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SSS 2008-01-30

时间:2010-05-13 01:41来源:互联网 提供网友:0922013129   字体: [ ]
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This is Scientific American’s 60-Second Science. I’m Karen Hopkin. This will just take a minute.

Every expecting mother gets asked the question: boy or girl? For mammals like us, it’s an easy call. Two X chromosomes1 you get pink booties. X and a Y you get blue. But for some reptiles2, the answer depends on the weather. Well, on the temperature to be precise. For many lizards4 and turtles and gators, the sex of the hatchlings depends on the temperature in the nest where the eggs incubate. But why would animals bother with such a seemingly slapdash system for assigning sex? And the only logical answer is, there must be some benefit. Each sex must fare better at the temperature that tends to produce that sex. A fine theory, but no one has been able to test it until now. In the January 20 online issue of Nature, scientists at Iowa State University describe how they used hormones5 to produce lizards with the wrong sex:animals that came out male even though they were incubated at the female temperature, and vice6 versa. They found that females born and raised at the female temperature made more babies than females hatched at the wrong, male temperature, Ditto for the males. Call it the Goldilocks principle: you are born at a temperature that’s just right, at least if you are a lizard3.

Thanks for the minute for a Scientific Americans' 60-Second Science. I’m Karen Hopkin.
 


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1 chromosomes 11783d79c0016b60332bbf1856b3f77d     
n.染色体( chromosome的名词复数 )
参考例句:
  • Chromosomes also determine the sex of animals. 染色体也决定动物的性别。 来自《简明英汉词典》
  • Each of four chromosomes divide longitudinally. 四种染色体的每一种都沿着纵向分裂。 来自《现代汉英综合大词典》
2 reptiles 45053265723f59bd84cf4af2b15def8e     
n.爬行动物,爬虫( reptile的名词复数 )
参考例句:
  • Snakes and crocodiles are both reptiles. 蛇和鳄鱼都是爬行动物。 来自《简明英汉词典》
  • Birds, reptiles and insects come from eggs. 鸟类、爬虫及昆虫是卵生的。 来自《现代汉英综合大词典》
3 lizard P0Ex0     
n.蜥蜴,壁虎
参考例句:
  • A chameleon is a kind of lizard.变色龙是一种蜥蜴。
  • The lizard darted out its tongue at the insect.蜥蜴伸出舌头去吃小昆虫。
4 lizards 9e3fa64f20794483b9c33d06297dcbfb     
n.蜥蜴( lizard的名词复数 )
参考例句:
  • Nothing lives in Pompeii except crickets and beetles and lizards. 在庞培城里除了蟋蟀、甲壳虫和蜥蜴外,没有别的生物。 来自辞典例句
  • Can lizards reproduce their tails? 蜥蜴的尾巴断了以后能再生吗? 来自辞典例句
5 hormones hormones     
n. 荷尔蒙,激素 名词hormone的复数形式
参考例句:
  • This hormone interacts closely with other hormones in the body. 这种荷尔蒙与体內其他荷尔蒙紧密地相互作用。
  • The adrenals produce a large per cent of a man's sex hormones. 肾上腺分泌人体的大部分性激素。
6 vice NU0zQ     
n.坏事;恶习;[pl.]台钳,老虎钳;adj.副的
参考例句:
  • He guarded himself against vice.他避免染上坏习惯。
  • They are sunk in the depth of vice.他们堕入了罪恶的深渊。
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