专业指导英语写作服务
专业批改、翻译英语作文
留言给我们 站内搜索
作文地带QQ群:81784028
作文地带-有翻译的英语作文网 数十人的翻译团队,提供有原创翻译的英语作文,作文地带是您英语学习的好帮手!英语作文网
当前位置: 英语作文>英语训练>

托福考试写作之历年托福考生优秀范文17

时间:2012-02-07来源:liuxuepaper栏目:作者:liuxuepaper 英语作文收藏:收藏本文
为了方便广大考生更好的复习,作文地带综合整理了托福考试写作之历年托福考生优秀范文17,以供各位考生考试复习参考,希望对考生复习有所帮助。

托福考试写作之历年托福考生优秀范文17

Evolution of sleep

Sleep is very ancient. In the electroencephalographic sense we share it with all the primates and almost all the other mammals and birds: it may extend back as far as the reptiles.

There is some evidence that the two types of sleep, dreaming and dreamless, depend on the life-style of the animal, and that predators 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 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 pray 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 genera 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 University of Florida and Ray Middies of London University have suggested this to be the case. It is conceivable that animals who are too stupid to be quite 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.

英语作文
在百度搜索更多与“托福考试写作之历年托福考生优秀范文17”相关英语作文
“托福考试写作之历年托福考生优秀范文17”一文包含以下关键字,请点击获取相关文章
------分隔线----------------------------
今日最新更新英语作文
------分隔线----------------------------
栏目推荐