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A. living
B. Lively
C. alive
D. live
答案
更多“If a baby bird stays ______ for two or three weeks after leaving the nest, it has a fair c”相关的问题
第1题
If a baby bird stays （） for two or three weeks after leaving the nest, it has a fair chance of becoming an adult.
A.living
B.lively
C.alive
D. live
第2题
What kind of birds came to the bird houses？
A．Soon robins came to the bird houses.
B．Soon bluebirds built nests in the bird houses.
C．Soon purple martins built nests in the bird houses.
D．Soon baby birds built nests in the bird houses.
第3题
听力原文： Many African mothers carry babies on their back. In this way, a working mother knows that her baby is safe on her back while her hands are free for her work. On the other hand, the baby stays in close contact with his mother and feels safe and warm. However, back-nesting is not suitable in summer. Besides, (29) back-nesting does not give babies freedom and chance to use their hands and legs. Children need to observe and explore the environment. What's more, this sense of security given by back-nesting may be suddenly broken when the child can no longer be carried. He may be put down and expected to behave like a grown-up child. (30) But he has been over protected for so long that now he feels very insecure and many behave like a baby. Once I visited a friend's home, where the mother was carrying her eleven-month-old son on her back. I found the mother had nothing special to do with her hands and the baby was restless. I asked her to put the baby down. At first, (31 ) she didn't want to because she firmly believed that if she carried the baby on her back, he could sleep longer, keep quieter and make less mess. I tried my best to persuade her and finally she gave in. Immediately the child began examining the toy drum before him. He looked much live her and happier.
(30)
A．It is not safe for the children.
B．The children can not communicate with mothers face to face.
C．The mothers may feel very tired.
D．The children have no chance to use hands and legs.
第4题
听力原文： The European cuckoo is notorious for its odd way of raising its young. The parents normally live in various regions of Asia or Africa, but migrate to England in the warm months. The first cuckoos reach England in April, and each year people write to newspapers to claim that they have heard the first cuckoo. The bird's call "Cue-coo" is regarded in North Europe as a sign that summer has nearly arrived. After the ice and snow of winter, the sound "Cue-coo" is most welcome, so the bird has a special significance for many Europeans.
The female cuckoo manages to reproduce her species by laying eggs which she then abandons. Each cuckoo tends to lay her eggs in the nest of one particular species. It is amazing that the female will lay eggs which have very similar colours and markings to the eggs of the host bird. This ability helps to prevent the host bird from rejecting the cuckoo's egg.
The cuckoo lays about a dozen eggs altogether at about two-day intervals. Each egg is in a different nest. Having laid her eggs for the year, the female's role as mother is completed. In late July or early August, she flies to the south to a warmer climate.
Meanwhile, each young cuckoo is busy looking after itself and doing the job quite well. The chicks hatch after 12 or 13 days, which is usually much sooner than any of the foster-mother's brood. The young cuckoos lift up any other eggs or chicks so that they fall over the side of the nest. In this way, the cuckoo removes any competition for the foster-mother's attention.
The young cuckoo grows much faster than the foster-mother's own chicks. It gets most of the food brought back to the nest by the foster-mother. After a few weeks, the cuckoo chick grows too big to sit in the nest, and much bigger than the foster-mother. But it is still not ready to fly, and remains on the nest, screaming for the food. The foster-mother is stimulated by this noise and has to work hard all day searching for the food.
After about three weeks, the cuckoo chick starts to fly. But it still stays at the nest most of the time for a further one or two weeks, until it is completely independent. And at this time, it can fly well and find its own food. The bird then remains in Britain until September. And then it too, like its parents, migrates for the winter to the warmer countries of the south.
Questions:
16. How long does a cuckoo stay in Britain according to the talk？
17.What does the bird's call "Cuc-coo" suggest for North Europeans？
18.Where does a female cuckoo lay her eggs？
19.When will a young cuckoo leave its foster-mother's nest？
20.which of the following is TRUE about the cuckoos？
(36)
A．All the year around.
B．For 10 months.
C．For about half a year.
D．For three or four months in summer.
第5题
【A2】
A.THE INTRODUCTION OF PREDATORS.
B.PREVENTING THE KIWI DECLIN
E.
C.REASONS FOR CONCER
N.
D.EXPLANATION FOR LARGER BIRD POPULATIONS.
