Narrator: Listen to part of a lecture in a biology class.

旁白：听一段生物课的演讲。

Professor: Ways in which animals adapt to their environment are often quite ingenious actually.

教授：事实上，动物们适应环境的方法往往是非常新颖的。

And as an example of this, let me tell you about a fish, a group of fish known as the Notothenioids.

作为这个的一个例子，让我来说说一种鱼，这种鱼叫做Notothenioids。

There's over 90 known species of Notothenioids and they inhabit both shallow and very deep waters, mostly around Antarctica.

Notothenioids有90个已知的种类，并且他们可以栖息在浅水，也可以栖息在深水，大部分在南极洲附近。

Many are fairly small, though the largest species can weigh up to 150 kilograms.

很多都非常小，尽管最大的种类可能重达150公斤。

Notothenioids can be identified by their large eyes, which are covered by a thick insulating layer of clear tissue.

Notothenioids可以通过他们的大眼睛被识别，被一层透明的绝缘组织覆盖。

This tissue protects their eyes from freezing.

这种组织保护他们的眼睛不被冻坏。

Remember, the freezing point of ocean water, salt water, is lower than for fresh water, negative 1.9 degree Celsius (-1.9°C).

要知道，海洋水的冰点，也就是咸水，要比淡水来的低，-1.9°C。

So it can get a lot colder for fish in an ocean, say, than in a river or lake.

比起河流或者湖泊里的鱼，海水对海洋里的鱼来说要冷的多。

So this means that the ocean waters around Antarctica are cold enough to freeze most types of fish, but Notothenioids don't freeze.

这也就意味着南极洲附近的海水足够冻住大部分品种的鱼类，但是Notothenioids不会被冻住。

In fact, they thrive.

事实上，他们能够存活。

They account for some 95% of all fish in the southern ocean, the ocean that surrounds Antarctica.

他们占到南极洋鱼类的95%，南极洋就是环绕南极州的海域。

So, how unusual is that?

那么，这个又有什么不寻常的呢？

To have a single family of fish dominating an entire ocean.

让单一种类的鱼群占领整个海域。

I mean, think of…say, tropical or temperate marine environments, which have incredibly diverse fish populations.

我的意思是，想想热带或者温带的海洋环境，那里有着非常丰富种类的鱼群。

Coral reefs, for example, support over 4000 types of fish, along with sponges, crustaceans, and many other organisms.

例如，珊瑚礁支持着4000种鱼类，连同海绵、甲壳累和许多其他的生物。

So, exactly when and how did the Notothenioids come to dominate the southern ocean?

那么，是在什么时候、通过什么方法Notothenioids占领了南极洋的呢？

Well, around 30 million years ago, the waters around Antarctica were a lot warmer than they are today.

大约在30,000,000年前，在南极洲附近的水域比现在要温暖一些。

Um...at that time, Antarctica was connected to South America, which means that warm air from the north could flow southward and heat up the Antarctica waters.

额……在那个时候，南极洲和南美洲相连，这也就意味着北部的热空气可以向南流动并且使南极洲海域升温。

Because the water around Antarctica then was relatively warm, it supported many types of fish.

因为南极洲附近的海域相对温暖，它支持着很多种类的鱼。

And we know this from fossil evidence.

我们可以从化石中得知这些。

But the 90 or so species of Notothenioids that exist today didn't exist at all back then.

但是，现在尚存的90种左右的Notothenioids在那个时候并不都存在。

In fact, only one ancestral Notothenioid species existed.

事实上，只有一种祖先Notothenioids存在着。

But somewhere between 5 million and 14 million years ago, two major changes took place.

但是在大约5,000,000到14,000,000年前，2个重要的改变发生了。

First, what we call a chance mutation.

第一，发生了机遇性的突变。

A tiny genetic change occurred in that one Notothenioid species.

在一种Notothenioids中发生了非常小的基因改变。

Its DNA allowed for the production of a special protein, a protein that prevents the fish from freezing.

