『新东方在线托福听力』为托福考生准备了ETS托福TPO/Official 36 Lec 4听力练习：What is the main purpose of the lecture?原文题目答案解析，TPO/Official 36 Lec 4听力原文范文音频翻译。

托福TPO/Official 36 Lec 4听力原文What is the main purpose of the lecture?【新东方在线】

旁白：请听一段生物学课的节选。

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

教授：好的，让我们回到20世纪30年代，一个名为G. F. 高斯的提出了被称为高斯假设的理论。

Professor: OK. Back in the 1930's, a biologist named G.F. Gause first proposed what's known as "Gause's hypothesis".

高斯说不论何时，都存在两个相似的物种竞争同样的有限资源，其中的一个物种会占据一些优势，无论这个优势开始的时候多么小，最终都会导致这个物种占据优势地位，最终排挤掉另一种物种，甚至可能导致另一个物种灭绝。

Gause said that whenever you've got two similar species competing for the exact same limited resources, one of them will have some sort of advantage, however slight that'll eventually enable this species to dominate and ultimately exclude the other one, even cause it to become extinct.

这就是为什么高斯的假设被称为是竞争排斥原理。

That's why Gause's hypothesis came to be called "The competitive exclusion principle".

高斯做了一些实验室实验，像是把两种草履虫物种放在一个环境下，在那里它们需要竞争相同的食物。

Gause did some lab experiments like placing two Paramecium species in the same environment where they would have to compete for the same food.

他发现，随着时间过去，一个物种总是可以排挤掉另一种，减少它的数量，就像他的假设所讲那样。

He found that, over time, one species was consistently able to drive out the other, to eliminate it from the habitat, just as his hypothesis predicted.

对于高斯假设的早期批评之一是：“当然了，这个假设在简单的实验环境里是有作用的，这样的话在一个可控的环境里，存在两种竞争关系的物种，但是当这个假设被用到更加复杂的自然生态环境中的时候，它就没什么用处了。”

Now, one of the early criticisms of Gause's hypothesis was that: "sure, it works in simple lab experiments where you have just two competing species in a controlled environment, but the hypothesis falls apart when applied to natural ecosystems where things are more complex".

在现实世界里，确实有很多例子可以反驳高斯的理论。

Now, it's true that in the real world there are lots of examples that seem to contradict the hypothesis.

例如，在新英格兰的森林里，美国的东北部，生存着一些小的会唱歌的鸟儿，名为wobbler，在相同的区域里，你会发现五种wobbler，都是相同大小，吃相同种类的昆虫，这些昆虫生活在树上或者树木周围。

For example, in the forest of New England, in the northeastern United States, there are some small songbirds called wobblers and right in the same area you've got five species of wobbler, all about the same size and all having similar diets of insects, uh, insects that are found on and around trees.

然而，这五种wobbler一直共存得很好。

Yet, these five wobbler species all managed to coexist.

没有一种称为优势物种，也没有任何一种因为竞争而被别的物种排斥出去。

There is no dominance, no exclusion of one species by another.

我们发现，有一种wobbler吃的是最高层的树木的昆虫，另外的则是吃中层的昆虫，其余的则是以树木底部的昆虫为食。

Well, turns out that one wobbler species feeds in the uppermost branches, while others favor the middle branches and others feed toward the bottom of the tree.

还有，不同的wobbler在一年中不同时候繁育后代。

Also, each wobbler species breeds at a different time of year.

这就使得食物需求高峰期，也就是鸟类哺育它们幼鸟的时期，是不同的。

This way the period of peak food requirement, um, when the birds are feeding their chicks, varies from one species to the next.

学生：但是这真的反驳了高斯的理论吗？

Student: But does that really contradict Gause's hypothesis?

我的意思是，这五种wobbler真的在竞争相同的食物吗？

Because, I mean, are those different wobbler species really competing for the same food?

我觉得它们更像是合作关系，它们之间不需要竞争。

I think they're more like, you know, almost cooperating so that they don't have to compete.

教授：很好！对于粗心的观察者，wobbler确实看起来像是在反驳高斯的假设。它们看上去的确是住在一个地方，吃相同种类的昆虫。

Professor: Excellent! To the casual observer, the wobblers do seem to contradict Gause's hypothesis since they all live in the same place and eat the same types of insects.

但是如果你仔细观察这些鸟儿，五种wobbler之间并不是在同一时间竞争同一种食物。这就让我们开始关注一个重要的生态学概念：生态位。

But if you observe these birds more closely, the wobbler species are not really competing with one another for the exact same food at the exact same time, which brings us to a really important concept in ecology: the niche.

Mark, can you tell us what an ecological niche is?

学生：植物或动物居住的地方，它的栖息地。

Student: The place where the plant or animal lives, you know, its habitat.

学生：例如北极熊生活在北极，在冰面上。

Student: Like the polar bear living in the Arctic on the ice sheet.

北极就是它的生态位，是他可以存活的栖息地。

The Artie is its niche, the habitat it's adapted to survive in.

教授：好的。这就是大多数人认为的生态位是什么。

Professor: Okay. That's what most people think of.

但是对于生物学家来说，生态位的概念也包括了有机物在生物的栖息地里运作的方式，它是怎么和其他动植物相互影响的，怎么和土壤、空气、水源以及其他的物质相互影响的。

But for biologists, the concept of a niche also includes the way an organism functions in its habitat, how it interacts with other plant and animal species, with the soil, the air, the water and so on.

如果有两种相似的物种，在竞争同一种生态位，那么会发生什么？Susan？

If you have two similar species competing in the same niche, what's going to happen? Susan?

学生：其中一种会占据生态位，另一种则消亡。

Student: One will dominate the other and eventually eliminate it.

所以更弱势的那一种物种要怎么增强自己的存活几率呢？

So what could the weaker species do to improve its chances of survival?

学生：可以迁移到别的地区，远离竞争者。

Student: Maybe just move to some other area, you know, away from the competitor.

But think of the scientific definition of a niche.

学生：也许它们可以找到在栖息地生存下去的新办法，这样它们就不用和强势物种竞争了。

Student: Maybe it could find some new way of functioning in its habitat so that it wouldn't have to compete with the dominant species.

它们还是留在同样的栖息地里，却不是相同的生态位。

Keep the same habitat but not the exact same niche.

教授：是的，有很多种办法可以做到。

Professor: Yes, and there are many ways to do that.

强势物种以树木的某一部分为食，弱势物种可以以另一部分为食。

The dominant species feeds in one part of the tree and you feed in another.

学生：如果强势物种需要很多水资源，弱势物种可以发展靠很少水存活的能力。

Student: If the dominant species needs a lot of water you develop the ability to survive on very little water.

教授：弱势物种依靠强势物种残留下来的资源而活：水资源，食物，筑巢或者育儿地，或者是别的什么。

Professor: You survive on what's left over: water, food, nesting or breeding sites, whatever.

According to Gause's hypothesis, what happens when two similar species compete for limited resources in the same habitat?

How do the five species of warbler described by the professor manage to coexist?

What is the professor's opinion about Gause's hypothesis?

What does the professor imply about the relationship between an organism's niche and its habitat?

Listen again to part of the Lecture.Then answer the question. Why does the professor say this:

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