六级英语阅读专项训练题

　　六级英语阅读专项训练题原文

　　Decades of studies of bird flocks led researchers to predict extra alertness in the morevulnerable, end-of-the-row sleepers, Sure enough, the end birds tended to watch carefully onthe side away from their companions. Ducks in the inner spots showed no preference for gazedirection.

　　Also, birds dozing(打盹)at the end of the line resorted to single-hemisphere sleep, ratherthan total relaxation, more often than inner ducks did. Rotating 16 birds through the positionsin a four-duck row, the researchers found outer birds half-asleep during some 32 percent ofdozing time versus about 12 percent for birds in internal spots.

　　“We believe this is the first evidence for an animal behaviorally controlling sleep andwakefulness 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 aneye on the lookout side could be widespread, he predicts. He’s seen it in a pair of birds dozingside-by-side in the zoo and in a single pet bird sleeping by mirror. The mirror-side eye closed asif 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 asleeping animal to surface occasionally to avoid drowning.

　　Studies of birds may offer unique insights into sleep. Jerome M. Siegel of the UGLA says hewonders if birds’ half-brain sleep “is just the tip of the iceberg(冰山)”. He speculates thatmore examples may turn up when we take a closer look at other species.

　　六级英语阅读专项训练题

　　11. A new study on birds’ sleep has revealed that ____________.

　　A) birds can control their half-brain sleep consciously

　　B) birds seldom sleep with the whole of their brain at rest

　　C) half-brain sleep is found in a wide variety of birds

　　D) half-brain sleep is characterized by slow brain waves

　　12. According to the passage, birds often half sleep because ______________.

　　A) they have to constantly keep an eye on their companions

　　B) the two halves of their brain are differently structured

　　C) they have to watch out for possible attacks

　　D) their brain hemisphere take turns to rest

　　13. The example of a bird sleeping in front of a mirror indicates that _____________.

　　A) birds prefer to sleep in pairs for the sake of security

　　B) the phenomenon of birds dozing in pairs is widespread

　　C) a single pet bird enjoys seeing its own reflection in the mirror

　　D) even an imagined companion gives the bird a sense of security

　　14. While sleeping, some water mammals tend to keep half awake in order to__________.

　　A) avoid being swept away by rapid currents

　　B) emerge from water now and then to breathe

　　C) alert themselves to the approaching enemy

　　D) be sensitive to the ever-changing environment

　　15. By “just the tip of the iceberg” (Line 2, Para.8), Siegel suggests that____________.

　　A) half-brain sleep is a phenomenon that could exist among other species

　　B) most birds living in cold regions tend to be half sleepers

　　C) the mystery of half-brain sleep is close to being solved

　　D) half-brain sleep has something to do with icy weather

　　六级英语阅读专项训练题答案

　　11. A

　　12. C

　　13. D

　　14. B

　　15. A