Notothenioids托福听力原文翻译及问题答案

Notothenioids托福听力原文翻译及问题答案

一、Notothenioids托福听力原文：

NARRATOR:Listen to part of a lecture in a biology class.FEMALE PROFESSOR:...Ways in which animals adapt to their environment are often quite ingenious actually.And as an example of this,let me tell you about a fish,a group of fish known as the Notothenioids.There's over 90 known species of Notothenioids and they inhabit both shallow and very deep waters—mostly around Antarctica.Many are fairly small,though the largest species can weigh up to 150 kilograms.

Notothenioids can be identified by their large eyes,which are covered by a thick insulating layer of clear tissue.This tissue protects their eyes from freezing.Remember,the freezing point of ocean water—salt water—is lower than for fresh water—negative 1.9 degree Celsius...so it can get a lot colder for fish in an ocean,say,than in a river or lake.So...this means that the ocean waters around Antarctica are cold enough to freeze most types of fish,but Notothenioids don't freeze.In fact,they thrive.They account for some 95%of all fish in the southern ocean,the ocean that surrounds Antarctica.So,how unusual is that?To have a single family of fish dominating an entire ocean.I mean,think of,say,tropical or temperate marine environments,which have incredibly diverse fish populations.Coral reefs,for example,support over 4000 types of fish,along with sponges,crustaceans,and many other organisms.So,exactly when and how did the Notothenioids come to dominate the southern ocean?Well,around 30 million years ago,the waters around Antarctica were a lot warmer than they are today.Um...at that time,Antarctica was connected to South America,which means that warm air from the north could flow southward and heat up the Antarctica waters.Because the water around Antarctica then was relatively warm,it supported many types of fish.And we know this from fossil evidence.But the 90 or so species of Notothenioids that exist today didn't exist at all back then.In fact,only one ancestral Notothenioid species existed.But somewhere between 5 million and 14 million years ago,two major changes took place.First,what we call a chance mutation.A tiny genetic change occurred in that one Notothenioid species.Its DNA allowed for the production of a special protein,a protein that prevents the fish from freezing.The way this—this anti-freeze protein works is:it binds to any ice crystals that form inside the fish.This binding action prevents the ice crystals from growing larger.And this is what prevents Notothenioids from freezing.Now,at that time,the waters the Notothenioids inhabited were still not freezing cold,so the protein didn't really make a difference as far as the fish's survival.But this would change,because in the same period of geologic time there was a shift in the earth's continental plates.Continental drift caused Antarctica to move apart from the landmass of South America and to drift into the Southern Polar Region.

This resulted in a powerful water current encircling Antarctica,which prevented the Antarctic waters from mixing with warmer water.So the southern ocean,isolated from that warm airflow from the north,cooled down drastically,to the kinds of sub-freezing temperatures we associate with it today.Now,most fish species couldn't survive in this frigid environment and they became extinct.But that one Notothenioid species,with its unique ability to produce that anti-freeze protein,thrived.It had virtually the entire southern ocean to itself!

So?Well,there was little or no competition for food or space.You might think of it as,um...as a—a kind of ecological vacuum.And the Notothenioids exploited fully.The species migrated into different habitats throughout the southern ocean.And its population increased dramatically,with various sub-populations migrating into different parts of the ocean.Over time these sub-populations in all those different habitats...well,they developed very different physical traits.They adapted to survive in their particular ecological niche,their...their position within a particular ecosystem.

We call this type of species diversification within a species adaptive radiation.And what adaptive radiation is:an evolutionary process by which a parent species rapidly undergoes changes resulting in various new species in order to fill multiple ecological niches.So in the case of the Notothenioids,that single species started colonizing empty habitats to such an extent that it evolved into a broad range of new species,the 90 or so Notothenioid species that we have today.So let me switch to adaptive radiation with regard to another species that's also been very successful....

二、Notothenioids托福听力中文翻译：

旁白：听生物课上的一节课。女教授：……实际上，动物适应环境的方式往往非常巧妙。作为一个例子，让我告诉你一条鱼，一组被称为脊椎动物的鱼。已知的脊椎动物有90多种，它们生活在浅水区和深水区，大多在南极洲附近。虽然最大的物种可以重达150公斤，但许多都相当小。

