『新东方在线托福听力』为托福考生准备了ETS托福TPO/Official 66 Lec1听力练习：According to the hypotheses discussed by the professor, what determines how alert we feel at a particular time of the day? Click on 2 answers.原文题目答案解析，TPO/Official 66 Lec1听力原文范文音频翻译。

托福TPO/Official 66 Lec1听力原文According to the hypotheses discussed by the professor, what determines how alert we feel at a particular time of the day? Click on 2 answers.【新东方在线】

Listen to a part of lecture in a biology class

好的，今天我想谈谈睡眠。我们都要睡觉。人类睡觉，许多动物也睡觉。

Professor: OK, today, I want to talk about sleep. We all sleep. Human sleep, many animal sleep.

当我们睡觉时，我们实际上并不是无意识的，而是处于一种对周围环境意识减弱的状态。

When we sleep, we aren't actually unconscious, but in a state of reduced awareness of our surroundings.

那么，如果野生动物处于这种状态，这对它们意味着什么呢?这时，它们是无法监控它们周围的环境。

Now, what does that mean for animals in the wild, if they are in a state like that? Unable to monitor their environment?

男学生：它们很无助，可能在捕食者面前更容易受到侵害。

Male Student: Well, they're helpless, vulnerable to predators, maybe.

教授：确实。它们很容易受到捕食者的攻击。是的,因为它们在睡觉。

Professor: Right. They are vulnerable to predators. Yeah, they sleep.

让我们来谈谈从生物学的角度，为什么需要睡眠。

So let's talk about why, the biology of sleep.

我想让你们明白的第一件事是睡觉是非常危险的行为。

So the first thing l want you to understand is that sleeps a very risky behavior.

这种风险行为是不会进化的，除非它给动物带来的好处，而这种好处超过了风险本身。

And risky don't evolve unless they bring the animals some kind of benefit that outweighs that risk.

所以睡眠一定有一个非常重要的功能。

So sleep must have a really important function.

我想强调的是，睡眠和其他形式的不活动(如有规律的休息)是有区别的。

And I want to emphasize that there is a difference between sleep and other forms of inactivity, like regular rest.

例如，昆虫会休息。但他们不睡觉。

The insects, for instance, rest. But they don't sleep.

睡眠的特殊之处在于，大脑会改变许多日常大脑活动，包括大脑与感觉和运动器官的连接，大脑会关闭这些连接。

What's specific to sleep is that the brain alters many of its usual activities, including its connection to sensory and motor organs, it shuts those connections down.

所以睡觉的动物通常既不会感知外界也不会移动。我说通常是因为…我们马上就会讲到。

So a sleeping animal can usually neither sense nor move. And I say usually because…well, we will get to that in a minute.

所以，基本上所有的哺乳动物和鸟类都会睡觉。但是有一些不同寻常的睡眠方式。

So, basically all mammals and birds sleep. But there are some unusual ways of sleeping.

水生哺乳动物，比如海豚需要时不时游到水面换气，所以它们不能完全关闭所有的运动和感觉器官。

Take marine mammals. Like dolphins, dolphins need to swim up for air once in a while, so they can't completely shut off all movement and sensation.

所以他们的大脑不能完全不工作。但海豚是如何做到的呢?

So their brain can't shut down completely. But dolphins get around this. How?

它们不是只有一个大脑半球在睡觉吗?

won't they sleep one brain hemisphere at a time?

睡觉的海豚实际上看起来只是在休息，它们其实醒着，而且偶尔会游上来换气。

Sleeping dolphins actually look like they're just resting, awake and occasionally swim up for air.

那如何判定它们是在睡觉还是没有睡觉呢？我们测试它们的大脑活动，当它们睡觉的时候，回忆一半的大脑继续活跃而另一半在睡觉。这是一个适应环境的行为。

So how can we even tell their sleeping? Well, we measured their brain activity which showed that 1/2 was active while the other was sleeping. That's some adaptation, uh?

那么，睡眠的作用是什么呢?就像我说的，睡眠一定很重要，但为什么呢?

So, what is the function of sleep? As I said, it must be important, but why?

好吧。我知道你们都想说，当整个身体休息时，睡眠是我们从体力活动中恢复的机制。

Okay. I know you're all tempted to say, uh, that sleeps when the whole body rests that sleep is our mechanism to recover from physical activity.

这种说法没错。当你睡觉的时候，你的肌肉会失去张力，会放松，身体会储存能量。

And it's true. When you sleep, your muscles lose their tone, they relax, the body saves energy.

