『新东方在线托福听力』为托福考生准备了ETS托福TPO/Official 18 Lec 4听力练习，Official 18 Lec 4原文答案解析，Official 18 Lec 4听力原文练习音频翻译。

托福TPO/Official 18 Lec 4听力原答案解析-音频翻译【新东方在线】

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

教授：嗯，现在看来，春天终于要到来了。

Professor: Well, it's finally looking like spring is arriving.

几天之后，最后的冬雪将会融化。

The last of the winter snow would be melting away in a few days.

所以，在我们今天结束课程之前，我想谈谈一个与冬春换季有关的生物学事例，这个事情你们如果有耐心的话，自己出门儿就能观察到。

So before we close today, I thought I'd mention a biological event that's a part of the transition from winter to spring, something you can go outside and watch if you have some patience.

这个片区内生活着一群小动物——你们很可能已经见过了。

There is a small creature that lives in this area; you've probably seen it.

现在林蛙不是特别好找，因为它们和地面贴得很近，而且藏在树叶等与它们外形相似、可以掩盖它们踪迹的隐蔽物下面。

Now the wood frog's not that easy to spot since it stays pretty to close to the ground, under leaves and things and it blends in really well with its background as you can see.

但是，它们值得你们费这番功夫，因为它们有一个非常奇妙的本领，这项本领你们想来绝对不可思议。

But they are worth the effort because they do something very unusual, something you might not have even thought possible.

好的，北美林蛙生活的地域是非常广阔的。

OK. North American wood frogs live over a very broad territory or range.

从美国北部一直到加拿大和阿拉斯加甚至到北极圈，你们都能够看到它的身影。

They're found all over the northeastern United States and all through Canada and Alaska, even inside the Arctic Circle.

没有另外一种蛙类可以生活在如此遥远的北地。

No other frog is able to live that far and north.

但不管它们到底生活在那一个地方，一旦天气变冷，气温达到冰点以下，甚至只要林蛙碰到了一小点冰渣或冻土，它马上就会被冷冻起来。

But wherever they live, once the weather starts to turn cold and the temperature starts to drop below freezing, as soon as the frog even touches an ice crystal or a bit of frozen ground, well, it begins to freeze.

学生：等一下，您的意思是，它是活着的，但它是冰冻、不动的？

Student: Wait, you mean it's still alive but it freezes, solid?

在林蛙的体内，除了细胞之外的空间里，到处都是冰。

Ice forms in all the spaces outside the cells but never within a cell.

学生：但是……这样的话，它的心脏怎么跳动呢？

Student: But… then how does its heart beat?

教授：它的心脏那时已经不跳了。

教授：你是想知道这是怎么一回事吗？

Professor: You are gonna do such a thing?

嗯，林蛙接触冰这个动作触发了林蛙体内的生理反应。

Well, that first touch of ice apparently triggers a biological response inside the frog.

首先，这个反应会导致体腔内脱水，所以，在林蛙的中部，它的内部器官，包括心脏、肺、肝都会变得越来越干燥，当水流出的时候在器官周围形成水坑就在皮肤下面。

That first of all starts drawing water away from the center of its body, so the middle part of the frog, its internal organs, its heart, lungs, liver, these start getting drier and drier while the water that's being pulled away is forming a puddle around the organs just underneath the skin.

And then that puddle of water starts to freeze.

好的，到了现在这一步，林蛙的心脏依旧是在跳跃，对吗？

OK, up to now, the frog's heart is still beating, right?

越来越慢，但是……到结冰前的几个小时里，它的体内会释放葡萄糖这一血糖到全身的循环系统，这种葡萄糖似乎起到的是抗冻剂的作用。

Slower and slower but…and in those last few hours before it freezes, it distributes glucose, a blood sugar throughout its body, its circulatory system, sort of acts like an antifreeze.

学生：林蛙的这种释放葡萄糖的这种做法，就像我们在冬季往车里加抗冻剂一样吗？

Student: A solution of antifreeze like you put in your car in the winter?

