2017年GRE阅读理解冲刺题（三）
P1
Biologists have long maintained that two groups of pinnipeds, sea lions and walruses, are descended from a terrestrial bearlike animal, whereas the remaining group, seals, shares an ancestor with weasels.
But the recent discovery of detailed similarities in the skeletal structure of the flippers in all three groups undermines the attempt to explain away superficial resemblance as due to convergent evolution—the independent development of similarities between unrelated groups in response to similar environmental pressures.
Flippers may indeed be a necessary response to aquatic life; turtles, whales, and dugongs also have them.
But the common detailed design found among the pinnipeds probably indicates a common ancestor.
Moreover, walruses and seals drive themselves through the water with thrusts of their hind flippers, but sea lions use their front flippers.
If anatomical similarity in the flippers resulted from similar environmental pressures, as posited by the convergent-evolution theory, one would expect walruses and seals, but not seals and sea lions, to have similar flippers. (162 words)
1. The author implies that which of the following was part of the long-standing view concerning pinnipeds?
□A Pinnipeds are all descended from a terrestrial bearlike animal.
□B Pinnipeds share a common ancestor with turtles, whales, and dugongs
□C Similarities among pinnipeds are due to their all having had to adapt to aquatic life.
2. The author implies which of the following about the fact that turtles, whales, and dugongs all have flippers?
○A It can be explained by the hypothesis that turtles, whales, and dugongs are very closely related.
○B It can be explained by the idea of convergent evolution.
○C It suggests that turtles, whales, and dugongs evolved in separate parts of the world
○D It undermines the view that turtles, whales, and dugongs are all descended from terrestrial ancestors.
○E It is the primary difference between turtles, whales, and dugongs, on the one hand, and pinnipeds, on the other.
3. Select the sentence in the passage in which the author shows that the implication of the common view is contradicted by a new finding.
P2
According to astronomer S.A. Phinney, kicking a rock hard enough to free it from Earth’s gravity would require a meteorite capable of making a crater more than 60 miles across.
Moreover, even if Earth rocks were freed by meteorite impact, Mars’s orbit is much larger than Earth’s, so Phinney estimates that the probability of these rocks hitting Mars is about one-tenth as great as that of Mars’s rocks hitting Earth.
To demonstrate this estimate, Phinney used a computer to calculate where 1,000 hypothetical particles would go if ejected from Earth in random directions.
He found that 17 of the 1,000 particles would hit Mars.
4. Which of the following, if true, would cast most doubt on Phinney’s estimate of the probability of Earth rocks hitting Mars?
○A Rather than going in random directions, about 25 percent of all particles ejected from Earth go in the same direction into space.
○B Approximately 100 meteorites large enough to make a noticeable crater hit the Earth each year.
○C No rocks of Earth origin have been detected on Mars.
○D The velocity of rocks escaping from Earth’s gravity is lower than the velocity of meteorites hitting the Earth.
○E No craters more than 60 miles across have been found on Mars.
本文导航第1页试题第2页答案
P1
1
Biologists have long maintained that two groups of pinnipeds, sea lions and walruses, are descended from a terrestrial bearlike animal, whereas the remaining group, seals, shares an ancestor with weasels.
生物学家一直以来都认为，海狮和海象这两种属于鳍脚亚目的动物，是某种陆生的类似熊的动物的后代，而另一种(鳍脚亚目动物)海豹则跟鼬鼠(黄鼠狼)有着共同的祖先。
2
But the recent discovery of detailed similarities in the skeletal structure of the flippers in all three groups undermines the attempt to explain away superficial resemblance as due to convergent evolution—the independent development of similarities between unrelated groups in response to similar environmental pressures.
但最近的研究，发现了三种动物的鳍足骨骼结构上有详实的近似，这使我们不能简单地把这种相似归结为趋同效应造成的表面上的近似，趋同指不同物种在相似环境影响下独立地发展出某些相似特点。
3
Flippers may indeed be a necessary response to aquatic life; turtles, whales, and dugongs also have them.
鳍足也许确实是一种对水生生活的必要适应;龟，鲸，儒艮也有鳍足。
4
But the common detailed design found among the pinnipeds probably indicates a common ancestor.
但鳍脚亚目动物中发现的这些共同的构造细节可能表明它们来自共同的祖先。
5
Moreover, walruses and seals drive themselves through the water with thrusts of their hind flippers, but sea lions use their front flippers.