E.LAND OF THE KIW
I. KIWIS ARE FLIGHTLESS BIRDS ENDEMIC TO NEW ZEALAND, AND BY FAR THE SMALLEST LIVING RAT-ITES AND LAY THE LARGEST EGG IN RELATION TO THEIR BODY SIZE OF ANY SPECIES OF BIRD IN THE WORL
D. 【A1】______ THE KIWI IS SYNONYMOUS WITH NEW ZEALAND, SO MUCH SO THAT AUSTRALIANS ENDEARINGLY REFER TO NEW ZEALANDERS AS "KIWI" —PEOPLE FROM THE LAND OF THE KIW
I.THIS UNIQUE BIRD, RECOGNIZABLE BY ITS SHORT SQUAT BODY AND ELONGATED BEAK, IS UNDER THREAT.ITS SMALL, CLAWLIKE WINGS RENDER THE KIWI FLIGHTLESS; IT MUST OF NECESSITY LIVE ON THE GROUN
D.THE KIWI IS THUS EASY PREY TO MARAUDING ENEMIES SUCH AS HUMANS AND MAMMALS. 【A2】______ WHEN THE GREAT LAND MASS OF THE SOUTH SPLIT 75 MILLION YEARS AGO, THE KIWI AND MANY OTHER GROUND-LIVING BIRD SPECIES BECAME SEPARATED FROM PREDATORY MAMMALS WITHIN WHAT WAS LATER TO BECOME KNOW AS NEW ZEALAN
D.THE BIRDS WERE ABLE TO MULTIPLY AND FLOURISH BECAUSE THERE WERE VERY FEW MAMMALS LANDLOCKED WITHIN THE ISLANDS.KIWIS HAVE EVOLVED CERTAIN MAMMALIAN CHARACTERISTICS OVER TIME, LIVING ON THE GROUND AND FREE AS THEY WERE FROM ATTACK BY MAMMALS. 【A3】______ HOWEVER, WHEN THE POLYNESIANS ARRIVED ABOUT 1,000 YEARS AGO BRINGING WITH THEM DOGS AND RATS, THE KIWI POPULATION AND OTHER VULNERABLE BIRD SPECIES SOON SUFFERED A SEVERE REDUCTION IN NUMBERS.THE COMING OF THE EUROPEANS IN THE EIGHTEENTH CENTURY BROUGHT EVEN MORE DETERMINED PREDATORS, INCLUDING THE CAT AND, ESPECIALLY, THE STOAT —A KIND OF WEASEL INTRODUCED TO CONTROL RABBITS.THE STOAT IS A VERY VICIOUS AND EFFICIENT KILLER OF KIWIS. 【A4】______ THERE ARE SIX TYPES OF KIWIS, AND ALL SIX ARE THREATENE
D.TWO ARE "CRITICALLY ENDANGERED" BECAUSE THEY HAVE POPULATIONS OF LESS THAN 250 MATURE BIRDS.TWO ARE "ENDANGERED" MEANING THAT IT IS ESTIMATED THAT WITHIN THREE GENERATIONS THEIR NUMBERS WILL HAVE DECLINED BY 50%.THE OTHER TWO ARE DESIGNATED "VULNERABLE" —ONE BECAUSE ITS HABITAT IS SHRINKING, THE OTHER BECAUSE IT IS POTENTIALLY UNDER THREAT FROM STOATS AND OTHER MAMMALS. 【A5】______ 100 YEARS AGO THERE WERE MORE THAN 5 MILLION NORTH ISLAND BROWN KIWIS.TODAY, THERE ARE PROBABLY AROUND 30,000 AND THE POPULATION IS DECREASING AT A RATE OF 6% A YEAR. ONLY THE LITTLE SPOTTED KIWI IS INCREASING BECAUSE OF SUCCESSFUL ATTEMPTS TO TRANSFER THE CREATURE TO PREDATOR-FREE OFFSHORE ISLANDS.THERE ARE FURTHER REASONS FOR HOP
E.TRAPPING PREDATORS AND REARING BABY CHICKS FOR LATER RELEASE INTO THE WILD CAN HAVE A DRAMATIC EFFECT ON KIWINUMBERS; BUT IT WILL BE NECESSARY TO DO SO ON A LARGE SCAL
E. IT WOULD BE TRAGIC IF NEW ZEALAND WERE TO LOSE ITS NATIONAL SYMBOL, THE KIW
I.SURELY THE STRANGEST BIRD IN EXISTENCE, UNABLE TO FLY, IT SNIFFS OUT ITS FOOD WITH A REMARKABLY STRONG SENSE OF SMELL.ITS LEGS ARE POWERFUL AND MUSCULAR, FOR THE KIWI IS A BURROWER LIVING IN DENS—SOME SPECIES EVEN PREFERRING TUNNELS, YET ANOTHER SIMILARITY IT SHARES WITH SOME MAMMALS.BUT IT CANNOT SHARE ITS HABITAT WITH THEM WITHOUT EVENTUALLY LOSING THE BATTLE FOR SURVIVAL.
