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  3. Large animals that inhabit the desert have evolved a number of adaptations for reducing the effects of extreme heat. One adaptat

Large animals that inhabit the desert have evolved a number of adaptations for reducing the effects of extreme heat. One adaptat

admin2010-06-11  69
问题     Large animals that inhabit the desert have evolved a number of adaptations for reducing the effects of extreme heat. One adaptation is to be light in color, and to reflect rather than absorb the Sun’s rays. Desert mammals also depart from the normal mammalian practice of maintaining a constant body temperature. Instead of trying to keep down the body temperature deep inside the body, which would involve the expenditure of water and energy, desert mammals allow their temperatures to rise to what would normally be fever height, and temperatures as high as 46 degrees Celsius have been measured in Grant’s gazelles. The overheated body then cools down during the cold desert night, and indeed the temperature may fall unusually low by dawn, as low as 34 degrees Celsius in the camel. This is an advantage since the heat of the first few hours of daylight is absorbed in warming up the body, and an excessive buildup of heat does not begin until well into the day.
    Another strategy of large desert animals is to tolerate the loss of body water to a point that would be fatal for non-adapted animals. The camel can lose up to 30 percent of its body weight as water without harm to itself, whereas human beings die after losing only 12 to 13 percent of their body weight. An equally important adaptation is the ability to replenish (Sheik) this water loss at one drink. Desert animals can drink huge volumes in a short time, and camels have been known to imbibe (吸收) over 100 liters in a few minutes. A very dehydrated person, on the other hand, cannot drink enough water to rehydrate at one session, because the human stomach is not sufficiently big and because a too rapid dilution of the body fluids causes death from water intoxication. The tolerance of water loss is of obvious advantage in the desert, as animals do not have to remain near a water hole but can obtain food from grazing sparse pastures. Desert-adapted mammals have the further ability to feed normally when extremely dehydrated, it is a common experience in people that appetite is lost even under conditions of moderate thirst.
What does the author imply about desert-adapted mammals?
选项 A、They do not need to eat much food.
B、They can eat large quantities quickly.
C、They easily lose their appetites.
D、They can travel long distances looking for food.
答案D
解析 本题是有关适应沙漠生活的动物的问题，因此要在第一段和第二段两段中找到答案，其中A说的是他们没有吃足够的事物，在文章中没有提到，因此是错误的。而同样的道理，B讲的是沙漠的动物要吃大量的事物，在文中也没有提到，因此也是错误的。最后一段最后一句的前半句“Desert-adapted mammals have the further ability to feed normally when extremely dehydrated．”说的是适应沙漠生活的哺乳动物可以在脱水的情况下正常进食，与C说的失去胃口相悖，因此C是错误的。而D讲的是它们可以旅行很长的距离去寻找食物，在文章第二段倒数第二句讲过“animals do not have to remain near a water hole but can obtain food from grazing sparse pastures”动物不必呆在离水很近的地方，就象它们可以去广袤的草原去寻找事物，这耕暗示着食物离它们很远，因此D是符合题意的。
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