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Listen to part of a lecture in a biology class.
聽一段生物學課程。
Professor: Ways in which animals adapt to their environment are often quite ingenious actually.
其實，動物適應所處環境的方式通常都是非常具有獨創性的。
And as an example of this, let me tell you about a fish, a group of fish known as the Notothenioids.
舉個例子，讓我給你們講講一種魚吧，這類魚稱為南極魚類。
There's over 90 known species of Notothenioids and they inhabit both shallow and very deep waters, mostly around Antarctica.
南極魚類一共超過90種，它們棲息在淺水和深水域，主要在南極洲附近。
Many are fairly small, though the largest species can weigh up to 150 kilograms.
很多南極魚都很小，盡管最大的那種魚體重能達到150千克。
Notothenioids can be identified by their large eyes, which are covered by a thick insulating layer of clear tissue.
南極魚可通過它們的大眼睛被辨認出來，上面覆蓋著一層厚厚的絕緣層，由透明組織形成。
This tissue protects their eyes from freezing.
這些組織保護它們的眼睛不被凍傷。
Remember, the freezing point of ocean water, salt water, is lower than for fresh water, negative 1.9 degree Celsius (-1.9°C) .
記住，海水的結冰點，即鹽水，是比淡水低的，零下1.9攝氏度。
So it can get a lot colder for fish in an ocean, say, than in a river or lake.
所以，對魚來說，在海里比在河里或湖里冷多了。
So this means that the ocean waters around Antarctica are cold enough to freeze most types of fish, but Notothenioids don't freeze.
這就意味著，南極洲附近的海水非常冷，足以凍住大多數魚類，但南極魚則不會。
In fact, they thrive.
事實上，它們非常興旺。
They account for some 95% of all fish in the southern ocean, the ocean that surrounds Antarctica.
南極魚在南部海域魚類里占幾乎95%，即南極洲周圍海域。
So, how unusual is that?
這多么不尋常??？
To have a single family of fish dominating an entire ocean.
一種魚類主宰了整片海域。
I mean, think of...say, tropical or temperate marine environments, which have incredibly diverse fish populations.
我是指，想想熱帶或溫帶的海洋環境，那兒的魚非常多樣。
Coral reefs, for example, support over 4000 types of fish, along with sponges, crustaceans, and many other organisms.
比如說珊瑚礁，就養活了超過4000種魚，還有別的海綿生物、甲殼類生物和其它生物。
So, exactly when and how did the Notothenioids come to dominate the southern ocean?
那么，到底是什么時候，以及通過什么方式，南極魚類統治了南方海域呢？
Well, around 30 million years ago, the waters around Antarctica were a lot warmer than they are today.
在大約三千萬年前，南極洲周圍水域比現在暖和多了。
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.
那時候，南極洲連著南美洲，也就是說，從北方來的暖空氣可以一直流向南方，加熱南極洲水域。
Because the water around Antarctica then was relatively warm, it supported many types of fish.
因為那時候南極洲附近水域相對暖和，也就給很多魚類提供了生存環境。
And we know this from fossil evidence.
我們是從化石證據中知道的。
But the 90 or so species of Notothenioids that exist today didn't exist at all back then.
但現在存在的90多種的南極魚類在那時候還沒出現呢。
In fact, only one ancestral Notothenioid species existed.
實際上，（那時候）只有一種古老的南極魚。
But somewhere between 5 million and 14 million years ago, two major changes took place.
但在一千四百萬年到五百萬年前，發生了兩個重大變化。
