新东方英语背诵美文50篇 第十六篇 Evolution of sleep
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?
_小精灵 儿童网
新东方英语背诵美文50篇 | |
- 新东方英语背诵美文30篇 第一篇 Youth 青春
- 新东方英语背诵美文30篇 第二篇 Three Days to See(Excerpts) 假如给我三天光明
- 新东方英语背诵美文30篇 第三篇 Companionship of Books 以书为伴
- 新东方英语背诵美文30篇 第五篇 Ambition 抱负
- 新东方英语背诵美文30篇 第四篇 If I Rest, I Rust 如果我休息,我就会生锈
- 新东方英语背诵美文30篇 第六篇 What I have Lived for 我为何而生
- 新东方英语背诵美文30篇 第七篇 When Love Beckons You 爱的召唤
- 新东方英语背诵美文30篇 第八篇 The Road to Success 成功之道
- 新东方英语背诵美文30篇 第九篇 On Meeting the Celebrated 论见名人
- 新东方英语背诵美文30篇 第十篇 The 50-Percent Theory of Life 生活理论半对半