Mutualism托福听力原文翻译及问题答案

Mutualism托福听力原文翻译及问题答案

一、Mutualism 托福听力原文：

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

FEMALE PROFESSOR: OK. Today I'd like to spend some time going into more detail about symbiosis. Symbiosis. What is it? Anyone?

MALE STUDENT: I thought it's when two organisms are in a relationship that they both benefit from, well, at least that’s what I thought it was until I did the reading last night. Now I'm kinda confused about it because the book used that definition to describe mutualism.Could you explain the difference?

FEMALE PROFESSOR: Good. I was hoping that someone would bring that up. Sometimes scientists working in different fields use the term “symbiosis” to mean slightly different things, and it can get confusing, for example, when “symbiosis” is used as a synonym for “mutualism.” But there are quite a few of us out there who think there should be a clearer distinction made between the two.

Ok, where to begin... Um, the original definition of symbiosis is pretty simple. It simply means living together. So, any close relationship between two organisms of different species would be considered a symbiotic relationship, including positive and negative relationships.

Mutualism then is a kind of symbiosis, a specific type of symbiotic relationship where both organisms benefit somehow. So, your book is correct.

Now, I want to make it clear that, um, the positive result from being in a mutualistic relationship doesn't have to be equal for both organisms. It's not a one-to-one ratio here.

Is everyone with me so far? Symbiosis—general term, mutualism—a narrower, more specific kind of symbiosis.

Now let's take a closer look at mutualistic relationships. I'll start off by describing a case of mutualism that involves a certain butterfly species found in South Africa and Australia. It’s a good example of how dependence on a mutualistic relationship can vary.

OK, there's this butterfly family, and I'll spare you the fancy Latin name because it's not important for our purposes here. I'll call them coppers and blues, well…because most members of this family have blue or copper-colored wings. I think this is one of the most interesting cases of mutualism: These butterflies require the presence of ants to complete their life cycle—their interaction with ants is obligatory.

So this is what happens. A female butterfly of these coppers and blues will lay eggs only on vegetation where there’re ants of a particular species. The butterflies can smell…well, ants leave behind pheromones—a special chemical signal. The butterfly recognizes the ants'pheromones on the plant…and then the newly hatched butterflies, the caterpillars, will feed on this plant after they hatch from the eggs. As the caterpillar gets a little older and finds shelter under nearby rocks or stones to protect itself from predators, it’s always attended or escorted by ants. And it always makes its way back to the host plant to feed, guided by the ants—the ant escort service—so to speak.

Now why would the ants go through all this trouble? What's their benefit? Mary?

FEMALE STUDENT: It's probably related to food …

FEMALE PROFESSOR: Uh huh, you’re onto something …

FEMALE STUDENT: OK. Ants feed on sweet stuff, right? So the caterpillar must have some kind of special access to honey, or sugars, or something like that. Maybe caterpillars produce honey somehow. On second thought…I'm probably way off.

FEMALE PROFESSOR: You're pretty close, actually. The caterpillars have a “honey gland”—an organ that secretes an amino acid and carbohydrate liquid. The caterpillar secretes the liquid from the honey gland—rather large quantities—enough to feed several ants. But what makes this relationship obligatory for the caterpillar? Well, if the ants don’t feed regularly on the liquid from the caterpillar’s honey gland, the gland overloads and gets infected. The infection will kill the caterpillar and it'll never reach its final stage of development—becoming a butterfly. John?<br>

MALE STUDENT: OK. I just wanna make sure I'm following here. The caterpillar needs the ants, or it won't make it to the stage where it can become a butterfly. And, the ants do this because they get an easy meal out of it, right? But the ants don't absolutely need the caterpillar for survival 'cuz they can get food from other places, right? So it's still called mutualism even though it seems like the caterpillar's getting way more out of it?  Oh. Wait. You said they don't have to equally benefit.Never mind. Sorry.

FEMALE PROFESSOR: Yes, but there is a type of mutualism where the relationship is necessary for both organisms to survive.It's called obligatory mutualism. We'll talk about that in next class.

二、Mutualism 托福听力中文翻译：

旁白：在生物课上听一节课的一部分。

女教授：好的。今天，我想花点时间详细介绍一下共生。共生这是怎么一回事？任何人

男学生：我以为两个有机体处于一种关系中时，它们都会从中受益，好吧，至少在我昨晚阅读之前，我一直是这么认为的。现在我有点困惑了，因为这本书用这个定义来描述互惠主义。你能解释一下区别吗？

女教授：好。我希望有人能提出来。有时，在不同领域工作的科学家使用“共生”一词来表示略有不同的事物，这可能会令人困惑，例如，当“共生”被用作“互惠”的同义词时但我们当中有相当多的人认为，应该对两者进行更明确的区分。