脊椎动物的大眼睛覆盖着一层厚厚的透明组织，可以通过它们的大眼睛来识别。这种组织保护他们的眼睛免受冰冻。记住，海水-盐水的冰点低于淡水-负1.9摄氏度…因此，海洋中的鱼比河流或湖泊中的鱼要冷得多。因此…这意味着南极洲周围的海水足够冷，可以冻结大多数类型的鱼，但没有哪种鱼类不会冻结。事实上，它们茁壮成长。它们约占南极洲周围海域南大洋所有鱼类的95%。那么，这有多不寻常？让一个鱼群主宰整个海洋。我的意思是，想想，比如说，热带或温带海洋环境，那里的鱼类种群极其多样。例如，珊瑚礁支撑着4000多种鱼类，还有海绵、甲壳类动物和许多其他生物。那幺，到底是什么时候，是如何在南大洋占据统治地位的？嗯，大约3000万年前，南极洲周围的水域比现在温暖得多。嗯…当时，南极洲与南美洲相连，这意味着来自北方的暖空气可以向南流动，并加热南极洲水域。因为当时南极洲周围的海水相对温暖，所以它可以养活多种鱼类。我们从化石证据中知道这一点。但今天存在的大约90种脊椎动物在当时根本不存在。事实上，只有一个祖先的脊椎动物物种存在。但是大约在500万到1400万年前，发生了两次重大变化。首先，我们称之为偶然突变。在这一种非特异性物种中发生了微小的基因变化。它的DNA允许产生一种特殊的蛋白质，这种蛋白质可以防止鱼冻结。这种抗冻蛋白的作用方式是：它与鱼体内形成的任何冰晶结合。这种结合作用防止冰晶变大。这就是防止类脊椎动物冻结的原因。现在，在那个时候，脊椎动物居住的水域还没有结冰，所以蛋白质对鱼类的生存并没有真正的影响。但这会改变，因为在同一地质时期，地球大陆板块发生了变化。大陆漂移导致南极洲远离南美洲大陆，漂移到南极地区。

这导致一股强大的水流环绕南极洲，阻止了南极洲水域与温暖的海水混合。因此，与来自北方的暖流隔绝的南大洋，急剧冷却，达到我们今天认为的亚冰点温度。现在，大多数鱼类无法在这种寒冷的环境中生存，它们灭绝了。但是，这一种具有独特能力产生抗冻蛋白的非特异性物种却蓬勃发展。它几乎拥有整个南大洋！

所以嗯，几乎没有或根本没有食物或空间的竞争。你可能会认为这是一种生态真空。并充分利用了脊椎动物。这些物种迁移到整个南大洋的不同栖息地。它的种群数量急剧增加，各种亚种群迁移到海洋的不同地区。随着时间的推移，这些亚种群在所有这些不同的栖息地…嗯，它们发展出非常不同的身体特征。他们适应了生存在他们特定的生态位他们…他们在特定生态系统中的位置。

我们称这种物种多样性为物种适应性辐射。适应性辐射是什么：一个进化过程，通过这个过程，一个亲本物种迅速经历变化，产生各种新物种，以填补多个生态位。因此，在脊椎动物的例子中，单个物种开始在空旷的栖息地定居，以至于进化成了范围广泛的新物种，即我们今天拥有的大约90个脊椎动物物种。所以，让我来谈谈另一个物种的适应性辐射，它也非常成功。。。。

三、Notothenioids托福听力问题：

Q1:1.What is the lecture mainly about?

A.How various proteins function in notothenioids

B.How notothenioids became the dominant type of fish in the Southern Ocean

C.An example that contradicts the theory of adaptive radiation

D.Changes in ocean habitats caused by continental drift

Q2:2.Why does the professor mention that coral reefs support more than 4,000 species of fish?

A.To find out what students know about tropical fish

B.To contrast two types of ocean environments

C.To imply that there may be species in the Southern Ocean that have not been discovered yet

D.To imply that there may be fossil evidence of coral reefs in the Southern Ocean

Q3:3.What characteristic of notothenioids helps them survive in subfreezing temperatures?

A.They maintain an unusually high body temperature.

B.A special tissue in their eyes enables them to see through ice.

C.Special proteins make their blood circulate too fast to freeze.

D.Ice crystals in their bodies are prevented from growing large enough to harm them.

Q4:4.Why did the antifreeze protein initially give no special advantage to the earliest notothenioids?

A.Many other types of fish had the same protein.

B.The notothenioids were not living in subfreezing temperatures.

C.The effect of the antifreeze protein was neutralized by other proteins.

D.The antifreeze protein functioned only in the smallest notothenioids.

Q5:5.According to the professor,what factors led to the rapid distribution of notothenioids throughout the Southern Ocean?[Click on 2 answers.]

A.A genetic mutation occurred in the DNA of the earliest notothenioid.

B.There was an increase in competition for food in temperate waters.

C.Antarctica broke off and drifted away from the South American continent.

D.The waters around Antarctica temporarily warmed up.

Q6:6.According to the professor,what happened to notothenioids that migrated to different areas of the Southern Ocean?

A.They evolved into a wide variety of notothenioid species.

B.They developed the ability to tolerate a wide range of temperatures.

C.Some of them became extinct because of new predators.

D.Some of them developed additional antifreeze proteins.

四、Notothenioids托福听力答案：

A1:正确答案：B

A2:正确答案：B

A3:正确答案：D

A4:正确答案：B

A5:正确答案：AC

A6:正确答案：A

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