school gradually became dominant in Sunni, or orthodox, Islam, and they still prevail among most Muslims. The tendency of the Sunnis, however, has been to tolerate and accommodate minor differences of opinion and to emphasize the consensus of the community in matters of doctrine.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >As is the case with any religious group, ordinary Muslims have not always been concerned with detailed theological controversies. For ordinary Muslims the central belief of Islam is in the oneness of God and in his prophets and messengers, culminating in Muhammad. Thus Muslims believe in the scriptures that God sent through these messengers, particularly the truth and content of the Qur’an. Whatever their specific religious practices, most Muslims believe in angels, the Day of Judgment, heaven, paradise, and hell.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >VI<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >THE PROPHET MUHAMMAD<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Belief in the message of Muhammad comes second only to belief in the one God. Muhammad was born around the year 570 and was orphaned at an early age. He was eventually raised by his uncle, who had religious prominence within the main Quraysh tribe of Mecca but was of modest financial means. At age 25, Muhammad married Khadija, a well-to-do, 40-year-old woman. At age 40, during a retreat in the hills outside Mecca, Muhammad had his first experience of Islam. The angel Gabriel appeared to a fearful Muhammad and informed him that he was God's chosen messenger. Gabriel also communicated to Muhammad the first revelation from God. Terrified and shaken, Muhammad went to his home. His wife became the first person to accept his message and convert to Islam. After receiving a series of additional revelations, Muhammad started preaching the new religion, initially to a small circle of relatives and friends, and then to the general public. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >The Meccans first ignored Muhammad, then ridiculed him. As more people accepted Muhammad's call, the Meccans became more aggressive. After failing to sway Muhammad away from the new religion they started to persecute his less prominent followers. When this approach did not work, the opposing Meccans decided to persecute Muhammad himself. By this time, two main tribes from the city of Yathrib, about 300 km (200 mi) north of Mecca, had invited Muhammad to live there. The clan leaders invited Muhammad to Yathrib as an impartial religious authority to arbitrate disputes. In return, the leaders pledged to accept Muhammad as a prophet and thus support the new religion of Islam.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >Hegira <o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >In the year 622, Muhammad immigrated to Yathrib, and the name of the city was changed to Medina, meaning city of the Prophet. This date was designated by later Muslims as the beginning of the Muslim calendar, year one of hegira (Arabic <i>hijra</i>, “immigration”). Only two years after Muhammad's arrival in Medina, the core community of Muslims started to expand. At Medina, in addition to preaching the religious and moral message of Islam, Muhammad organized an Islamic society and served as head of state, diplomat, military leader, and chief legislator for the growing Muslim community. Hostilities soon broke out between the Muslims in Medina and the powerful Meccans. In 630, after a series of military confrontations and diplomatic maneuvers, the Muslims in Medina extended their authority over Mecca, the most important city of Arabia at the time. Before Muhammad died in 632, the whole Arabian Peninsula was united for the first time in its history, under the banner of Islam.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >Muhammad’s Humanity<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Early accounts of Muhammad contain some stories that describe supernatural events such as his night journey from Mecca to Jerusalem and his subsequent ascent to heaven on the back of a supernatural winged horse. Despite such stories, the primary focus of the biographies, as well as Islamic doctrine in general, is on the humanity of Muhammad. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Like all prophets before him, Muhammad was a mortal man, commissioned by God to deliver a message to his people and to humanity. Like other prophets, Muhammad was distinguished from ordinary people by certain powers and faculties. For example, Muslims believe that the distinction of being sinless was granted to Muhammad by God to support his career as a prophet. Thus Muhammad is portrayed in the Qur’an as a person who makes mistakes but who does not sin against God. However, God corrected Muhammad’s mistakes or errors in judgment, so that his life serves as an example for future Muslims to follow. This emphasis on Muhammad's humanity serves as a reminder that other humans can reasonably aspire to lead a good life as he did.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >VII<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >THE QUR’AN</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3180/2771174142_99399031e6.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Muslim Boys Studying the Qur’an<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >The Qur’an is at the center of Muslim life. Muslims recite verses from it in their daily prayers and at important public and private events. Many Muslims also memorize this holy scripture so that they can keep it in their hearts. Before touching the holy book, Muslims follow rituals for purification, including washing and preparing the mind, body, and spirit. Care must be taken that the Qur’an does not come into contact with any unclean substance, and it is never to be laid upon the ground.