达尔文进化论

Observing Natural Selection Paragraph1 Witnessing natural selection would not seem possible to Darwin because he assumed natural selection was too slow and gradual for short-term minds to perceive. Yet later biologists have been able to witness flashes of evolution 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 few of predators can move upstream past the waterfall and craggy rocks. 1. According to paragraph1, compared to the views of modern biologists, Darwin’ s view of natural selection was limited by his belief that A. Natural selection only occurred over a very long period of time B. Natural selection could only be witnessed in some species C. We could also be able to witness flashes of evolution change which is called natural selection D. Darwin assumed that natural selection is more likely to be observed in certain species. 2. The word “witness” in the passage is closest in meaning to A. observeB. occupyC. resumeD. pursue Paragraph2 Like all animals, guppies have a timetable for their liveshow 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. Paragraph3 In ponds with a lot of predators, guppies that grow fast should be more successful than slow-growing ones. With the treat 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 puppy 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. 3. The word “offset” in the passage is closest in meaning to A. offloadB. overlapC. overrunD. counteract 4. Which of the following reason is mentioned in paragraph3 to explain why growing fast is an advantage for guppies that live in ponds with many predators A. they are more successful in reproduction B. they have more food and energy C. they will produce more offspring. D. they could do better in feeding their young 5. What is the author’s primary in presenting the ination in paragraph 3 A. to give an example of how could a predator evolve in different environment B. to refute Darwin’s evolutionary theory C. to explain Reznick’s reasoning about why it would be an advantage for guppies with predators to mature quickly. D. to illustrate a common phenomenon of fishes in ponds Paragraph4 To see whether