英語聽力文摘503 生命的足跡
納尼!還不對?
那究竟是什么呢?
今天的節(jié)目將為您講述生命的起源……
Life Traces in Lava
Don: Can I ask you something, Ya?l?
Ya?l: Sure!
D: Do you ever stop to think about how all living things are ultimately related?
Y: Eh…Yeah, sure.
D: Bu...but I'm serious. Doesn’t it amaze you to realize that we can trace life back millions and millions of years ago to single-celled organisms floating around in the ocean?
Y: Millions? Actually, it's billions and billions.
D: Billions?
Y: Yes, billion! Scientists have discovered lava rock taken from the ocean floor that contains remnants of life that are billions of years old. Three point five billion years, to be precise.
D: What do they find, fossils?
Y: Sort of. At certain spots the ocean floor oozeslava, which cools and forms rock formations. Microorganisms set up shop on the surface of these rocks and thrive on their rich chemical content. The microbes leave traces of their presence in the rocks in the form of tiny tubes.
When researchers looked at three billion plus year old rocks and saw these kinds of tubes, they suspected that microbes once inhabited them. The most convincing piece of evidence was a type of carbon found in the tubes that’s produced by living things. So far, this is one of the oldest traces of life ever found.
熔巖中的生命足跡
Don: Y 我能問你一個事情嗎?
Ya?l: 當(dāng)然!
D: 你有沒有停下來想過人類最初是怎么來的呢?
Y: 額…當(dāng)然啦!
D: 我認(rèn)真的!當(dāng)你意識到人類的起源可以追溯到數(shù)百萬年前漂浮在海洋里的單細(xì)胞生物時(shí)，難道你一點(diǎn)也不驚嘆于造物的神奇?
Y: 數(shù)百萬?實(shí)際上，應(yīng)該是“數(shù)十億”吧!
D: 十億?
Y: 恩，十億。科學(xué)家在海洋底部發(fā)現(xiàn)了含有數(shù)十億年前的生物殘余的熔巖。準(zhǔn)確的說，是35億年前。
D: 他們發(fā)現(xiàn)的是什么?化石?
Y: 好像是。海底的某些地方會滲出巖漿，冷卻過后便形成了巖石。微生物便在這些巖石表面“安營扎寨”，靠著巖石中豐富的化學(xué)成分生長繁衍。這些微生物在巖石中呈微型管狀，留下了他們存在的“足跡”。
當(dāng)研究人員對這些經(jīng)歷了30多億年“磨煉”的巖石進(jìn)行研究時(shí)，發(fā)現(xiàn)了這些微型的小管，便設(shè)想微生物曾經(jīng)棲居于這些巖石之上。最有力的證據(jù)是科學(xué)家在這些管狀物中發(fā)現(xiàn)了一種碳，而這種碳物質(zhì)僅由生物產(chǎn)生。這是迄今為止發(fā)現(xiàn)的最早的生命的“足跡”。
