小站备考
托福
托福听力
Official24听力真题

托福official24听力lecture3 Megafauna原文解析+翻译音频

展开
Tip:单击查看句义;划选/双击查生词

[00:00.00]NARRATOR: Listen to part of a lecture in an archaeology class.[00:06.56]FEMALE PROFESSOR: Between 11,000 and 10,000 B.C.E., North America was populated by a wide variety of great beasts like mammoths and mastodons—both elephant-like creatures with big tusks—and camels, giant sloths...mm, the list goes on...[00:26.81]By about 10,000 B.C.E., all those giant creatures, the megafauna of North America, were gone. [00:34.21]Uh, we don't know exactly what happened to them, but there are some theories.[00:38.39] One theory is that they were hunted to extinction by humans. [00:42.14]The humans who coexisted with these giant species in North America at that time were what we today call the Clovis people.[00:50.49]And there's a Clovis site in a valley in Southern California where the remains of thirteen mammoths were found. [01:02.97]And spear points, tools for processing meat, and fireplaces.
[01:08.44]That would appear to be some pretty compelling evidence. [01:11.71]Mammoth bones have also been found at some other Clovis sites...[01:15.60]But then, at other Clovis sites, uh, there's also a lot of evidence that the Clovis people mostly gathered plants and hunted small game, like rabbits and wild turkeys...
[01:27.19] Also, there are several places in North America where you have natural accumulations of mammoth bones—uh, that look very similar to the accumulations at the Clovis sites, except there's no human debris—where the mammoths almost certainly died as the result of some kind of natural disaster...[01:44.15]So I think it's quite likely that those thirteen mammoths in Southern California also died of natural causes...and that the Clovis people simply took advantage of the situation.[01:55.90]Um, OK, that's the hunting theory.
[01:59.19]Now let's look at another theory—uh, an alternative to the hunting theory—the climate change theory. [02:06.01]At around 11,500 B.C.E., the world was coming out of an ice age. [02:20.49]And with that came increased seasonality; that is, the summers became warmer and the winters actually became colder. [02:28.29]These extreme shifts would have put a lot of stress on the bodies of animals that were used to a more moderate range of temperatures.
[02:36.63]But the most important impact of this increased seasonality may very well have been its effect on the distribution of plants. [02:44.89]Today we take for granted that there are horizontal bands of plant communities: [02:50.19] in the far north is tundra, which gives way to forest as you move southward, [02:55.12] and even farther south, grasslands take over. [02:58.37]But during the ice age, these plant communities actually grew together, mixed with one another. [03:05.15] So ice-age animals had access to many different types of plants, different types of food.
[03:11.63] But when the seasons became more distinct, the plant communities were pulled apart. That meant that in any given area there was less plant diversity. [03:21.76]And as a result, uh, so the theory goes, the ice-age animals that depended on plant diversity couldn't survive...[03:29.94]and the great beasts were the ones that needed the most diversity in their diet.[03:35.09]Again, we have what at first seems like a pretty attractive theory...But then, how do you explain the fact that this had happened before—[03:44.26]you know, global cooling followed by global warming—and there was no extinction then...
[03:50.32] Uh, you know, I recently read an interesting article about an archaeologist who tried to solve this puzzle with the help of his computer. [03:58.46] What he did was, he wrote a computer program to simulate what would happen to mammoths under certain conditions; [04:05.72]um, say, for example, there's a drought for a couple of decades; or, uh, hunters are killing off 5 percent of the population, and so on...
[04:14.71]One thing he found was that humans didn't necessarily have to kill these animals in great numbers in order to nudge them toward extinction. [04:23.87]That's because very large animals have a slow rate of reproduction, so all you have to do is remove a few young females from the herd, and you can—fairly quickly—significantly reduce the population...
[04:36.06] And then he came up with a scenario that combined some hunting by humans with some environmental stress—and bang! [04:44.00]The simulated mammoths were extinct within decades. [04:47.52]So it seems the mixture of hunting and climate change is a likely scenario...[04:53.66]Uh, of course, computer simulations are not a substitute for hard evidence...

1.What is the lecture mainly about?

你的答案:
正确答案:D
题目解析:
 后才能查看题目解析,还没有账号? 马上注册
By about 10,000 B.C.E., all those giant creatures, the Metgauna of North America were gone. We don't know exactly what happened to them, but there are some theories. 在文章开头部分先介绍相关的背景知识,提到物种灭绝,然后信号词but后再给出今天的主旨,提到some theories. 后文介绍了两种,一种是hunted to extinction by human 另一种是climate change theory. 最后说到两者的相互作用。D选项中的explanation 还有disappearance 与原文最为吻合,是对全文主旨最准确的概括。

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