VOA标准英语2014--Dinosaur Descendants Shrank to Survive
时间：2019-01-14 作者：英语课 分类：VOA标准英语2014年(五月)
Dinosaur 1 Descendants Shrank to Survive
Not all dinosaurs 2 went extinct. Some are alive today in the form of birds. A new study finds that shrinking helped these birds continue to thrive and evolve.
“If we really want to know how birds came about, then we need to study the line leading to birds, which includes this big diversity of animals like triceratops and stegosaurus and T. Rex,” said Roger Benson, associate professor of paleontology at Oxford 3 University and lead author of the study reported PLOS Biology.
His team followed the evolution more than 400 dinosaurs, noting their size and what they weighed.
“The largest dinosaur in our study we believed weighed 90 tons, and the smallest dinosaur was a bird called Qiliania and that weighed 15 grams," Benson said. "So you could fit Qiliania six million times inside Argentinosaurus, the largest dinosaur.”
Since these species are extinct, Benson's team calculated that weight with an analysis of fossil limbs which, like pillars, would hold up the weight of the dinosaur.
“And there’s a welcome strained relationship between the robustness 4 of those pillars and the mass of the animal that is observed among modern mammals and reptiles 5, and so it’s fairly reliable for knowing the masses of extinct animals,” he said.
The study examined how fast body size changed on the entire family tree of dinosaurs, based on the thickness of their thigh 6 bones. It found dinosaurs quickly evolved big bodies, soon after their origins about 220 million years ago.
Then the rates of growth slowed and these giants went extinct after 20 million years. Benson says the one exception was the line leading to birds, which kept evolving a range of body mass, including radically 7 smaller body sizes.
“We find that fast rates of evolution are maintained for the whole study period, so for nearly 200 million years," Benson said. "So this is a very evolvable lineage. There’s a long ancient background to the modern radiation [spread] of birds through which their ancestors were constantly finding new ecological 8 opportunities and inventing new ways of being an organism.”
He says the long journey evident in the fossil record that connects the 10,000 bird species alive today underscores a bigger evolutionary 9 question.
“We're no longer asking how the radiation of living birds proceeded over, let's say, 100 million years," he said. "Instead we're asking where does biological diversity come from over very long time scales and ultimately those time scales might be relevant in establishing how life evolved in general, not just birds or just even vertebrates, but just organisms or animals in general?”
Benson says what is clear from this study is that evolving different sizes was important to the success of the feathered dinosaur lineage. His next step is to look at other patterns in dinosaur evolution to see how other features changed over time.
- Are you trying to tell me that David was attacked by a dinosaur?你是想要告诉我大卫被一支恐龙所攻击？
- He stared at the faithful miniature of the dinosaur.他凝视著精确的恐龙缩小模型。
- 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》
- At present he has become a Professor of Chemistry at Oxford.他现在已是牛津大学的化学教授了。
- This is where the road to Oxford joins the road to London.这是去牛津的路与去伦敦的路的汇合处。
- There were other reasons for concern about the robustness of an economic recovery. 人们还有其他一些原因对经济恢复的健全程度表示关心。 来自英汉非文学 - 政府文件
- Robustness analysis attracts more and more attention in these years. 鲁棒性分析是近几年学术界较为关注的问题。 来自互联网
- 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》
- He is suffering from a strained thigh muscle.他的大腿肌肉拉伤了，疼得很。
- The thigh bone is connected to the hip bone.股骨连着髋骨。
- I think we may have to rethink our policies fairly radically. 我认为我们可能要对我们的政策进行根本的反思。
- The health service must be radically reformed. 公共医疗卫生服务必须进行彻底改革。
- The region has been declared an ecological disaster zone.这个地区已经宣布为生态灾难区。
- Each animal has its ecological niche.每种动物都有自己的生态位.
- 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。