[外语类试卷]大学英语六级模拟试卷666(无答案).doc
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1、大学英语六级模拟试卷 666(无答案)一、Part I Writing (30 minutes)1 Directions: For this part, you are allowed 30 minutes to write A Letter Applying for a Bank Loan. You should write at least 150 words following the outline given below in Chinese:1. 点明写信的目的并且对个人情况作介绍2. 申请助学贷款的原因及数额3. 你的还款打算 二、Part II Reading Comprehe
2、nsion (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 statement agrees with the information given in the passage;N (for NO) if the statem
3、ent contradicts the information given in the passage;NG (for NOT GIVEN) if the information is not given in the passage.1 Part Reading Comprehension (Skimming and Scanning)Directions: In this part, you will have 15 minutes to go over the passage quickly and answer the questions on Answer Sheet 1.For
4、questions 1-4, markY (for YES) if the statement agrees with the information given in the passage;N (for NO) if the statement contradicts the information given in the passage;NG (for NOT GIVRN) if the information is not given in the passage.For questions 5-10, complete the sentences with the informat
5、ion given in the passage.Unity and DiversityMany physicists are engaged in the search for a “theory of everything“. Biologists, smugly, think they have found one already. Organisms that survive long enough to reproduce and are attractive enough to find a mate pass their genes on to the next generati
6、on. Those that do not are evolutionary cul-de-sacs. But the detailshow you go on from the basic principles of evolution to explain large-scale patterns in biologyare more divisive. Scientific camps form. Their leaders step onto soap boxes. And only rarely do people concede that their own theories an
7、d those of their opponents are not always mutually exclusive.Since the early 1970s, the two grandest patterns of lifehow species are arranged in space and how they are arranged in timehave divided their opposing camps quite neatly. Those who squabble over space disagree about why there are more spec
8、ies in the tropics than anywhere else. To them, the tropics are either where species are more often born (cradles of diversity) or where they tend not to die (museums of diversity). By contrast, biologists concerned with patterns in time tenaciously debate whether new species come into being in a sm
9、ooth and gradual manner, or whether the history of life is actually a series of bursts of change that are interspersed with periods when nothing much happens.Two papers just published in Science have cast light on these questions, and their findings, if not necessarily resulting in compromise, do sh
10、ow the value of taking leaves out of other peoples books. The “space biologists“ have looked into time, namely the fossil record over the past 11m years. Meanwhile the “time biologists“ have looked at the here and now and found evidence in living species for periods of rapid evolution in their genes
11、.Biological SpacetimeThe space biologists have the advantage that they agree about the pattern they are trying to explain. Almost all groups of life that have been studiedbe they fungi, plants, vertebrates or invertebrates, and no matter whether they occur in forests, streams or seasseem to have mor
12、e species the closer they are to the equator.To decide whether the tropics are a cradle or a museum, though, involves picking this pattern apart with statistics. And statistics work best when you have more than one sample. That is the reason for reaching into the past.David Jablonski, of the Univers
13、ity of Chicago, and his colleagues created their samples by dividing the past 11m years into three periods. For simplicitys sake, they also chopped the Earths surface into two: tropical regions and everywhere else, which they called the “extratropics“.To avoid sampling bias, they restricted their an
14、alysis to one group of animalsthe bivalve molluscsthat fossilise well. This allowed them to follow 431 “lineages“ of marine bivalve through the course of geological time. The vast majority of these lineages appear in the tropics and then spread into the extratropics, in other words, the tropics do,
15、indeed, act as cradles of biodiversity.In fact, the pattern Dr Jablonski reports is probably more marked than his data suggest. That is because palaeontologists themselves are generally a temperate species and are most commonly found in the northern hemisphere. That means rocks in this region have b
16、een oversampled compared with those in the tropics. Also, tropical rocks tend to experience deep weathering, rarely poking above the ground as outcrops. That makes sampling them harder, even if you bother to look in the first place.The tropics do, indeed, act as cradles of biodiversity. Both of thes
17、e facts mean it is likely that some lineages which seem to make their first appearance in the extratropical fossil record actually started out near the equator. The cradle hypothesis, then, looks strong. But that does not necessarily mean the museum hypothesis is wrongfor, at the same time as the tr
18、opics were generating diversity they seem to have been preserving it as well. Although the bivalve lineages Dr Jablonski studied spread out from the equator in waves, they did not become extinct in the wake of these waves. Instead of being forced out of tropical regions as they travelled poleward, t
19、hey accumulated there.Common ground appears to be forming in time biology as well. The dispute is between the gradualists and those who think that the sudden shifts in fossil types seen in the geological record are real, rather than a consequence of the irregular way that rocks are laid down. It got
20、 rather personal a few years ago, with references to evolution by creeps and evolution by jerks. But, in a similar way to Dr Jablonskis study, which suggests that models of cradles and museums present a false dichotomy, a paper from a member of the gradualist camp of time biology endorses some featu
21、res of jerky evolution.Some Jerks, Some CreepsMark Pagel and his colleagues at the University of Reading, in England, reasoned that the theory of punctuated equilibria (the formal name given to evolution in bursts) predicts a relation between the rate at which new species are formed and the rate of
22、genetic change in an organisms recent past. A lineage that has spun off a lot of species will show more genetic change than one that has not. The alternative view, that evolutionary changes tick along gradually, suggests mutations would accumulate incrementally as time goes by, independently of how
23、many new species a lineage spins off.Dr Pagel studied 122 family trees this way. He found that in about a third of them, there was more change in the DNA in those trees where more species had been generated. He also found that punctuated evolution explained about 22% of such genetic changes, with th
24、e remainder unfolding smoothly through time. This means, among other things, that when biologists have calculated how long ago two lineages diverged by assuming change is regular, they may have their dates wrong.Both Dr Jablonski and Dr Pagel, then, have found a degree of resolution between opposing
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