查看听力原文
NARRATOR:Listen to part of a lecture in a biology class.
FEMALE PROFESSOR:Okay, so that's how the arctic ground squirrel is able to cope in this extreme environment ...Now let's talk about your reading assignment,about reindeer...also typically found in Siberia and other far-northern regions.Who’d like to start off? [calling on student] Yes,Mike?
MALE STUDENT:Well, for one thing, they've got thick hair all over their body, even on their noses.
FEMALE PROFESSOR:Yes.They are very well insulated, and the thickness of their fur varies depending on the season.Good.[calling on another student] Yes?
FEMALE STUDENT:Um...newborn reindeer are very adult-like, like they can stand as soon as they're born, and by their second day they can already run as fast as a human.
FEMALE PROFESSOR:Critical. Food is very scarce in far north, so reindeer herds have to cover lots of ground, every day.And in the fall they might easily trek a thousand kilometers or more to get to their winter feeding site.So if you are a newborn, you've got to get up to speed fast.Okay, Other adaptations?
MALE STUDENT:Also, reindeer don't have to keep their legs as warm as their main body, so they don't have to use up as much energy keeping them warm.
FEMALE PROFESSOR:Yes, so that means they can allocate less energy to heating their extremities, and more energy to maintaining stable temperature in their body core, where their vital organs are located.And you know I don't think it is mentioned in your textbook, but even different parts of a reindeers leg are adapted for optimal cold weather performance.The fat in the lower part of their legs—the part that gets coldest—that fat has a different chemical structure from the fat in the upper parts of the leg, so it doesn't get hard; even at temperatures down around freezing; it stays kind of gel-like, kind of oily.Okay, good.What about food? What do you remember about that?
FEMALE STUDENT:Well, they are pretty flexible.
FEMALE PROFESSOR:Okay. Can you explain that a little more?
FEMALE STUDENT:Well, they can eat a lot of different kinds of plants, so that improves their chances of coming across something they can eat.I think they said that they found that the reindeer in one herd had eaten something like 37 different kinds of plants.
FEMALE PROFESSOR:OK, yes. [pleased] You've really done your reading.And reindeer also eat a number of different plant species that most animals are not very interested in. Which means ...
FEMALE STUDENT:They don't have a lot of competition when it comes to that food.
FEMALE PROFESSOR:That's right. In particular, your reading mentions lichens.
Lichens are plants you'll find growing on rocks in the far north, sometimes referred to as “reindeer moss.” [getting off track]They look pretty basic, you know, just a little moss on a rock. But lichens are actually quite complex.They are not just a single organism, they’re actually a kind of combination of some sort of a fungus and some sort of algae that live together in a symbiotic relationship.[realizing she’s off topic] Anyway. Okay, reindeer. Um… [one last thought] Oh, yes, and one more thing about lichens.They crank out a lot of chemicals, which is probably at least part of the reason why they are not considered all that tasty by most animals.Anyway. Does anyone remember what your reading said about them?
MALE STUDENT:Yeah, somehow, when reindeer eat lichens, they’re able to draw a lot more nutrients from them than other animals.Like if a cow or a sheep eats lichens, they’re only going to get like half as much nutrition out of them as a reindeer would.
FEMALE PROFESSOR:That's right, and in winter, lichens are crucial for reindeer because their supply energy, but they don't have all the proteins and minerals the reindeer need.
Um, so when reindeer get to the end of the long winter, they’re often very thin, with low levels of minerals.In spring they have to eat different plants and replenish what they've lost over the winter.So what reindeer have done is, they’ve developed the ability to digest different plants in different seasons by adjusting the microbes in their digestive systems.As you know, microbes are microorganisms, like bacteria, that help to digest or break down food.And well, what’s interesting about reindeer is that they change the proportion of different microbes in their digestive system.Uh, so you…so the reindeer might have more of one kind of microbe in winter to help digest the plants it eats then, and in the summer, uh, it would have more of another kind of microbe to help it digest summer plants.That way the reindeer gets more nutrition out of different foods at different times of the year.