教授：嗯，一会儿我讲完了你来告诉我吧。

在林蛙体内，超量的葡萄糖会使得它们在冬季时细胞内部的水分很难结冰。

In frogs, the extra glucose makes it harder for the water inside the cells to freeze.

所以，那时细胞仅仅会湿润一些，而这个湿度恰恰是保证它们在冬季的生存的程度。

So the cells stay just slightly wet, enough so that they can survive the winter.

等到了那时，心脏的全部机能都会停止。

Then after that, the heart stops beating altogether.

所以，你还觉得你的比喻恰当吗？

学生：我真的不知道，不过，这种状态会持续多久呢？

Student: I don't really know, but how long does it stay that way?

教授：嗯，长则几个月，甚至整个冬天，短则几天，实际上，嗯，心脏不需要输送血液，因为血液也是凝固的。

Professor: Well, it could be days or even months, all winter in fact but umm, see the heart really doesn't need to do any pumping now because the blood is frozen too.

学生：我想，只是这样想，我不明白，它这种状态为什么还是活着的，因为按照临床医学的经验来说，它已经死了。

Student: I just, I guess I just don't see how it isn't, you know, clinically dead.

教授：嗯，那就是它的神奇所在。并且，它的解冻过程，也是令人吃惊的。

Professor: Well, that's the amazing thing and how it revives is pretty amazing too.

在长达数月的心脏停跳期后，春季再次降临，地球又重新开始温暖如春，突然某一天，一声脉搏的颤动之后，接着又来了一个……脉搏恢复了大概10到12个小时之后，林蛙就彻底恢复了。

After months without a heartbeat, spring time came around again, the earth starts to warm up and suddenly one day, ping, a pulse, followed by another one, then another until maybe ten, twelve hours later, the animal is fully recovered.

学生：那么这种解冻的过程是否也有一个触发点呢？

Student: And does the thawing process have some kind of trigger as well?

教授：嗯，我们目前也不清楚，我们可能会想到的是，当温暖的阳光叫醒青蛙之后，它的躯体内部包括大脑、心脏等会率先恢复。

Professor: Well, we are not sure actually, the clearer thing is even though the sun is warning the frog up on the outside, its inside thaw out first, the heart and brain and everything.

但事实上，每次春季的时候，林蛙的身体解冻是一次性到位的。

But somehow it all just happens that way every spring.

学生：解冻之后呢？对它们有影响吗？比如它们的寿命？

Student: And after they thaw? Does it affect them? Like their lifespan?

教授：嗯，我们现在还没有研究清楚一只林蛙正常情况下会存活多久，有可能是几年，但是没有证据表明冰冻过程会影响它的寿命。

Professor: Well, hmm, we really don't know a lot about how long a wood frog normally lives, probably just a few years but there is no evidence that the freezing process affects its longevity.

但这个过程对林蛙的其他方面倒有一定影响。

一些研究中，我们发现到了繁殖季，有过冰冻经历的雄性林蛙交配次数会减少。

In studies, we found that when it comes to reproduction, freezing diminishes the mating performance of males.

在它们冰冻——解冻之后，它们鸣叫求偶的欲望并不十分强烈。

After they've been frozen and thawed of course, they don't seem quite as vocal.

它们跑动得很慢，而且更难找到一个潜在的雌性交配。

They move slower and they seem to have a harder time recognizing a potential mate.

所以，如果雄性林蛙能够设法避免进入冰冻周期的话，它交配的成功率就会大一些。

So if the male frog could manage not to go through this freezing cycle, he'd probably have more success in mating.

Why does the professor first mention the arrival of spring?

What happens to a wood frog as it begins to freeze?

What are two points the professor makes about the thawing process of the wood frog?

What impact does freezing have on some thawed wood frogs?

