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  • Mutualism托福听力原文翻译及问题答案

    时间:2023-07-09 13:38:00 来源:www.ivyeducation.cn


    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:



















    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:











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