『新东方在线托福听力』为托福考生准备了ETS托福TPO/Official 10 Lec 1听力练习：According to the professor, what three aspects of the Ambulocetus fossil make Ambulocetus a likely bridge between land mammals and sea mammals?原文题目答案解析，TPO/Official 10 Lec 1听力原文范文音频翻译。

托福TPO/Official 10 Lec 1听力原文According to the professor, what three aspects of the Ambulocetus fossil make Ambulocetus a likely bridge between land mammals and sea mammals?【新东方在线】

旁白：听一段关于海洋生物学的讲座。

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

演讲者:我们知道鲸鱼是哺乳动物，而且他们从陆地生物进化而来。

Professor: We know whales are mammals and that they evolved from land creatures.

所以需要解开的谜团是他们怎样变成海洋生物的。

So the mystery is figuring out how they became ocean dwellers.

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。

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.

幸运的是最近一些化石证据能使这个进化图稍显清晰了。

Fortunately, some recent fossil discoveries have made the picture a little bit clearer.

比如几年前在巴基斯坦，发现了一具像狼一样的头盖骨。

For example, a few years back in Pakistan, they found a skull of a wolf-like creature.

科学家以为这和以前的化石一样，但事实上，它有所不同。

Scientists had seen this wolf-like creature before, but this skull was different.

在它耳朵区域的头骨是有水声哺乳动物的特点，特别像鲸。

The ear area of the skull had characteristics seen only in aquatic mammals, specifically whales.

而且也在巴基斯坦，我们找到了另一具生物化石，称之为陆行鲸。

Uh, well, then also in Pakistan, they found a fossil of another creature, which we call Ambulocetus Natans.

陆行鲸这个名字来自于拉丁语，意为能行走的游泳鲸。

The name Ambulocetus natans comes from Latin of course, and means walking whale that swims.

It clearly had four limbs that could have been used for walking.

也有一个和哺乳动物一样的长细尾巴，尽管现代鲸没有了。

It also had a long thin tail, typical of mammals, something we don't see in today's whales.

But, it also had a long skeletal structure.

而且这个骨架结构表明它是水生生物。

And that long skeletal structure suggests that it was aquatic.

而且最近在埃及，他们发现了一具骨架，称之为龙王鲸。

And very recently in Egypt, they found a skeleton of Basilosaurus.

龙王鲸是我们已经知道百年的生物了。

Basilosaurus was a creature that we've already known about for over a hundred years.

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。

And it has been linked to modern whales because of its long whale-like body.

但这具新化石有4个腿骨，这是之前所没有过的。

But this new fossil find showed a full set of leg bones, something we didn't have before.

而且没有链接到手掌，也不能支撑那么大的躯体重量。

They weren't even connected to its pelvis and couldn't have supported its weight.

但能很清楚的证明龙王鲸是由陆地生物进化而来。

But it clearly shows Basilosaurus's evolution from land creatures.

所以这是在正确研究方向上的重大进步。

So that's a giant step in the right direction.

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。

Even better, it establishes Ambulocetus as a clear link between the wolf-like creature and Basilosaurus.

但这发现不能完全将谜团解开。

Now these discoveries don't completely solve the mystery.

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。

I mean, Ambulocetus is a mammal that shows a sort of bridge between walking on land and swimming.

但陆行鲸与今天的鲸鱼仍有很大不同。

But it also is very different from the whales who know today.

所以我们在几个大困惑上兜圈子。

So really we are working with just a few pieces of a big puzzle.

有一个包涵最近关于DNA研究的话题。

Um...a related debate involved some recent DNA studies.

记住，DNA是有关任何生物的基因密码。

Remember, DNA is the genetic code for any organism.

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 the DNA from two different species is similar, it suggests that those two species are related.

当我们拿鲸的DNA与其他生物比对时，我们惊奇的发现。

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.

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？

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?

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。

Unfortunately, this revelation about the hippopotamus apparently contradicts the fossil record, which suggests that the hippopotamus is only a very distant relative of the whale, not an ancestor.

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生物的后代。

And of course as I mentioned, that the whales are descendant not from hippos but from that distant wolf-like creature.

所以我们有了个相矛盾的证据。

随着更多的研究衍生出更多的问题，继而得到更多的辩驳。

And more research might just raise more questions and create more controversies.

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，不可能两者都正确。

We can believe the molecular data, the DNA, or we can believe the skeleton trail, but unfortunately, probably not both.

Um...and there have been some other interesting findings from DNA research.

以前我们认为，有牙齿的鲸鱼，比如座头鲸和虎鲸，他们是有一定联系的。

For a long time, we assumed that all whales that had teeth including sperm whales and killer whales were closely related to one another.

