托福阅读常考话题及练习题推荐四：冰川（3）

► Paragraph 5：In contrast, Paul Colinvaux has offered a counterargument based on the analysis of pollen in lake sediments dating to the last ice age. He found that the amount of pollen recovered in these sediments is so low that the Beringian landscape during the peak of the last glaciation was more likely to have been what he termed a “polar desert,” with little or only sparse vegetation. In no way was it possible that this region could have supported large herds of mammals and thus, human hunters. Guthrie has argued against this view by pointing out that radiocarbon analysis of mammoth, horse, and bison bones from Beringian deposits revealed that the bones date to the period of most intense glaciation.

9. In paragraph 5, the amount of pollen in Beringian Lake sediments from the last ice age is used to explain

A. how long the ice age lasted

B. how important pollen is as a source of food

C. how many different kinds of plants produce pollen

D. how little vegetation must have been present at that time

10. According to paragraph 5, how did Dale Guthrie use the information about radiocarbon analysis of bones from Beringian deposits?

A. To suggest that Colinvaux should have used different methods to measure the amount of pollen in ice-age lake sediments

B. To argue that the large Beringian mammals must have eaten plants that produce little, if any, pollen

C. To show that the conclusions that Colinvaux drew from the analysis of pollen in ice-age lake sediments cannot be correct

D. To explain why so-called polar deserts are incapable of supporting such large animals as mammoth, horse, and bison

► Paragraph 6：The argument seemed to be at a standstill until a number of recent studies resulted in a spectacular suite of new finds. The first was the discovery of a 1,000-square-kilometer preserved patch of Beringian vegetation dating to just over 17,000 years ago—the peak of the last ice age. The plants were preserved under a thick ash fall from a volcanic eruption. Investigations of the plants found grasses, sedges, mosses, and many other varieties in a nearly continuous cover, as was predicted by Guthrie. But this vegetation had a thin root mat with no soil formation, demonstrating that there was little long-term stability in plant cover, a finding supporting some of the arguments of Colinvaux. A mixture of continuous but thin vegetation supporting herds of large mammals is one that seems plausible and realistic with the available data.

11. The word “plausible” in the passage is closest in meaning to

A. preferable

B. practical

C. reasonable

D. advantageous

► Paragraph 6：The argument seemed to be at a standstill until a number of recent studies resulted in a spectacular suite of new finds. The first was the discovery of a 1,000-square-kilometer preserved patch of Beringian vegetation dating to just over 17,000 years ago—the peak of the last ice age. The plants were preserved under a thick ash fall from a volcanic eruption. Investigations of the plants found grasses, sedges, mosses, and many other varieties in a nearly continuous cover, as was predicted by Guthrie. But this vegetation had a thin root mat with no soil formation, demonstrating that there was little long-term stability in plant cover, a finding supporting some of the arguments of Colinvaux. A mixture of continuous but thin vegetation supporting herds of large mammals is one that seems plausible and realistic with the available data.

12. Which of the following best describes the organization of paragraph 6?

A. Two contrasting views are presented, and a study that could decide between them is proposed.

B. An argument is offered, and reasons both for and against the argument are presented.

C. A claim is made, and a study supporting the claim is described.

D. New information is presented, and the information is used to show that two competing explanations can each be seen as correct in some way.

► Paragraph 3：The Beringian landscape was very different from what it is today. .■ Broad, windswept valleys; glaciated mountains; sparse vegetation; and less moisture created a rather forbidding land mass. .■This land mass supported herds of now-extinct species of mammoth, bison, and horse and somewhat modern versions of caribou, musk ox, elk, and saiga antelope. .■These grazers supported in turn a number of impressive carnivores, including the giant short-faced bear, the saber-tooth cat, and a large species of lion.■

13. Look at the four squares [ ■ ] that indicate where the following sentence could be added to the passage. Where would the sentence best fit?

Nevertheless, large animals managed to survive in Beringia.

14. An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage.

During the last ice age, human hunters pursued large mammals across Beringia, a land whose climatic characteristics have been in dispute.

Answer Choices

A. Strong evidence indicates that large mammals like mammoth and bison survived in the harsh ice-age Beringian landscape.

B. Beringian mammals crossed easily from northeastern Asia to Alaska across the Bering Land Bridge, though there are indications that they usually went back to Asia for the brief, but warm, summers.

C. Carnivores such as the saber-tooth cat were primarily responsible for the disappearance of the largest of the grazing animals, but the harsh winters caused some grazers to die of starvation.

D. Analyses of ice-age sediments uncovered very small amounts of pollen, suggesting that Beringia lacked the quantity of vegetation needed to support large herds of mammals.

E. The discovery that grasses, sedges, and mosses survived under the thick ash from a large volcanic eruption proved that the ice-age Beringian plant cover was extremely resistant to climatic extremes.

F. Recent discoveries suggest that shallow-rooted plants created a fairly continuous cover over ice-age Beringia, though the cover most likely was variable and uncertain in any one location.