托福阅读加试机经.docx

1、托福阅读加试机经托福阅读经典加试题：达尔文进化论英文原文及答案Observing Natural SelectionWitnessing natural selection would not have seemed possible to Darwin because he assumed natural selection was too slow and gradual for our short-term minds to perceive. Yet later biologists have been able to witness flashes of evolutionary c

2、hange. In the late 1980s, for example, biologist David Reznick began to use the guppies that swim in the streams of Trinidad forests in natural experiment. At lower elevations these guppies face the assault of predatory fishes, but the ones in higher waters live in peace because few of the predators

3、 can move upstream past the waterfalls and craggy rocks.Like all animals, guppies have a timetable for their lives - how long they take to reach sexual maturity how fast they grow during that time, how long they live as adults. Theoretical biologists have predicted that the life history of animals c

4、an evolve if mutations that alter it bring the animals more reproductive success. Reznick put their predictions to the test.In ponds with a lot of predators, guppies that grow fast should be more successful than slow-growing ones. With the threat of death hanging over a guppy, it will grow as quickl

5、y as possible so that it can start mating as soon as possible and have as many offspring as possible. Of course, the strategy comes with a heavy price. By growing so quickly, a guppy may shorten its own natural life span, and by quickly giving birth to babies, female guppy cannot take time to suppor

6、t her offspring with energy, which put them at risk of dying young. But Reznick reasoned, that the threat ,of an early death offset by other risk.To see whether this trade-off was real, Reznick relocated guppies that were being terrorized in the downstream by putting them in pools with relatively fe

7、w predators. Eleven years in these conditions produced guppies that were, on average, in less of a rush. They took 10 percent longer to mature than their ancestors and were over 10 percent heavier by the time they were fully grown. They were also laying smaller broods of eggs. but each of the new gu

8、ppies that hatched from those was bigger.nSometimes nature runs evolutionary experiments of its own without any help from humans whatsoever. nIn 1973 Peter and Rosemary Grant, husband-and-wife biologists, arrived on the Galapagos Islands to study the effects of natural selection on the birds. Most y

9、ears on the Galapagos, the weather follows a standard pattern. nFor the first five months of the years it is hot and rainy, followed by a cool, dry period. nBut in 1977 the wet season never came. A periodic disturbance of the Pacific ocean called La Nina altered weather patterns over the Galapagos,

10、causing a disastrous drought.On Daphne Island, where the Grants worked, the drought was lethal. Out of the 1,200 medium ground finches Geospiza fortis that lived on the Island, more that 1,000 died. But the Grants discovered that the decimation was not random. G fortis lives mainly on seeds, which i

11、t cracks with its strong beak. Small G. fontis can break only small seeds, but larger birds have beaks that are strong enough to break big ones. The drought had lingered for a few months, the small finches ran out of small seeds and began dying off. But the big finches managed to survive, because th

12、ey could eat seeds that the smaller ones couldnt get to. (In particular, they depended on a plant called caltrop, which grows spiked shells to protect it seeds).The survivors on the 1977 drought mated in 1978, and the Grants could see evolutions mark on their offspring. A new generation of G. fortis

13、 was born, and the Grants student Peter Boag discovered that, on average, their beaks were 4 percent larger than those of the previous generation. The big-beaked finches, which had fared better during the drought had put their trait to their offspring, altered the profile of the population.In the ye

14、ars since the drought the finches changed. In 1983, for example, there was a season of heavy rain, abundant seeds favored finches with smaller beaks and Grants found that by 1985 their average size had dropper 5 percent. The finches can change quickly, but it seems that are swinging back and forth l

15、ike a pendulum.中文大意：关于natural selection，Darwin认为是长期且渐进的。后来，科学家却在短时间内目击witness(词汇题)到进化。接着用两个relatively short evolutions examples 来support natural selection。1st，人为控制条件。有一种鱼guppy，在predator多的时候，长得快，但代价是life-span变短。不过研究人员认为，这代价被其他危险抵销offset(词汇题)了。然后，再将一部分放入predator少的pool中，offspring发生了很多changes，比如比它们的ance

16、stor size上要大，下egg少了，等等。2ed，自然条件变化。我们需要做的只是observe。讲的是finch，有关它们beak的大小的。又举了一个bird的例子。一对夫妇学者在一个群鸟研究一种雀鸟，有一年岛上发生致命的lethal(词汇题)干旱，他们发现，当干旱 (drought)时，鸟的大量死亡decimation(词汇题)并不是随机的。那些有大而硬的beak的bird往往能生存下来，这样一来这一地区的 这种bird很快都有了大而硬的beak。干旱的时候小种子少，嘴小的鸟死了，嘴长的鸟存活。存活的鸟和第二年的鸟交配，后代的鸟嘴整体变长。雨量又充足 的时候，又足够小种子，这个时候，新出

