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SSS 2009-07-08

时间:2010-05-18 03:10来源:互联网 提供网友:mark@li   字体: [ ]
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This is Scientific American's 60-second Science. I'm Cynthia Graber, this will just take a minute.

 

Sex might seem like one of those little gifts from evolution. But it’s pretty inefficient1 from an evolutionary2 perspective. It’d be much easier to reproduce if you could do away with finding the right member of the opposite sex to help you create the next generation. So why did evolution come up with sex?Biologists have hypothesized that one driving force might have been parasites4. Now scientists have had a chance to test that theory. Asexual reproduction leads to clones. Being genetically6 identical, clones are also weak in the same ways, and thus more likely to all succumb7 to a parasite3. But sex keeps shuffling8 the genetic5 deck.

 

Well, there’s a snail9 common in New Zealand lakes that does both—some populations have sex and some reproduce asexually. So researchers spent 10 years monitoring the two populations, and the number of parasites living off both groups. As expected, cloned snails10 that were plentiful11 at the beginning of the study suffered big losses as they became infected with parasites. But the sexual snail populations remained stable, results published in the journal American Naturalist12. So, next time you’re feeling sexy, thank a parasite.

 

This is Scientific American's 60-second Science. I'm Cynthia Graber.
 


点击收听单词发音收听单词发音  

1 inefficient c76xm     
adj.效率低的,无效的
参考例句:
  • The inefficient operation cost the firm a lot of money.低效率的运作使该公司损失了许多钱。
  • Their communication systems are inefficient in the extreme.他们的通讯系统效率非常差。
2 evolutionary Ctqz7m     
adj.进化的;演化的,演变的;[生]进化论的
参考例句:
  • Life has its own evolutionary process.生命有其自身的进化过程。
  • These are fascinating questions to be resolved by the evolutionary studies of plants.这些十分吸引人的问题将在研究植物进化过程中得以解决。
3 parasite U4lzN     
n.寄生虫;寄生菌;食客
参考例句:
  • The lazy man was a parasite on his family.那懒汉是家里的寄生虫。
  • I don't want to be a parasite.I must earn my own way in life.我不想做寄生虫,我要自己养活自己。
4 parasites a8076647ef34cfbbf9d3cb418df78a08     
寄生物( parasite的名词复数 ); 靠他人为生的人; 诸虫
参考例句:
  • These symptoms may be referable to virus infection rather than parasites. 这些症状也许是由病毒感染引起的,而与寄生虫无关。
  • Kangaroos harbor a vast range of parasites. 袋鼠身上有各种各样的寄生虫。
5 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。
6 genetically Lgixo     
adv.遗传上
参考例句:
  • All the bees in the colony are genetically related. 同一群体的蜜蜂都有亲缘关系。
  • Genetically modified foods have already arrived on American dinner tables. 经基因改造加工过的食物已端上了美国人的餐桌。 来自英汉非文学 - 生命科学 - 基因与食物
7 succumb CHLzp     
v.屈服,屈从;死
参考例句:
  • They will never succumb to the enemies.他们决不向敌人屈服。
  • Will business leaders succumb to these ideas?商业领袖们会被这些观点折服吗?
8 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
9 snail 8xcwS     
n.蜗牛
参考例句:
  • Snail is a small plant-eating creature with a soft body.蜗牛是一种软体草食动物。
  • Time moved at a snail's pace before the holidays.放假前的时间过得很慢。
10 snails 23436a8a3f6bf9f3c4a9f6db000bb173     
n.蜗牛;迟钝的人;蜗牛( snail的名词复数 )
参考例句:
  • I think I'll try the snails for lunch—I'm feeling adventurous today. 我想我午餐要尝一下蜗牛——我今天很想冒险。 来自《简明英汉词典》
  • Most snails have shells on their backs. 大多数蜗牛背上有壳。 来自《简明英汉词典》
11 plentiful r2izH     
adj.富裕的,丰富的
参考例句:
  • Their family has a plentiful harvest this year.他们家今年又丰收了。
  • Rainfall is plentiful in the area.这个地区雨量充足。
12 naturalist QFKxZ     
n.博物学家(尤指直接观察动植物者)
参考例句:
  • He was a printer by trade and naturalist by avocation.他从事印刷业,同时是个博物学爱好者。
  • The naturalist told us many stories about birds.博物学家给我们讲述了许多有关鸟儿的故事。
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TAG标签:   SSS  evolution
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