Notothenioids托福聽力原文翻譯及問題答案

Notothenioids托福聽力原文翻譯及問題答案

一、Notothenioids托福聽力原文：

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托福聽力中文翻譯：

旁白：聽生物課上的一節(jié)課。女教授：……實(shí)際上，動物適應(yīng)環(huán)境的方式往往非常巧妙。作為一個例子，讓我告訴你一條魚，一組被稱為脊椎動物的魚。已知的脊椎動物有90多種，它們生活在淺水區(qū)和深水區(qū)，大多在南極洲附近。雖然最大的物種可以重達(dá)150公斤，但許多都相當(dāng)小。

脊椎動物的大眼睛覆蓋著一層厚厚的透明組織，可以通過它們的大眼睛來識別。這種組織保護(hù)他們的眼睛免受冰凍。記住，海水-鹽水的冰點(diǎn)低于淡水-負(fù)1.9攝氏度…因此，海洋中的魚比河流或湖泊中的魚要冷得多。因此…這意味著南極洲周圍的海水足夠冷，可以凍結(jié)大多數(shù)類型的魚，但沒有哪種魚類不會凍結(jié)。事實(shí)上，它們茁壯成長。它們約占南極洲周圍海域南大洋所有魚類的95%。那么，這有多不尋常？讓一個魚群主宰整個海洋。我的意思是，想想，比如說，熱帶或溫帶海洋環(huán)境，那里的魚類種群極其多樣。例如，珊瑚礁支撐著4000多種魚類，還有海綿、甲殼類動物和許多其他生物。那幺，到底是什么時候，是如何在南大洋占據(jù)統(tǒng)治地位的？嗯，大約3000萬年前，南極洲周圍的水域比現(xiàn)在溫暖得多。嗯…當(dāng)時，南極洲與南美洲相連，這意味著來自北方的暖空氣可以向南流動，并加熱南極洲水域。因?yàn)楫?dāng)時南極洲周圍的海水相對溫暖，所以它可以養(yǎng)活多種魚類。我們從化石證據(jù)中知道這一點(diǎn)。但今天存在的大約90種脊椎動物在當(dāng)時根本不存在。事實(shí)上，只有一個祖先的脊椎動物物種存在。但是大約在500萬到1400萬年前，發(fā)生了兩次重大變化。首先，我們稱之為偶然突變。在這一種非特異性物種中發(fā)生了微小的基因變化。它的DNA允許產(chǎn)生一種特殊的蛋白質(zhì)，這種蛋白質(zhì)可以防止魚凍結(jié)。這種抗凍蛋白的作用方式是：它與魚體內(nèi)形成的任何冰晶結(jié)合。這種結(jié)合作用防止冰晶變大。這就是防止類脊椎動物凍結(jié)的原因。現(xiàn)在，在那個時候，脊椎動物居住的水域還沒有結(jié)冰，所以蛋白質(zhì)對魚類的生存并沒有真正的影響。但這會改變，因?yàn)樵谕坏刭|(zhì)時期，地球大陸板塊發(fā)生了變化。大陸漂移導(dǎo)致南極洲遠(yuǎn)離南美洲大陸，漂移到南極地區(qū)。

這導(dǎo)致一股強(qiáng)大的水流環(huán)繞南極洲，阻止了南極洲水域與溫暖的海水混合。因此，與來自北方的暖流隔絕的南大洋，急劇冷卻，達(dá)到我們今天認(rèn)為的亞冰點(diǎn)溫度?，F(xiàn)在，大多數(shù)魚類無法在這種寒冷的環(huán)境中生存，它們滅絕了。但是，這一種具有獨(dú)特能力產(chǎn)生抗凍蛋白的非特異性物種卻蓬勃發(fā)展。它幾乎擁有整個南大洋！

所以嗯，幾乎沒有或根本沒有食物或空間的競爭。你可能會認(rèn)為這是一種生態(tài)真空。并充分利用了脊椎動物。這些物種遷移到整個南大洋的不同棲息地。它的種群數(shù)量急劇增加，各種亞種群遷移到海洋的不同地區(qū)。隨著時間的推移，這些亞種群在所有這些不同的棲息地…嗯，它們發(fā)展出非常不同的身體特征。他們適應(yīng)了生存在他們特定的生態(tài)位他們…他們在特定生態(tài)系統(tǒng)中的位置。

我們稱這種物種多樣性為物種適應(yīng)性輻射。適應(yīng)性輻射是什么：一個進(jìn)化過程，通過這個過程，一個親本物種迅速經(jīng)歷變化，產(chǎn)生各種新物種，以填補(bǔ)多個生態(tài)位。因此，在脊椎動物的例子中，單個物種開始在空曠的棲息地定居，以至于進(jìn)化成了范圍廣泛的新物種，即我們今天擁有的大約90個脊椎動物物種。所以，讓我來談?wù)劻硪粋€物種的適應(yīng)性輻射，它也非常成功。。。。

三、Notothenioids托福聽力問題：

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托福聽力答案：

A1:正確答案：B

A2:正確答案：B

A3:正確答案：D

A4:正確答案：B

A5:正確答案：AC

A6:正確答案：A

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