恐龙灭绝后 哺乳动物体型迅速增大-凯发k8官网

恐龙灭绝后 哺乳动物体型迅速增大
文章来源:未知 文章作者:meng 发布时间:2010-11-26 03:14 字体: [ ] 
(单词翻译:双击或拖选)

researchers demonstrate that the 1 of 2 65 million years ago made way for mammals to get bigger - about a thousand times bigger than they had been. the study, which is published in the 3(有名望的) journal science, is the first to show this new pattern of increased body size of mammals after the exit of the dinosaurs. "basically, the dinosaurs disappear and all of a sudden there is nobody else eating the vegetation. that's an open food source and mammals start going for it, and it's more efficient to be an herbivore(食草动物) when you're big," says paper co-author dr. jessica theodor, associate professor in the department of biological sciences at the university of calgary.

theodor says as well as confirming the dramatic(戏剧的,引人注目的) growth in mammalian size after the dinosaurs, the study shows that the 4 is able to 5 itself 6 quickly.

"you lose dinosaurs 65 million years ago, and within 25 million years the system is reset to a new maximum for the animals that are there in terms of body size. that's actually a pretty short time frame, geologically speaking," she says. "that's really rapid evolution."

theodor says mammals grew from a maximum of about 10 kilograms when they were sharing the earth with dinosaurs to a maximum of 17 tonnes afterwards.

"nobody has ever demonstrated that this pattern is really there. people have talked about it but nobody has ever gone back and done the math," says theodor one of the 20 researchers from around the world who worked on the study. "we went through every time period and said ok, for this group of mammals what's the biggest one? and then we estimated its body mass."

in order to document how big mammals grew after the 'competitive release' caused by the extinction of dinosaurs, researchers collected data on the maximum size for major groups of land mammals on each continent, including perissodactyla, odd-toed ungulates(有蹄类动物) such as horses and 7(犀牛) ; proboscidea(长鼻目) , which includes elephants, 8(猛犸象) and mastodon(乳齿象) ; xenarthra, the anteaters(食蚁兽) , tree 9, and armadillos(犰狳) ; as well as a number of other extinct groups.

the results give clues as to what sets the limits on mammal size on land; the amount of space available to each animal and the climate they live in. the colder the climate, the bigger the mammals seem to get, as bigger animals 10 heat better. it also shows that no one group of mammals dominates the largest size class – the absolute largest mammal belongs to different groups over time and space.



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1 spwzp     
n.熄灭,消亡,消灭,灭绝,绝种
参考例句:
  • the plant is now in danger of extinction.这种植物现在有绝种的危险。
  • the island's way of life is doomed to extinction.这个岛上的生活方式注定要消失。
2 87f9c39b9e3f358174d58a584c2727b4     
n.恐龙( dinosaur的名词复数 );守旧落伍的人,过时落后的东西
参考例句:
  • the brontosaurus was one of the largest of all dinosaurs. 雷龙是所有恐龙中最大的一种。 来自《简明英汉词典》
  • dinosaurs have been extinct for millions of years. 恐龙绝种已有几百万年了。 来自《简明英汉词典》
3 nq2xn     
adj.有威望的,有声望的,受尊敬的
参考例句:
  • the young man graduated from a prestigious university.这个年轻人毕业于一所名牌大学。
  • you may even join a prestigious magazine as a contributing editor.甚至可能会加入一个知名杂志做编辑。
4 wq4xz     
n.生态系统
参考例句:
  • this destroyed the ecosystem of the island.这样破坏了岛上的生态系统。
  • we all have an interest in maintaining the integrity of the ecosystem.维持生态系统的完整是我们共同的利益。
5 rkhzyj     
v.重新安排,复位;n.重新放置;重放之物
参考例句:
  • as soon as you arrive at your destination,step out of the aircraft and reset your wristwatch.你一到达目的地,就走出飞机并重新设置手表时间。
  • he is recovering from an operation to reset his arm.他做了一个手臂复位手术,正在恢复。
6 bkqzs3     
adv.比较...地,相对地
参考例句:
  • the rabbit is a relatively recent introduction in australia.兔子是相对较新引入澳大利亚的物种。
  • the operation was relatively painless.手术相对来说不痛。
7 195f9b9fd8128a29dac773077994698f     
n.犀牛(rhino的复数形式)
参考例句:
  • there are many reports of people taming and even training indian rhinos. 有许多关于人们驯养甚至训练印度犀牛的记载。 来自辞典例句
  • the rhinos had fed during the night in the rice fields of these villagers. 犀牛夜里在这些村民的庄稼地里也已吃饱了。 来自辞典例句
8 u2wy8     
n.长毛象;adj.长毛象似的,巨大的
参考例句:
  • you can only undertake mammoth changes if the finances are there.资金到位的情况下方可进行重大变革。
  • building the new railroad will be a mammoth job.修建那条新铁路将是一项巨大工程。
9 99bb49e2cc8aa5774736e771d9f65efa     
懒散( sloth的名词复数 ); 懒惰; 树獭; (经济)停滞。
参考例句:
  • mummies of pleistocene ground sloths, with original skin, hair, tendons and claws have been found. 还发现了保存原有皮肤,毛发,腱和爪的更新世时期地面树懒的木乃伊。
  • he was inspired by fossils of armadillos and sloths. 犰狳和树懒化石让他获得了灵感。
10 vyryp     
vt.保存,保护,节约,节省,守恒,不灭
参考例句:
  • he writes on both sides of the sheet to conserve paper.他在纸张的两面都写字以节省用纸。
  • conserve your energy,you'll need it!保存你的精力,你会用得着的!
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tag标签: food dinosaurs mammals
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