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SSS 2008-11-06

时间:2010-05-15 05:57来源:互联网 提供网友:木渐浅。   字体: [ ]
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This is Scientific American's 60-Second Science. I'm Karen Hopkin. This will just take a minute.

 

Why bother with sex? It’s a question that’s bugged1 biologists since they first noticed that some critters do it and some don’t. The answer they’ve come up with is that sex generates genetic2 diversity, which could allow a species to better adapt to changing environments. That’s because sex mixes together the genes3 from mom and dad. And, like shuffling4 a deck of cards and dealing5 new hands, sometimes the kids will get a better combination of genes than their parents had.

So how do species that reproduce by cloning weather change? It turns out not all clones are alike. Scientists from Melbourne were studying a kind of mite6 that reproduces asexually. In the process, sometimes rare mutations occur, so a clone might be a little different from its parent, and from the rest of the population.

What the scientists found is that sometimes these rare mutants are favored by natural selection. Maybe they’re a little better at hiding from predators7. So they leave behind more offspring, and eventually come to dominate the population. When circumstances change, another rare mutant might gain favor, results that appear in the current issue of the Proceedings8 of the National Academy of Sciences. So sex isn’t necessary, as long as you’re willing to back somebody different when it’s time for a change.

 

Thanks for the minute for Scientific American's 60-Second Science. I'm Karen Hopkin.

 


点击收听单词发音收听单词发音  

1 bugged 095d0607cfa5a1564b7697311dda3c5c     
vt.在…装窃听器(bug的过去式与过去分词形式)
参考例句:
  • The police have bugged his office. 警察在他的办公室装了窃听器。 来自《简明英汉词典》
  • He had bugged off before I had a chance to get a word in. 我还没来得及讲话,他已经走了。 来自《简明英汉词典》
2 genetic PgIxp     
adj.遗传的,遗传学的
参考例句:
  • It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
  • Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。
3 genes 01914f8eac35d7e14afa065217edd8c0     
n.基因( gene的名词复数 )
参考例句:
  • You have good genes from your parents, so you should live a long time. 你从父母那儿获得优良的基因,所以能够活得很长。 来自《简明英汉词典》
  • Differences will help to reveal the functions of the genes. 它们间的差异将会帮助我们揭开基因多种功能。 来自英汉非文学 - 生命科学 - 生物技术的世纪
4 shuffling 03b785186d0322e5a1a31c105fc534ee     
adj. 慢慢移动的, 滑移的 动词shuffle的现在分词形式
参考例句:
  • Don't go shuffling along as if you were dead. 别像个死人似地拖着脚走。 来自英汉文学 - 嘉莉妹妹
  • Some one was shuffling by on the sidewalk. 外面的人行道上有人拖着脚走过。 来自英汉文学 - 嘉莉妹妹
5 dealing NvjzWP     
n.经商方法,待人态度
参考例句:
  • This store has an excellent reputation for fair dealing.该商店因买卖公道而享有极高的声誉。
  • His fair dealing earned our confidence.他的诚实的行为获得我们的信任。
6 mite 4Epxw     
n.极小的东西;小铜币
参考例句:
  • The poor mite was so ill.可怜的孩子病得这么重。
  • He is a mite taller than I.他比我高一点点。
7 predators 48b965855934a5395e409c1112d94f63     
n.食肉动物( predator的名词复数 );奴役他人者(尤指在财务或性关系方面)
参考例句:
  • birds and their earthbound predators 鸟和地面上捕食它们的动物
  • The eyes of predators are highly sensitive to the slightest movement. 捕食性动物的眼睛能感觉到最细小的动静。 来自《简明英汉词典》
8 proceedings Wk2zvX     
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
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