它的DNA可以使得一种特别的蛋白产生，这种蛋白可以防止鱼被冻死。

The way this…this anti-freeze protein works is: it binds to any ice crystals that form inside the fish.

这种防冻蛋白工作的方式是：它会绑定在鱼身体内部任意的冰晶。

This binding action prevents the ice crystals from growing larger.

这种绑定的行为防止冰晶变大。

And this is what prevents Notothenioids from freezing.

并且这就是那个防止Notothenioids冻死的东西。

Now, at that time, the waters the Notothenioids inhabited were still not freezing cold, so the protein didn't really make a difference as far as the fish's survival.

在那个时候，由于Notothenioids栖息的海域还没有那么冷，因此这种蛋白并没有那么大的区别，没有达到影响鱼的生存。

But this would change, because in the same period of geologic time there was a shift in the earth's continental plates.

当时，这个会发生改变，在同一个地质时期，在地球的大陆板块发生了移动。

Continental drift caused Antarctica to move apart from the landmass of South America and to drift into the Southern Polar Region.

大陆板块漂移使得南极洲从南美洲板块分离，并且飘到了南极区域。

This resulted in a powerful water current encircling Antarctica, which prevented the Antarctic waters from mixing with warmer water.

这个导致了非常强大的环绕南极洲的水流，这个防止了南极洲海域和其他温暖一点的海域混合。

So the southern ocean, isolated from that warm airflow from the north, cooled down drastically, to the kinds of sub-freezing temperatures we associate with it today.

因此，和北部温暖气流分隔的南极洋迅速的降温，降温到如今我们会将低于冰点和它联系起来。

Now, most fish species couldn't survive in this frigid environment and they became extinct.

现在，大部分的鱼类无法在这个寒冷的环境下生存并且他们灭绝了。

But that one Notothenioid species, with its unique ability to produce that anti-freeze protein, thrived.

但是那个有特殊能力生产抗冻蛋白的Notothenioids存活了下来。

It had virtually the entire southern ocean to itself!

在整个南极洲海域几乎只有它一种鱼。

So? Well, there was little or no competition for food or space.

那么会怎样？对于食物和空间都没有了竞争。

You might think of it as…um…as a…a kind of ecological vacuum.

你可能会认为它可能是一种生态真空。

And the Notothenioids exploited fully.

并且Notothenioids彻底得开发利用了这块地方。

The species migrated into different habitats throughout the southern ocean.

这种鱼类移居到南极洋不同栖息地。

And its population increased dramatically, with various sub-populations migrating into different parts of the ocean.

并且，这种鱼的数量急剧增加，这种鱼类的分支移居到海洋的不同区域。

Over time these sub-populations in all those different habitats…well, they developed very different physical traits.

经过一段时间，这些在不同区域的分支发展出了不同的身体性状。

They adapted to survive in their particular ecological niche, their…their position within a particular ecosystem.

他们适应他们不同的生态位去生存，生态位指的是在特定生态系统中的位置。

We call this type of species diversification within a species adaptive radiation.

我们将这种在一个物种中种类多样化称之为适应性扩张。

And what adaptive radiation is is: an evolutionary process by which a parent species rapidly undergoes changes resulting in various new species in order to fill multiple ecological niches.

适应性扩张是：为了适应不同的生态位，由一种本家物种经历变化而产生各种各样的新物种的进化过程。

So in the case of the Notothenioids, that single species started colonizing empty habitats to such an extent that it evolved into a broad range of new species, the 90 or so Notothenioid species that we have today.

那么在Notothenioids这个案例中，这个单一物种开始在空旷的栖息地大量的繁殖，到达可以进化出很大范围不同种类的程度，也就是我们今天拥有的90种左右的Notothenioids种类。

So let me switch to adaptive radiation with regard to another species that's also been very successful.

那么，让我转向其他一些也非常成功的适应性扩张的物种。