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When global warming finally came, it stuck with a vengeance (异乎寻常地). In some regions, temperatures rose several degrees in less than a century. Sea levels shot up nearly 400 feet, flooding coastal settlements and forcing people to migrate inland. Deserts spread throughout the world as vegetation shifted drastically in North America, Europe and Asia. After driving many of the animals around them to near extinction, people were forced to abandon their old way of life for a radically new survival strategy that resulted in widespread starvation and disease. The adaptation was farming: the global-warming crisis that gave rise to it happened more than 10,000 years ago.
As environmentalists convene in Rio de Janeiro this week to ponder the global climate of the future, earth scientists are in the midst of a revolution in understanding how climate has changed in the past—and how those changes have transformed human existence. Researchers have begun to piece together an illuminating picture of the powerful geological and astronomical forces that have combined to change the planet's environment from hot to cold, wet to dry and back again over a time period stretching back hundreds of millions of years.
Most important, scientists are beginning to realize that the climatic changes have had a major impact on the evolution of the human species. New research now suggests that climate shifts have played a key role in nearly every significant turning point in human evolution: from the dawn of primates (灵长目动物）some 65 million years ago to human ancestors rising up to walk on two legs, from the huge expansion of the human brain to the rise of agriculture. Indeed, the human history has not been merely touched by global climate change, some scientists argue, it has in some instances been driven by it.
The new research has profound implications for the environmental summit in Rio. Among other things, the findings demonstrate that dramatic climate change is nothing new for planet Earth. The benign (宜人的）global environment that has existed over the past 10,000 years—during which agriculture, writing, cities and most other features of civilization appeared—is a mere bright spot in a much larger pattern of widely varying climate over the ages. In fact, the pattern of climate change in the past reveals that Earth’s climate will almost certainly go through dramatic changes in the future—even without the influence of human activity.
1
Farming emerged as a survival strategy because man had been obliged ____.
A.
to give up his former way of life
B.
to leave the coastal areas
C.
to follow the ever-shifting vegetation
D.
to abandon his original settlement
本题答案：
A
B
C
D
参考答案：
A
系统解析：
文章第1段最后两句提到“人类在将其周围的许多种动物逼向濒临灭绝的境地之后，也被迫放弃他们已导致饥荒、疾病的旧有生活方式而选择全新的求生策略。这种策略就是农业”。A与文章的意思相符合。
2
Earth scientists have come to understand that climate ____.
A.
is going through a fundamental change
B.
has been getting warmer for 10,000 years
C.
will eventually change from hot to cold
D.
has gone through periodical changes
本题答案：
A
B
C
D
参考答案：
D
系统解析：
文章第2段第2句提到“研究者已经开始综合出一幅有关强大的地质和天文力量发生作用的说明性的图片，在过去的几百万年中，这两种力量结合在一起改变着地球的环境：从炎热到寒冷，从潮湿到干燥，如此反 复，循环不止”，D与文章的意思一致，因而正确。
3
Scientists believe that human evolution _____.
A.
has seldom been accompanied by climatic changes
B.
has exerted little influence on climatic changes
C.
has largely been affected by climatic changes
D.
has had a major impact on climatic changes
本题答案：
A
B
C
D
参考答案：
C
系统解析：
文章第3段第1、2句提到“最重要的是，科学家已经开始意识到气候的变化对人种的进化有着主要的影响。现在新的研究表明几乎在人类进化的每一个重大的转折时期天气变化都起着关键的作用”，所以人类进化受到气候变化的影响。因此，C正确。
4
Evidence of past climatic changes indicates that _____.
A.
human activities have accelerated changes of Earth’s environment
B.
Earth’s environment will remain mild despite human interference
C.
Earth’s climate is bound to change significantly in the future
D.
Earth’s climate is unlikely to undergo substantial changes in the future
本题答案：
A
B
C
D
参考答案：
C
系统解析：
文章最后一句提到“事实上，过去气候变化的模式表明地球的气候在将来肯定会经历重大的变化——即使是没有人类活动的影响”，因此，C与文章所表达的意思一致。
5
The message the author wishes to convey in the passage is that ____.