好的，从哪里开始。。。嗯，共生最初的定义很简单。这仅仅意味着住在一起。因此，不同物种的两种生物之间的任何密切关系都将被视为共生关系，包括积极和消极的关系。

互利共生是一种共生，一种特定类型的共生关系，两种生物都能从中受益。所以，你的书是正确的。

现在，我想说明的是，嗯，互惠关系的积极结果不一定对两种生物体都是平等的。这不是一对一的比例。

到目前为止大家都跟我在一起吗？共生的总称，互惠共生——一种更狭隘、更具体的共生。

现在让我们仔细看看互惠关系。首先，我将描述一个互惠共生的案例，涉及在南非和澳大利亚发现的某种蝴蝶物种。这是一个很好的例子，说明对互惠关系的依赖是如何变化的。

好吧，这里有一个蝴蝶家族，我不想给你起这个花哨的拉丁名字，因为它对我们这里的目的并不重要。我会叫它们铜色和蓝色，因为这个家族的大多数成员都有蓝色或铜色的翅膀。我认为这是互惠主义最有趣的例子之一：这些蝴蝶需要蚂蚁的存在才能完成它们的生命周期。它们与蚂蚁的互动是必须的。

这就是发生的事情。这种铜色和蓝色的雌性蝴蝶只会在有特定种类蚂蚁的植被上产卵。蝴蝶能闻到……嗯，蚂蚁会留下信息素——一种特殊的化学信号。蝴蝶识别蚂蚁在植物上的信息素……然后新孵出的蝴蝶，即毛虫，从卵中孵化出来后，将以这种植物为食。随着毛毛虫年龄的增长，它会在附近的岩石或石头下找到避难所，以保护自己免受捕食者的袭击，它总是有蚂蚁的陪伴。它总是在蚂蚁的引导下返回寄主植物觅食，可以说是蚂蚁护送服务。

蚂蚁为什么要经历这些麻烦呢？他们的好处是什么？玛丽？

女生：可能跟食物有关…

女教授：嗯，你发现了什么…

女学生：好的。蚂蚁吃甜食，对吗？因此，毛虫必须有某种特殊的途径获得蜂蜜、糖或类似的东西。也许毛毛虫会产生蜂蜜。再想想……我可能已经走远了。

女教授：事实上，你很接近。毛毛虫有一个“蜂蜜腺”——一个分泌氨基酸和碳水化合物液体的器官。毛虫从蜂蜜腺分泌大量的液体，足以喂养几只蚂蚁。但是，是什么让这种关系对毛毛虫来说是必须的呢？嗯，如果蚂蚁不定期食用毛虫蜂蜜腺中的液体，那么蜂蜜腺就会超载并被感染。这种感染会杀死毛虫，而且它永远也不会发展到成为蝴蝶的最后阶段。约翰<br>

男学生：好的。我只是想确定我在这里。毛毛虫需要蚂蚁，否则它就无法变成蝴蝶。蚂蚁这样做是因为它们能很容易地从中得到一顿饭，对吗？但是蚂蚁并不完全需要毛虫生存，因为它们可以从其他地方获得食物，对吗？所以它仍然被称为互惠主义，尽管看起来毛毛虫从中获得了更多？哦等待你说过他们不必平等受益。不要介意。很抱歉

女教授：是的，但有一种互惠互利的关系，这种关系是两种生物生存所必需的。这叫做强制性互惠主义。我们将在下节课上讨论这个问题。

三、Mutualism 托福听力问题：

Q1:1.What is the professor mainly discussing?

A. Different ways that scientists use the term “symbiosis”

B. A specific kind of symbiotic relationship between organisms

C. A butterfly species that competes with another insect species

D. Reasons why symbiosis is considered a subtype of mutualism

Q2:2.What does the professor imply about the term“symbiosis”?

A. It is often used with too narrow a meaning.

B. It is used incorrectly in the students' textbook.

C. The original definition is difficult to understand.

D. It is applied only to organisms of the same species.

Q3:3.How do the butterflies mentioned by the professor facilitate the relationship between caterpillars and ants of a certain species?

A. The butterflies have a sweet smell that attracts the ants.

B. The butterflies lay their eggs under rocks where the ants lay their eggs.

C. The butterflies lay their eggs on plants where the ants are present.

D. The butterflies identify a food source for both ants and caterpillars.

Q4:4.In the example the professor mentions, how do the ants benefit from their interaction with the caterpillars?

A. The caterpillars protect the ants' eggs from predators.

B. The caterpillars help the ants find a particular plant.

C. The caterpillars produce a liquid to prevent ants from getting infections.

D. The caterpillars produce a liquid from a species gland to feed the ants.

Q5:5.What aspect of mutualism does the professor illustrate with the example of the caterpillars and the ants?

A. Both organisms need the relationship for survival.

B. It is not necessary for both organisms to benefit equally from the relationship.

C. There is more benefit for the organism that is less dependent on the relationship.

D. The relationship does not need to be beneficial to both organisms.

Q6:6.What can be inferred about the student when she says this: (Female student) Maybe caterpillars produce honey somehow. On second thought . . . I'm probably way off.

A. She needs more time to think about the answer.

B. She is almost certain that caterpillars produce honey.

C. She thinks her statement may be misunderstood.

D. She doubts that her statement is correct.

四、Mutualism 托福听力答案：

A1:正确答案：B

A2:正确答案：A

A3:正确答案：C

A4:正确答案：D

A5:正确答案：B

A6:正确答案：D