GWD27-Q4居然没人问过 深深怀疑我智商！！

lxt7

Twoopposing scenarios, the “arboreal” hypothesis and the “cursorial” hypothesis,have traditionally been put forward concerning the origins of bird flight. The“arboreal” hypothesis holds that bird ancestors began to fly by climbing treesand gliding down from branches with the help of incipient feathers: the heightof trees provides a good starting place for launching flight, especiallythrough gliding. As feathers became larger over time, flapping flight evolvedand birds finally became fully air-borne. This hypothesis makes intuitive sense,but certain aspects are troubling. Archaeopteryx (the earliest known bird) andits maniraptoran dinosaur cousins have no obviously arboreal adaptations, suchas feet fully adapted for perching. Perhaps some of them could climb trees, butno convincing analysis has demonstrated how Archaeopteryx would have bothclimbed and flown with its forelimbs, and there were no plants taller than afew meters in the environments where Archaeopteryx fossils have been found. Evenif the animals could climb trees, this ability is not synonymous with glidingability. (Many small animals, and even some goats and kangaroos, are capable ofclimbing trees but are not gliders.) Besides, Archaeopteryx shows no obviousfeatures of gliders, such as a broad membrane connecting forelimbs and hindlimbs.


 The“cursorial”(running) hypothesis holds that small dinosaurs ran along the groundand stretched out their arms for balance as they leaped into the air afterinsect prey or, perhaps, to avoid predators. Even rudimentary feathers onforelimbs could have expanded the arm’s surface area to enhance lift slightly.Larger feathers could have increased lift incrementally, until sustained flightwas gradually achieved. Of course, a leap into the air does not provide the accelerationproduced by dropping out of a tree; an animal would have to run quite fast totake off. Still, some small terrestrial animals can achieve high speeds. Thecursorial hypothesis is strengthened by the fact that the immediate theropoddinosaur ancestors of birds were terrestrial, and they had the traits neededfor high lift off speeds: they were small, agile, lightly built, long-legged, andgood runners. And because they were bipedal, their arms were free to evolveflapping flight, which cannot be said for other reptiles of their time.

Q 4: The passage presents which of the following facts as evidence that tends to undermine the arboreal hypothesis?
A.    Feathers tend to become larger over time
B.    Flapping flight is thought to have evolved gradually over time
C.    Many small animals are capable of climbing trees.
D.    lants in Archaeopteryx’s known habitats were relatively small
E.    Leaping into the air does not provide as much acceleration as gliding out of a tree

答案是D 但是C 也有支持Many small animals, and even some goats and kangaroos, are capable of climbing trees but are not gliders。
意思不就是小动物会爬树 但是没发展出飞翔能力 所以否定了原文么？？？
求NN。。。

lxt7

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waterliting

我前几天也刚做了这篇，是不是因为有evidence，所以要选D呀，因为文中给的证据就是D, there were no plants taller than afew meters in the environments where Archaeopteryx fossils have been found.

lumiko

我前几天也刚做了这篇，是不是因为有evidence，所以要选D呀，因为文中给的证据就是D, there were no plants taller than afew meters in the environments where Archaeopteryx fossils have been found.

-- by 会员 waterliting (2012/10/21 16:14:21)

一方面，D选项确实提供了evidence (如waterliting解释的那样）
另一方面，C选项不能构成完整的evidence, 应为”Many small animals are capable of climbing trees
but are not gliders."--以说明argument“即使它会爬树也不表明会滑翔”来undermine the arboreal hypothesis