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Piers Benatar/Panos Pictures<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >As with other prophets and messengers, God supported Muhammad by allowing him to work miracles and thus prove that he was a genuine prophet. The singular miracle of Muhammad and the ultimate proof of the truthfulness of Islam is the Qur’an. In accordance with the words of the scripture itself, Muslims believe that the Qur’an is the timeless word of God, “the like of which no human can produce.” This trait of the scripture, called inimitability<i> </i>(<i>i'jaz</i>), is based on belief in the divine authorship of the Qur’an. Unlike earlier religions, the miracle of Islam is a literary miracle, and Muhammad's other supernatural acts are subordinate to it. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >This belief in the unique nature of the Qur’an has led Muslims to devote great intellectual energies to the study of its contents and form. In addition to interpreting the scripture and deriving doctrines and laws from it, many disciplines within Qur’anic studies seek to understand its linguistic and literary qualities as an expression of its divine origins.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >The Format of the Holy Book</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3214/2770327367_ed1d3e884e.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Illustrated Text of the Qur’an<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >This beautifully decorated page comes from a Qur’an of the late 8th century or early 9th century. Muslims believe that the Qur’an is an infallible transcription of God’s message to Muhammad. As the messenger of God and seal of the prophets, Muhammad was charged with the responsibility of relaying this message to all believers. Divided into 114 <i>suras,</i> or chapters, the Qur’an is meant to be recited or chanted as part of Islamic worship.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Bojan Brecelj/Corbis<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >The Qur’an is made up of 114 chapters, called <i>suras,</i> which appear, from the second chapter onward, roughly in order of length, beginning with the longest and ending with the shortest chapters. The first chapter, al-Fatiha (“the Opening”), is a short chapter that is recited during each of the five daily prayers and in many other ritual prayers. All but one chapter begin with the formula 'in the name of God, the Merciful Lord of Mercy' (<i>bism Allah al-Rahman al-Rahim</i>). Each chapter is divided into verses called <i>ayat</i> (singular <i>aya</i>, meaning “sign” or “proof”). With few exceptions the verses are randomly organized without a coherent narrative thread. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >A typical chapter of the Qur’an may address any combination of the following themes: God and creation, prophets and messengers from Adam to Jesus, Muhammad as a preacher and as a ruler, Islam as a faith and as a code of life, disbelief, human responsibility and judgment, and society and law. Later Muslim scholars have argued that the text’s timelessness and universality explain the lack of narrative coherence and the randomness of the topics. In other words, the multiple meanings of the Qur’an transcend linear narrative as they transcend any particular historical moment.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >The Qur’an and the Bible<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Islam recognizes the divine origins of the earlier Hebrew and Christian Scriptures and represents itself as both a restoration and a continuation of their traditions. Because of this, the Qur’an draws on biblical stories and repeats many biblical themes. In particular, the stories of several biblical prophets appear in the Qur’an, some in a condensed form; other stories, such as those of Abraham, Moses, and Jesus, are given in elaborate detail and even with subtle revisions of the biblical accounts. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >One of the important differences between the Qur’anic and biblical stories of Abraham's sacrifice of his son, for example, is that the Qur’an suggests this son is Ishmael, from whom Arabs are descended, and not Isaac, from whom the tribes of Israel are descended. A more substantial difference relates to the Islamic story of Jesus, who according to the Qur’an is a mortal, human prophet. The Islamic faith categorically rejects the idea that God was ever born, as opposed to Christian belief that Jesus was born the son of God. Islam also rejects the idea that God shared his divinity with any other being.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Another important idea elaborated in the Qur’an and later Islamic doctrine, in conscious distinction from the biblical accounts, is that although prophets are capable of human errors, God protects them from committing sins and also protects them from excruciating suffering or humiliating experiences. God would not abandon his prophets in times of distress. Therefore, the Qur’an maintains that God interfered to save Jesus from torture and death by lifting him to heaven and replacing him on the cross with someone who looked like him.