题目内容
Birds that are half-asleep — with one brain hemisphere (半球) alert(警觉) and the other sleeping — control which side of the brain remains awake, according to a new study of sleeping ducks.
Earlier studies have recorded 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 groups led researchers to predict extra alertness in the end-of-the-row sleepers which tend to be attacked more easily. 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(注视) direction.
Also, birds napping (打盹) at the end of the line depend on single-hemisphere sleep, rather than total relaxation, more often than inner ducks did. Turning 16 birds through the positions in a four-duck row, the researchers found that compared with 12 percent for birds in inner spots, outer birds half-asleep during some 32 percent of napping time.
“We believe this is the first evidence for an animal behaviorally controlling sleep and wakefulness at the same time in different regions of the brain,” the researchers say.
The results provide the best evidence for a long-standing assumption that single-hemisphere sleep developed over time 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 napping 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 animals 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.” He supposes that more examples may turn up when we take a closer look at other species.
1.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 organized
D. they have to constantly keep an eye on their companions
2.What is implied about the example of a bird’s sleeping in front of a mirror?
A. An imagined companion gives the bird a sense of security.
B. Birds prefer to sleep in pairs for the sake of their security.
C. The phenomenon of birds napping in pairs is widespread.
D. A single pet bird enjoys seeing its own reflection in the mirror.
3.It can be inferred that _______.
A. Birds never sleep with both hemispheres resting at once.
B. Inner ducks depend on single-hemisphere sleep, rather than total relaxation, as often as birds napping at the end of the line do
C. It is not the first time for scientists to research on birds’ half-brain sleep
D. Birds hardly sleep without a companion
4.By saying “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 solved
C. most birds living in cold regions tend to be half sleepers
D. half-brain sleep may exist among other species
1.A
2.A
3.C
4.D
【解析】
1.细节理解题。结合single-hemisphere sleep developed over time as creatures scanned for enemies(半睡眠是动物为防范敌人进化而来的)可知答案。
2.推理判断题。结合第六段后两句,即鸟在镜子前睡觉的例子是对本段前两句的进一步佐证。The preference for opening an eye on the lookout side... 是为了对敌人的进攻保持警觉,而The mirror-side eye closed是因为as if the reflection were a companion(好像镜中的影像是它的同伴一样) 为鸟提供安全感。
3.推理判断题。结合Earlier studies have recorded half-brain sleep in a wide range of birds可知答案。
4.推理判断题。根据最后一段可知“对鸟类的研究或许能使人们以独特的视角了解睡眠。M. Siegel说,他认为鸟类的半睡眠‘只是冰山浮出水面的那一角’,并推断当我们更深入地研究其他物种时还会发现更多类似的例子。”故D项为正确答案。
If you’d like to go sightseeing, the following World Heritage Sites may be your best choices.
Jiuzhaigou Valley Scenic and Historic Interest Area
The Jiuzhaigou Valley, which lies in the northern part of Sichuan Province, reaches a height of more than 4,800 meters, with a series of different forest ecosystems(生态系统). There you can enjoy watching excellent waterfalls. Some 140 kinds of birds also live in the valley, as well as a number of endangered plants and animals, including the giant panda. For more information, please visit http://whc.unesco.org/en/list/637.
Khami Ruins National Monument
The city of Khami, which developed after the capital of Great Zimbabwe had been given up in the mid-16th century, is of great archaeological(考古的)interest. The discovery of objects from Europe and China shows that Khami was a major centre for trade over a long period of time. For more information, please visit http://whc.unesco.org/en/list/365.
Henderson Island
Henderson Island, which lies in the eastern South Pacific, is one of the few atolls(环礁)in the world whose ecology(生态)has not been touched by human beings. It is especially famous for the ten plants and four land birds that can only be seen on the island. For more information, please visit http://whc.unesco.org/en/list/487.
The Old City of Jerusalem
As a holy city for three different religions in the Middle East, Jerusalem has always been of great religious importance. It was given a World Heritage Status in 1981 and placed on the “List of World Heritage in Danger” the following year. For more information, please visit http://whc.unesco.org/en/list/148.
1.What can we know about the Jiuzhaigou Valley?
A.It sits at the foot of a 4,800-meter-high mountain. |
B.It has different forest ecosystems. |
C.Most of China’s endangered plants can be found there. |
D.In all about 140 kinds of birds and animals live there. |
2.The discovery of some of the objects in Khami shows that the city .
A.had a very short history |
B.was ruined in the mid-16th century |
C.was once Great Zimbabwe’s largest city |
D.once played a great role as a trade center |
3.From the passage we can learn that Henderson Island .
A.hasn’t been greatly influenced by human activities |
B.isn’t suitable for humans to live on |
C.has been open to visitors for years |
D.is made up of a few large atolls |
4.If you are interested in religion, you should visit .
A.http://whc.unesco.org/en/list/148 |
B.http://whc.unesco.org/en/list/365 |
C.http://whc.unesco.org/en/list/487 |
D.http://whc.unesco.org/en/list/637 |