艾斯英语听力材料

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[00:00.00]This is What’s Trending Today...

[00:03.09]Three million years may seem like a long time.

[00:08.25]But when you consider that planet Earth is more than 4.5 billion years old, it is a pretty short period of time.

[00:19.43]And it is over that shorter time period that the whales in our oceans today got to be so large.

[00:30.08]The blue whale is the largest animal that has ever lived.

[00:34.80]They weigh more than even the biggest dinosaurs.

[00:40.35]They can grow to 30 meters long and weigh up to 130,000 kilograms.

[00:49.64]Blue whales are part of the baleen whale family.

[00:54.17]Baleen is a kind of food-filtering structure in the mouths of the whales.

[01:00.51]The whales developed this system about 30 million years ago.

[01:07.09]Other whales in the baleen family include fin whales, bowhead whales, and right whales.

[01:16.45]Today, these whales can weigh well over 70,000 kilograms.

[01:23.74]But for millions of years, they were not nearly that large, scientists say.

[01:31.07]“All of a sudden – ‘boom’ – we see them get very big, like blue whales,” scientist Nick Pyenson told the New York Times.

[01:42.26]He and other researchers recently published an article on whale size in the British research journal Proceedings of the Royal Society B.

[01:55.73]“It’s like going from whales the size of minivans to longer than two school buses,” Pyenson added.

[02:04.32]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.

[02:21.25]This change led to food becoming more easily available.

[02:26.46]An oncoming ice age made the ocean water cold.

[02:30.96]High winds mixed the water in the ocean faster than before.

[02:36.77]Rain and snow made more nutrients run off from the land into the water.

[02:44.14]The nutrients resulted in algae.

[02:47.68]That attracted small fish and shrimp called krill.

[02:53.52]The mixture of nutrients resulted in more food for large whales to eat.

[02:59.90]Whales that were able to quickly eat a lot of food survived. And they got larger.

[03:07.11]Whales that had teeth instead of baleen, however, did not survive.

[03:13.65]The largest baleen whales then produced other large whales.

[03:19.78]Over the next three or four million years, the baleen whales grew 10 times bigger than they had been, the researchers say.

[03:30.65]It is possible that the largest whales are gone, the researchers said.

[03:36.63]But, as they told the BBC, blue whales could grow even bigger -- or they could slowly die – depending on Earth’s changing climate.

[03:49.80]And that’s What’s Trending Today.

[03:52.30]I’m Dan Friedell.