Birds that are literally half-asleep─with one brain hemisphere alert and the other sleeping─control which side of the brain remains awake, according to a new study of sleeping ducks.
Earlier studies have documented half-brain sleep in a wide range of birds. The brain hemispheres take turns sinking into the sleep stage characterized by slow brain waves. The eye controlled by the sleeping hemisphere keeps shut, while the wakeful hemisphere s eye stays open and alert. Birds also can sleep with both hemispheres resting at once.
Decades of studies of bird flocks led researchers to predict extra alertness in the more vulnerable, end-of-the-row sleepers. Sure enough, the end birds tended to watch carefully on the side away from their companions. Ducks in the inner spots showed no preference for gaze direction.
Also, birds dozing at the end of the line resorted to single-hemisphere sleep, rather than total relaxation, more often than inner ducks did. Rotating 16 birds through the positions in a four-duck row, the researchers found outer birds half-asleep during some 32 percent of dozing time versus about 12 percent for birds in internal spots.
We believe this is the first evidence for an animal behaviorally controlling sleep and wakefulness simultaneously in different regions of the brain, the researchers say.
The results provide the best evidence for a long-standing supposition that single-hemisphere sleep evolved as creatures scanned for enemies. The preference for opening an eye on the lookout side could be widespread, he predicts. He s seen it in a pair of birds dozing side-by-side in the zoo and in a single pet bird sleeping by a mirror. The mirror-side eye closed as if the reflection were a companion and the other eye stayed open.
Useful as half-sleeping might be, it s only been found in birds and such water mammals(哺乳动物)as dolphins, whales, and seals. Perhaps keeping one side of the brain awake allows a sleeping animal to surface occasionally to avoid drowning.
Studies of birds may offer unique insights into sleep. Jerome M. Siegel of the UCLA says he wonders if birds half-brain sleep is just the tip of the iceberg(冰山). He speculates that more examples may turn up when we take a closer look at other species.
11.A new study on birds sleep has revealed that .
A) half-brain sleep is found in a wide variety of birds
B) half-brain sleep is characterized by slow brain waves
C) birds can control their half-brain sleep consciously
D) birds seldom sleep with the whole of their brain at rest
12.According to the passage, birds often half sleep because .
A) they have to watch out for possible attacks
B) their brain hemispheres take turns to rest
C) the two halves of their brain are differently structured
D) they have to constantly keep an eye on their companions
13.The example of a bird sleeping in front of a mirror indicates that .
A) the phenomenon of birds dozing in pairs is widespread
B) birds prefer to sleep in pairs for the sake of security
C) even an imagined companion gives the bird a sense of security
D) a single pet bird enjoys seeing its own reflection in the mirror
14.While sleeping, some water mammals tend to keep half awake in order to .
A) alert themselves to the approaching enemy
B) emerge from water now and then to breathe
C) be sensitive to the ever-changing environment
D) avoid being swept away by rapid currents
15.By just the tip of the iceberg , Siegel suggests that .
A) half-brain sleep has something to do with icy weather
B) the mystery of half-brain sleep is close to being sleepers
C) most birds living in cold regions tend to be half sleepers
D) half-brain sleep is a phenomenon that could exist among other species
11.C 12.A 13.C 14.B 15.D
上一篇: 四级考试阅读主旨题解题技巧实战(15)
下一篇: 四级考试阅读主旨题解题技巧实战(18)
2017届高考英语一轮复习语法专题讲练:第5讲 介 词(新人教版含答案)
美味的混搭:日本餐厅推出棉花糖披萨(组图)
2017届高考英语一轮复习强化增分练:Unit 6《Design》(北师大版含解析)
2017届高考英语一轮复习考点落实练:Unit 18《Beauty》(北师大版含解析)
2017届高考英语一轮复习阅读理解提速练:Unit 16《Stories》(北师大版含解析)
2017届高考英语一轮复习考点落实练:Unit 20《New Frontiers》(北师大版含解析)
体坛英语资讯:Spanish football club signs accord to coach Chinese players
五年高考(2011-2015)英语试题分项精解:专题09 非谓语动词(原卷版)
2017届高考英语一轮复习强化增分练:Unit 11《The Media》(北师大版含解析)
2017届高考英语一轮复习考点落实练:Unit 15《Learning》(北师大版含解析)
2017届高考英语一轮复习语法专题讲练:第1讲 构词法(新人教版含答案)
2017届高考英语一轮复习强化增分练:Unit 8《Adventure》(北师大版含解析)
2017届高考英语一轮复习考点落实练:Unit 17《Laughter》(北师大版含解析)
2017届高考英语一轮复习考点落实练:Unit 23《Conflict》(北师大版含解析)
国内英语资讯:Xiongan New Area restricts housing purchase, construction
2017届高考英语一轮复习强化增分练:Unit 7《The Sea》(北师大版含解析)
五年高考(2011-2015)英语试题分项精解:专题11 名词性从句(原卷版)
国内英语资讯:Chinese president arrives in Finland for state visit
2017届高考英语一轮复习同步训练:综合演练(新人教版含答案)
体坛英语资讯:Germains double propels Monaco into French Cup semi-finals
体坛英语资讯:Iran to compete at Asian Womens Volleyball Championship
国内英语资讯:China hands over 4,000 tonnes of rice to Namibia
体坛英语资讯:Hoffenheim upset Bayern, Dortmund win in German Bundesliga
2017届高考英语一轮复习语法专题讲练:第2讲 名词与冠词(新人教版含答案)
国内英语资讯:Chinese president congratulates Serbian president-elect
网络缩略语小考 看你能闯到第几关
2017届高考英语一轮复习语法专题讲练:第3讲 数词和主谓一致(新人教版含答案)
2017届高考英语一轮复习考点落实练:Unit 21《Human Biology》(北师大版含解析)
2017届高考英语一轮复习语法专题讲练:第6讲 形容词、副词(新人教版含答案)
五年高考(2011-2015)英语试题分项精解:专题09 非谓语动词(解析版)