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >C<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >The Preservation of the Qur’an<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >From its inception during the lifetime of Muhammad, Islamic doctrine gave priority to the preservation of the scripture. As a result, one of the earliest expressions of religiosity focused on studying, reciting, and writing down the scripture. When Muhammad died, the preservation of the scripture was also a conscious concern among his companions and successors. Early historical sources refer to immediate efforts undertaken by successors of Muhammad to collect the chapters of the Qur’an, which were written down by his various companions. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Within about two decades after the death of the Prophet, various existing copies of parts of the Qur’an were collected and collated by a committee of close companions of Muhammad who were known for their knowledge of the Qur’an. This committee was commissioned by the third successor of Muhammad, Uthman ibn Affan, and the committee’s systematic effort is the basis of the codified official text currently used by Muslims. The thematic randomness of the verses and chapters of the Qur’an in its current format clearly illustrates that the early companions who produced this official version of the Qur’an were primarily concerned with establishing the text and made no attempt to edit its contents in order to produce a coherent narrative. Because of this, scholars agree that the Uthmanic text genuinely reflects, both in its content and form, the message that Muhammad preached.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >D<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >Interpretations of the Qur’an<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Despite the consensus among Muslims on the authenticity of the current format of the Qur’an, they agree that many words in the Qur’an can be interpreted in equally valid ways. The Arabic language, like other Semitic languages, has consonants and vowels, and the meanings of words are derived from both. For several centuries, the written texts of the Qur’an showed only the consonants, without indicating the vowel marks. As a result, there are different ways in which many words can be vocalized, with different meanings; this allows for various legitimate interpretations of the Qur’an. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >One of the disciplines for the study of the Qur’an is exclusively dedicated to the study and documentation of acceptable and unacceptable variant readings. According to Muslim scholars, there are some 40 possible readings of the Qur’an, of which 7 to 14 are legitimate. The legitimacy of different possible interpretations of the scripture is supported by a statement in the Qur’an that describes verses as either unambiguously clear, or as ambiguous because they carry a meaning known only to God. Therefore, with the exception of a small number of unquestionably clear injunctions, the meaning of the Qur’anic verses is not always final. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >The Qur’an is the primary source of authority, law and theology, and identity in Islam. However, in many cases it is either completely silent on important Islamic beliefs and practices or it gives only general guidelines without elaboration. This is true of some of the most basic religious obligations such as prayer, which the Qur’an prescribes without details. Details elaborating on the teachings and laws of the Qur’an are derived from the <i>sunna</i>, the example set by Muhammad’s life, and in particular from <i>hadith</i>, the body of sayings and practices attributed to him.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >VIII<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >HADITH</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3159/2770327519_00b543053b.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Shrine of Abbas<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >The shrine of Abbas in Karbalā, Iraq, is a pilgrimage site for Shia Muslims. Abbas was the son of Ali, the son-in-law of the prophet Muhammad. Abbas was martyred and buried in Karbalā. His tomb is in a domed chamber that shimmers with silver mirrors.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Eddie Adams/Leo de Wys, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >As the second source of authority in Islam, hadith complements the Qur’an and provides the most extensive source for Islamic law. The ultimate understanding of the Qur’an depends upon the context of Muhammad’s life and the ways in which he demonstrated and applied its message. There is evidence that Muhammad's sayings and practices were invoked by his companions to answer questions about Islam. Unlike the Qur’an, however, in the early periods hadith was circulated orally, and no attempts were made to establish or codify it into law until the beginnings of the second century of Islam.<o:p></o:p></span></p> <span style=";font-family:";font-size:9;color:black;" >Due to the late beginnings of the efforts to collect and compile reports about Muhammad's traditions, Muslim scholars recognize that the authenticity of these reports cannot be taken for granted. Many spurious reports were often deliberately put into circulation to support claims of various political and sectarian groups. Other additions resulted from the natural tendency to confuse common practices that predated Islam with new Islamic laws and norms. The fading of memory, the dispersion of the companions of the prophet over vast territories, and the passing away of the last of these companions also contributed to the problem of authenticating Muhammad’s traditions.