第6题
【A1】
A.THE INTRODUCTION OF PREDATORS.
B.PREVENTING THE KIWI DECLIN
E.
C.REASONS FOR CONCER
N.
D.EXPLANATION FOR LARGER BIRD POPULATIONS.
E.LAND OF THE KIW
I. KIWIS ARE FLIGHTLESS BIRDS ENDEMIC TO NEW ZEALAND, AND BY FAR THE SMALLEST LIVING RAT-ITES AND LAY THE LARGEST EGG IN RELATION TO THEIR BODY SIZE OF ANY SPECIES OF BIRD IN THE WORL
D. 【A1】______ THE KIWI IS SYNONYMOUS WITH NEW ZEALAND, SO MUCH SO THAT AUSTRALIANS ENDEARINGLY REFER TO NEW ZEALANDERS AS "KIWI" —PEOPLE FROM THE LAND OF THE KIW
I.THIS UNIQUE BIRD, RECOGNIZABLE BY ITS SHORT SQUAT BODY AND ELONGATED BEAK, IS UNDER THREAT.ITS SMALL, CLAWLIKE WINGS RENDER THE KIWI FLIGHTLESS; IT MUST OF NECESSITY LIVE ON THE GROUN
D.THE KIWI IS THUS EASY PREY TO MARAUDING ENEMIES SUCH AS HUMANS AND MAMMALS. 【A2】______ WHEN THE GREAT LAND MASS OF THE SOUTH SPLIT 75 MILLION YEARS AGO, THE KIWI AND MANY OTHER GROUND-LIVING BIRD SPECIES BECAME SEPARATED FROM PREDATORY MAMMALS WITHIN WHAT WAS LATER TO BECOME KNOW AS NEW ZEALAN
D.THE BIRDS WERE ABLE TO MULTIPLY AND FLOURISH BECAUSE THERE WERE VERY FEW MAMMALS LANDLOCKED WITHIN THE ISLANDS.KIWIS HAVE EVOLVED CERTAIN MAMMALIAN CHARACTERISTICS OVER TIME, LIVING ON THE GROUND AND FREE AS THEY WERE FROM ATTACK BY MAMMALS. 【A3】______ HOWEVER, WHEN THE POLYNESIANS ARRIVED ABOUT 1,000 YEARS AGO BRINGING WITH THEM DOGS AND RATS, THE KIWI POPULATION AND OTHER VULNERABLE BIRD SPECIES SOON SUFFERED A SEVERE REDUCTION IN NUMBERS.THE COMING OF THE EUROPEANS IN THE EIGHTEENTH CENTURY BROUGHT EVEN MORE DETERMINED PREDATORS, INCLUDING THE CAT AND, ESPECIALLY, THE STOAT —A KIND OF WEASEL INTRODUCED TO CONTROL RABBITS.THE STOAT IS A VERY VICIOUS AND EFFICIENT KILLER OF KIWIS. 【A4】______ THERE ARE SIX TYPES OF KIWIS, AND ALL SIX ARE THREATENE
D.TWO ARE "CRITICALLY ENDANGERED" BECAUSE THEY HAVE POPULATIONS OF LESS THAN 250 MATURE BIRDS.TWO ARE "ENDANGERED" MEANING THAT IT IS ESTIMATED THAT WITHIN THREE GENERATIONS THEIR NUMBERS WILL HAVE DECLINED BY 50%.THE OTHER TWO ARE DESIGNATED "VULNERABLE" —ONE BECAUSE ITS HABITAT IS SHRINKING, THE OTHER BECAUSE IT IS POTENTIALLY UNDER THREAT FROM STOATS AND OTHER MAMMALS. 【A5】______ 100 YEARS AGO THERE WERE MORE THAN 5 MILLION NORTH ISLAND BROWN KIWIS.TODAY, THERE ARE PROBABLY AROUND 30,000 AND THE POPULATION IS DECREASING AT A RATE OF 6% A YEAR. ONLY THE LITTLE SPOTTED KIWI IS INCREASING BECAUSE OF SUCCESSFUL ATTEMPTS TO TRANSFER THE CREATURE TO PREDATOR-FREE OFFSHORE ISLANDS.THERE ARE FURTHER REASONS FOR HOP
E.TRAPPING PREDATORS AND REARING BABY CHICKS FOR LATER RELEASE INTO THE WILD CAN HAVE A DRAMATIC EFFECT ON KIWINUMBERS; BUT IT WILL BE NECESSARY TO DO SO ON A LARGE SCAL
E. IT WOULD BE TRAGIC IF NEW ZEALAND WERE TO LOSE ITS NATIONAL SYMBOL, THE KIW
I.SURELY THE STRANGEST BIRD IN EXISTENCE, UNABLE TO FLY, IT SNIFFS OUT ITS FOOD WITH A REMARKABLY STRONG SENSE OF SMELL.ITS LEGS ARE POWERFUL AND MUSCULAR, FOR THE KIWI IS A BURROWER LIVING IN DENS—SOME SPECIES EVEN PREFERRING TUNNELS, YET ANOTHER SIMILARITY IT SHARES WITH SOME MAMMALS.BUT IT CANNOT SHARE ITS HABITAT WITH THEM WITHOUT EVENTUALLY LOSING THE BATTLE FOR SURVIVAL.
