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时差N小时:海洋杀手

时间:2012-02-21 14:04:12 编辑:beck 可可英语APP下载 | 可可官方微信:ikekenet

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Time now for another episode of a Moment of Science. Did you know?

So Yael, did you know that there've been 23 mass extinctions since life begun on earth.

I know there've been a few extinctions, Don, but not that many.

Yep, many were prehistoric bacteria and other single cell microorganisms, but in the past 540 million years or so, there've been about 5 mass extinctions.

Many are marine plants and animals but also off land organisms.

I know that the dinosaurs disappeared about 65 million years ago possibly due to a large meteor crushing into earth and block out the sun.

But what cause all those other extinctions?

That's been a mystery for a long time.

But now some scientists think that most mass extinctions have been driven by the rise and fall of sea level.

That may sound strange.

But consider that millions and millions years ago, a shallow sea covered the entire middle section of North America.

That sea grew and shrank back several times.

Each time it drained, it caused entire species of sea plants and creatures to die off.

The last time it drained was around 65 million years ago when the dinosaurs disappeared.

OK, I understand that was sea vanishing would kill of the marine life.

But did the sea's disappearing also have something to do with the dinosaurs going extinct?

Maybe.

When the sea disappears, it has big effect on climate.

All that water provides heat and moisture.

And when the sea drains, the climate becomes drier and colder.

So the changing climate may have combine with meteor impact to kill off the dinosaurs.

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1. extinction n.熄灭，消灭
例句：His movie of the extinction of dinosaurs was a great success. 他的关于恐龙灭绝的电影取得了巨大的成功F))P;97j*2UV42zkoP*。
2. prehistoric a.史前的
例句：Prehistoric man used flint knives. 史前人用打火石刀-^D6jk@7I2_5]!T([。
3. marine a. 海的, 海产的
例句：Cultivation of marine organisms in their natural habitats is usually for commercial purposes. 在海洋生物的天然栖息地养殖这些生物，通常是出于商业目的8Y!@z^#)79E+%zYnE,。

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重点单词		查看全部解释
impact	['impækt,im'pækt]	想一想再看 n. 冲击(力), 冲突，影响(力) vt.	联想记忆 X 单词impact 联想记忆： im进入，pact压紧的－进入压紧的状态－冲击；影响力
combine	[kəm'bain]	想一想再看 v. 结合，联合，使结合 n. 集团，联合企业	联想记忆 X 单词combine 联想记忆： com共同，一起，bine捆，绑－捆绑在一起－结合
prehistoric	['pri:his'tɔrik]	想一想再看 adj. 史前的 =prehistorical
mass	[mæs]	想一想再看 n. 块，大量，众多 adj. 群众的，大规模
extinct	[iks'tiŋkt]	想一想再看 adj. 灭绝的，熄灭的，耗尽的	联想记忆 X 单词extinct 联想记忆： tin熄灭；
shallow	['ʃæləu]	想一想再看 adj. 浅的，薄的 n. 浅滩，浅处	联想记忆 X 单词shallow 联想记忆： shal，low低的－浅的
extinction	[iks'tiŋkʃən]	想一想再看 n. 消失，消减，废止	联想记忆 X 单词extinction 联想记忆： ex+stinct刺激+ion→灭绝
block	[blɔk]	想一想再看 n. 街区，木块，石块 n. 阻塞(物), 障
understand	[.ʌndə'stænd]	想一想再看 vt. 理解，懂，听说，获悉，将 ... 理解为，认为<
commercial	[kə'mə:ʃəl]	想一想再看 adj. 商业的 n. 商业广告	联想记忆 X 单词commercial 联想记忆： commerce商业+ial表形容词，“有…的”→商业的