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第1段
1 .<-NARRATOR:->Listen to part of a lecture in a biology class.
旁白：听下面一段的生物学课程。
第2段
1 .<-FEMALE PROFESSOR:->Now James, you said you've been to the state of Maine, right?
教授：詹姆斯，你说你去过缅因州，是吗？
第3段
1 .<-MALE STUDENT:->Yeah, actually, I lived in western Maine till I was about 16.
学生：是的，老师。其实我在十六岁以前一直都住在缅因州西部。
第4段
1 .<-FEMALE PROFESSOR:->Great. So why don't you tell everybody what it's like there in the winter.
教授：好的，你能告诉我们一下那儿的冬天是怎样的吗？
第5段
1 .<-MALE STUDENT:->[Chuckling]In the winter? Well, it's cold ... and there's lots of snow. You wouldn't believe how much snow we used to get.
冬天？嗯，冷。许多雪，雪之厚，令人难以想象。
第6段
1 .<-FEMALE PROFESSOR:->Actually, I would. I did field research up there a couple of winters, and it really is an incredible environment.
教授：实际上我知道。我在那儿做过好几次田野调查。那儿的环境真实令人难以置信。
2 .And to survive in that sort of environment, animals have to adapt ... to evolve in response to their surroundings.
要在那样的环境下生活，动物们必须得进化... 随着周围环境的变化而进化。
3 .As you'll recall, an adaptation is any feature- uh, physical or behavioral feature-of a species that helps it survive and reproduce.
物种的进化，即在它们的行为或肢体上为在某个环境下生存和繁衍做出的改变。
4 .And in adapting to extreme climates-like Maine in the wintertime- animals can evolve in pretty interesting ways.
为了适应极端的气候地带的生存环境，譬如缅因州的冬天，动物们以各式各样的方式进化，其中有一些非常有趣。
5 .Take, for example, the snowshoe hare.
这里我们就以缅因州的白靴兔为例谈谈这些进化吧！
第7段
1 .OK, the snowshoe hare-and of course that's[ spell out the word ]"H-A-R-E," like a rabbit ... though I probably should mention that technically a hare is not exactly the same as a rabbit, even though it is very similar.
好的，白靴兔，顾名思义，当然是一种野兔。不过学术上讲，野兔与我们一般的兔子是有区别的，虽然它们很相似。
2 .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.
野兔与家兔的主要区别是，家兔出生时是看不见东西的，而且没有胎毛；野兔出生时能够见物，且全身都有胎毛覆盖。
第8段
1 .[pause]Now, this snowshoe hare ... tell me ... what sort of adaptations do you think it's developed that help it survive the Maine winters?
现在，同学们，你们想一想，白靴兔到底在哪些方面发生了进化，从而能够在缅因州的冬天生存下来？
2 .I'll give you a hint. Food isn't an issue.
我给你们一些提示。食物不是问题。
3 .The hare actually has abundant food in the small twigs it finds.
白靴兔充裕的食物主要来源是植物的细枝。
第9段
1 .<-MALE STUDENT:->Well, I don't know. I mean, I know we used to try to look for those rabbits, ... uh hares, when we went hiking in the winter, but it was often hard to find them in the snow.
学生：嗯，我想我不知道。我的意思是，我们曾到处找这些兔子，在冬季远足的时候，但在雪里面根本找不到它们。
第10段
1 .<-FEMALE PROFESSOR:->Yes, that's exactly right.
教授：是的！实际情况是这样的。
2 .The major concern of the snowshoe hare in the winter is predators, and now that includes humans.
白靴兔在冬季最大的顾虑是它的捕食者，现在又多了人类。
3 .So one of its adaptations is basically camouflage.
所以，它最基本的一项进化就是伪装。
4 .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.
换句话说，它的毛色，从夏天的灰色变成了冬天的白色，这使得捕食者很难从雪地里找到它。
第11段
1 .<-MALE STUDENT:->Yeah, but I could swear I remember seeing rabbits in the snow a couple of times ... I mean hares ... that were brown.
学生：是的，但我发誓我记得有几回我在雪地里看到过白靴兔，它们的颜色是棕色的。
第12段
1 .<-FEMALE PROFESSOR:->Well, you may very well have.
