<-NARRATOR:->Listen to a conversation between a student and his biology professor.

旁白：听一段学生和生物学教授的对话。

<-MALE STUDENT:->Well, you know, I’m writing my paper about whales and the paths they travel as they swim through the ocean, their migration patterns…

学生：你知道的，我正在写有关鲸鱼的论文，关于它们游过海洋的旅行轨迹，它们的洄游模式。

<-FEMALE PROFESSOR:->Yes, I remember.

教授：对，我记得。

<-MALE STUDENT:->And, well, I was thinking about it and I realized I don’t understand how they hold their breath underwater.It’s a little crazy for me to be writing a paper about migration patterns without actually knowing how they stay underwater for so long.

学生：我正在想这件事，我发现我不明白它们怎么在水下闭气的。让我写一篇关于它们洄游模式的论文，但我实际上却不知道它们怎么在水底待这么长时间的，这有点疯狂。

<-FEMALE PROFESSOR:->Did you do any research to find out how they do it?

教授：你有没有查过资料来弄明白它们怎么做到的？

<-MALE STUDENT:->Yeah, I did. I searched on the Internet and there was a lot of information about whales, their habitats, the way they communicate — you know, their songs… but if there was anything about whales and how they hold their breath, I missed it. I’ve got a bunch of books — actually I’ve got so much information it’s a little overwhelming.

学生：我有。我在网上搜索过，网上有很多关于鲸鱼的信息，它们的栖息地，它们的交流方式，你知道的，它们的歌声。但假如真的有关于鲸鱼怎么憋气的信息，我一定是看漏了。我有一大摞书。事实上我得到了大量的信息，有点让人受不了。

<-FEMALE PROFESSOR:->Well, I’m surprised there was nothing about it in any of those books.

教授：我很惊讶在这些书里竟然没有与此相关的信息。

<-MALE STUDENT:->Well, to be honest, I’ve only skimmed them so far. I’m still working on finding sources.

学生：坦白说，我目前只是把它们粗看了一遍。我还在寻找信息。

<-FEMALE PROFESSOR:->OK. I know I encouraged everyone in class to look at a substantial number of sources — but I don’t want you to get overwhelmed.Looking at a number of sources gives you a good knowledge base, but students only have a limited amount of time to work on each paper —I don’t expect you to read a dozen books on whales for this assignment. Focus on just a few.

教授：好了，我明白我鼓励班上的每个人去看大量相关资料，但我不想你看太多以致无从下手。通过看一定数量的资料，你会得到一个很好的知识储备，但学生在每份论文上都只有很有限的时间。我不希望你为了这次作业看一大堆关于鲸鱼的书，集中看几本就行了。

<-MALE STUDENT:->OK, thanks.

学生：好的，谢谢！

<-FEMALE PROFESSOR:->You know, since you’re already here, I can give you a quick summary of how whales hold their breath underwater; it’s just a matter of certain adaptations in their anatomy — specifically in their circulatory system.

教授：既然你已经来了，我能给你简单讲讲鲸鱼是怎么在水下闭气的，这不过是它们身体构造里的一些适应性进化，准确地说是它们的循环系统。

<-MALE STUDENT:->So the blood flow is what makes the difference?

学生：所以血流是关键？

<-FEMALE PROFESSOR:->Yes. And in a couple of ways. First, blood makes up a larger share of a whale’s weight than in other mammals.

教授：对，通过不同的方式。首先，与其他哺乳动物相比，血液在鲸鱼体重中占的比重更大。

<-MALE STUDENT:->So they can store more oxygen because they have more blood?

学生：所以鲸鱼能储更多的氧，就因为它们的血量更多？

<-FEMALE PROFESSOR:->Yes, but that’s only part of it. They also have a greater capacity than land animals to store oxygen in their blood.

教授：对，但这只是一部分原因。它们在血内储氧的能力比陆生动物也高出许多。

<-MALE STUDENT:->[Quizzically]So, how does having more oxygen in their blood help them stay underwater longer?

学生：那么，血液中拥有更多的氧是怎么帮助它们在水下待得更久的？

It’s the way the whale’s blood carries oxygen to the rest of its body.Whales carefully conserve their oxygen when underwater in a couple of ways.When a whale dives, its metabolic rate drops, causing its heartbeat to slow down.And the blood flow to its muscles and some of its nonvital organs, like its kidneys, is also cut off.A whale’s muscles and nonvital organs are able to function without oxygen for an extended period of time.

这是靠鲸鱼的血液将氧气运输到身体其它部分的方式。在水下时，鲸鱼通过不同的方法谨慎地储氧。当鲸鱼潜入水中时，它的代谢速率会下降，心跳随之减缓。而且通向肌肉和一些非要害器官（如肾脏）的血流也停止了。鲸鱼肌肉和非要害器官能在缺氧情况下持续运作一段时间。

<-MALE STUDENT:->I see… well, now I can concentrate on my topic!

学生：我懂了，现在我我能专注于我的课题了。