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动物植物类
鸟类如何学习飞行
总共两段，讲鸟类是怎么进化成可以飞的。
第一段：有两个理论，第一个是说鸟类是由一些爬树能力强的动物进化，它们可以爬到树上，从树枝上跳下，然后逐渐进化成翅膀，有鳞片变成羽毛啥的blablab。。。然后有个新理论，说在XX挖出来的一个Axxxx的化石，被认为是鸟类的祖先，说他的爬树能力不强，而且让步说，就算他们中有些能爬树，但是根据出土那个化石的地方附近没有发现很高植物的化石，所以第一个理论是被否了。
第二段：开始说理论二，会飞的鸟类是由一些奔跑速度快的动物进化的，他们在地上快速奔跑，然后展开双手，渐渐的双手进化成翅膀，然后就可以飞了。然后说了好多第二个理论的优点，符合什么现象啦，就是对比于第一个观点，表示支持的态度。
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１） 主题题。
２） 第二个理论里面提到的那种动物的特点是什么，可以定位到第二段的中间部分找。
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附：GWD27-Q3--Q6
Two opposing 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 trees and gliding down from branches with the 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, flapping flight evolved and birds finally became fully air-borne. This hypothesis makes intuitive sense, but certain aspects are troubling. Archaeopteryx (the earliest known bird) and its maniraptoran dinosaur cousins have no obviously arboreal adaptations, such as feet fully adapted for perching. Perhaps 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 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 synonymous with gliding ability. (Many small animals, and even some goats and kangaroos, are capable of climbing trees but are not gliders.) Besides, Archaeopteryx shows no obvious features of gliders, such as a broad membrane connecting forelimbs and hind limbs.
The “cursorial” (running) 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, to avoid predators. Even rudimentary feathers on forelimbs could have expanded the arm’s surface area to enhance lift slightly. Larger feathers could have increased lift incrementally, until sustained flight was gradually achieved. Of course, a leap into the air does not provide the acceleration produced by dropping 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 hypothesis is strengthened by the fact that the immediate theropod dinosaur ancestors of birds were terrestrial, and they had the traits needed for high 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, which cannot be said for other reptiles of their time.
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Q1: The primary purpose of the passage is to
A. present counterevidence to two hypotheses concerning the origins of bird flight
B. propose and alternative to two hypotheses concerning the origins of bird flight
C. correct certain misconceptions about hypotheses concerning the origins of bird flight
D. refute a challenge to a hypothesis concerning the origins of bird flight
E. evaluate competing hypotheses concerning the origins of bird flight
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Q2: 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
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Q3: Which of the following is included in the discussion of the cursorial hypothesis but not in the discussion of the arboreal hypothesis?
A. A discussion of some of the features of Archaeopteryx
B. A description of the environment known to have been inhabited by bird ancestors
C. A possible reason why bird ancestors might have been engaging in activities that eventually evolved into flight
D. A description of the obvious features of animals with gliding ability
E. An estimate of the amount of time it took for bird ancestors to evolve the kind of flapping flight that allowed them to become completely airborne
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Q4: The passage suggests which of the following regarding the climbing ability of Archaeopteryx?
A. Its ability to climb trees was likely hindered by the presence of incipient feathers on its forelimbs.
B. It was probably better at climbing trees than were its maniraptoran dinosaur cousins.
C. It had certain physical adaptations that suggest it was skilled at climbing trees.
D. Scientists have recently discovered fossil evidence suggesting it could not climb trees.
E. Scientists are uncertain whether it was capable of climbing trees | 