此外，海象和海豹划水主要靠后鳍推进，海狮则是用前鳍。
6
If anatomical similarity in the flippers resulted from similar environmental pressures, as posited by the convergent-evolution theory, one would expect walruses and seals, but not seals and sea lions, to have similar flippers. (162 words)
如果是类似的环境压力导致了这些动物的鳍足有解剖学意义上的近似，根据趋同理论，海象和海豹应该有近似的鳍足，而不是海豹和海狮。
1. The author implies that which of the following was part of the long-standing view concerning pinnipeds?
□A Pinnipeds are all descended from a terrestrial bearlike animal.
□B Pinnipeds share a common ancestor with turtles, whales, and dugongs
□C Similarities among pinnipeds are due to their all having had to adapt to aquatic life.
选C
A 根据句 1 可判断在瞎聊。
B 句 3 告诉我们，这些不同种的动物进化出同一个特征是因为同样的环境压力，也就是汇聚理论，并非因为它们有着共同的祖先。
C 正确。
儒艮是这样的一种动物，有点像海牛
2. The author implies which of the following about the fact that turtles, whales, and dugongs all have flippers?
○A It can be explained by the hypothesis that turtles, whales, and dugongs are very closely related.
○B It can be explained by the idea of convergent evolution.
○C It suggests that turtles, whales, and dugongs evolved in separate parts of the world
○D It undermines the view that turtles, whales, and dugongs are all descended from terrestrial ancestors.
○E It is the primary difference between turtles, whales, and dugongs, on the one hand, and pinnipeds, on the other.
选B
句 2 是个长句，其中详细解释了什么叫做convergent evolution
But the recent discovery of detailed similarities in the skeletal structure of the flippers in all three groups undermines the attempt to explain away superficial resemblance as due toconvergent evolution—the independent development of similarities between unrelated groups in response to similar environmental pressures.
可见不同种的动物因为类似的环境压力彼此独立地发展出一些共同点，就叫convergent evolution，也就是趋同理论，所以B的描述是对的。
3. Select the sentence in the passage in which the author shows that the implication of the common view is contradicted by a new finding.
也是第 2 句。
But the recent discovery of detailed similarities in the skeletal structure of the flippers in all three groups undermines the attempt to explain away superficial resemblance as due to convergent evolution—the independent development of similarities between unrelated groups in response to similar environmental pressures.
以前生物学家认为海豹，海狮，海象都有鳍足，是一种趋同现象，他们的祖先不同，只是相似的环境压力使他们不约而同地进化出了相同的鳍状足。
句 1 告诉我们的，海象海狮是一种陆生熊祖先的后代，海豹则跟黄鼠狼有亲缘关系。
句 2 告诉我们，现在发现了新证据，它们的鳍足的骨骼结构的一些细节，证明他们可能有着共同的祖先，也就是说以前的那种common view被反驳了。
P2
1
According to astronomer S.A. Phinney, kicking a rock hard enough to free it from Earth’s gravity would require a meteorite capable of making a crater more than 60 miles across.
根据天文学家P的观点，用足够大的力道去踢一块石头使它能脱离地球引力，这种力量相当于一块能够造成直径60英里大坑的陨石的破坏力。
2
Moreover, even if Earth rocks were freed by meteorite impact, Mars’s orbit is much larger than Earth’s, so Phinney estimates that the probability of these rocks hitting Mars is about one-tenth as great as that of Mars’s rocks hitting Earth.
另外，即便石头得到了陨石那么大的冲击力脱离地球，火星的轨道也比地球大得多，所以P估计这些石头到达火星的概率只有火星的时候到达地球的十分之一。
3
To demonstrate this estimate, Phinney used a computer to calculate where 1,000 hypothetical particles would go if ejected from Earth in random directions.
为了论证这种估计，P用电脑模拟了假设有1000个质点缘随即方向从地球发射，会去往何处。
4
He found that 17 of the 1,000 particles would hit Mars.
他发现，1000个质点有17个会到达火星。
4. Which of the following, if true, would cast most doubt on Phinney’s estimate of the probability of Earth rocks hitting Mars?
○A Rather than going in random directions, about 25 percent of all particles ejected from Earth go in the same direction into space.
○B Approximately 100 meteorites large enough to make a noticeable crater hit the Earth each year.
○C No rocks of Earth origin have been detected on Mars.
○D The velocity of rocks escaping from Earth’s gravity is lower than the velocity of meteorites hitting the Earth.
○E No craters more than 60 miles across have been found on Mars.
选A
文段不长，但谈的细节不少，注意题目问的是哪一个选项可以质疑地球发射的石头击中火星的概率。
根据句3我们已经知道模拟试验是随机发射1000个质点，以此来计算概率。所以选项必须跟试验内容或条件假设有关的内容，才可能用来质疑结果，理由中出现的与其他内容相关的描述和数据，可以直接排除。
所以选A。
