評論
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Narrator:Listen to part of a lecture in a biology class.
獨白:聽下面一段的生物學課程。
Now, James, you said you had been to the State of Maine, right?
詹姆斯，你說你去過緬因州，是嗎？
Yeah, actually I lived in western Maine until I was about sixteen.
是的，老師。其實我在十六歲以前一直都住在緬因州西部。
Great. So why don't you tell everybody what is like there in the winter?
好的，你能告訴我們一下那兒的冬天是怎樣的嗎？
The winter? Well, it's cold.
冬天？嗯，冷。
And there's lots of snow, you wouldn't believe how much snow we used to get.
許多雪，雪之厚，令人難以想象。
Actually I would. I did field research up there a couple of winters.
實際上我知道。我在那兒做過好幾次田野調查。
And it really is an incredible environment.
那兒的環境真實令人難以置信。
And to survive in that sort of environment, animals have to adapt, to evolve in response to their surroundings.
要在那樣的環境下生活，動物們必須得進化。
As you recall, an adaptation is any feature, um... physical or behavioral feature of a species that helps it survive and reproduce.
物種的進化，即在它們的行為或肢體上為在某個環境下生存和繁衍做出的改變。
And in adapting to extreme climates, like Maine in the winter time, animals can evolve in pretty interesting ways.
為了適應極端的氣候地帶的生存環境，譬如緬因州的冬天，動物們以各式各樣的方式進化，其中有一些非常有趣。
Take, for example, the snowshoe hare.
這里我們就以緬因州的白靴兔為例談談這些進化吧！
Ok, the snowshoe hare, and of course, that's H-A-R-E, like a rabbit.
好的，白靴兔，顧名思義，當然是一種野兔。
Although I probably should mention that technically a hare is not exactly the same as a rabbit, even though it is very similar.
雖然，野兔與我們一般的兔子，嚴格地說，是有區別的，雖然它們很相似。
The primary difference is that a rabbit's young are born blind and without fur, while a hare's babies are born with a full coat and able to see.
野兔與家兔的主要區別是，家兔出生時是看不見東西的，而且沒有胎毛；野兔出生時能夠見物，且全身都有胎毛覆蓋。
Now, the snowshoe hare, tell me, what sort of adaptations do you think it has developed that help it survive the Maine winters?
現在，同學們，你們想一想，白靴兔到底在哪些方面發生了進化，從而能夠在緬因州的冬天生存下來？
I'll give you a hint. Food isn't an issue.
我給你們一些提示。
The hare actually has abundant food in the small twigs it finds.
白靴兔的食物主要來源是植物的細枝。
Well, I don't know.
嗯，我想我不知道。
I mean, I know we used to try to look for these rabbits, eh... hares, when we went hiking in the winter, but it was often hard to find them in the snow.
我的意思是，我們曾在冬季遠足的時候到處找這些兔子，但在雪里面根本找不到它們。
Yes. That's exactly right. The major concern of the snowshoe hare in the winter is predators.
是的！實際情況是這樣的。白靴兔在冬季最大的顧慮是它的捕食者，
And now that includes humans.
現在又多了人類。
So one of its daptations is basically camouflage.
所以，它最基本的一項進化就是偽裝。
In other words, its coat, its fur, turns from brown in the summer to white in the winter, which makes it harder for the hare's predators to see it against the white snow.
換句話說，它的毛色，從夏天的灰色變成了冬天的白色，這使得捕食者很難從雪地里找到它。
Yeah, but I could swear I remembered seeing rabbits in the snow a couple of times, I means hares, that were brown.
是的，但我發誓我記得有幾回我在雪地里看到過白靴兔，它們的顏色是棕色的。
Well, you may very well have.
嗯，你看到的很可能是真實的。
Timing is really important, but the snowshoe hare doesn't always get it exactly right.
變色的時機是很重要的，但白靴兔并不能一直都把時機把握好。
Its chances for survival are best if it turns white about the time of the first snowfall.