教授：嗯，你看到的很可能是真实的。
2 .Timing is really important, but the snowshoe hare doesn't always get it exactly right.
变色的时机是很重要的，但白靴兔并不能一直都把时机把握好。
3 .Its chances for survival are best if it turns white about the time of the first snowfall.
如果它们能在第一次降雪的时候变成白色，这对它们的生存无疑是最为有利的。
4 .And, it's the amount of daylight that triggers the changing of the hare's coat.
引发白靴兔变色的是日光量。
5 .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.
当白天变短的时候，即太阳高悬在天空中的时间越来越短的时候，白靴兔开始长出白毛，棕毛脱落。
6 .The hare does a pretty good job with its timing, but sometimes-when there's a really early or late snow-it stands out.
白靴兔一向把握时机的本领都很强，但是有时降雪时间或早或晚，它的颜色就在雪里面显露出来了。
7 .Plus, it takes about a month for the snowshoe hare's coat to completely change color, so if there's a particularly early snowfall, it's very likely that the hare's fur would not yet be totally white.
而且，从开始脱毛到棕毛完全脱尽需要花费一个月的时间，这样的话，假如一场雪来得早了，白靴兔的毛可能还没有完全变白。
8 .And that would make this a particularly dangerous time for the hare.
这段时间对于它们来说是非常为危险的。
9 .[pause] OK, what else? Other adaptations? Susan?
好的，还有补充吗？苏珊？
第13段
1 .<-FEMALE STUDENT:->Well, it's called snowshoe hare. So are its feet somehow protected from the cold?
学生：嗯，这种兔子叫做“白靴兔”，顾名思义，是不是它的脚能够起到保暖的作用？
第14段
1 .<-FEMALE PROFESSOR:->Well, this animal's name does have to do with an adaptation of its feet, though not like it has warm furry boots or something, to keep its feet from getting cold.
教授：嗯，这种动物得名，确实与它的脚的进化有关。尽管并不像是它有暖和的多毛的长靴或者其它的东西来不让自己变冷。
2 .You've probably never needed to wear snowshoes, but ... well, snowshoes are not like thick furry shoes designed to keep the feet warm.
我们可能从来都不需要雪地靴，但是，雪地靴并不是那种很厚实的保暖靴。
3 .They're actually quite thin, but very wide.
实际上这它很薄，但很宽。
4 .What they do is spread out the weight of the foot coming down on the snow.
它的作用是把脚面展开，从而把身体重量施加给雪面的压力减小。
5 .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，麻烦就在于你每走一步，脚可能就陷下去一次。
6 .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，你就不会陷下去，就能够在雪面上行走了。
7 .It makes walking through the Maine countryside in the winter much easier.
穿上它，在缅因州的乡村道路上行走就容易得多了。
第15段
1 .Anyway, the snowshoe hare has an adaptation that plays on this same idea- it has hind feet that act like snowshoes.
总之，白靴兔有一项进化，原理与雪地靴差不多。它的后脚，与雪地靴的功能相似。
2 .I mean, its paws are wide, and they allow the hare to hop and run just at the surface of deep snow.
它的脚掌很宽，使得白靴兔能够在雪的表面上疾速奔跑。
3 .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.
这对白靴兔来说是一个巨大的优势，相比之下，它们捕食者总是在雪地行动时陷入雪地里面。
第16段
1 .Now, another advantage related to this is that, unlike many animals in winter, snowshoe hares can stay lean and lightweight- they accumulate essentially no body fat.
这项进化带来的另一项优势是，白靴兔可以保持的身体精瘦。 它们身体中几乎没有脂肪。
2 .Can anyone guess why this is so?
有同学能想到这是怎么回事吗？
第17段
1 .<-FEMALE STUDENT:->They don't eat very much?
学生：它们吃得很少？
第18段
1 .Well, yes. But not because there isn't enough food around.
嗯，对！但这并不是因为它们能找到的食物不够。
2 .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.
这是因为，如我前面讲的，它们的食物随时触手可及，因此它们无须在严酷的冬季储食。