第7题
【A4】
A.THE INTRODUCTION OF PREDATORS.
B.PREVENTING THE KIWI DECLIN
E.
C.REASONS FOR CONCER
N.
D.EXPLANATION FOR LARGER BIRD POPULATIONS.
E.LAND OF THE KIW
I. KIWIS ARE FLIGHTLESS BIRDS ENDEMIC TO NEW ZEALAND, AND BY FAR THE SMALLEST LIVING RAT-ITES AND LAY THE LARGEST EGG IN RELATION TO THEIR BODY SIZE OF ANY SPECIES OF BIRD IN THE WORL
D. 【A1】______ THE KIWI IS SYNONYMOUS WITH NEW ZEALAND, SO MUCH SO THAT AUSTRALIANS ENDEARINGLY REFER TO NEW ZEALANDERS AS "KIWI" —PEOPLE FROM THE LAND OF THE KIW
I.THIS UNIQUE BIRD, RECOGNIZABLE BY ITS SHORT SQUAT BODY AND ELONGATED BEAK, IS UNDER THREAT.ITS SMALL, CLAWLIKE WINGS RENDER THE KIWI FLIGHTLESS; IT MUST OF NECESSITY LIVE ON THE GROUN
D.THE KIWI IS THUS EASY PREY TO MARAUDING ENEMIES SUCH AS HUMANS AND MAMMALS. 【A2】______ WHEN THE GREAT LAND MASS OF THE SOUTH SPLIT 75 MILLION YEARS AGO, THE KIWI AND MANY OTHER GROUND-LIVING BIRD SPECIES BECAME SEPARATED FROM PREDATORY MAMMALS WITHIN WHAT WAS LATER TO BECOME KNOW AS NEW ZEALAN
D.THE BIRDS WERE ABLE TO MULTIPLY AND FLOURISH BECAUSE THERE WERE VERY FEW MAMMALS LANDLOCKED WITHIN THE ISLANDS.KIWIS HAVE EVOLVED CERTAIN MAMMALIAN CHARACTERISTICS OVER TIME, LIVING ON THE GROUND AND FREE AS THEY WERE FROM ATTACK BY MAMMALS. 【A3】______ HOWEVER, WHEN THE POLYNESIANS ARRIVED ABOUT 1,000 YEARS AGO BRINGING WITH THEM DOGS AND RATS, THE KIWI POPULATION AND OTHER VULNERABLE BIRD SPECIES SOON SUFFERED A SEVERE REDUCTION IN NUMBERS.THE COMING OF THE EUROPEANS IN THE EIGHTEENTH CENTURY BROUGHT EVEN MORE DETERMINED PREDATORS, INCLUDING THE CAT AND, ESPECIALLY, THE STOAT —A KIND OF WEASEL INTRODUCED TO CONTROL RABBITS.THE STOAT IS A VERY VICIOUS AND EFFICIENT KILLER OF KIWIS. 【A4】______ THERE ARE SIX TYPES OF KIWIS, AND ALL SIX ARE THREATENE
D.TWO ARE "CRITICALLY ENDANGERED" BECAUSE THEY HAVE POPULATIONS OF LESS THAN 250 MATURE BIRDS.TWO ARE "ENDANGERED" MEANING THAT IT IS ESTIMATED THAT WITHIN THREE GENERATIONS THEIR NUMBERS WILL HAVE DECLINED BY 50%.THE OTHER TWO ARE DESIGNATED "VULNERABLE" —ONE BECAUSE ITS HABITAT IS SHRINKING, THE OTHER BECAUSE IT IS POTENTIALLY UNDER THREAT FROM STOATS AND OTHER MAMMALS. 【A5】______ 100 YEARS AGO THERE WERE MORE THAN 5 MILLION NORTH ISLAND BROWN KIWIS.TODAY, THERE ARE PROBABLY AROUND 30,000 AND THE POPULATION IS DECREASING AT A RATE OF 6% A YEAR. ONLY THE LITTLE SPOTTED KIWI IS INCREASING BECAUSE OF SUCCESSFUL ATTEMPTS TO TRANSFER THE CREATURE TO PREDATOR-FREE OFFSHORE ISLANDS.THERE ARE FURTHER REASONS FOR HOP
E.TRAPPING PREDATORS AND REARING BABY CHICKS FOR LATER RELEASE INTO THE WILD CAN HAVE A DRAMATIC EFFECT ON KIWINUMBERS; BUT IT WILL BE NECESSARY TO DO SO ON A LARGE SCAL
E. IT WOULD BE TRAGIC IF NEW ZEALAND WERE TO LOSE ITS NATIONAL SYMBOL, THE KIW