如果它們能在第一次降雪的時候變成白色，這對它們的生存無疑是最為有利的。
And it's the amount of daylight that triggers the changing of the hare's coat.
引發白靴兔變色的是日光量。
As the days get shorter, that is, as the Sun is up for a shorter and shorter time each day, the snowshoe hare starts growing white fur and shedding its brown fur.
當白天變短的時候，即太陽高懸在天空中的時間越來越短的時候，白靴兔開始長出白毛，棕毛脫落。
The hare does a pretty good job with its timing, but sometimes when there's a really early or late snow, it stands out.
白靴兔一向把握時機的本領都很強，但是有時降雪時間或早或晚，它的顏色就在雪里面顯露出來了。
Plus, it takes about a month for the snowshoe hare's coat to completely change color.
而且，從開始脫毛到棕毛完全脫盡需要花費一個月的時間，
So if there's a particularly early snowfall, it's very likely that the hare's fur would not yet be totally white.
這樣的話，假如一場雪來得早了，白靴兔的毛可能還沒有完全變白。
And that would make this a particularly dangerous time for the hare.
這段時間對于它們來說是非常為危險的。
OK. What else? Other adaptations? Susan?
好的，還有補充嗎？蘇珊？
Well, it's called the snowshoe hare, so are its feet somehow protect it from the cold?
嗯，這種兔子叫做“白靴兔”，顧名思義，是不是它的腳能夠起到保暖的作用？
Well, this animal's name does have to do with an adaptation of its feet. Uh... though, not like it has warm furry boots or something to keep its feet from getting cold.
嗯，這種動物得名，確實與它的腳的進化有關。盡管并不像是它有暖和的多毛的長靴或者其它的東西來不讓自己變冷。
You've probably never needed to wear snowshoes.
我們可能從來都不需要雪地靴，
But, well, snowshoes are not like thick furry shoes designed to keep the feet warm, they are actually quite thin, but very wide.
但是，雪地靴并不是那種很厚實的保暖靴，實際上這它很薄，但很寬。
What they do is spread out the weight of the foot coming down on the snow.
它的作用是把腳面展開，從而把身體重量施加給雪面的壓力減小。
See, the problem with walking on snow is that you sink in with every step.
大家都知道吧，在雪地里行走，麻煩就在于你每走一步，腳可能就陷下去一次。
But with snowshoes, you don't sink in; you walk on top of the snow.
但是，一旦穿上了雪地靴，你就不會陷下去，就能夠在雪面上行走了。
It makes walking through the Maine countryside in the winter much easier.
穿上它，在緬因州的鄉村道路上行走就容易得多了。
Anyway, the snowshoe hare has an adaptation that plays on the same idea.
總之，白靴兔有一項進化，原理與雪地靴差不多。
It has hind feet that act like snowshoes.
它的腳部有肉墊，與雪地靴的功能相似。
I mean, its paws are wide and they allow the hare to hop and run just at the surface of deep snow.
它的腳掌很寬，使得白靴兔能夠在雪的表面上疾速奔跑。
And this is a huge advantage for the snowshoe hare since by contrast; the feet of its predators usually sink right down into the snow.
這對其捕食者而言，是一項很大的優勢:它們捕食者總是在雪地行動時陷入雪地里面。
Now, another advantage related to this is that unlike many animals in winter, snowshoe hares can stay lean and light weight.
這項進化帶來的另一項優勢是，白靴兔可以保持身體姿勢的傾斜，負重低。
They accumulate essentially no body fat.
它們身體中幾乎沒有脂肪。
Can anyone guess why this is so?
有同學能想到這是怎么回事嗎？
They don't eat very much?
它們吃得很少？
Well, yes. But not because there isn't enough food around.
嗯，對！但這并不是因為它們能找到的食物不夠。
It's because, like I said, food is almost always within reach, and they don't have to store up a lot of food energy for the harsh winters.
這是因為，如我前面講的，它們的食物隨時觸手可及，因此它們無須在嚴酷的冬季儲食。