A.
human civilization remains glorious though it is affected by climatic changes
B.
mankind is virtually helpless in the face of the dramatic changes of climate
C.
man has to limit his activities to slow down the global warming process
D.
human civilization will continue to develop in spite of the changes of nature
本题答案：
A
B
C
D
参考答案：
B
系统解析：
全文围绕气候变化给人类带来的影响展开，而文章最后一句“地球气候几乎注定要在将来发生巨大的变化——甚至无须人类的干预”，说明人类无力改变自然，B为正确答案。
Most growing plants contain much more water than all other materials combined. C. R Barnes has suggested that it is as proper to term the plant a water structure as to call a house composed mainly of brick a brick building. Certain it is that all essential processes of plant growth and development occur in water. The mineral elements from the soil that are usable by the plant must be dissolved in soil solution before they can be taken into the root. They are carried to all parts of the growing plant and are built into essential plant materials while in a dissolved state. The carbon dioxide (CO2)from the air may enter the leaf as a gas but is dissolved in water in the leaf before it is combined with a part of the water to form simple sugars—the base material from which the plant body is mainly built. Actively growing plant parts are generally 75 to 90 percent water. Structural parts of plants, such as woody stems no longer actively growing, may have much less water than growing tissues.
The actual amount of water in the plant at any one time, however, is only a very small part of what passes through it during its development. The processes of photosynthesis, by which carbon dioxide and water are combined—in the presence of chlorophyll (叶绿素）and with energy derived from light—to form sugars, require that carbon dioxide from the air enter the plant. This occurs mainly in the leaves. The leaf surface is not solid but contains great numbers of minute openings, through which the carbon dioxide enters. The same structure that permits the one gas to enter the leaf, however, permits another gas—water vapor—to be lost from it. Since carbon dioxide is present in the air only in trace quantities (3 to 4parts in 10,000 parts of air) and water vapor is near saturation in the airspaces within the leaf (at 80°F, saturated air would contain about 186 parts of water vapor in 10,000 parts of air), the total amount of water vapor lost is many times the carbon dioxide intake. Actually, because of wind and other factors, the loss of water in proportion to carbon dioxide intake may be even greater than the relative concentrations of the two gases. Also, not all of the carbon dioxide that enters the leaf is synthesized into carbohydrates (碳水化合物).
6
A growing plant needs water for all the following except ______.
A.
forming sugars
B.
sustaining woody stems
C.
keeping green
D.
producing carbon dioxide
本题答案：
A
B
C
D
参考答案：
D
系统解析：
文章谈到的二氧化碳都是空气中的二氧化碳，不是植物“产生的二氧化碳”，故可知D项符合题意。A、B、C项都是植物的生长发育过程。尽管C项并没有在文中明言,但它也是植物内水分的作用之一。
7
The essential function of photosynthesis in terms of plant needs is ______
A.
to form sugars
B.
to derive energy from light
C.
to preserve water
D.
to combine carbon dioxide with water
本题答案：
A
B
C
D
参考答案：
A
系统解析：
根据第2段第2句可知，光合作用的主要作用是利用叶绿素，在光能的作用下.把二氧化味和水结合形成糖，由此可以归纳光合作用的最终目的是生产植物所需的糖，A符合题意。B项和D项都是光合作用发生的条件而非目的。
8
The second paragraph uses facts to develop the essential idea that ______
A.
a plant efficiently utilizes most of the water it absorbs
B.
carbon dioxide is the essential substance needed for plant development
C.
a plant needs more water than is found in its composition
D.
the stronger the wind, the more the water vapor loss
本题答案：
A
B
C
D
参考答案：
C
系统解析：
从第2段的首句“植物在任何特定时期的含水量都只是其生长过程中流经植物的水总置的一小部分”可以判断C符合题意。其他三个选项也都符合原文意思，但都不是第二段的分话题。
9
From the passage, we learn that _____.
A.
the mineral elements will not be absorbed by the plant unless they are dissolved in its root
B.
the woody stems contain more water than the leaves
C.
air existing around the leaf is found to be saturated
D.
only part of the carbon dioxide in the plants is synthesized
本题答案：
A
B
C
D
参考答案：
D
系统解析：
第2段最后一句话明确指出，并非所有进入植物叶片的二氧化碳都与水化合成为碳水化合物。故D正确。A与第1段第4句不符，即矿物质需溶解在土壤溶液(soil solution)中而非植物的根部(root)；C在倒数第3句可以找到反证，即水蒸气在叶片空隙中接近饱和状态，而非如C项所说“在叶片周围呈饱和状态”；B在文中未提及。
10
This passage is mainly about _____.
A.
the functions of carbon dioxide and water
B.
the role of water in a growing plant
C.
the process of simple sugar formation
D.
the synthesis of water with carbon dioxide
本题答案：
A
B
C
D
参考答案：
B
系统解析：
从本文主题来看,应当是水在植物生长过程中的重要性,B最符合题意。本文第二段花许多篇幅介绍了光合作用，其目的还是为了说明水的作用。A、C、D项偏重于讲光合作用，并非全文主题。
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