60秒科学:鸟能飞的原因
鸣禽类的骨骼或是空的，以便飞行，然而，其骨骼密度事实上比同大小的哺乳动物要高，这样可以使身体更加有力、坚硬，满足飞行的需要。
For earthbound creatures like us, flight just seems so fantastical. How do birds and bats and other flying beasties manage to get off and stay off the ground? Well, having wings obviously helps. And bird bones are hollow and seem delicate, which should help lighten the load.
Or so you’d think. But a new study shows that songbirds’ bones are actually pretty tough. In fact, they’re more dense 1 than the bones of mammals of the same size. The results appear in the Proceedings 2 of the Royal Society: Biological Sciences. For centuries, biologists have known that bird bones are thin and hollow. Yet bird skeletons don’t actually weigh any less than the skeletons of similarly sized mammals. To sort out this seeming discrepancy 3, Elizabeth Dumont of the University of Massachusetts Amherst studied the skulls 4 and limb bones of song birds, rodents 5 and bats. And she found that, on average, bird bones are the densest 6, with bat bones coming in a close second.
That denseness 7 makes Tweety’s thin little bones surprisingly strong and stiff, good structural 8 features for flight. And thus for keeping those bones from winding 9 up in the mouth of a hungry mammal. Sorry, Sylvester.
- The general ambushed his troops in the dense woods. 将军把部队埋伏在浓密的树林里。
- The path was completely covered by the dense foliage. 小路被树叶厚厚地盖了一层。
- 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
- The discrepancy in their ages seemed not to matter.他们之间年龄的差异似乎没有多大关系。
- There was a discrepancy in the two reports of the accident.关于那次事故的两则报道有不一致之处。
- One of the women's skulls found exceeds in capacity that of the average man of today. 现已发现的女性颅骨中，其中有一个的脑容量超过了今天的普通男子。
- We could make a whole plain white with skulls in the moonlight! 我们便能令月光下的平原变白，遍布白色的骷髅！
- Rodents carry diseases and are generally regarded as pests. 啮齿目动物传播疾病，常被当作害虫对待。 来自《简明英汉词典》
- Some wild rodents in Africa also harbor the virus. 在非洲，有些野生啮齿动物也是储毒者。 来自辞典例句
- Past Botoi some of the densest jungle forests on Anopopei grew virtually into the water. 过了坊远湾，岛上的莽莽丛林便几乎直长到水中。
- Earth is the densest of all of these remaining planets. 地球是所剩下行星中最致密的星球。
- Real estate industry is one of the typical capital denseness industries. 房地产业是一个非常典型的资本密集型行业。
- India is one of the countries that have great denseness in population. 印度是人口高度密集的国家之一。
- The storm caused no structural damage.风暴没有造成建筑结构方面的破坏。
- The North American continent is made up of three great structural entities.北美大陆是由三个构造单元组成的。