The atmosphere forms a gaseous, pro

The atmosphere forms a gaseous, protective envelope around Earth. It protects the planet from the cold of space, from harmful ultraviolet light, and from all but the largest meteors. After traveling over 93 million miles, solar energy strikes the atmosphere and Earth’s surface, warming the planet and creating what is known as the biosphere, the region of Earth capable of sustaining life. Solar radiation in combination with the planet’s rotation causes the atmosphere to circulate. Atmospheric circulation is one important reason that life on Earth can exist at higher latitudes because equatorial heat is transported pole ward, moderating the climate.
(2) The equatorial region is the warmest part of the earth because it receives the most direct and, therefore, strongest solar radiation. The plane in which the earth revolves around the sun is called the ecliptic. Earth’s axis is inclined 2313degrees with respect to the ecliptic. This inclined axis is responsible for our changing seasons because, as seen from the earth, the sun oscillates back and forth across the equator in an annual cycle. On or about June 21 each year, the sun reaches the Tropic of Cancer, 2313degrees north latitude. This is the northernmost point where the sun can be directly overhead. On or about December 21 of each year, the sun reaches the Tropic of Capricorn, 2313degrees south latitude. This is the southernmost point at which the sun can be directly overhead. The polar regions are the coldest parts of the earth because they receive the least direct and, therefore, the weakest solar radiation. Here solar radiation strikes at a very oblique angle and thus spreads the same amount of energy over a greater area than in the equatorial regions. A static envelope of air surrounding the earth would produce an extremely hot, uninhabitable equatorial region, while the polar regions would remain inhospitably cold.
(3) The transport of water vapor in the atmosphere is an important mechanism by which heat energy is redistributed pole ward. When water evaporates into the air and becomes water vapor, it
absorbs energy. At the equator, air saturated with water vapor rises high into the atmosphere where winds aloft carry it pole ward. As this moist air approaches the polar regions, it cools and sinks back to earth. At some point, the water vapor condenses out of the air as rain or snow, releasing energy in the process. The now-dry polar air flows back toward the equator to repeat the convection cycle. In this way, heat energy absorbed at the equator is deposited at the poles and the temperature gradient between these regions is reduced.
(4) The circulation of the atmosphere and the weather it generates is but one example of the many complex, interdependent events of nature. The web of life depends on the proper functioning of these natural mechanisms for its continued existence. Global warming, the
hole in the atmosphere’s ozone layer, and increasing air and water pollution pose serious, long-term threats to the biosphere. Given the high degree of nature’s interconnectedness, it is quite possible that the most serious threats have yet to be recognized.
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1.Which of the following best expresses the main idea of the passage?
A. The circulation of atmosphere, threatened by global warming and pollution, protects the biosphere and makes life on Earth possible.
B. If the protective atmosphere around the earth is too damaged by human activity, all life on Earth will cease.
C. Life on Earth is the result of complex interdependent events of nature, and some of these events are a result of human intervention.
D. The circulation of atmosphere is the single most important factor in keeping the biosphere alive, and it is constantly threatened by harmful human activity.
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2.Which of the following best represents the organization of the passage?
A.I. Definition and description of the circulation of the atmosphere
II. How the atmosphere affects heat and water in the biosphere
III. How the circulation of the atmosphere works
IV. What will happen if human activity destroys the atmosphere and other life-sustaining mechanisms
B.I. Origin of the atmosphere and ways it protects the biosphere
II.How the circulation of the atmosphere affects the equator and the poles
III.How the circulation of the atmosphere interrelates with other events in nature to protect life on Earth
IV.Threats to life in the biosphere
C.I.Definition and description of the circulation of the atmosphere
II.Protective functions of the circulation of the atmosphere
III.Relationship of the circulation of the atmosphere to other life-sustaining mechanisms
IV.Threats to nature’s interconnectedness in the biosphere
D.I.The journey of the atmosphere 93 million miles through space.
II.How the atmosphere circulates and protects the biosphere
III.How the atmosphere interrelates with weather in the biosphere
IV.How damage to the biosphere threatens life on Earth
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3.Which of the following is the best definition of the underlined word biosphereas it is used in the passage?
A.the protective envelope formed by the atmosphere around the living earth
B.that part of the earth and its atmosphere in which life can exist
C.the living things on Earth whose existence is made possible by circulation of the atmosphere
D.the circulation of the atmosphere’s contribution to life on Earth
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4.Which of the following sentences from the passage best supports the author’s point that circulation of the atmosphere is vital to life on Earth?
A.The equatorial region is the warmest part of the earth because it receives the most direct and, therefore, strongest solar radiation.
B.The circulation of the atmosphere and the weather it generates is but one example of the many complex, interdependent eventsof nature.
C.[The atmosphere] protects Earth from the cold of space, from harmful ultraviolet light, and from all but the largest meteors.
D.A static envelope of air surrounding the earth would produce an extremely hot, uninhabitable equatorial region, while the polar regions would remain inhospitably cold.
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5.Based on the passage, which of the following is directly responsible for all temperature changes on Earth?
A. variations in the strength of solar radiation B. variations in the amount of ultraviolet light
C. variation of biologic processes in the biosphere D. variation in global warming
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6.The first paragraph of the passage deals mainly with which of the following effects of the atmosphere on the earth?
A. its sheltering effect
B. its reviving effect
C. its invigorating effect
D. its cleansing effect