</span><br /><img src="http://farm4.static.flickr.com/3236/2771174564_230a96c56b.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Preaching in the Mosque<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Book illustration was an essential Islamic art, which flourished from the 7th to the 18th century. This manuscript page shows Abu Zayd preaching in the mosque of Samarqand. Islamic art focused on book arts rather than easel painting because it was believed that art should serve a function, that of education.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Bridgeman/Art Resource, NY<o:p></o:p></span></p> <span style=";font-family:";font-size:9;color:black;" >To establish the authority of hadith on firmer ground, Muslim scholars developed several disciplines dedicated to examining and verifying the relative authenticity of various reports attributed to the Prophet. The contents of sayings, as well as the reliability of those who transmitted them, were carefully scrutinized, and the hadiths were classified into groups granted varying degrees of authenticity, ranging from the sound and reliable to the fabricated and rejected. This systematic effort culminated in the 9th century, some 250 years after the death of Muhammad, in the compilation of several collections of sound (<i>sahih</i>) hadith. Of six such highly reliable compilations, two in particular are considered by Muslims to be the most important sources of Islamic authority after the Qur’an. These are <i>Sahih Muslim</i> and <i>Sahih Bukhari</i> (the sound books of Muslim and Bukhari).</span><br /><img src="http://farm4.static.flickr.com/3143/2770327879_e4a007be83.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Jumeirah Mosque<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >The Jumeirah Mosque is located in the city of Dubai, in the United Arab Emirates. Dubai is the chief port and commercial center of the Emirates. <o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >SIME/Schmid Reinhard/4Corners Images<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Historically, the compilation of hadith went hand in hand with the elaboration of Islamic law and the parallel development of Islamic legal theory. Initially, neither the law nor its procedures were systematically elaborated, although there can be little doubt that both the Qur’an and hadith were regularly invoked and used to derive laws that governed the lives of Muslims. By the beginning of the 9th century, the use of these two sources was systematized and a complex legal theory was introduced. In its developed form, this theory maintains that there are four sources from which Islamic law is derived. These are, in order of priority, the Qur’an, the hadith, the consensus of the community (<i>ijma</i>), and legal analogy (<i>qiyas</i>). Functional only when there is no explicit ruling in the Qur’an or hadith, consensus confers legitimacy retrospectively on historical practices of the Muslim community. In legal analogy, the causes for existing Islamic rulings are applied by analogy to similar cases for which there are no explicit statements in either the Qur’an or hadith. Using these methods, a vast and diverse body of Islamic law was laid out covering various aspects of personal and public life. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >In addition to the laws pertaining to the five pillars, Islamic law covers areas such as dietary laws, purity laws, marriage and inheritance laws, commercial transaction laws, laws pertaining to relationships with non-Muslims, and criminal law. Jews and Christians living under Muslim rule are subject to the public laws of Islam, but they have traditionally been permitted to run their internal affairs on the basis of their own religious laws.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >IX<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >THE SPREAD OF ISLAM</span></p></td></tr></tbody></table><br /><img src="http://farm3.static.flickr.com/2024/2770328095_3d2235254b.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Spread of Islam<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >In the 7th and 8th centuries the religion of Islam spread through conversion and military conquest throughout the Middle East and North Africa. By 733, just 100 years after the death of Muhammad, the founder of Islam, an ordered Islamic state stretched from India in the east to Spain in the west.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Since its inception Islam has been perceived by Muslims to be a universal code. During Muhammad's lifetime, two attempts were made to expand northward into the Byzantine domain and its capital in Constantinople, and within ten years after Muhammad’s death, Muslims had defeated the Sassanids of Persia and the Byzantines, and had conquered most of Persia, Iraq, Syria, and Egypt. The conquests continued, and the Sassanian Empire was soon after destroyed and the influence of Byzantium was largely diminished (<i>see </i>Byzantine Empire). For the next several centuries intellectuals and cultural figures flourished in the vast, multinational Islamic world, and Islam became the most influential civilization in the world.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >A<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >The Rightly Guided Caliphs</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3231/2771175276_9d480e11a7.