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

旁白：听生物课的部分讲座。

Professor: Ok, today I'd like to spend some time going into more detail about symbiosis.

教授：好的，今天我想花一些时间去了解更多关于共生的细节。

Symbiosis, what is it? Anyone?

共生，是什么？任何人？

Student: Um, I thought it's when two organisms are in a relationship that they both benefit from.

学生：嗯，我想这是两个生物在一个关系，它们都从中受益。

Well, at least that's what I thought it was until I did the reading last night.

好吧，至少这是我之前想的，直到我昨晚做了阅读。

Now, I am kind of confused about it, because the book used that definition to describe mutualism.

现在，我很困惑，因为这本书用这个定义来描述互惠。

Could you explain the difference?

你能解释一下差别吗？

Professor: Good. I was hoping that someone would bring that up.

教授：好。我希望有人会把这点提出来。

Sometimes scientists working in different fields use the term symbiosis to mean slightly different things.

有时，在不同领域工作的科学家使用术语共生表示着稍微不同的东西。

And it can get confusing.

它可能让人困惑。

Uh, for example, when symbiosis is used as a synonym for mutualism.

例如，当共生被用作互惠的同义词时。

But there are quite a few of us out there who think there should be a clearer distinction made between the two.

但是我们还有很多人认为这两者应该有更加清晰的区别。

Ok, where to begin... Um, the original definition of symbiosis is pretty simple.

好吧，从哪里开始……嗯，共生的原始定义是很简单。

It simply means living together.

它只是意味着生活在一起。

So, any close relationship between two organisms of different species would be considered a symbiotic relationship, including positive and negative relationships.

因此，不同物种的两种生物之间的任何密切关系将被认为是共生关系，包括正面和负面关系。

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

互惠是一种共生，一种特定类型的共生关系，两种生物都以某种方式受益。

So, your book is correct.

所以，你的书是正确的。

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.

现在，我想说明的是，嗯，对于两种生物体，处于互惠关系的正面结果不一定是相等的。

It's not a one-to-one ratio here.

这不是一对一的比例。

Is everyone with me so far?

大家都明白我讲的内容吗？

Symbiosis, general term; mutualism, a narrower or more specific kind of symbiosis. Okay.

共生，通用术语；互惠，范围更小或更具体的共生。好的。

Now, let's take a closer look at mutualistic relationships.

现在，让我们仔细看看互惠的关系。

Um, I'll start off by describing a case of mutualism that involves a certain butterfly species found in South Africa and Australia.

嗯，我先从描述一个涉及在南非和澳大利亚发现的某种蝴蝶物种的互惠的情况开始。

It's a good example of how dependence on a mutualistic relationship can vary.

这是一个很好的例子，说明依赖互惠关系的程度可以有所不同。

Ok, there's this butterfly family and I'll spare you the fancy Latin name because it is not important for our purposes here.

好吧，现在这个蝴蝶科，我会省去花哨的拉丁名，因为它对我们的讲课目的不重要。

Uh, I'll call them Coppers and Blues, well, because most members of this family have blue or copper colored wings.

呃，我叫他们Coppers和Blues，好吧，因为这个科的大多数成员有蓝色或铜色的翅膀。呃，我叫他们Coppers和Blues，好吧，因为这个家族的大多数成员有蓝色或铜色的翅膀。

I think this is one of the most interesting cases of mutualism.

我认为这是互利的最有趣的例子之一。

These butterflies require the presence of ants to complete their life cycle.

这些蝴蝶需要蚂蚁的存在来完成它们的生命周期。

Their interaction with ants is obligatory.

它们与蚂蚁的相互作用是必须有的。

So, this is what happens.

所以，事情是这样的。

A female butterfly of these Coppers and Blues will lay eggs only on vegetation where there are ants of a particular species.

这些Coppers和Blues的雌性蝴蝶将只在住着特定种类的蚂蚁的植被上产卵。

The butterflies can smell, well, ants leave behind pheromones, a special chemical signal.

蝴蝶可以闻到，很好，蚂蚁留下信息素，一种特殊的化学信号。

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.

蝴蝶识别植物上的蚂蚁的信息素，然后是新孵出的蝴蝶，毛虫在从卵孵化后将在这个植物上觅食。

As the caterpillar gets a little older and find shelter under nearby rocks or stones to protect itself from predators.

随着毛虫年龄的增长，它会找到附近的岩石或石头作为庇护，以保护自己免受捕食者的威胁。

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.

总是由蚂蚁参与或护送。总是让它回到宿主植物饲养，由蚂蚁引导，蚂蚁护送服务，可以这么说。

Now, why would the ants go through all this trouble?

现在，为什么蚂蚁会经历这样的麻烦？

What's their benefit? Mary?

它们的好处是什么？Mary？

Student: It's probably related to food?

学生：这可能与食物有关？

Professor: Uh-huh? You are onto something.

教授：嗯？你想到了一些。

Student: Ok, ants feed on sweet stuff, right?

学生：好吧，蚂蚁吃甜的东西，对吧？

So the caterpillar must have some kind of special access to honey or sugars, or something like that.

所以毛虫必须有某种特殊的蜂蜜或糖，或类似的东西。

Maybe caterpillars produce honey somehow.

也许不知怎么的毛毛虫产生蜂蜜。

On second thought, um, I'm probably way off.

经过进一步思考，嗯，我可能是想远了。

Professor: You are pretty close actually.

教授：你真的很接近事实了。

The caterpillars have a honey gland, an organ that secretes an amino acid and carbohydrate liquid.

毛虫具有蜂蜜腺，分泌氨基酸和碳水化合物液体的器官。

The caterpillar secretes the liquid from the honey gland, rather large quantities, enough to feed several ants.

毛虫分泌来自蜂蜜腺的液体，相当大量，足以喂几个蚂蚁。

But what makes this relationship obligatory for the caterpillar?

但是什么使得这种关系对于毛毛虫来说是必须的？

Well, if the ants don't feed regularly on the liquid from the caterpillar's honey gland, the gland overloads and gets infected.

好吧，如果蚂蚁不经常食用来自毛虫的蜂窝腺的液体，那么腺体分泌过量并被感染。

The infection will kill the caterpillar and it will never reach its final stage of development, becoming a butterfly. John?

感染将杀死毛虫，它永远不会达到其发展的最后阶段，成为一只蝴蝶。约翰？

Student: Ok, I just want to make sure I'm following here.

学生：好的，我只是想确认我听懂了。

The caterpillar needs the ants or it won't make it to the stage where it can become a butterfly.

毛虫需要蚂蚁不然它不会使它到达可以成为一只蝴蝶的阶段。

And the ants do this because they get an easy meal out of it, right?

而蚂蚁这样做，是因为它们可以轻松获取食物，对吧？

But the ants don't absolutely need the caterpillar for survival, cause they can get food from other places right?

但蚂蚁不是绝对需要毛毛虫的生存，因为它们可以从其它地方得到食物吗？

So it's still called mutualism even though it seems like the caterpillar's getting way more out of it.

所以它仍然称为互惠，即使它似乎对毛毛虫的更多的利处。

Oh, wait, you said they don't have to equally benefit.

哦，等一下，你说过它们不必对等受益。

Never mind, sorry.

别介意，对不起。

Professor: Yes. But there is a type of mutualism where the relationship is necessary for both organisms to survive.

教授：是。但是存在一种互惠关系，其中关系对于两种生物体都是必需的。

It's called obligatory mutualism.

它被称为强制共生。

And we'll talk about that in the next class.

我们将在下一堂课中讨论这个问题。