Question

Read the following passage and mark the letter A, B, C or D to indicate the correct answer to each of the questions from 43 to 50.

It is estimated that over 99 percent of all species that ever existed have become extinct. What causes extinction? When a species is no longer adapted to a changed environment, it may perish. The exact causes of a species' death vary from situation to situation. Rapid ecological change may render an environment hostile to a species. For example, temperatures may change and a species may not be adapted. Food resources may be affected by environmental changes, which will then cause problems for a species requiring these resources. Other species may become better adapted to an environment, resulting in competition and, ultimately, in the death of a species.

The fossil record reveals that extinction has occurred throughout the history of Earth. Recent analyses have also revealed that on some occasions many species became extinct at the same time - a mass extinction. One of the best-known examples of mass extinction occurred 65 million years ago with the demise of dinosaurs and many other forms of life. Perhaps the largest mass extinction was the one that occurred 225 million years ago, when approximately 95 percent of all species died. Mass extinctions can be caused by a relatively rapid change in the environment and can be worsened by the close interrelationship of many species. If, for example, something were to happen to destroy much of the plankton in the oceans, then the oxygen content of Earth would drop, even affect organisms not living in the oceans. Such a change would probably lead to a mass extinction.

One interesting, and controversial, finding is that extinctions during the past 250 million years have tended to be more intense every 26 million years. The periodic extinction might be due to intersection of the earth's orbit with a cloud of comets, but this theory is purely speculative. Some researchers have also speculated that extinction may often be random. That is, certain species may be eliminated and others may survive for no particular reason. A species' survival may have nothing to do with its ability or inability to adapt. If so, some of revolutionary history may reflect a sequence of essentially random events.

Why is "plankton" mentioned?

A. to illustrate a comparison between organisms that live on the land and those that live in the ocean

B. to point out that certain species could never become extinct.

C. to demonstrate the interdependence of different species

D. to emphasize the importance of food resources in preventing mass extinction.

Answer 1

Đáp án C

Dịch nghĩa: Tại sao “plankton” - sinh vật phù du lại được đề cập?

A. để so sánh giữa những sinh vật sống trên cạn và sinh vật sống dưới biển

B. để chỉ ra rằng một số loài nhất định có thể sẽ không bao giờ tuyệt chủng

C. để chứng minh sự phụ thuộc lẫn nhau của các loài khác nhau

D. để nhấn mạnh sự quan trọng của nguồn thức ăn trong việc hạn chế tuyệt chủng hàng loạt

Giải thích: Thông tin nằm ở “. . .can be worsened by the close interrelationship of many species. If, for example, something were to happen to destroy much of the plankton in the oceans, then the oxygen content of Earth would drop, even alfect organisms not living in the oceans. Such a change would probably lead to a mass extinction” Tác giả nói về sự tuyệt chủng hàng loạt có thể gây ra bởi thay đổi môi trường sống, và sự phụ thuộc lẫn nhau khiến nó tệ hơn nữa. Sau đó, tác giả nói về việc các sinh vật phù du chết ảnh hưởng đến lượng oxy, rồi ảnh hưởng đến các loài không sống trong đại dương. Đây chính là mối liên hệ giữa các loài.