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托福阅读素材:鸟类飞行的起源

2018-10-24 16:07 来源: 未知 作者:admin 浏览
核心提示: 很多考生会抱怨托福阅读时间不够,还没完全理解文章就做题,正确率不高。其实这是我们对托福阅读素材不熟悉造成的,下面 济南环球雅思 老师整理了一下 托福阅读考试最新的素材 ,希望能帮助大家更加快速高效的备考托福。 托福阅读素材:鸟类飞行的起源 内容

  很多考生会抱怨托福阅读时间不够,还没完全理解文章就做题,正确率不高。其实这是我们对托福阅读素材不熟悉造成的,下面济南环球雅思老师整理了一下托福阅读考试最新的素材,希望能帮助大家更加快速高效的备考托福。

  托福阅读素材:鸟类飞行的起源

  内容回忆:

  第 1 段说明说明大家比较达成共识的是会 A 这种化石应该可以提示鸟类的飞行能力是如何起源的,但是具体有两种理论可以参考。

  第 2 段讲到了理论之一是 tree-down theory。既起源于树上。 reptile 身上比较长的鳞片会帮助从树上俯冲向下 gliding;越来越长了之后就发展成了羽毛,并且有助于隔热和培养出 endothermy ,A 鸟脚上的 grasping feature 就能体现该特征。第 3 段介绍了 ground-up 理论,既一开始是在地上的。先有高体温帮助 power the muscle , 然后发展出羽毛可以帮助在抓猎物的时候保持平衡,并帮助隔热。

  参考阅读:

  The origin of birds refers to the scientific question within which larger group of animals birds evolved. The present scientific consensus is that birds are a group of theropod dinosaurs that originated during the Mesozoic Era.[1]

  A close relationship between birds and dinosaurs was first proposed in the nineteenth century after the discovery of the primitive bird Archaeopteryx in Germany. Birds share many unique skeletal features with dinosaurs.[2] Moreover, fossils of more than twenty species of dinosaur have been collected with preserved feathers. There are even very small dinosaurs, such as Microraptor and Anchiornis, which have long, vaned, arm and leg feathers forming wings. The Jurassic basal avialan Pedopenna also shows these long foot feathers. Witmer in 2009 concluded that this evidence is sufficient to demonstrate that avian evolution went through a four-winged stage.[3] Fossil evidence also demonstrates that birds and dinosaurs shared features such as hollow, pneumatized bones, gastroliths in the digestive system, nest-building and brooding behaviors.

  The ground-breaking discovery of fossilized Tyrannosaurus rex soft tissue allowed a molecular comparison of cellular anatomy and protein sequencing of collagen tissue, both of which demonstrated that T. rex and birds are more closely related to each other than either is to Alligator.[4] A second molecular study robustly supported the relationship of birds to dinosaurs, though it did not place birds within Theropoda, as expected. This study utilized eight additional collagen sequences extracted from a femur of Brachylophosaurus canadensis, a hadrosaur.[5] A study comparing embryonic, juvenile and adult archosaur skulls concluded that bird skulls are derived from those of theropod dinosaurs by progenesis, a type of paedomorphic heterochrony, which resulted in retention of juvenile characteristics of their ancestors.[6]

  The origin of birds has historically been a contentious topic within evolutionary biology. However, only a few scientists still debate the dinosaurian origin of birds, suggesting descent from other types of archosaurian reptiles. Within the consensus that supports dinosaurian ancestry, the exact sequence of evolutionary events that gave rise to the early birds within maniraptoran theropods is hotly disputed. The origin of bird flight is a separate but related question for which there are also several proposed answers.

  所考词汇:

  1. repetitive =done many times

  2. elaborate=complicated

  3. retention = keeping

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