『新东方在线托福听力』为托福考生准备了ETS托福TPO/Official 63 Lec3听力练习：What is the lecture mainly about?原文题目答案解析，TPO/Official 63 Lec3听力原文范文音频翻译。

托福TPO/Official 63 Lec3听力原文What is the lecture mainly about?【新东方在线】

旁白：听一段生物学课堂上的讲座。

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

教授：我认为眼睛的晶状体是人体中最迷人的部分之一。

Professor: I think the lens of the eyes is just about the most fascinating part of the body.

首先，它是唯一，我重复一遍，唯一透明的细胞组织。实际上，真正的透明组织在自然界中非常少见。

For one, it's the only, I repeat, only transparent cellular tissue in the human body. In fact, truly transparent tissue is very uncommon in nature.

海洋和河流中生活着一些半透明的生物，比如水母。它们的准透明特性使它们能够与水融为一体以逃避捕食者。

There are some sort of clear creatures that live in oceans and rivers, like the jellyfish. Their quasi transparency allows them to blend in with the water to escape predators.

我说“准”，因为水母是半透明的，不像晶状体那样完全透明。所以你不得不问为什么晶状体是透明的，透明组织是如何实现的？Marlene？

I say quasi, because jellyfish are translucent, they're not totally see-through like the lenses. So you have to wonder why the lens is, how is transparent tissue possible? Marlene?

学生：这部分眼睛没有直接的血液供应。

STUDENT: There's no direct blood supply to that part of the eye.

教授：很好。正是如此，Marlene。血液和血管会使晶状体着色。晶状体可能最终看起来有点粉红色，但这只是解释的一部分。还有什么？

Professor:  Good. Exactly, Marlene. The blood and blood vessels would color the lens. The lens would probably end up looking pinkish, but that's only part of the explanation. What else?

学生：我们读的那一章里提到了晶体和纤维。书中说晶状体有时被称为生物晶体，不是像钻石那样的真晶体，但它有非常规则的细胞排列。细胞精确对齐并紧密堆积。

STUDENT: Well, there was something about crystals and fibers in the chapter we read. It said that the lens is sometimes called a biological crystal, not a true crystal, like a diamond, but it has a very regular arrangement of cells. The cells are exactly aligned and tightly compacted.

教授：正确。它由一层层细胞组成，但所有这些细胞都是同一种类型，一种称为晶状体纤维的刚性细长细胞。

Professor: Right. It's made up of layers of cells, but the cells are all of one type, a rigid elongated cell that's called a lens fiber.

因为它全部由一种类型的细胞构成，并且由于它们规则地排列，你不会遇到不同类型的细胞拼接在一起时产生的各种角度，这会折射光线，在通过时使其弯曲，这有助于其透明度。

Because it's all one kind of cell and because they're aligned so regularly, you don't have all the angles you get when different types of cells are fitted together, which refract light, bend it as it passes through, and that contributes to its transparency.

但是晶状体纤维缺少了某些东西。晶状体纤维没有包含什么？

But there's something missing in a lens fiber. What doesn't a lens fiber have?

学生：我们已经说了血管，对吗？

STUDENT: Well, we said blood vessels, right?

教授：对于晶状体本身来说，对吗？还有别的吗？没有人知道？这不是全部。

Professor: The lens itself, right. Is that it? Anybody? No?

这一点非常重要。晶状体纤维不含细胞器。

This is very important. The lens fibers don't have organelles.

细胞器是像微型器官一样功能的部分，是细胞的特化结构，比如储存DNA的细胞核或作为细胞动力源的线粒体。明白了吗？

Organelles are parts that function like miniature organs, specialized parts of a cell, like the nucleus that stores the DNA or mitochondria, which are the powerhouse of a cell. Okay?

现在有趣的是，当晶状体纤维刚开始形成时，它们起初是有细胞器的细胞。但随着眼睛的发展，这些细胞失去了所有的细胞器，包括细胞核。

Now what's interesting here is that lens fibers as their first forming, they start out as cells with organelles. But as the eye develops, the cells lose all of them, including the nuclei.

没有了细胞器，晶状体纤维就变得干净透明，所有这些晶状体纤维紧密堆积形成了一个漂亮的透明晶状体。

And without organelles, the lens fiber is nice and clear, and all those lens fibers pack together make a nifty crystal clear lens.

但是这种清晰是有代价的。那么，Marlene，它的缺点是什么？

But that clarity comes at a cost. So, Marlene, what's the downside of this?

学生：实际上，如果它没有细胞器，我的意思是DNA或其他物质，那么如果晶状体受损会发生什么？

STUDENT: Actually, well, if it doesn't have organelles, I mean DNA or whatever, and then what happens if the lens is damaged or something?

教授：这就是问题所在。拥有透明晶状体的代价就是晶状体纤维无法像其他细胞那样再生或自我修复，这就引出了我要说的下一点。

Professor: And that's the problem. The price of clear vision of transparent lenses is that the lens fibers can't regenerate or repair themselves, as other cells do, which leads me to this.

随着年龄的增长，晶状体会变得模糊或发黄。可能是白内障，也可能是衰老的结果。

As we get older, the lens can get cloudy or yellow. It can be cataracts, or happen just from aging.

导致这种情况的原因有很多，但归根结底，事实是晶状体纤维无法自我修复。

There are lots of possible causes of that, but when you get down to it, the fact remains that the lens fibers just can't repair themselves.

所以当晶状体变色时，你认为你的视力会发生什么变化？

So when the lens gets discolored, what do you think happens to your sight?

学生：颜色感知会改变，不是吗？

STUDENT: Well, would change your color perception.Wouldn't it?

教授：确实如此。变色的晶状体会吸收某些波长的光，因此有些光线不会到达视网膜，因此某些波长不能被处理，这会影响你的色彩视觉。

Professor: Exactly.Discolored lenses absorb certain wavelengths of light, so some light rays won't reach the retina, so some wavelengths aren't processed, which will affect your color vision.

我刚刚读了一篇关于法国印象派画家克劳德·莫奈的文章。非常有趣，因为它展示了他的一些画作的例子。

I just read an article about the French impressionist painter Claude Monet. And it was really interesting because it showed examples of his paintings.

你可以从他的后期作品中看到他所看到的东西，他是如何看待世界的变化的。

And you could see from his later paintings what he was seeing, how his eyes with his eyesight had changed.

随着年龄的增长，某些颜色开始在他的作品中占据主导地位，如黄色、红色和棕色。他主要看到这些颜色是因为他的晶状体变黄且不再透明。

As he got older, certain colors began to dominate his work, yellows and reds and browns. He was mostly seeing those colors because his lenses had yellowed and weren't transparent anymore.

Why does the professor compare the lens of the human eye to jellyfish?

The professor mentions several features of the lens that contribute to its transparency. Indicate below for each phrase whether it is a feature that contributes to the transparency of the lens.(Click in the correct boxes.)

What does the professor imply about cells that do not contain organelles?

Why does the professor mention French painter Claude Monet?

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