托福阅读常考话题及练习题推荐二：恐龙大灭绝（2）

1托福阅读常考话题-恐龙大灭绝练习题

Paragraph1: Dinosaurs rapidly became extinct about 65 million years ago as part of a mass extinction known as the K-T event, because it is associated with a geological signature known as the K-T boundary, usually a thin band of sedimentation found in various parts of the world (K is the traditional abbreviation for the Cretaceous, derived from the German name Kreidezeit). Many explanations have been proposed for why dinosaurs became extinct. For example, some have blamed dinosaur extinction on the development of flowering plants, which were supposedly more difficult to digest and could have caused constipation or indigestion—except that flowering plants first evolved in the Early Cretaceous, about 60 million years before the dinosaurs died out. In fact, several scientists have suggested that the duckbill dinosaurs and horned dinosaurs, with their complex battery of grinding teeth, evolved to exploit this new resource of rapidly growing flowering plants Others have blamed extinction on competition from the mammals, which allegedly ate all the dinosaur eggs—except that mammals and dinosaurs appeared at the same time in the Late Triassic, about 190 million years ago, and there is no reason to believe that mammals suddenly acquired a taste for dinosaur eggs after 120 million years of coexistence. Some explanations (such as the one stating that dinosaurs all died of diseases) fail because there is no way to scientifically test them, and they cannot move beyond the realm of speculation and guesswork.

1. In paragraph 1, why does the author include a discussion of when flowering plants evolved?

A. To help explain why some scientists believe that the development of flowering plants led to dinosaur extinction

B. To cast doubt on the theory that the development of flowering plants caused dinosaurs to become extinct

C. To suggest that dinosaurs were able to survive for as long as they did because of the availability of flowering plants

D. To emphasize that duckbill dinosaurs and horned dinosaurs were the first dinosaurs to become extinct

2. The word “allegedly” in the passage is closest in meaning to

A. inevitably

B. gradually

C. supposedly

D. increasingly

3. According to paragraph 1 the extinction of the dinosaurs is unlikely to have been the result of competition from mammals because

A. mammals would not have been capable of eating dinosaur eggs

B. mammals did not appear in any significant numbers until after the Late Triassic

C. mammals and dinosaurs did not, in fact, compete for any of the same resources

D. mammals and dinosaurs lived together for roughly 120 million years before the extinction

Paragraph 2: This focus on explaining dinosaur extinction misses an important point: the extinction at the end of the Cretaceous was a global event that killed off organisms up and down the food chain. It wiped out many kinds of plankton in the ocean and many marine organisms that lived on the plankton at the base of the food chain. These included a variety of clams and snails, and especially the ammonites, a group of shelled squidlike creatures that dominated the Mesozoic seas and had survived many previous mass extinctions. The K-T event marked the end of the marine reptiles, such as the mosasaurs and the plesiosaurs, which were the largest creatures that had ever lived in the seas and which ruled the seas long before whales evolved. On land, there was also a crisis among the land plants, in addition to the disappearance of dinosaurs. So any event that can explain the destruction of the base of the food chain (plankton in the ocean, plants on land) can better explain what happened to organisms at the top of the food chain, such as the dinosaurs. By contrast, any explanation that focuses strictly on the dinosaurs completely misses the point. The Cretaceous extinctions were a global phenomenon, and dinosaurs were just a part of a bigger picture.

4. According to paragraph 2, what is problematic about some scientists' focus on dinosaur extinction?

A. Dinosaurs became extinct so long ago that no theory about their disappearance can be proven scientifically.

B. Dinosaurs were not the only organisms that went extinct at the end of the Cretaceous period.

C. More marine organisms went extinct during the Cretaceous than did dinosaur species.

D. It is more important to understand how plankton and other marine organisms came to thrive during the Cretaceous period.

5. According to paragraph 2, each of the following became extinct during the K-T event EXCEPT

A. early species of whales

B. marine reptiles

C. various species of clams

D. many species of land plants

6. What makes the extinction of “the ammonites” especially significant?

A. They were among the largest creatures that ever lived.

B. They existed at the lowest level of the food chain.

C. They had been able to survive in the Mesozoic seas.

D. They had survived many previous mass extinctions.

7. The word “halted” in the passage is closest in meaning to

A. slowed

B. stopped

C. contracted

D. declined

8. The word “strictly" in the passage is closest in meaning to

A. exclusively

B. mainly

C. initially

D. wrongly

9. The word “crisis” in the passage is closest in meaning to

A. collapse

B. disturbance

C. critical situation

D. loss