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  3. Large animals living in the desert have developed a number of adaptations for reducing the effects of extreme heat. One adaptati

Large animals living in the desert have developed a number of adaptations for reducing the effects of extreme heat. One adaptati

admin2011-03-01  54
问题    Large animals living in the desert have developed 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 animals also depart from other animals’ normal practice of maintaining a constant body temperature. Instead of trying to keep down the body temperature deep inside the body, which would involve the loss of water and energy, large desert animals 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 over-heated 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% of its body weight as water without harm to itself, whereas human beings die after losing only 12%-13% of their body weight. An equally important adaptation is the ability to recover this water loss at one drink. Desert animals can drink massive volumes of water in a short time, and camels have been known to drink over 100 liters in a few minutes. A person who severely loses water, on the other hand, cannot drink enough water for recovery at one session, because the human stomach is not sufficiently big and because a too rapid mixing of the body liquid with water 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 by searching quite a few distant places. Desert-adapted animals have the further ability to feed normally when extremely thirsty: it is a common experience in people that appetite is lost even under conditions of moderate thirst.
The author lists the following as adaptation of large desert animals except ______.
选项 A、changing body temperature
B、drinking water quickly
C、not losing appetite even when very thirsty
D、being active at night
答案D
解析 综合判断题。纵观全篇，可以知道一次性快速饮水、改变体温以及在体内缺水极度口渴的情况下仍能正常进食均是沙漠动物的适应性表现。只有最后一项是例外。
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