[外语类试卷]大学英语六级模拟试卷762及答案与解析.doc
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1、大学英语六级模拟试卷 762及答案与解析 一、 Part I Writing (30 minutes) 1 Directions: For this part, you are allowed 30 minutes to write a letter to ask for some information about an international conference held in your city. You should write at least 150 words following the outline given below. 有一个会议在你所在的城市召开,你想去参加。给
2、会议的组织者写一封信。说一下你想参加的原因,并简单介绍一下自己。并请他提供一些会议的相关登信息。 二、 Part II Reading Comprehension (Skimming and Scanning) (15 minutes) Directions: In this part, you will have 15 minutes to go over the passage quickly and answer the questions attached to the passage. For questions 1-4, mark: Y (for YES) if the state
3、ment agrees with the information given in the passage; N (for NO) if the statement contradicts the information given in the passage; NG (for NOT GIVEN) if the information is not given in the passage. 1 How Birds Find Way Home? The ability of birds to return to a familiar place from any distance is a
4、 remarkable feat of nature. For centuries people have taken advantage of this ability in homing pigeons by using them to take messages from distant points back to familiar sites. Homing pigeons are domesticated non-migratory birds with an instinct to return to their lofts (nesting sites) that is imp
5、roved with training and by selective breeding. Training is started at short distances from the nesting site; over time, this distance is gradually increased to hundreds of miles from its loft at a completely unfamiliar location and it can fly in the direction of home within a minute or two of its re
6、lease. How does this extraordinary behavior work? Understanding homing behavior is one of the greatest challenges to ornithologists (鸟类学家 ). Fortunately, because they are able to carefully control the conditions under which the pigeons are released, researchers have been able to learn a great deal a
7、bout how the birds navigate their way home. Although homing ability has been fostered in pigeons by careful breeding and selecting of stock, it appears that training is not always necessary: Many species of wild birds perform similarly remarkable feats. One such bird is the migratory Manx Shearwater
8、 (剪嘴鸥 ). Built like tiny albatrosses, these seabirds spend most of their lives skimming over the ocean surface far from the sight of land. They come ashore only to nest in burrows, which they dig in the ground on offshore islands in order to be safe from predators. The ease of locating and observing
9、 their nests make shearwaters ideal subjects for homing experiments. Great Bird Navigators Many migratory birds are remarkably faithful to previous nesting and overwintering places. Though a bird might be able to come close to these sites merely by flying in a general direction during the course of
10、migration, at some point more sophisticated navigating techniques must take over to guide the bird to its precise destination. Many animals are able to find their way home. One way of doing this is to directly sense the goalto see, hear, or smell it. Another way is to memorize the details of the out
11、ward journey and then reverse the route based on an integration of that information. Birds, however, apparently rely on a completely different process to find their way. To explain bird navigation, we have what is known as the “map-and-compass“ theory. The compass component of this theory gives dire
12、ction-north, south, east, west; the map component tells the bird where it is, or gives locality. Scientists have learned a great deal more about the compass component than they have about mapping. They know that birds have several means of determining compass directions, but unfortunately, they stil
13、l have no satisfactory explanation for how birds use biological “maps“ to guide them to a precise location from an unfamiliar starting point. Bird Sun Navigators Some observations indicate that birds might use the sun as, a visual cue to determine compass directions. Starlings (八哥 ), for example, se
14、em able to negotiate the proper direction only if they have a view of the clear sky and sun; cloud cover seems to induce confusion. In an experiment in which the suns apparent position was changed with mirrors attached to an orientation cage containing starlings, observers noted that the direction o
15、f the starlings hopping, which earlier had been correlated to the direction that chose to migrate, was shifted accordingly. Even birds that migrate exclusively at night pay considerable attention to the sun. At first this may seem odd because, after all, the sun is not visible to the nocturnal (夜间活动
16、的 ) birds when they are flying. On the other hand, it is a predominant feature in the sky at a time of day (dusk)when birds may well be making decisions about whether to fly that night and in what direction. Radar studies have shown that most night migrants take off during this twilight period. Like
17、 many other animals, birds are endowed with a built-in clock that tells them the time of day. Using this internal clock, young pigeons, at least, learn the suns path of movement across the sky. Many birds are known to have an internal clock, and many are known to have a sun compass, but it is only i
18、n pigeons that ornithologists can watch the learning process develop. Bird Star Navigators Most birds migrate not by day, but at night. Employing conical (圆锥形的 ) cages, researchers quickly observed that night migrants exhibited hopping behavior similar to that of day migrants and that they oriented
19、themselves in the proper direction under clear, starry skies but became disoriented when it was cloudy. The decisive tests were performed in a planetarium (天文馆 ), where star patterns can be controlled at will. The experiments indicated that night-migrating birds learn and orient by spatial relations
20、hips among the constellations (星座 ), rather than using information supplied by any single star. More recently, scientists have discovered that birds begin to develop star compass capability when they are quite young, and as experienced adults they can use many parts of the sky to recognize compass d
21、irections. Magnetic Bird Navigators A sun compass for migration during the day, a star compass for nocturnal migration life would be much simpler had this been the end of the story. For a long time there has been a popular theory that birds have a magnetic compass guiding their navigatory behavior.
22、There is a good reason for that idea-it would be a convenient system to use during overcast days or nights. But many respected biologists assured ornithologists that for birds to sense such force was almost impossible because the Earths magnetic field is such a weak force. A group of German ornithol
23、ogists conducted research that provided evidence to the contrary. In the study, night migrants that were placed in orientation cages indoors in closed rooms showed weak but consistent and seasonally appropriate hopping directions, which suggested that they did not need the sun or stars to determine
24、direction. By placing the cages within sets of wire coils through which a weak electric current was passed, it was possible to change the configuration of the magnetic field surrounding the birds to determine if they respond in a predictable way. Although their responses continued to be weak, the bi
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- 外语类 试卷 大学 英语六级 模拟 762 答案 解析 DOC
