托福阅读真题Official 45 Passage 1（四）

托福阅读真题Official 45 Passage 1（四）

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 7 of 14

According to paragraph 4,Guthrie believes that the teeth of ice-age fauna support which of the following conclusions?

A.Large mammals would not have been able to survive in the Beringian landscape.

B.Grasslands were part of the Beringian landscape.

C.Strong winds exposed dry grasses under the snow.

D.Horses and bison did not have the ability to search for food through deep snow cover.

正确答案：B

题目详解

题型分类：事实信息题

原文定位：根据teeth定位到第四段第二句

选项分析：

B选项Grasslands对应定位句grasses and sedges，B选项正确。

A选项not have been able to survive与第一句The presence of mammal species矛盾，根据本文讨论对象，这些存在的哺乳动物里有大型动物。

C选项与倒数第一句有关，但是C选项观点的证据出自倒数第二句based on the anatomy of horse and bison，而不是the teeth of ice-age fauna。

D选项与倒数第二句有关，与the teeth of ice-age fauna无关。

Question 8 of 14

According to paragraph 4,which of the following statements is true of the relationship between ice-age Beringian animals and their environment?

A.When present in sufficient quantities,lichens and mosses provide enough nutrients to satisfy the needs of herds of large mammals.

B.The anatomy of certain animals present in that environment provides information about the intensity of winds there at that time.

C.The structure of the teeth of most ice-age fauna indicates that they preyed on animals such as the mammoth,horse,and bison.

D.Horses and bison are large enough that their feet can easily penetrate deep snow and uncover areas where they can feed on plant material.

正确答案：B

题目详解

题型分类：事实信息题

原文定位：第四段整段都在讲环境和ice-age Beringian animals的关系，根据选项定位

选项分析：

B选项出自第三句和第四句，The anatomy of certain animals对应第四句based on the anatomy of horse and bison，the intensity of winds对应第三句intense and continuous winds。

A选项，lichens and mosses provide enough nutrients与第二句could not have been supported by a modern flora of mosses and lichens矛盾。

C选项，they preyed on animals与第二句had teeth that indicate an adaptation to grasses and sedges矛盾。

D选项，penetrate deep snow与倒数第二句not have the ability to search for food through deep snow cover矛盾。

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