旁白：听一段生物课的讲座。
教授：好吧，这就是北极地松鼠如何能够应对这种极端环境的原因。现在让我们来讨论你们的阅读作业，关于驯鹿，它们也经常在西伯利亚和其他北方地区被发现。谁先开始？好的，迈克？
学生：嗯，一方面，它们浑身都有浓密的毛发，甚至在鼻子上也有。
教授：是的，它们的隔热性很好，毛皮的厚度随季节而变化。好的，还有谁？
学生：嗯...刚出生的驯鹿非常像成年的鹿，比如：它们一出生就可以站立，到第二天它们就可以跑得和人类一样快了。
教授：这个很关键。在遥远的北方，食物非常稀少，所以驯鹿每天必须走过很多土地。在秋天，他们可能要跋涉一千公里或甚至更远的距离，才能到达它们冬季觅食的地点。所以，如果你是一个新生儿，你必须加速成长。好的，（驯鹿）还有其他的适应性吗？
学生：驯鹿不必像保持它们的身体温度那样去保持它们的腿温，所以它们就不必消耗过多的能量来保暖。
教授：是的，这意味着他们可以分配更少的能量来加热他们的四肢，分配更多的能量来保持稳定身体核心部位的温度，这些部位是重要器官的所在。我认为这在你们的教科书中没有提到过，但即使是驯鹿的腿部的不同部分，都为寒冷天气作出了最佳的调整。腿下部的脂肪是最冷的部分，它的脂肪与腿上部脂肪的化学结构不同，所以它不会僵硬，即使在温度下降到冰点左右，它保持凝胶状，有点油质的。好的，好的。那么食物呢？你们还记得什么？
学生：嗯，他们很会变通。
教授：好的，你能多解释一点吗？
学生：嗯，他们可以吃很多不同种类的植物，这样就能增加他们吃到的东西的机会。我记得阅读的文章中说，他们发现在一群驯鹿中，可能会食用37种不同的植物。
教授：好的，是的。你真的读过了。而且驯鹿也吃许多不同的植物，大多数动物对这些植物不感兴趣，这意味着什么？
学生：就那些食物而言，他们没有很多竞争对手？
教授：是的！尤其是你们阅读中提到的地衣。
你会发现地衣植物生长在遥远的北方的岩石上，有时被称为驯鹿苔。他们看起来很的低级，只是在岩石上的一点青苔，但实际上，地衣是相当复杂的。他们不仅仅是一个有机体，他们实际上是某种真菌和一些藻类以共生关系生长在一起的混合体。反正...好吧，驯鹿，还有一件关于地衣的事情。他们制造许多化学物质，这可能是它们被大多数动物认为不好吃的部分原因。不管怎样，有人记得你们的阅读是如何描述它们的吗？
学生：是的，当驯鹿吃当地衣时，比起其他动物，它们能以某种方式从中得出更多的营养。比如一头牛或羊吃地衣，它们只会获得驯鹿一半的营养。
教授：正确，并且在冬季，地衣对驯鹿是至关重要的，因为它们可以提供能量，但他们没有驯鹿所需要的所有的蛋白质和矿物质。
所以，当驯鹿度过漫长的冬天时，它们通常都很瘦，矿物质含量很低。在春天，他们不得不吃不同的植物来补充他们在冬季失去的（营养成分）。驯鹿所做的是，通过调节消化系统中的微生物，培养出不同季节不同植物的消化能力。正如你们所知，微生物是微小的生物，如细菌，有助消化或分解食物。好的，有意思的是，驯鹿会改变它们消化系统中不同微生物的比例。所以，在冬季，驯鹿可能会有更多的某种微生物来帮助消化那时候所吃的植物；在夏季又有另一种微生物来帮助消化夏天所食用的植物。通过这种方式，驯鹿可以在一年四季从不同的食物中获取更多的营养。
如果对题目有疑问，欢迎来提出你的问题，热心的小伙伴会帮你解答。