2. 自考
  3. Evolution of Sleep Sleep is very ancient. In the electroencephalographic (脑电图仪的) sense we share it with all the primates(灵长动

Evolution of Sleep Sleep is very ancient. In the electroencephalographic (脑电图仪的) sense we share it with all the primates(灵长动

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问题                            Evolution of Sleep
    Sleep is very ancient. In the electroencephalographic (脑电图仪的) sense we share it with all the primates(灵长动物的) and almost all the other mammals and birds: it may extend back as far as the reptiles (爬行动物).
    There is some evidence that the two types of sleep, dreaming and dreamless, depend on the life-style of the animal, and that predators(食肉动物) are statistically much more likely to dream than prey, which are in turn much more likely to experience dreamless sleep. In dream sleep, the animal is powerfully immobilized (使固定不动) and remarkably unresponsive to external stimuli.
    Dreamless sleep is much shallower, and we have all witnessed cats or dogs cocking their ears to a sound when apparently fast asleep. The fact that deep dream sleep is rare among prey today seems clearly to be a product of natural selection, and it makes sense that today, when sleep is highly evolved, the stupid animals are less frequently immobilized by deep sleep than the smart ones.
    But why should they sleep deeply at all? Why should a state of such deep immobilization ever have evolved? Perhaps one useful hint about the original function of sleep is to be found in the fact that dolphins and whales and aquatic mammals in general seem to sleep very little. There is, by and large, no place to hide in the ocean. Could it be that, rather than increasing an animal’s vulnerability, the function of sleep is to decrease it? Wilse Webb of the University of Florida and Ray Meddis of London University have suggested this to be the case. It is conceivable that animals who are too stupid to be quiet on their own initiative are, during periods of high risk, immobilized by the implacable arm of sleep. The point seems particularly clear for the young of predatory animals. This is an interesting notion and probably at least partly true.
The passage is mainly concerned with the______.
选项 A、types and function of sleep
B、psychological role of dreams
C、history of reptilian sleep patterns
D、influence of evolution on young animals
答案A
解析 本文第一段指出睡眠是非常古老的现象，第二段一开始就提出睡眠的种类，第三段则提出它的原始功能。三个段落都从不同角度讨论睡眠，因而不包含sleep这个词的选项B和D可以排除。选项C虽然有sleep，但本文占较大篇幅的二、三两段均未涉及爬行动物睡眠形式的历史，因此可以排除。
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