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RC-20:鸟为什么会飞的两种理论
【版本1】GWD-27-Q3-Q6 鸟为什么会飞的两种理论
Two opposing scenarios, 两种解释鸟飞的假设：树栖和疾走。
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 树栖论说鸟祖先爬上树滑行下来，随
that bird ancestors began to fly 着羽毛越来越大，最终飞了起来。
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 树栖论的问题：始祖鸟和M恐龙没有
Sense, but certain aspects are 明显的栖树适应性，如合适的脚。
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 没分析显示始祖鸟曾用前肢爬树和飞，
(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 始祖鸟化石发现的地方也没有发现高
meters in the environments where 树。
Archaeopteryx fossils have been
found. Even if the animals could 即使它会爬树也不表明会滑翔。
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 它没明显的滑翔特征。
a broad membrane connecting
forelimbs and hind limbs.
The “cursorial”(running)
(45) hypothesis holds that small 疾走论认为鸟为了躲避猎食者，奔跑
dinosaurs ran along the ground 并张开双臂平行
and stretched out their arms for
balance as they leaped into the
air after insect prey or, perhaps,
(50) to avoid predators. Even rudi- 前肢的原始特征能帮助身体稍微升高
mentary feathers on forelimbs
could have expanded the arm’s
surface area to enhance lift
slightly. Larger feathers could 然后鸟慢慢就飞起来了。
(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- 兽脚亚目恐龙祖先拥有各种疾走的
ropod dinosaur ancestors of 特点。
birds were terrestrial, and they
had the traits needed for high
(70) lift off speeds: they were small,
agile, lightly built, long-legged, 另外，
and good runners. And because 它们用两足走，双臂有空用来拍打。
they were bipedal, their arms
were free to evolve flapping flight,
(75) which cannot be said for other
reptiles of their time.
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Q 3:
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
correct certain misconceptions about hypotheses concerning the origins of bird flight
C. (missing)
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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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. Plants 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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Q 5:
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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Q 6:
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 | 
时期M动物的灭绝