Official 20 Set 6

  • Q1
  • Q2
  • Q3
  • Q4
  • Q5
  • Q6

Snowshoe Hare

  • Q1
  • Q2
  • Q3
  • Q4
  • Q5
  • Q6
What is the lecture mainly about?
  • A. Typical features of the snowshoe hare that do not result from adaptation

  • B. Various strategies used by snowshoe hares to find food during the winter

  • C. Characteristics that snowshoe hares have developed in response to their environment

  • D. Interactions between snowshoe hares and human populations in the state of Maine

显示答案 正确答案: C

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

    FEMALE PROFESSOR:Now James, you said you've been to the state of Maine, right?

    MALE STUDENT:Yeah, actually, I lived in western Maine till I was about 16.

    FEMALE PROFESSOR:Great. So why don't you tell everybody what it's like there in the winter.

    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.

    FEMALE PROFESSOR:Actually, I would. I did field research up there a couple of winters, and it really is an incredible environment.And to survive in that sort of environment, animals have to adapt ... to evolve in response to their surroundings.As you'll recall, an adaptation is any feature- uh, physical or behavioral feature-of a species that helps it survive and reproduce.And in adapting to extreme climates-like Maine in the wintertime- animals can evolve in pretty interesting ways.Take, for example, the snowshoe hare.

    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.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.

    [pause]Now, this snowshoe hare ... tell me ... what sort of adaptations do you think it's developed that help it survive the Maine winters?I'll give you a hint. Food isn't an issue.The hare actually has abundant food in the small twigs it finds.

    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.

    FEMALE PROFESSOR:Yes, that's exactly right.The major concern of the snowshoe hare in the winter is predators, and now that includes humans.So one of its adaptations is basically camouflage.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.

    MALE STUDENT:Yeah, but I could swear I remember seeing rabbits in the snow a couple of times ... I mean hares ... that were brown.

    FEMALE PROFESSOR:Well, you may very well have.Timing is really important, but the snowshoe hare doesn't always get it exactly right.Its chances for survival are best if it turns white about the time of the first snowfall.And, it's the amount of daylight that triggers the changing of the hare's coat.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.The hare does a pretty good job with its timing, but sometimes-when there's a really early or late snow-it stands out.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.And that would make this a particularly dangerous time for the hare.[pause] OK, what else? Other adaptations? Susan?

    FEMALE STUDENT:Well, it's called snowshoe hare. So are its feet somehow protected from the cold?

    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.You've probably never needed to wear snowshoes, but ... well, snowshoes are not like thick furry shoes designed to keep the feet warm.They're actually quite thin, but very wide.What they do is spread out the weight of the foot coming down on the snow.See, the problem with walking on snow is that you sink in with every step.But with snowshoes, you don't sink in, you walk on top of the snow.It makes walking through the Maine countryside in the winter much easier.

    Anyway, the snowshoe hare has an adaptation that plays on this same idea- it has hind feet that act like snowshoes.I mean, its paws are wide, and they allow the hare to hop and run just at the surface of deep snow.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.

    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.Can anyone guess why this is so?

    FEMALE STUDENT:They don't eat very much?

    Well, yes. But not because there isn't enough food around.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.

  • 旁白:听下面一段的生物学课程。





    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。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。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。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。这里我们就以缅因州的白靴兔为例谈谈这些进化吧!










    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。有同学能想到这是怎么回事吗?



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    音频定位:And in adapting to extreme climateslike Maine in the wintertimeanimals can evolve in pretty interesting ways. Take, for example, the snowshoe hare.

    选项分析:讲座一开始就说缅因州冬天很难过,物种需要适应恶劣天气,拿snowshoe hare举例开始谈论snowshoe hare





Snowshoe Hare