17、生的鸟的鸟嘴又变短了。考题：(1) According to paragraph 1, compared to the views of modern biologists, Darwins view of natural selection was limited by his belief that答案：(A) natural selection only occurred over a very long period of time IS- natural selection could only be witnessed in some species(2)The word witn

18、ess in the passage is closest in meaning to答案：(A) observe(3)The word offset in the passage in meaning to答案：(D) balanced(4)Which of the following reason is mentioned in paragraph 3 to explain why growing fast is an advantage for guppies that live in ponds with many predators答案：(A) They will product m

19、ore offspring.(5)What is the authors primary in presenting the information in paragraph 3答案：(C) To explain Reznicks reasoning about why it would be an advantage for guppies with predators to mature quickly(6)All of the following are mentioned in paragraph 4 as change in the guppy population eleven y

20、ears after guppies were transferred to upstream ponds EXCEPT答案：(B) More offspring were produced.(7)The word lethal in the passage is closest in meaning to答案：(C) deadly(8)The word decimation in the passage is closest in meaning to答案：(A) destruction(9)According to paragraph 6, what disadvantage did sm

21、all-beaked finches have compared to large-beaked fiches答案：(A) Small-beaked finches were not able to crack open the large seeds.(10)According to paragraph 7, the new generation of G. fortis on average differed from earlier population in答案：(B) the size of their beaks(11)According to paragraph 8, how s

22、hort-term changes to the environment affect the r natural election of traits in G. fortis答案：(A) Short-term changes result in quick reversals of the trait selected.(12)How were the results of the natural experiment with the finches similar to the results of Reznicks experiment with the guppies答案：(B)

23、In both cases, evolutionary changes occurred in a relatively short period of time.(13)Look at the four squares that indicate where the following sentence could be added to the passage.In such case, if biologists are lucky enough to be present, they simply have to observe.答案：(B) 第二个方块。(14)总结题。Evoluti

24、onary changes resulting from changes in the environment can occur in relatively short period on time.Guppies taken from upstream pools and precede in downstream pools produced offspring that had significantly shorter life spans.The survival of finches with big beaks during a severe drought in Galapa

25、gos resulted in more big beaks finches in the next generation.背景知识补充：Reznicks experimentGuppies are small fresh-water fish that biologists have studied for long.A UC Riverside-led research team has found that as some populations of an organism evolve a longer lifespan, they do so by increasing only

26、that segment of the lifespan that contributes to fitness the relative ability of an individual to contribute offspring to the next generation.Focusing on guppies, small fresh-water fish biologists have studied for long, the researchers found that guppies living in environments with a large number of

27、 predators have adapted to reproduce earlier in life than guppies from low-predation localities. Moreover, when reproduction ceases, guppies from high-predation localities are far older, on average, than guppies from low-predation localities, indicating that high-predation guppies enjoy a long repro

28、ductive period the time between first and last reproduction.The study supports the controversial hypothesis that natural selection the process in nature by which only organisms best adapted to their environment tend to survive and pass on their genetic characters in increasing numbers to succeeding

29、generations introduces changes in only a specific segment of an organisms lifespan.The Grants observationThe Galapagos finches have been intensely studied by biologists Peter and Rosemary Grant since 1973.The Grants have done nothing less than witness Darwins theory of evolution unfold before their

30、eyes. That would have stunned Darwin, who thought natural selection operated over vast periods of time and couldnt be observed.In their natural laboratory, the 100-acre island called Daphne Major, the Grants and their assistants watched the struggle for survival among individuals in two species of s

31、mall birds called Darwins finches. The struggle is mainly about fooddifferent types of seedsand the availability of that food is dramatically influenced by year-to-year weather changes.The Grants wanted to find out whether they could see the force of natural selection at work, judging by which birds

32、 survived the changing environment.Natural selection at its most powerful winnowed certain finches harshly during a severe drought in 1977. That year the small, soft seeds were quickly exhausted by the birds, leaving mainly large, tough seeds that the finches normally ignore. Under these drastically changing conditions, the struggle to survive favored the larger birds with deep, strong beaks for opening the hard seeds.Smaller finches with less-powerful beaks perished.The Grants found that the offspring of the birds that survived the