托福考試閱讀加試之達(dá)爾文進(jìn)化論(原文).pdf

托?？荚囬喿x加試之達(dá)爾文進(jìn)化論 原文 Observing Natural Selection Witnessing 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 change 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 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 can 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 quickly 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 support 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 few 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 guppies 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 years 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 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 it 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 they could eat seeds that the smaller ones couldn t 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 evolution s mark on their offspring A new generation of G fortis 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 years 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 like a pendulum 中文大意 關(guān)于natural selection Darwin認(rèn)為是長(zhǎng)期且漸進(jìn)的 后來(lái) 科學(xué)家卻在短時(shí)間內(nèi)目擊witness 詞匯題 到進(jìn)化 接著用兩個(gè)relatively short evolution s examples 來(lái)support natural selection 1st 人為控制條件 有一種魚(yú)guppy 在predator多的時(shí)候 長(zhǎng)得快 但代價(jià)是life span變短 不過(guò)研究人員認(rèn)為 這代價(jià)被其他危險(xiǎn)抵銷offset 詞匯題 了 然后 再將一部分放入predator少的pool中 offspring發(fā)生了很多changes 比如比它們的ance stor size上要大 下egg少了 等等 2ed 自然條件變化 我們需要做的只是observe 講的是finch 有關(guān)它們beak的大小的 又舉了一個(gè)bird的例子 一對(duì)夫婦學(xué)者在一個(gè)群鳥(niǎo)研究一種雀鳥(niǎo) 有一年島上發(fā)生致命的lethal 詞 匯題 干旱 他們發(fā)現(xiàn) 當(dāng)干旱 drought 時(shí) 鳥(niǎo)的大量死亡decimation 詞匯題 并不是隨機(jī)的 那 些有大而硬的beak的bird往往能生存下來(lái) 這樣一來(lái)這一地區(qū)的這種bird很快都有了大而硬的bea k 干旱的時(shí)候小種子少 嘴小的鳥(niǎo)死了 嘴長(zhǎng)的鳥(niǎo)存活 存活的鳥(niǎo)和第二年的鳥(niǎo)交配 后代的鳥(niǎo) 嘴整體變長(zhǎng) 雨量又充足的時(shí)候 又足夠小種子 這個(gè)時(shí)候 新出生的鳥(niǎo)的鳥(niǎo)嘴又變短了 考題 1 According to paragraph 1 compared to the views of modern biologists Darwin s 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 witness 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 more offspring 5 What is the author s primary in presenting the information in paragraph 3 答案 C To explain Reznick s 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 years 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 small 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 short 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