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托福TPO-10 Lecture 1

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Narrator:Listen to part of a lecture in a Marine Biology Class

独白:听下面一段海洋生物学的讲座。
Professor:We know whales are mammals and that they evolved from land creatures.
演讲者:我们知道鲸鱼是哺乳动物,而且是从陆地生物进化而来。
So the mystery is figuring out how they became ocean dwellers.
所以需要解开的谜团是他们怎样变成海洋生物。
Because until recently there was no fossil record of what we call “the missing link”-that is evidence of species that show the transition between land-dwelling mammals and today's whales.
因为至今为止,我们还没有发现所谓关于二者联系消失的化石证据。这是很重要的证据来证明陆上生物到鲸鱼的进化。
Fortunately, some recent fossil discoveries have made the picture a little bit clearer.
幸运的是最近一些化石证据能使这一“进化图”稍显清晰了。
For example, a few years back in Pakistan, they found a skull of a wolf-like creature.
比如几年前在巴基斯坦,发现了一具像狼一样的头盖骨,
It's about 50 million years old. Scientists had seen this wolf-like creature before, but this skull was different.
距今 15 百万年,科学家以为这和以前的化石一样,但事实上,它有所不同。
The ear area of the skull had characteristics seen only in aquatic mammals, specifically whales.
在它耳朵区域的头骨是有水声哺乳动物的特点,特别像鲸。
Err, well, then also in Pakistan they found a fossil of another creature, which we call Ambulocetus natans.
而且也在巴基斯坦,我们找到了另一具生物化石,称为陆行鲸。
The name Ambulocetus natans comes from Latin of course, and means “walking whale that swims”.
那很。陆行鲸这个名字来自于拉丁语,意为能行走的游泳鲸。
It clearly had four limbs that couldn't have been used for walking. It also had a long thin tail, typical of mammals, something we don't see in today's whales.
它有四肢可以行走,也有一个和哺乳动物一样的长细尾巴,尽管现代鲸没有了。
But, it also had a long skeletal structure.
而且还有一副修长骨架结构,
And that long skeletal structure suggests that it was aquatic.
而且这个骨架结构表明它是水生生物。
And very recently in Egypt, they found a skeleton of Basilosaurus.
而且最近在埃及,他们发现了一具骨架,称之为龙王鲸。
Basilosaurus was a creature that we've already known about for over a hundred years.
龙王鲸是我们已经知道百年的生物了,
And it has been linked to modern whales because of its long whale-like body.
而且他们也与鲸有关系,因为他们有着修长的鲸一样的身体。
But this new fossil find showed a full set of leg bones, something we didn't have before.
但这具新化石有 4 个腿骨,这是之前所没有过的。
The legs were too small to be useful.
它们腿骨太小而无用,
They weren't even connected to its Power San and couldn't have supported its weight.
而且没有链接到手掌,也不能支撑那么大的躯体重量。
But it clearly shows Basilosaurus an evolution from land creature.
但能很清楚的证明龙王鲸是由陆地生物进化而来。
So that's a giant step in the right direction.
所以这是在正确研究方向上的重大进步。
Even better, it established Ambulocetus natans as a clear link between the wolf-like creature and Basilosaurus.
更有甚者,这指明了陆行鲸这样的狼型生物与龙王鲸之间的关系。
Now these discoveries don't completely solve the mystery.
但这发现不能完全将谜团解开。
I mean, Ambulocetus natans is a mammal that shows a sort of bridge between walking on land and swimming.
我的意思是,尽管陆行鲸已经指明一个路上行走动物和水中游泳动物的清晰联系,
But it also is very different from the whales who know today.
但陆行鲸与今天的鲸鱼仍有很大不同。
So really we are working just a few pieces of a big puzzle.
所以我们在几个大困惑上兜圈子。
Emm…a related debate involved some recent DNA studies.
有一个包涵最近关于DNA研究的话题。
Remember, DNA is the genetic code for any organism.
记住,DNA是有关任何生物的基因密码,
And when the DNA from two different species is similar, it suggests that those two species are related.
当两种不同种类的生物DNA相似是,这说明二者是有一定关联的。
And when we compared some whale DNA with DNA from some other species, we got quite a surprise. The DNA suggests that whales are descendants of the hippopotamus.
当我们拿鲸的DNA与其他生物比对时,我们惊奇的发现,鲸鱼竟然是河马的后代!
Yes, the hippopotamus!Well, it came as a bit of a shock.
对,就是河马,这一定让你们大吃一惊了。
I mean, that a four-legged land and river dweller could be the evolutionary source of a completely aquatic creature up to 25 times its size.
我是说,一个在河里生活有四条腿的陆生生物能成为比自己大25倍的水生生物的进化源么?
Unfortunately this evolution of the hippopotamus apparently contradicts the fossil record, which suggests that the hippopotamus is only a very distant relative of the whale, not an ancestor.
很不幸,河马进化理论与化石是有冲突的。我们只能说,河马是鲸鱼的一个远亲,并不是祖先。
And of course as I mentioned, that whales are descendent not from hippos but from that distant wolf-like creatures.
当然我提到了,鲸并不是河马的后代,而是由那个久远的狼型化石的后代。
So we have contradictory evidences.
所以我们有了个相矛盾的证据,
And more research might just raise more questions and create more controversies. At any rate, we have a choice.
随着更多的研究衍生出更多的问题,继而得到更多的辩驳,总之,我们可以选择,
We can believe the molecular data- the DNA, or we can believe the skeleton trail, but unfortunately, not both.
我们可以相信分子数据—DNA 理论,也可以相信骨架结构踪迹理论,但事实上,都不是。
Err… and there have been some other interesting findings from DNA research.
有一些 DNA 研究有趣的发现。
For a long time, we assumed that all whales that had teeth including sperm whales and killer whales were closely related to one another.
以前我们认为,有牙齿的鲸鱼,比如巨头鲸和虎鲸,他们是有一定联系的,
And the same for the toothless whales, like the blue whale and other baleen whales, we assumed that they be closely related.
没有牙齿的鲸鱼,比如蓝鲸和须鲸,他们是有一定联系的,
But recent DNA studies suggest that that's not the case at all.
但DNA 研究表明,根本就没这回事儿。
The sperm whale was actually closely related to the baleen whale, and it's only distantly related to the toothed-whales.
现在 DNA 表明,巨头鲸与须鲸有关联,而且仅仅与有齿鲸有遥远的关系,
So that's the real surprise to all of us.
所以这让我们都很惊奇。

重点单词   查看全部解释    
transition [træn'ziʃən]

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n. 过渡,转变

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typical ['tipikəl]

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adj. 典型的,有代表性的,特有的,独特的

 
err [ə:]

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v. 犯错,做错 v. 偏离,入歧途

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solve [sɔlv]

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v. 解决,解答

 
debate [di'beit]

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n. 辩论,讨论
vt. 争论,思考

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mystery ['mistəri]

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n. 神秘,秘密,奥秘,神秘的人或事物

 
evolution [.i:və'lu:ʃən]

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n. 进化,发展,演变

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related [ri'leitid]

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adj. 相关的,有亲属关系的

 
code [kəud]

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n. 码,密码,法规,准则
vt. 把 ...

 
evidence ['evidəns]

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n. 根据,证据
v. 证实,证明

联想记忆

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