I.SURELY THE STRANGEST BIRD IN EXISTENCE, UNABLE TO FLY, IT SNIFFS OUT ITS FOOD WITH A REMARKABLY STRONG SENSE OF SMELL.ITS LEGS ARE POWERFUL AND MUSCULAR, FOR THE KIWI IS A BURROWER LIVING IN DENS—SOME SPECIES EVEN PREFERRING TUNNELS, YET ANOTHER SIMILARITY IT SHARES WITH SOME MAMMALS.BUT IT CANNOT SHARE ITS HABITAT WITH THEM WITHOUT EVENTUALLY LOSING THE BATTLE FOR SURVIVAL.
第8题
【A3】
A.THE INTRODUCTION OF PREDATORS.
B.PREVENTING THE KIWI DECLIN
E.
C.REASONS FOR CONCER
N.
D.EXPLANATION FOR LARGER BIRD POPULATIONS.
E.LAND OF THE KIW
I. KIWIS ARE FLIGHTLESS BIRDS ENDEMIC TO NEW ZEALAND, AND BY FAR THE SMALLEST LIVING RAT-ITES AND LAY THE LARGEST EGG IN RELATION TO THEIR BODY SIZE OF ANY SPECIES OF BIRD IN THE WORL
D. 【A1】______ THE KIWI IS SYNONYMOUS WITH NEW ZEALAND, SO MUCH SO THAT AUSTRALIANS ENDEARINGLY REFER TO NEW ZEALANDERS AS "KIWI" —PEOPLE FROM THE LAND OF THE KIW
I.THIS UNIQUE BIRD, RECOGNIZABLE BY ITS SHORT SQUAT BODY AND ELONGATED BEAK, IS UNDER THREAT.ITS SMALL, CLAWLIKE WINGS RENDER THE KIWI FLIGHTLESS; IT MUST OF NECESSITY LIVE ON THE GROUN
D.THE KIWI IS THUS EASY PREY TO MARAUDING ENEMIES SUCH AS HUMANS AND MAMMALS. 【A2】______ WHEN THE GREAT LAND MASS OF THE SOUTH SPLIT 75 MILLION YEARS AGO, THE KIWI AND MANY OTHER GROUND-LIVING BIRD SPECIES BECAME SEPARATED FROM PREDATORY MAMMALS WITHIN WHAT WAS LATER TO BECOME KNOW AS NEW ZEALAN
D.THE BIRDS WERE ABLE TO MULTIPLY AND FLOURISH BECAUSE THERE WERE VERY FEW MAMMALS LANDLOCKED WITHIN THE ISLANDS.KIWIS HAVE EVOLVED CERTAIN MAMMALIAN CHARACTERISTICS OVER TIME, LIVING ON THE GROUND AND FREE AS THEY WERE FROM ATTACK BY MAMMALS. 【A3】______ HOWEVER, WHEN THE POLYNESIANS ARRIVED ABOUT 1,000 YEARS AGO BRINGING WITH THEM DOGS AND RATS, THE KIWI POPULATION AND OTHER VULNERABLE BIRD SPECIES SOON SUFFERED A SEVERE REDUCTION IN NUMBERS.THE COMING OF THE EUROPEANS IN THE EIGHTEENTH CENTURY BROUGHT EVEN MORE DETERMINED PREDATORS, INCLUDING THE CAT AND, ESPECIALLY, THE STOAT —A KIND OF WEASEL INTRODUCED TO CONTROL RABBITS.THE STOAT IS A VERY VICIOUS AND EFFICIENT KILLER OF KIWIS. 【A4】______ THERE ARE SIX TYPES OF KIWIS, AND ALL SIX ARE THREATENE
D.TWO ARE "CRITICALLY ENDANGERED" BECAUSE THEY HAVE POPULATIONS OF LESS THAN 250 MATURE BIRDS.TWO ARE "ENDANGERED" MEANING THAT IT IS ESTIMATED THAT WITHIN THREE GENERATIONS THEIR NUMBERS WILL HAVE DECLINED BY 50%.THE OTHER TWO ARE DESIGNATED "VULNERABLE" —ONE BECAUSE ITS HABITAT IS SHRINKING, THE OTHER BECAUSE IT IS POTENTIALLY UNDER THREAT FROM STOATS AND OTHER MAMMALS. 【A5】______ 100 YEARS AGO THERE WERE MORE THAN 5 MILLION NORTH ISLAND BROWN KIWIS.TODAY, THERE ARE PROBABLY AROUND 30,000 AND THE POPULATION IS DECREASING AT A RATE OF 6% A YEAR. ONLY THE LITTLE SPOTTED KIWI IS INCREASING BECAUSE OF SUCCESSFUL ATTEMPTS TO TRANSFER THE CREATURE TO PREDATOR-FREE OFFSHORE ISLANDS.THERE ARE FURTHER REASONS FOR HOP
