英语听力精选进阶版 7119（在线收听）

Background: 一项新研究对长期未解的一个科学问题提供了答案，这就是睡眠究竟有什么意义。科学家原来以为睡眠对于大脑修复，保持长期记忆力和扭转清醒时候压力过渡导致的损害都有意义。然而最新的研究之出睡眠主要的作用在于让各种动物更好地适应生存环境。

Pythons, bats and giant armadillos are among the longest sleepers at over 18 hours a day. Human babies need 16 hours, and most of us probably feel we need around eight hours sleep to function well.

Professor Jerry Seigel, from the University of California, Los Angeles, conducted a study of the sleep times of a broad range of animals, and found that they vary widely. Some, like migrating birds, can survive long periods without sleeping at all. He believes that shows sleep evolved to conserve energy:

“It's animals that are needlessly active that will not survive, but animals that are most efficient and use their waking time to do vital functions, and are otherwise asleep that will survive.”

Sleep helps make best use of limited resources. In humans, when we're awake, our brain accounts for 20 percent of the energy we use when just sitting around. Sleeping also makes us less likely to get injured and less likely to be detected by predators.

GLOSSARY 词汇表

pythons 蟒蛇类动物 

giant armadillos 巨犰狳 

function well 正常运作 

conducted a study 展开了一项研究 

migrating birds 迁徙的鸟类 

evolved 演变 

conserve energy 保存能量 

needlessly 不需要地 

survive 生存 

vital functions 主要的功能 

limited resources 有限的资源 

accounts for 占… 的比例 

sitting around 闲坐着 

get injured 受伤 

detected 发现/发觉 

predators 捕食其他动物的动物

Questions and Answers

True or false? Human babies need twice as much sleep as adults. 

True. Human babies need around 16 hours while adults need around eight.

True or false? We are more likely to be discovered by predators when awake. 

False. Sleeping makes us less likely to be detected by predators.

Why does Professor Seigel think sleep evolved? 

He thinks it evolved to help animals conserve energy and make use of limited resources.

Do migrating birds need to sleep for long periods? 

No, migrating birds can survive for long periods without sleep.