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Mosque at Mazār-e Sharīf<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Muslims from all over the country make pilgrimages to the 15th-century mosque at Mazār-e Sharīf in northern Afghanistan. The religious significance of the site derives from the belief that the tomb of Ali, fourth caliph of Islam and son-in-law of Muhammad, the founder of Islam, lies within the mosque. More than 99 percent of the population of Afghanistan practices Islam.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >George Hunter/ALLSTOCK, INC.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >The first four successors of Muhammad, known as rightly guided caliphs, ruled for some 30 years (<i>see </i>Caliphate). Their rule, together with that of Muhammad, is considered by most Muslims to constitute the ideal Islamic age. The second caliph, Umar, ruled from <span style="text-transform: uppercase;">ad</span> 634 to 644; he is credited with being the first caliph to found new Islamic cities, Al Başra (<span style="text-transform: uppercase;">ad</span> 635) and Kūfah (<span style="text-transform: uppercase;">ad</span> 638). The administration of the eastern and western Islamic provinces was coordinated from these two sites. After the third caliph, Uthman, was murdered by a group of Muslim mutineers, the fourth caliph, Ali, succeeded to power and moved his capital to Kūfah in Iraq. From this capital he fought the different opposition factions. Among the leaders of these factions, Mu’awiyah, governor of the rich province of Syria and a relative of Uthman, outlasted Ali. After Ali’s death in 661, Mu’awiyah founded the Umayyad dynasty, which ruled a united Islamic empire for almost a century. Under the Umayyads the Islamic capital was shifted to Damascus. <i>See </i>Spread of Islam.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >B<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >Shia Islam<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >The followers of Ali were known as the <i>Shia</i> (partisans) of Ali. Although they began as a political group, the Shia, or Shia Muslims, became a sect with specific theological and doctrinal positions. A key event in the history of the Shia and for all Muslims was the tragic death at Karbala of Husayn, the son of Ali, and Muhammad's daughter Fatima. Husayn had refused to recognize the legitimacy of the rule of the Umayyad Yazid, the son of Mu’awiyah, and was on his way to rally support for his cause in Kūfah. His plans were exposed before he arrived at Kūfah, however, and a large Umayyad army met him and 70 members of his family at the outskirts of the city. The Umayyads offered Husayn the choice between a humiliating submission to their rule or a battle and definite death. Husayn chose to fight, and he and all the members of his family with him were massacred. The incident was of little significance from a military point of view, but it was a defining moment in the history of Shia Islam. Although not all Muslims are Shia Muslims, all Muslims view Husayn as a martyr for living up to his principles even to death.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >The Twelver Shia, or <i>Ithna-‘Ashariyya</i>, is the largest of the Shia Muslim sects. They believe that legitimate Islamic leadership is vested in a line of descent starting with Muhammad's cousin and son-in-law, Ali, through Ali's two sons, Hasan and Husayn, and then through Husayn's descendants. These were the first 12 imams, or leaders of the Shia Muslim community. The Shia Muslims believe that Muhammad designated all 12 successors by name and that they inherited a special knowledge of the true meaning of the scripture that was passed from father to son, beginning with the Prophet himself. This family, along with its loyal followers and representatives, has political authority over the Shia Muslims.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >C<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >Sunni Islam<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Sunni Islam was defined during the early Abbasid period (beginning in <span style="text-transform: uppercase;">ad</span> 750), and it included the followers of four legal schools (the Malikis, Hanafis, Shafi’is, and Hanbalis). In contrast to the Shias, the Sunnis believed that leadership was in the hands of the Muslim community at large. The consensus of historical communities, not the decisions of political authorities, led to the establishment of the four legal schools. In theory a Muslim could choose whichever school of Islamic thought he or she wished to follow and could change this choice at will. The respect and popularity that the religious scholars enjoyed made them the effective brokers of social power and pitched them against the political authorities. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >After the first four caliphs, the religious and political authorities in Islam were never again united under one institution. Their usual coexistence was underscored by a mutual recognition of their separate spheres of influence and their respective duties and responsibilities. Often, however, the two powers collided, and invariably any social opposition to the elite political order had religious undertones.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >D<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >Sufism</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3020/2771175506_b29102f749.