E.TRAPPING PREDATORS AND REARING BABY CHICKS FOR LATER RELEASE INTO THE WILD CAN HAVE A DRAMATIC EFFECT ON KIWINUMBERS; BUT IT WILL BE NECESSARY TO DO SO ON A LARGE SCAL
E. IT WOULD BE TRAGIC IF NEW ZEALAND WERE TO LOSE ITS NATIONAL SYMBOL, THE KIW
I.SURELY THE STRANGEST BIRD IN EXISTENCE, UNABLE TO FLY, IT SNIFFS OUT ITS FOOD WITH A REMARKABLY STRONG SENSE OF SMELL.ITS LEGS ARE POWERFUL AND MUSCULAR, FOR THE KIWI IS A BURROWER LIVING IN DENS—SOME SPECIES EVEN PREFERRING TUNNELS, YET ANOTHER SIMILARITY IT SHARES WITH SOME MAMMALS.BUT IT CANNOT SHARE ITS HABITAT WITH THEM WITHOUT EVENTUALLY LOSING THE BATTLE FOR SURVIVAL.
第9题
Earlier studies have documented half-brain sleep in a wide range of birds. The brain hemi- spheres take turns sinking into the sleep stage characterized by slow brain waves. The eye con- trolled 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-or-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(打盹) 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.
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
第10题
Crocodiles(鳄鱼)lay their eggs and leave them under leaves or sand. Baby crocodiles have special sharp teeth with which to break their way out of the shells. Crocodiles only live where it is hot. They are found in India, Australia, Africa and America. They spend most of their time lying around in the mud or the rivers. The crocodiles long powerful tail is used when the animal is swimming. It is also an excellent weapon, because it can be swung with great speed and force. One blow will knock down a man or even a big animal at once. The crocodile is very well protected against its enemies by the hard bony plates which cover most of its body, but because of the way its neck is formed, it cannot turn its head from side to side and so it can only see in front of itself. The crocodile has its teeth cleaned by the crocodile bird. For its food this bird takes the bits left in the crocodiles mouth. This helps the crocodile, which cannot clean its own teeth, for it cannot move its tongue up and down. With its rows of terrible pointed teeth it seizes its food, which may be a fish, an animal, or even a careless human being, and then holds it below the water until it is drown to death. The long-nosed crocodile is shy and timid and because of this, the people of West Africa where it lives, sometimes catch it for food. Many, many centuries ago there were crocodiles in England. We know this because we have found their bones buried far down in the earth on which London is built. But the Britain of today is too cold for them to live in. Crocodiles may grow to over thirty feet in length. When they lie floating in the water, they look like floating tree-trunks and it is often impossible to tell that they are there.
The female crocodile______.
A．buries her eggs
B．sits on her eggs
C．carries her eggs
D．eats her eggs