What does the professor imply when she says this:

A：Well, it’s finally looking like spring is arriving. The last of the winter snow would be melting away in a few days. So before we close today, I thought I’d mention a biological event that’s a part of the transition from winter to spring, something you can go outside and watch if you have some patience. There is a small creature that lives in this area; you’ve probably seen it. It’s the North American wood frog. Now the wood frog’s not that easy tosspot since it stays pretty to close to the ground, under leaves and things and it blends in really well with its background as you can see. 
But they are worth the effort because they do something very unusual, something you might not have even thought possible. OK North American wood frogs live over a very broad territory or range. They’re found all over the northeastern United States and all through Canada and Alaska, even inside the Arctic Circle. No other frog is able to live that far and north. But wherever they live, once the weather starts to turn cold and the temperature starts to drop below freezing, as soon as the frog even touches an ice crystal or a bit of frozen ground, well, it begins to freeze. 
A：Well, it’s finally looking like spring is arriving. The last of the winter snow would be melting away in a few days. So before we close today, I thought I’d mention a biological event that’s a part of the transition from winter to spring, something you can go outside and watch if you have some patience. There is a small creature that lives in this area; you’ve probably seen it. It’s the North American wood frog. Now the wood frog’s not that easy tosspot since it stays pretty to close to the ground, under leaves and things and it blends in really well with its background as you can see. 
Yeah...yes to me. You look a little bit taken aback. 
B: Wait, you mean it’s still alive but it freezes, solid? 
A: Well, almost. Ice forms in all the spaces outside the cells but never within a cell. 
B: But… then how does its heart beat? 
A: It doesn’t. 
B: But…then how could it……. 
A: You are gonna do such a thing? Well, that first touch of ice apparently triggers a biological response inside the frog. That first of all starts drawing water away from the center of its body, so the middle part of the frog, its internal organs, its heart, lungs, liver, these start getting drier and drier while the water that’s being pulled away is forming a puddle around the organs just underneath the skin. And then that puddle of water starts to freeze. OK, up to known, the frog’s heart is still beating, right? Slower and slower but…and in those last few hours before it freezes, it distributes glucose, a blood sugar throughout its body, its circulatory system, sort of acts like an antifreeze. 
A: Well, that’s the amazing thing and how it revives is pretty amazing too. After months without a heartbeat, spring time came around again, the earth starts to warm up and suddenly one day, ping, a pulse, followed by another one, then another until maybe ten, twelve hours later, the animal is fully recovered. 
B: And does the thawing process have some kind of trigger as well? 
A: Well, we are not sure actually, the clearer thing is even though the sun is warning the frog up on the outside, its inside thaw out first, the heart and brain and everything. But somehow it all just happens that way every spring. 
B: But after they thaw does it affect them like their lifespan? 
A: Well, hmm, we really don’t know a lot about how long a wood frog normally lives, probably just a few years but there is no evidence its longevity. It does have some other impacts though. In studies, we found that when it comes to reproduction, freezing diminishes the mating performance of males. After they’ve been frozen and thawed of course, they don’t seem quite as vocal. They move slower and they seem to have a harder time recognizing a potential mate. So if the male frog could manage not to go through this freezing cycle, he’d probably have more success in mating. 
B: And does the thawing process have some kind of trigger as well? 
A: Well, we are not sure actually, the clearer thing is even though the sun is warning the frog up on the outside, its inside thaw out first, the heart and brain and everything. But somehow it all just happens that way every spring. 
B: But after they thaw does it affect them like their lifespan? 
A: Well, hmm, we really don’t know a lot about how long a wood frog normally lives, probably just a few years but there is no evidence its longevity. It does have some other impacts though. In studies, we found that when it comes to reproduction, freezing diminishes the mating performance of males. After they’ve been frozen and thawed of course, they don’t seem quite as vocal. They move slower and they seem to have a harder time recognizing a potential mate. So if the male frog could manage not to go through this freezing cycle, he’d probably have more success in mating. 
B: A solution of antifreeze like you put in your car in the winter? 
A: Well, you tell me. In frogs, the extra glucose makes it harder for the winter inside the cells to freeze. So the cells stay just slightly wet, enough so that they can survive the winter. Then after that, the heart stops beating altogether. So is that the same? 
B: I don’t really know, but how long dose it stay that way? 
A: Well, it could be days or months, all winter in fact but umm, see the heart really doesn’t need to do any pumping now because the blood is frozen too. 
B: I just, I guess I just don’t see how it isn’t, you know, clinically dead.

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