GWD27-Q 3 to Q6:

arthurman

GWD27-Q 3 to Q6:



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.




-------------------------------------------------------------------------------------------------------



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

大家这篇似乎都没有什么问题，都没有讨论过，我想问问4题，为什么不选C呢，C也是出现在驳斥第一个观点的地方的原话呀

还有我觉得D不妥，原文说的是environments where Archaeopteryx fossils have been
found，
没有说是known habitats的呀

tingting520

因为有AND，所以第一考虑就是平行啊。
平行的话，只能是和stressing 平行，时态平行应该是一个注意点。
GMAT 合并同类项是家常便饭，只要没有歧义。

laurawang2234

楼主我觉得C可能的确不是一个直接的evidence,但是这个例子也能说明,不是会爬树就能滑行的

看原文这句对A假设的定义:The “arboreal” hypothesis holds that bird ancestors began to fly by climbing trees and gliding down from branches with the help of incipient feathers

我觉得对于能否glider的判断应能反驳A假设吧

再看D,原文是:there were no plants taller than a few meters in the environments where Archaeopteryx fossils have been found.

注意是where Archaeopteryx fossils have been found,而D说的是Plants in Archaeopteryx’s known habitats 这两个应该是不等的吧

因为我觉得作者对于A假设的驳斥都是基于一种推测的驳斥(个人对作者语气的感觉)

所以如果真的有D说的Plants in Archaeopteryx’s known habitats were relatively small,那么就可以算是证据确凿了呀

欢迎讨论~

weixuan

arboreal hypothesis包括两个方面，一个要会爬树，一个要会滑翔
C只说了一个方面，可以看做是无关选项
D COMMON SENSE的话，化石被发现的地方就是A这个鸟祖先生存的地方，这些地方的树很矮，不构成滑翔的条件
原文有四个方面是UNDERMINE这个假设的：
Archaeopteryx (the



(20) earliest known bird) and its





maniraptoran dinosaur cousins





have no obviously arboreal





adaptations, such as feet fully

adapted for perching.没有爪子能抓牢

but no convincing analysis has





demonstrated how Archaeopteryx





would have both climbed and

flown with its forelimbs没有能飞的前肢

and there 后面就说没有比较高的树木的化石证据

再来否定GLIDING的能力，一个是即使动物能爬树，都不能滑翔，最后一句是这个鸟祖先没有连在一起的适合滑翔的什么什么

所以如果C要把它变成正确答案应该否定“都不能飞翔”应该是

C。Many small animals are capable of gliding

parispings

同意lz "arboreal hypothesis包括两个方面，一个要会爬树，一个要会滑翔,C只说了一个方面，可以看做是无关选项"

arthurman

不行，我还是要负隅顽抗一把~

tingting520:我觉得这道就是细节题，文章列举了四个细节，C是其中一个，注意，是一模一样的

如果这里问你：作者问什么要提Many small animals are capable of climbing trees？

答案就应该是in order to驳斥A假设的，因为它是为段中心服务的

weixuan:你也承认了这里有个逻辑上的gap，怎么能在做细节题的时候把common sence用上啊，我觉得这个就是陷阱的哈

williams

赶快讨论清楚啊！本月的题目啊！

我是支持C的，逻辑题里不是经常有给出具有同样特质的但不能做这件事来反对的嘛，而且是原话

D 原文说树不够高，没有说树小啊，tall和small不一样的啊！

tingting520

重新顶出这个帖子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

答案是C，为什么呢？

卮言浅夏

support C.

We cannot assume "the environments where A fossils have been found" are A's "known habitats". Besides, in fact this assumption is wrong.