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Whirling Dervishes<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >In the Middle Ages the great Sufi orders, which had several million adherents, were established; about 100 orders still exist, many of them in Turkey and Iran. One of the most influential founders of orders was the Persian poet Jalal al-Din Muhammad Rumi, who, in addition to composing poetry and other works, instituted devotional dances, particularly those of the whirling dervishes.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >BBC Worldwide Americas, Inc.<o:p></o:p></span></p> <span style=";font-family:";font-size:9;color:black;" >An ascetic tradition called Sufism, which emphasized personal piety and mysticism and contributed to Islamic cultural diversity, further enriched the Muslim heritage. In contrast to the legal-minded approach to Islam, Sufis emphasized spirituality as a way of knowing God. During the 9th century Sufism developed into a mystical doctrine, with direct communion or even ecstatic union with God as its ideal. One of the vehicles for this experience is the ecstatic dance of the Sufi whirling dervishes. Eventually Sufism later developed into a complex popular movement and was institutionalized in the form of collective, hierarchical Sufi orders.</span><br /><img src="http://farm4.static.flickr.com/3133/2770328665_2cdfba3bab.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Rumi<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Sufism, or Islamic mysticism, influenced the lyrical poetry of 13th-century Persian writer Jalal al-Din Rumi. He explored spiritual concepts such as the meaning of life and the ultimate need for the human soul to unite with God. Rumi often used the second person “you” in his poetry, but he frequently disguised the identity of the “you.” For example, the subject of Rumi’s poem 1245 (recited by an actor) may be a human lover, God, another part of himself, or a combination of all three.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >(p) 1994 Microsoft Corporation. All Rights Reserved./© Microsoft Corporation. All Rights Reserved.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >The Sufi emphasis on intuitive knowledge and the love of God increased the appeal of Islam to the masses and largely made possible its extension beyond the Middle East into Africa and East Asia. Sufi brotherhoods multiplied rapidly from the Atlantic coast to Indonesia; some spanned the entire Islamic world, others were regional or local. The tremendous success of these fraternities was due primarily to the abilities and humanitarianism of their founders and leaders, who not only ministered to the spiritual needs of their followers but also helped the poor of all faiths and frequently served as intermediaries between the people and the government.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"><tbody><tr style=""><td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >E<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >The Abbasid Dynasty</span></p></td></tr></tbody></table><br /><img src="http://farm4.static.flickr.com/3053/2771175944_390bfd7aa5.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Córdoba, Spain<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >The Moorish history of the city of Córdoba in Spain dates from the 8th century, when the city became a Muslim caliphate. The Moorish influence can still be seen in much of the architecture, including the city’s famous cathedral, originally an impressive mosque.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Poseidon Pictures London<o:p></o:p></span></p> <span style=";font-family:";font-size:9;color:black;" >Islamic culture started to evolve under the Umayyads, but it grew to maturity in the first century of the Abbasid dynasty. The Abbasids came to power in <span style="text-transform: uppercase;">ad</span> 750 when armies originating from Khorāsān, in eastern Iran, finally defeated the Umayyad armies. The Islamic capital shifted to Iraq under the Abbasids. After trying several other cities, the Abbasid rulers chose a site on the Tigris River on which the City of Peace, Baghdād, was built in 762. Baghdād remained the political and cultural capital of the Islamic world from that time until the Mongol invasion in 1258, and for a good part of this time it was the center of one of the great flowerings of human knowledge. The Abbasids were Arabs descended from the Prophet's uncle, but the movement they led involved Arabs and non-Arabs, including many Persians, who had converted to Islam and who demanded the equality to which they were entitled in Islam.</span><br /><img src="http://farm4.static.flickr.com/3172/2771176152_98900d008f.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Courtyard, Madrasa, Eşfahān<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >A madrasa is a place for learning and prayer. This view into the courtyard of the Madrasa Chahār Bāgh in Eşfahān, Iran, shows the domed mosque, central pool, and rooms around the courtyard for study and accommodation. The madrasa was built from 1706 to 1714.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Art Resource, NY<o:p></o:p></span></p> <span style=";font-family:";font-size:9;color:black;" >The Abbasids distributed power more evenly among the different ethnicities and regions than the Umayyads had, and they demonstrated the universal inclusiveness of Islamic civilization. They achieved this by incorporating the fruits of other civilizations into Islamic political and intellectual culture and by marking these external influences with a distinctly Islamic imprint.