我的意思是，这可能是昆虫休息时发生的事情。

But this could happen even during regular waking rest. I mean, that's probably what happens when insects rest.

你需要睡觉不是因为这些。如果你醒着休息，也能得到同样的好处。所以这并不能解释为什么我们需要睡眠。

You don't need sleep for that. You can get the same benefit by resting awake. So this doesn't explain why sleep involved.

要说明睡眠的真正功用，最重要的好处,你需要把注意力放在大脑上，而不是肌肉上。

To explain the real function, the most important benefit of sleep. You'll need to focus on the brain, not the muscles.

还记得我们是如何知道海豚睡觉不仅仅是休息的吗?这是因为它有一种独特的大脑活动模式，这表明睡眠功能与大脑有特殊的关系。

Remember how we can tell that a dolphin sleeping not just resting, is because of a unique pattern of brain activity, which is a clue that sleeps function has to do specifically with the brain.

这是普遍共识，这是可以解释睡眠为什么会进化了。

And that's the general consensus cause, that's what could explain by it evolved.

这也解释了为什么睡眠是哺乳动物和鸟类的特征，因为它们拥有所有动物中最复杂的大脑。

It also explains why sleep is a characteristic of mammals and birds, because they have the most complex brains of all animals.

更简单的大脑，呃，就像爬行动物，睡得很少，甚至不睡也能生存。

The simpler brain uh like a reptile gets by with little sleep or even without sleep.

好吧，我们知道睡眠对大脑有好处，但这是以什么方式呢? 我们还不确定。

OK, so we know that sleep benefits the brain but in what way? We are not sure yet.

好的。所以有一种假设是，在睡眠期间，大脑会合成醒着时正常工作所需的分子。

Okay. So one hypothesis is that during sleep, the brain's synthesize molecules that it needs for proper functioning when awake.

我们醒着的时间越长，这些分子消耗的就越多。

The longer we stay awake, the more those molecules get depleted.

所以大脑需要补充能量，而这中能量应该是在睡眠时积聚。

So the brain needs to replenish them, and this supposedly happens during sleep.

我说的是能量来源，比如糖原和一些神经递质，它们是神经细胞之间传递信号所必需的。

I'm talking about energy sources like glycogen and some types of neuro-transmitter that are needed to transmit signals between nerve cells.

睡眠补给了这些物质，这样第二天早上我们的大脑就会再次充满能量和神经递质。

So these get replenish during sleep and the next morning our brain is working with a full supply of energy and neuro-transmitters again.

这就解释了为什么我们在晚上睡觉后，第二天会感觉如此警觉和精神振奋。是的，Jim?

With that explains why we feel so alert and mentally refreshed after night sleep. Yes, Jim?

男学生：我早上的工作状态一点也不好。

Male Student: Well, you know, I don't work well in the morning at all.

女学生：是的，我都是晚上工作效率高。

Female Student: Yeah, I do my best work at night too.

不是每个人早上都处于最佳状态。我承认这一点。

Professor: Not everyone's at their best in the morning. I grant you that.

但这并不说补充能量假说这种说法不对。只是真实情况比我说的要复杂一点。

But that doesn't rule out the replenishment hypothesis. It's just a bit more complicated than I said.

科学家可以肯定的是，在睡眠之外还有另一种精神活动的节奏。

They were fairly sure that there's this other rhythm of mental activity going on that independent of sleep.

这就像一个24小时的程序循环。你的大脑活动在每天特定的时间达到顶峰，比如对你俩来说是晚上。

It's like a pre-program 24 hours cycle. Your mental activity peaks at a certain hour every day, like at night, for you two.

然后在另一时间点精力会下降。

And then it goes down at some other point.

但问题是，一个不眠之夜之后，峰值就不会像正常情况下那么高了，时间越长，峰值就越低。

But the point is that after a sleepless night, that peak is not as high as it would normally be, and the longer you go without, the lower those peaks get.

因此，可能需要大脑的能量补给来保证精神状态的峰值。这么说，明白吗？

So the replenishment may be needed to keep the mental peak high. Does that make sense?

这两种机制并不相互排斥。这就是我想说的。

The two mechanisms are not mutually exclusive. That's what I'm trying to say.

Why does the professor mention that sleep is a risky behavior?

According to the professor, why is the sleep of dolphins unusual?

What does the professor conclude about the view that the main function of sleep is to allow the body to recover from physical activity?

According to the hypotheses discussed by the professor, what determines how alert we feel at a particular time of the day? Click on 2 answers.

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