Official 36 Set 6

纠错
  • Q1
  • Q2
  • Q3
  • Q4
  • Q5
  • Q6
置顶

Gause's Hypothesis

纠错
  • Q1
  • Q2
  • Q3
  • Q4
  • Q5
  • Q6
What is the main purpose of the lecture?
  • A. To explain why a species of warbler might become extinct

  • B. To discuss the evidence that led Gause to formulate his hypothesis

  • C. To examine a hypothesis about what happens when species compete

  • D. To identify factors that allow some species to dominate others

显示答案 正确答案: C

我的笔记 编辑笔记

/
  • 原文
  • 译文
  • 查看听力原文

    关闭显示原文

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

    FEMALE PROFESSOR:Okay, back in the 1930s a biologist named G.F.Gause first proposed what's known as Gause's hypothesis.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.That's why Gause's hypothesis came to be called the "competitive exclusion principle."

    Gause did some lab experiments, like placing two paramecium species in the same environment where they'd have to compete for the same food.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.

    Now, one of the early criticisms of Gause's hypothesis was that, [speaking in critic’s voice, not her own] "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."[returning to her own voice] Now it's true that in the real world, there are lots of examples that seem to contradict the hypothesis.For example, in the forests of New England, in the northeastern United States, there are some small songbirds called warblers.

    And right in the same area you've got five species of warbler, all about the same size, and all having similar diets of insects-insects that are found on and around trees.Yet, these five warbler species all manage to coexist- there's no dominance, no exclusion of one species by another...How's this possible?Well, turns out that one warbler species feeds in the uppermost branches, while others favor the middle branches, and others feed toward the bottom of the tree.Also, each warbler species breeds at a different time of year.This way, the period of peak food requirement, when-when the birds are feeding their chicks, varies from one species to the next.[sees hand raised]Yes, Mark.

    MALE STUDENT:[formulating as he goes] But does that really contradict Gause's hypothesis?Because, I mean, are those different warbler species really competing for the same food?I don't think so.I-I think the you're more like, you know, almost cooperating so they don't have to compete.FEMALE PROFESSOR:Excellent. To the casual observer, the warblers do seem to contradict Gause's hypothesis since they all live in the same place and eat the same types of insects.But if you observe these birds more closely, the warbler 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?

    MALE STUDENT:The place where the plant or animal lives. You know, its habitat?

    FEMALE PROFESSOR:[eliciting] For example...

    MALE STUDENT:Uh, like the polar bear living in the Arctic, on the ice sheet.The Arctic is its niche, the habitat it's adapted to survive in.

    Okay, that's what most people think of...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...

    Okay, now let's put it all together:if you have two similar species competing in the same niche, what's going to happen?[sees hand raised] Susan?

    FEMALE STUDENT:One'll dominate the other, and eventually eliminate it.

    FEMALE PROFESSOR:Okay, so what could the weaker species do to improve its chances of survival?

    FEMALE STUDENT:[unsure, upspeak] Maybe just move to some other area, you know, away from the competitor?

    FEMALE PROFESSOR:That's one possibility. But think of the scientific definition of a niche. Think about the warblers.[sees hand raised] Mark?

    MALE STUDENT:Maybe it could find some new way of functioning in its habitat so it wouldn't have to compete with the dominant species... keep the same habitat, but not the same exact niche.

    FEMALE PROFESSOR:Yes, an-and there are many ways to do that [begins to give list of examples] - the dominant species feeds in one part of the tree, and you feed in another...

    MALE STUDENT:[interrupting politely] If the dominant species needs lots of water, you develop the ability to survive on very little water...

    FEMALE PROFESSOR:[summarizing WAMB point] You survive on what's left over. Water, food, nesting or breeding sites,... whatever.

  • 旁白:请听一段生物学课的节选。

    教授:好的,让我们回到20世纪30年代,一个名为G. F. 高斯的生物学家首次提出了所谓的高斯假设的理论。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。这就是为什么高斯的假设被称为是竞争排斥原理。

    高斯做了一些实验,比如在相同的环境中放置两种草履虫,在那里它们需要竞争相同的食物。他发现,随着时间过去,一个物种总是可以排挤掉另一种,把它从栖息地消除,就像他的假设所讲那样。

    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,在一个可控的环境里,只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。”在现实世界里,确实有很多例子可以反驳高斯的理论。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。然而,这五种wobbler一直共存得很好。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。这是如何成为可能的呢?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。还有,不同的wobbler在一年的中不同时候繁育后代。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,每个物种间是不同的。怎么了,Mark?

    学生:但是这真的反驳了高斯的理论吗?我的意思是,这五种wobbler真的在竞争相同的食物吗?我不这么认为。我觉得它们更像是合作关系,它们之间不需要竞争。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。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。

    Mark,你知道生态位是什么吗?

    学生:植物或动物居住的地方,它的栖息地。

    教授:比如

    学生:例如北极熊生活在北极,在冰面上。北极就是它的生态位,是他可以存活的栖息地。

    教授:好的。这就是大多数人认为的生态位是什么。但对于生物学家而言,生态位的概念也包括了生物体在其栖息地里的运作方式,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。

    好的。现在我们综合起来看。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?

    学生:其中一种会占据生态位,另一种则消亡。

    教授:所以更弱势的那一种物种要怎么增强自己的存活几率呢?

    学生:可以迁移到别的地区,远离竞争者。

    教授:这是一种可能。但是想想生态位的科学定义。再想想wobbler。Mark?

    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,它们还是留在同样的栖息地里,却不是相同的生态位。

    教授:是的,有很多种办法可以做到,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。

    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。

    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。

  • 官方解析
  • 网友贡献解析
  • 本题对应音频:
    2 感谢 不懂
    音频1
    解析

    题型分析:主旨题

    原文定位:

    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. That’s why Gause’s hypothesis came to be called the “competitive exclusion principle.”

    选项分析:

    原文开头Cause提出了一个假设,且后文对于这个理论严重实验,可以得知讲座主旨就是验证这个物种竞争的假设。故选项C正确

    标签

题目讨论

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。

如何吃透这篇文章?

Gause's Hypothesis

0人精听过

预计练习时间:15min58s

马上精听本文

最新提问