</span><br /><img src="http://farm4.static.flickr.com/3077/2770329535_b322e83a56.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Baghdād, Iraq<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Baghdād became the capital city of the newly created kingdom of Iraq in 1921, but the city’s history dates back many centuries more. Built in <span style="text-transform: uppercase;">ad</span> 762 on a fertile plain next to the Tigris River in central Iraq, Baghdād is the country's largest city and its center of transportation and manufacturing. In 1991, however, heavy bombing during the Persian Gulf War destroyed much of the city's industry and transportation network.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Barry Iverson/Woodfin Camp and Associates, Inc.<o:p></o:p></span></p> <span style=";font-family:";font-size:9;color:black;" >As time passed, the central control of the Abbasids was reduced and independent local leaders and groups took over in the remote provinces. Eventually the rival Shia Fatimid caliphate was established in Egypt, and the Baghdād caliphate came under the control of expanding provincial dynasties. The office of the caliph was nonetheless maintained as a symbol of the unity of Islam, and several later Abbasid caliphs tried to revive the power of the office.</span><br /><img src="http://farm4.static.flickr.com/3201/2771176684_5d103b5d0a.jpg?v=0" /><br /><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:8;" >Persian Manuscript<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >During the rule of the Abbasid caliphs, from 750 to 1258, Islamic culture flourished. This 13th-century Persian manuscript was created during this period. Islamic art used input from neighboring cultures including the Persians in the development of a cohesive Islamic style of art.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 11.25pt;"><span style=";font-family:";font-size:8;" >Bibliotheque Nationale, Paris/Laurie Platt Winfrey, Inc./Woodfin Camp and Associates, Inc.<o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >In 1258, however, a grandson of Mongol ruler Genghis Khan named Hulagu, encouraged by the kings of Europe, led his armies across the Zagros Mountains of Iran and destroyed Baghdād. According to some estimates, about 1 million Muslims were murdered in this massacre. In 1259 and 1260 Hulagu's forces marched into Syria, but they were finally defeated by the Mamluks of Egypt, who had taken over the Nile Valley. For the next two centuries, centers of Islamic power shifted to Egypt and Syria and to a number of local dynasties. Iraq became an impoverished, depopulated province where the people took up a transitory nomadic lifestyle. Iraq did not finally experience a major cultural and political revival until the 20th century.<o:p></o:p></span></p> <table class="MsoNormalTable" style="" border="0" cellpadding="0"> <tbody><tr style=""> <td style="padding: 0.75pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:18;" >X<o:p></o:p></span></p> </td> <td style="padding: 0.75pt; width: 3.75pt;" width="5"><br /></td> <td style="padding: 0.75pt 0.75pt 2.25pt;" valign="bottom"> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><span style=";font-family:";font-size:12;color:black;" >THE PRESENCE OF ISLAM IN THE 20TH CENTURY<o:p></o:p></span></p> </td> </tr> </tbody></table> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Many of the accepted Islamic religious and cultural traditions were established between the 7th and 10th centuries, during the classical period of Islamic history. However, Islamic culture continued to develop as Islam spread into new regions and mixed with diverse cultures. The 19th-century occupation of most Muslim lands by European colonial powers was a main turning point in Muslim history. The traditional Islamic systems of governance, social organization, and education were undermined by the colonial regimes. Nation-states with independent governments divided the Muslim community along new ethnic and political lines. <o:p></o:p></span></p> <p class="MsoNormal" style="line-height: 15pt;"><span style=";font-family:";font-size:9;color:black;" >Today about 1 billion Muslims are spread over 40 predominantly Muslim countries and 5 continents, and their numbers are growing at a rate unmatched by that of any other religion in the world. Despite the political and ethnic diversity of Muslim countries, a core set of beliefs continues to provide the basis for a shared identity and affinity among Muslims. Yet the radically different political, economic, and cultural conditions under which contemporary Muslims live make it difficult to identify what constitutes standard Islamic practice in the modern world. Many contemporary Muslims draw on the historical legacy of Islam as they confront the challenges of modern life. Islam is a significant, growing, and dynamic presence in the world. Its modern expressions are as diverse as the world in which Muslims live. <o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: 15pt;"><span style=";font-family:";font-size:12;" ><br />Contributed By:<br />Ahmad S. Dallal<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal;"><b><span style=";font-family:";font-size:9;" >Microsoft ® Encarta ® 2007.</span></b><span style=";font-family:";font-size:9;" > © 1993-2006 Microsoft Corporation. All rights reserved.<o:p></o:p></span></p> <p class="MsoNormal"><o:p> </o:p></p>ghozian karamihttp://www.blogger.com/profile/13214011599962806335noreply@blogger.com0