小站备考
托福
托福阅读
Official45阅读真题

OFFICIAL45 According to paragraph 5, how did Dale Guthrie use the information about radiocarbon analysis of bones fromBeringian deposits?

展开
The Beringia Landscape
Tip:单击查看句义;划选/双击查生词
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.

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

你的答案:
正确答案:C
题目解析:
 后才能查看题目解析,还没有账号? 马上注册
【题目翻译】根据第5段,Dale Guthrie是如何利用来自贝林根沉积物的骨骼的放射性碳分析的信息的? A:建议Col.ux应该用不同的方法测定冰河期湖泊沉积物中的花粉量。 B:认为大型贝林根哺乳动物一定吃了花粉很少的植物,如果有的话。 C:表明从冰河湖沉积物花粉分析中得出的结论是不正确的。 D:解释为什么所谓的极地沙漠不能养活像猛犸、马和野牛这样的大型动物。 【判定题型】:题目问的是文章中的具体细节信息,故根据题目问法可以判断本题为事实信息题。 【关键词定位】:根据关键词“adiocarbon analysis”,定位到Passage 5 ,原句为“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.”,意思是“Guthrie反对这种观点,他指出,对来自贝林根矿床的猛犸、马和野牛骨骼的放射性碳分析显示,这些骨骼可以追溯到最强烈的冰川作用时期。”。 【逻辑分析】根据原文,Dale Guthrie是反对Paul Colinvaux所得出的这个地区不可能养活一大群哺乳动物这个结论。因为Dale Guthrie从对一些动物的放射性的分析中发现:mammoth, horse and bison bones是确实存在于intense glaciation时期的,也就是他认为Paul Colinvaux的结论是错误的。 【选项分析】 A:未提到不同方法,故错误。 B:文章没有直接提到哺乳动物和花粉少得植物的直接关系。故错误。 C:符合文意,正确。 D:没有做解释,而是提出了他自己的论点。故错误。

学习页面

Medi

terr

anean

加强 + 政府 + 名词后缀

加强的政府——管理

原文例句

加入生词

本文生词 0

色块区域是你收藏过的生词;

查询次数越多,颜色越深哦~

显示文中生词

登录后才能收藏生词哦,现在登录注册>

本文重点词 45

文中加粗单词为本文重点词;

根据词频与核心词范围精心挑选,托福考试必掌握词汇。

显示文中重点词
学习本文词汇

文中划选/双击的生词、加粗重点词已收纳至词盒

可随时点击词盒查看哦~

只有在词句精学模式下才能开启词盒功能哦~

我知道了

词盒
收藏
笔记
我的笔记
5000
保存
反馈