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SSS 2009-06-17

时间:2010-05-18 02:53来源:互联网 提供网友:mark@li   字体: [ ]
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    (单词翻译:双击或拖选)

This is Scientific American's 60-second Science. I'm Karen Hopkin. This will just take a minute.

If you were a bird, how big could you be? Well, an ostrich1 can weigh 400 pounds—but it can’t get off the ground. So what if you want to fly? University of Washington scientists say it depends on how fast you can replace your flight feathers when you molt2. The report is in the journal Public Library of Science Biology.

Feathers don’t last forever. So birds periodically shed their plumage and then sprout3 replacements4. Small birds molt once or twice a year, and they replace their 9 or 10 primary flight feathers a few at a time over the course of a few weeks.

But bigger birds need bigger feathers. And that’s where the problem comes in. As birds increase in size, the rate at which they grow their feathers doesn’t keep up with their longer feather length. So if big birds tried to do like little birds, they’d spend the whole year molting5—leaving little time for finding food or mates. [“Hey, whaddya doing?” “Still molting.”]


Some large birds, like honking6 big geese and 30-pound swans, get around the problem by forgoing7 flight while they get all their molting over with in one fell swoop8. In other words, these birds of a feather defrock together.

 

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 ostrich T4vzg     
n.鸵鸟
参考例句:
  • Ostrich is the fastest animal on two legs.驼鸟是双腿跑得最快的动物。
  • The ostrich indeed inhabits continents.鸵鸟确实是生活在大陆上的。
2 molt Rj9yb     
n.换毛,脱皮,换毛期
参考例句:
  • The fourth time they molt,they change into pupae.换第四次皮时,它们蜕变成蛹。
  • This veterinary product is very effective in preventing animal molt.这种兽药对于防治兽类掉毛很有效。
3 sprout ITizY     
n.芽,萌芽;vt.使发芽,摘去芽;vi.长芽,抽条
参考例句:
  • When do deer first sprout horns?鹿在多大的时候开始长出角?
  • It takes about a week for the seeds to sprout.这些种子大约要一周后才会发芽。
4 replacements 1f6e0d51ec9f57961e86b4aa2e91ef29     
n.代替( replacement的名词复数 );替换的人[物];替代品;归还
参考例句:
  • They infiltrated behind the lines so as to annoy the emery replacements. 他们渗透敌后以便骚扰敌军的调度。 来自辞典例句
  • For oil replacements, cheap suddenly looks less of a problem. 对于石油的替代品来说,价格变得无足轻重了。 来自互联网
5 molting db85f1af31319318d646efa2505487ca     
n.蜕皮v.换羽,脱毛( molt的现在分词 )
参考例句:
  • The old cuticle is digested by molting fluid. 旧表皮被蜕皮液消化。 来自辞典例句
  • Molting in insects is triggered by rising levels of a hormone called ecdysone. 昆虫的脱皮是由于称为脱皮素激素的含量升高而引起的。 来自辞典例句
6 honking 69e32168087f0fd692f761e62a361acf     
v.(使)发出雁叫似的声音,鸣(喇叭),按(喇叭)( honk的现在分词 )
参考例句:
  • Cars zoomed helter-skelter, honking belligerently. 大街上来往车辆穿梭不停,喇叭声刺耳。 来自《简明英汉词典》
  • Flocks of honking geese flew past. 雁群嗷嗷地飞过。 来自《现代汉英综合大词典》
7 forgoing 63a17233a6a5541f25d34a5fd7c248cb     
v.没有也行,放弃( forgo的现在分词 )
参考例句:
  • Everything, in short, is produced at the expense of forgoing something else. 总之,每一种东西的生产,都得以牺牲放弃某些其他东西为代价。 来自互联网
  • These aren't the only ones forgoing the morning repast, of course. 当然,他们并不是放弃早餐的唯一几个。 来自互联网
8 swoop nHPzI     
n.俯冲,攫取;v.抓取,突然袭击
参考例句:
  • The plane made a swoop over the city.那架飞机突然向这座城市猛降下来。
  • We decided to swoop down upon the enemy there.我们决定突袭驻在那里的敌人。
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