VOA慢速英语2017--鲸鱼什么时候变得如此之大?

 

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Three million years may seem like a long time. But when you consider that planet Earth is more than 4.5 billion years old, it is a pretty short period of time.

And it is over that shorter time period that the whales in our oceans today got to be so large.

The blue whale is the largest animal that has ever lived. They weigh more than even the biggest dinosaurs¹. They can grow to 30 meters long and weigh up to 130,000 kilograms.

Blue whales are part of the baleen² whale family. Baleen is a kind of food-filtering structure in the mouths of the whales. The whales developed this system about 30 million years ago.

Other whales in the baleen family include fin³ whales, bowhead whales, and right whales. Today, these whales can weigh well over 70,000 kilograms.

But for millions of years, they were not nearly that large, scientists say.

“All of a sudden – ‘boom’ – we see them get very big, like blue whales,” scientist Nick Pyenson told the New York Times. He and other researchers recently published an article on whale size in the British research journal Proceedings⁴ of the Royal Society B.

“It’s like going from whales the size of minivans to longer than two school buses,” Pyenson added.

The researchers -- Pyenson, Jeremy Goldbogen and Graham Slater -- believe that a change in the Earth’s climate caused whales to get so large only about 3 million years ago.

This change led to food becoming more easily available.

An oncoming ice age made the ocean water cold. High winds mixed the water in the ocean faster than before. Rain and snow made more nutrients⁵ run off from the land into the water. The nutrients resulted in algae⁶. That attracted small fish and shrimp⁷ called krill.

The mixture of nutrients resulted in more food for large whales to eat.

Whales that were able to quickly eat a lot of food survived. And they got larger. Whales that had teeth instead of baleen, however, did not survive.

The largest baleen whales then produced other large whales.

Over the next three or four million years, the baleen whales grew 10 times bigger than they had been, the researchers say.

It is possible that the largest whales are gone, the researchers said. But, as they told the BBC, blue whales could grow even bigger -- or they could slowly die – depending on Earth’s changing climate.

Words in This Story

baleen – n. cartilage that filters food and water from the mouths of large whales

cartilage – n. a strong but flexible material found in some parts of the body (such as the nose, the outer ear, and some joints)

filter – n. a device that is used to remove something unwanted from a liquid or gas that passes through it

algae – n. simple plants that have no leaves or stems⁸ and that grow in or near water

minivan – n. a small van designed to carry people and families

1 dinosaurs   

n.恐龙( dinosaur的名词复数 )；守旧落伍的人，过时落后的东西

参考例句：

• The brontosaurus was one of the largest of all dinosaurs. 雷龙是所有恐龙中最大的一种。 来自《简明英汉词典》
• Dinosaurs have been extinct for millions of years. 恐龙绝种已有几百万年了。 来自《简明英汉词典》

2 baleen   

n.鲸须

参考例句：

• Other baleen whales have splash guards too,but not like this.一些须鲸物种头顶也有护住喷水孔的构造，但并不长成这样。
• Baleen whales often appear in this region. Be careful!这一带经常有须鲸出没，要注意安全啊。

3 fin   

n.鳍；(飞机的)安定翼

参考例句：

• They swim using a small fin on their back.它们用背上的小鳍游动。
• The aircraft has a long tail fin.那架飞机有一个长长的尾翼。

4 proceedings   

n.进程，过程，议程；诉讼(程序)；公报

参考例句：

• He was released on bail pending committal proceedings. 他交保获释正在候审。
• to initiate legal proceedings against sb 对某人提起诉讼

5 nutrients   

n.（食品或化学品）营养物，营养品( nutrient的名词复数 )

参考例句：

• a lack of essential nutrients 基本营养的缺乏
• Nutrients are absorbed into the bloodstream. 营养素被吸收进血液。 来自《简明英汉词典》

6 algae   

n.水藻，海藻

参考例句：

• Most algae live in water.多数藻类生长在水中。
• Algae grow and spread quickly in the lake.湖中水藻滋蔓。

7 shrimp   

n.虾，小虾；矮小的人

参考例句：

• When the shrimp farm is built it will block the stream.一旦养虾场建起来，将会截断这条河流。
• When it comes to seafood,I like shrimp the best.说到海鲜，我最喜欢虾。

8 stems   

n.（花草的）茎( stem的名词复数 )；词干；（高脚酒杯的）脚；烟斗柄v.遏制[阻止]（液体的流动等）( stem的第三人称单数 )；封堵；遏止

参考例句：

• The present wave of strikes stems from discontent among the lower-paid. 当前的罢工浪潮起因于低工资雇员们的不满情绪。 来自《简明英汉词典》
• Her interest in flowers stems from her childhood in the country. 她对花卉的兴趣产生于她在乡下度过的童年时代。 来自《简明英汉词典》