GMAT考试资料：GWD试题合集（四十七）.

　　以下将为正在备战GMAT考试的同学们整理一些经典的GMAT阅读试题，并分多个合集推出，希望能够为正在备考GMAT考试的考生提供或多或少的帮助。

　　26. GWD-27-Q3-Q6 鸟为什么会飞的两种理论

　　Two opposing scenarios,

　　the “arboreal” hypothesis and

　　the “cursorial” hypothesis, have

　　Line traditionally been put forward con-

　　(5) cerning the origins of bird flight.

　　The “arboreal” hypothesis holds

　　that bird ancestors began to fly

　　by climbing frees and gliding

　　down from branches with the

　　(10) help of incipient feathers: the

　　height of trees provides a good

　　starting place for launching flight,

　　especially through gliding. As

　　feathers became larger over time,

　　(15) flapping flight evolved and birds

　　finally became fully air-borne.

　　This hypothesis makes intuitive

　　Sense, but certain aspects are

　　Troubling. Archaeopteryx (the

　　(20) earliest known bird) and its

　　maniraptoran dinosaur cousins

　　have no obviously arboreal

　　adaptations, such as feet fully

　　adapted for perching. Perhaps

　　(25) some of them could climb trees,

　　but no convincing analysis has

　　demonstrated how Archaeopteryx

　　would have both climbed and

　　flown with its forelimbs, and there

　　(30) were no plants taller than a few

　　meters in the environments where

　　Archaeopteryx fossils have been

　　found. Even if the animals could

　　climb trees, this ability is not

　　(35) synonymous with gliding ability.

　　(Many small animals, and even

　　some goats and kangaroos,

　　are capable of climbing trees

　　but are not gliders.) Besides,

　　(40) Archaeopteryx shows no obvi-

　　ous features of gliders, such as

　　a broad membrane connecting

　　forelimbs and hind limbs.

　　The “cursorial”(running)

　　(45) hypothesis holds that small

　　dinosaurs ran along the ground

　　and stretched out their arms for

　　balance as they leaped into the

　　air after insect prey or, perhaps,

　　(50) to avoid predators. Even rudi-

　　mentary feathers on forelimbs

　　could have expanded the arm’s

　　surface area to enhance lift

　　slightly. Larger feathers could

　　(55) have increased lift incrementally,

　　until sustained flight was gradu-

　　ally achieved. Of course, a leap

　　into the air does not provide the

　　acceleration produced by drop-

　　(60) ping out of a tree; an animal

　　would have to run quite fast

　　to take off. Still, some small

　　terrestrial animals can achieve

　　high speeds. The cursorial

　　(65) hypothesis is strengthened by

　　the fact that the immediate the-

　　ropod dinosaur ancestors of

　　birds were terrestrial, and they

　　had the traits needed for high

　　(70) lift off speeds: they were small,

　　agile, lightly built, long-legged,

　　and good runners. And because

　　they were bipedal, their arms

　　were free to evolve flapping flight,

　　(75) which cannot be said for other

　　reptiles of their time.

　　以上就是本期GMAT试题的所有内容，考生可以此为据并进行针对性的练习，逐步掌握GMAT阅读的解题规律及技巧，以达到迅速提高GMAT考试成绩的目的。 相关链接：

1.GMAT考试资料：GWD试题合集（四十六）

2.GMAT考试资料：GWD试题合集（四十五）

3.GMAT考试资料：GWD试题合集（四十四）

想要获得更多咨询服务点击进入 >>>>有问题?找免费的澳际专家咨询! 或联系QQ客服： ，也可以通过在线咨询处留言，把您最关心的问题告诉我们。