没有牙齿的鲸鱼，比如蓝鲸和须鲸，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.

但DNA研究表明，根本就没这回事儿。

But recent DNA studies suggest that that's not the case at all.

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。

The sperm whale is actually closely related to the baleen whale, and it's only distantly related to the toothed-whales.

So that was the real surprise to all of us.

According to the professor, what three aspects of the Ambulocetus fossil make Ambulocetus a likely bridge between land mammals and sea mammals?

According to the professor, what does the discovery of Ambulocetus mean to researchers?

What evidence suggests that whale are descendants of the hippopotamus

What is the professor's opinion about recent genetic studies relating to whale evolution?

What does DNA evidence indicate about relationships among whales?

Narrator 
Listen to part of a lecture in a Marine Biology Class 
We know whales are mammals and that they evolved from land creatures. So the mystery is figuring out how they became ocean dwellers. 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. 
Fortunately some recent fossil discoveries have made the picture a little bit clear. For example, a few years back in Pakistan, they found a skull of wolf-like creature. It is about 50million years old. Scientists have seen this wolf-like creature before but this skull was different. The ear area of the skull had characteristics seen only in aquatic mammals, specifically whales. 
But then also in Pakistan, they found fossil of another creature which we call Ambulocetus Natans. That’s mouthfully. The name of Ambulocetus Natans comes from Latin of course, and means walking whale that swims. It clearly had four limbs that could have been used for walking and it also had a long fin tail, typical of mammals. Something we don’t see in today’s whales but it also had a long skeletal structure and that long skeletal structure suggests that was aquatic. 
And very recently, in Egypt, they found the skeleton of basilosaurus. Basilosaurus was a creature that we have already known about for over 100 years and it has been linked to modern whales because of its long whale-like body, but this new fossil-find showed a full set of leg bones, something we didn’t have before. The legs were too small to be useful, they weren’t even connected to its pelvis and couldn’t have supported its weight. But it clearly shows Basilosaurs evolution from land creatures. So that’s a giant step in the right direction, even better it establishes Ambulocetus as a clear link between the wolf-like creature and basilosaurus. Now these discoveries don’t completely solve the mystery, I mean ambulocetus is a mammal that shows a sort of a bridge between walking on land and swimming, but it also is very different from the whales we know today. So really we are working with just a few pieces of a big puzzle. 
But then also in Pakistan, they found fossil of another creature which we call Ambulocetus Natans. That’s mouthfully. The name of Ambulocetus Natans comes from Latin of course, and means walking whale that swims. It clearly had four limbs that could have been used for walking and it also had a long fin tail, typical of mammals. Something we don’t see in today’s whales but it also had a long skeletal structure and that long skeletal structure suggests that was aquatic. 
And very recently, in Egypt, they found the skeleton of basilosaurus. Basilosaurus was a creature that we have already known about for over 100 years and it has been linked to modern whales because of its long whale-like body, but this new fossil-find showed a full set of leg bones, something we didn’t have before. The legs were too small to be useful, they weren’t even connected to its pelvis and couldn’t have supported its weight. But it clearly shows Basilosaurs evolution from land creatures. So that’s a giant step in the right direction, even better it establishes Ambulocetus as a clear link between the wolf-like creature and basilosaurus. Now these discoveries don’t completely solve the mystery, I mean ambulocetus is a mammal that shows a sort of a bridge between walking on land and swimming, but it also is very different from the whales we know today. So really we are working with just a few pieces of a big puzzle. 
A related debate involves some recent DNA studies Remember, DNA is the genetic code for any organism and when the DNA from two different pieces is similar, it suggests that those two species are related. And when we compare some whale DNA with DNA from some other species, we got quite a surprise. The DNA suggests that whales are just descendants of hippopotamus. 
Yes, the hippopotamus, well, they came as a bit of a shock I mean that a 4-legged land and river dweller could be the evolutionary source of a completely aquatic creature up to 25 times its size, unfortunately this revelation about the hippopotamus apparently contradicts the fossil record which suggests that the hippopotamus is only a very distant relative of the whale not an ancestor. And of course as I mentioned that whales are descendants not from hippos but from that distant wolf-like creature. So we have contradictory evidence, and more research might just raise more questions and create more controversies, and anyway we have a choice. We can believe that molecular data-the DNA or we can believe that skeleton trial, but unfortunately probably not both. 
Um…and there have been other interesting findings from DNA research For a long time, we assume that all whales that had teeth including sperm whales and killer whales or closely related to one another, and same for the toothless whales like the blue whale and other baleen whales, we assumed that they be closely related, but recent DNA study suggests that that’s not the case at all, the sperm whale is actually closely related to the baleen whale, and it’s only distantly related to the toothed whales, so that was a real surprise to all of us.

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