托福閱讀真題Official 45 Passage 2（六）

托福閱讀真題Official 45 Passage 2（六）

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 11 of 14

The phrase“no wonder”in the passage is closest in meaning to

A.unsurprising

B.understandable

C.well-known

D.unfortunate

正確答案：A

題目詳解

題型分類：詞匯題

選項分析：

詞匯所在句“有這些花粉在空氣中漂浮，it is no wonder風媒傳粉的樹是過敏的主要來源”。由這句開頭的since可知，逗號前后為因果關系，A選項unsurprising意思為“不令人吃驚的”，符合語境。wonder原意為“驚訝；驚奇；驚異；驚嘆”。

B選項understandable可以理解的。

C選項well-known出名的。

D選項unfortunate不幸的。

因此，選項A符合題干詞意。

Question 12 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.Because smaller particles tend to stay trapped in the fast-moving air,they are blown much farther than other grains.

B.Smaller particles are trapped by the stigma when fast-moving air flows past it.

C.Small particles that are whisked past the waiting stigma gain speed and are often trapped in the fast-moving air.

D.While smallness helps pollen travel farther,it also makes it more likely to be blown past the stigma.

正確答案：D

題目詳解

題型分類：簡化句子題

原文分析：考察識別主干內容和核心邏輯的能力，注意原句的but，前后為轉折關系。句子大意為小顆?？赡軙淮颠h但也可能被風吹過花的柱頭。

選項分析：

D選項while對應原句的but，為轉折關系。travel farther對應原句be blown farther，past the stigma對應原句past the waiting stigma。D選項邏輯關系和內容都與原句對應，正確。

A選項因果關系不正確，trapped in the fast-moving air的結果是prone to be whisked past the waiting stigma，而不是blown much farther。

B選項沒有轉折關系。

C選項gain speed無中生有。

>> 雅思 托福 免費測試、量身規(guī)劃、讓英語學習不再困難<<