托福阅读真题Official 45 Passage 1（三）

托福阅读真题Official 45 Passage 1（三）

The Beringia Landscape

During the peak of the last ice age,northeast Asia(Siberia)and Alaska were connected by a broad land mass called the Bering Land Bridge.This land bridge existed because so much of Earth’s water was frozen in the great ice sheets that sea levels were over 100 meters lower than they are today.Between 25,000 and 10,000 years ago,Siberia,the Bering Land Bridge,and Alaska shared many environmental characteristics.These included a common mammalian fauna of large mammals,a common flora composed of broad grasslands as well as wind-swept dunes and tundra,and a common climate with cold,dry winters and somewhat warmer summers.The recognition that many aspects of the modern flora and fauna were present on both sides of the Bering Sea as remnants of the ice-age landscape led to this region being named Beringia.

It is through Beringia that small groups of large mammal hunters,slowly expanding their hunting territories,eventually colonized North and South America.On this archaeologists generally agree,but that is where the agreement stops.One broad area of disagreement in explaining the peopling of the Americas is the domain of paleoecologists,but it is critical to understanding human history:what was Beringia like?

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.

The presence of mammal species that require grassland vegetation has led Arctic biologist Dale Guthrie to argue that while cold and dry,there must have been broad areas of dense vegetation to support herds of mammoth,horse,and bison.Further,nearly all of the ice-age fauna had teeth that indicate an adaptation to grasses and sedges;they could not have been supported by a modern flora of mosses and lichens.Guthrie has also demonstrated that the landscape must have been subject to intense and continuous winds,especially in winter.He makes this argument based on the anatomy of horse and bison,which do not have the ability to search for food through deep snow cover.They need landscapes with strong winds that remove the winter snows,exposing the dry grasses beneath.Guthrie applied the term“mammoth steppe”to characterize this landscape.

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.

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.

Question 5 of 14

The word“continuous”in the passage is closest in meaning to

A.unpredictable

B.very cold

C.dangerous

D.uninterrupted

正确答案：D

题目详解

题型分类：词汇题

选项分析：

词汇所在句Guthrie还证明，这一景象必须受到强烈和continuous风的影响，尤其是在冬天”，而可以从后一句得知白令陆桥没有很深的积雪。D选项uninterrupted意思为“连续的、不间断的”，符合语境。continuous原意为“持续的”。

A选项unpredictable不可预知的。

B选项very cold很寒冷的。

C选项dangerous危险的。

Question 6 of 14

Which of the sentences below best expresses the essential information in the highlighted sentence in the passage?Incorrect choices change the meaning in important ways or leave out essential information.

A.According to biologist Dale Guthrie,mammal species require broad areas of vegetation to survive.

B.Dale Guthrie is an Arctic biologist who argued that broad areas of dense vegetation were surely enough to attract mammals such as mammoth,horse,and bison to Beringia.

C.Dale Guthrie argued that Beringia,though cold and dry,must have had enough dense vegetation to support the herds of mammoth,horse,and bison that lived there.

D.As long as Beringia was cold and dry,argued Dale Guthrie,dense vegetation grew in order to support the herds of mammoth,horse,and bison—the mammal species present there.

正确答案：C

题目详解

题型分类：简化句子题

原文分析：句子主干为The presence of mammal species has led Dale Guthrie to argue there must have been broad areas of dense vegetation to support herds of mammoth,horse,and bison。句子大意：哺乳动物的存在让Dale Guthrie认为即使寒冷且干燥，也一定有足够密集的植被来养活那些哺乳动物。

选项分析：

C选项大意为“Dale Guthrie认为白令陆桥即使寒冷干燥，也一定有足够密集的植被来养活那些哺乳动物”与原句意义符合。

A选项mammal species require broad areas of vegetation to survive为原句的前提条件部分，不是Dale Guthrie根据前提条件得出的结论。逻辑错误。

B选项attract mammals无中生有。

D选项as long as意为“只要”，而原文是while意思为“即使”，逻辑错误。