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2.2 Biology
2.2.1鸟类飞行
V1 by skipbeat
关于鸟类飞行的原因,有两个理论,一个是“ arbor” (词忘了,就是树的意思)是说鸟类最初是从爬树慢慢进化到会飞行的。举了个例子, A鸟,我估计是始祖鸟,说他是鸟类的祖先,但是没有任何迹象表明这种鸟是会爬树的。还有很多小动物也会爬树,爬树和XX是不一样的,所以"a"理论似乎不行第二段另外一个理论,鸟类是从跑步计划到飞行的,又举了小动物的例子 。。
V2 by clair1024
BIRD 飞行那篇 完全考古
问了professor 假设A会爬树那题;削弱科学家对A的理论——A生活的环境都是small plants ;有题问行文结构的
考古 by zhepeking(未确认)
Two opposing scenarios, the “arboreal(生活在树上)” hypothesis and the “cursorial”(适于奔跑的) 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(刚出现的) feathers: the height of trees provides a good starting place for launching(起飞) flight, especially through gliding. As feathers became larger over time, flapping flight evolved and birds finally became fully air-borne. This hypothesis makes intuitive(直觉的天生的) sense, but certain aspects are troubling. Archaeopteryx(始祖鸟) (the earliest known bird) and its maniraptoran dinosaur cousins have no obviously arboreal adaptations, such as feet fully adapted for perching(栖枝). Perhaps some of them could climb trees, but no convincing analysis has demonstrated how Archaeopteryx would have both climbed and flown with its forelimbs(前肢), 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(宽的) membrane(膜) connecting forelimbs(前肢) and hind limbs(后肢).
两个相反的假说:生活在树上 和 适于奔跑的,都是传统的关于鸟类飞行的观点
生活在树上:直观感觉,但某些方面困扰
例子:始祖鸟:没有明显住树适应性,没有令人信服的分析。几米以上的树上都没有找到始祖鸟的化石。就算会爬树,也和滑翔能力不是同义的。举例子山羊长颈鹿等小动物也能爬树但不能滑翔。身上也没有明显的滑翔物特点。
The “cursorial”(running) hypothesis holds that small dinosaurs ran along the ground and stretched out(伸出) their arms for balance as they leaped(跳) into the air after insect prey or, perhaps, to avoid predators. Even rudimentary(未成熟的) feathers on forelimbs(前肢) 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(加速度) 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(双足), their arms were free to evolve flapping flight, which cannot be said for other reptiles(爬行动物) of their time.
适于奔跑的:Even未成熟羽毛能稍微加强上升,大羽毛能增加上升。跑特快才能起飞。鸟类的直接兽脚亚目恐龙祖先是陆生的,他们很小,动作敏捷,轻盈,长脚,跑的快。
Q 3: The primary purpose of the passage is to
A. present counterevidence to two hypotheses concerning the origins ofbird 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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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 |
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