新东方网>留学>LSAT考试>LSAT辅导>LSAT历年真题>正文

实用备考资料:LSAT阅读理解真题25(含答案)

2011-11-25 19:06

来源:互联网

作者:

  为了方便广大考生更好的复习,新东方网综合整理了备考资料:LSAT真题系列文章,以供各位考生考试复习参考,希望对考生复习有所帮助。愿大家都能取得好成绩,更多有关留学考试的资讯与辅导资料敬请关注新东方网留学考试频道。             

  The old belief that climatic stability accounts for the high level of species diversity in the Amazon River basin of South America emerged, strangely enough, from observations of the deep sea. Sanders discovered high diversity among the mud-dwelling animals of the deep ocean. He argued that such diversity could be attributed to the absence of significant fluctuations in climate and physical conditions, without which the extinction of species should be rare. In the course of time (in the course of time: 随着时间[岁月]的推移, 总有一天) new species would continue to evolve, and so the rate of speciation (speciation: n.[生]物种形成,与 speciality 区别) would be greater than the rate of extinction, resulting in the accumulation of great diversity. Sanders argued that the Amazon tropical rain forest is analogous to the deep sea: because the rain forest has a stable climate, extinction should be rare. Evidence that some species of rain-forest trees have persisted for some 30 million years in the Amazon basin, added to the absence of winter and glaciation, supports this view.

  Recently however, several observations have cast doubt on the validity of the stability hypothesis and suggest that the climate of the Amazon basin has fluctuated significantly in the past. Haffer noted that different species of birds inhabit different corners of the basin in spite of the fact that essentially unbroken green forest spreads from the western edge to the eastern edge of the region. This pattern presented a puzzle to biologists studying the distributions of plants and animals: why would different species inhabit different parts of the forest if the habitat in which they lived had a stable climate?

  Haffer proposed a compelling explanation for the distribution of species. Observing that species found on high ground are different from those on low ground and knowing that in the Amazon lowlands are drier than uplands, he proposed that during the ice ages the Amazon lowlands became a near-desert arid plain; meanwhile, the more elevated regions became islands of moisture and hence served as refuges for the fauna and flora of the rain forest. Populations that were once continuous diverged and became permanently separated. Haffer’s hypothesis appears to explain the distribution of species as well as the unusual species diversity. The ice-age refuges would have protected existing species from extinction. But the periodic geographic isolation of related populations (there have been an estimated 13 ice ages to date) would have facilitated the development of new species as existing species on the lowlands adapted to changing climates.

  Although no conclusive proof has yet been found to support Haffer’s hypothesis, it has led other researchers to gauge the effects of climatic changes, such as storms and flooding, on species diversity in the Amazon basin. Their research suggests that climatic disturbances help account for the splendid diversity of the Amazon rain forest.

  15. As discussed in the first paragraph of the passage, Sanders’ analogy between the deep sea and the Amazon basin involves which one of the following assumptions?

  (A) Both the Amazon basin and the deep sea support an unusually high rate of speciation.

  (B) Both the rain-forest trees in the Amazon basin and the mud-dwelling animals in the deep sea have survived for 30 million years.

  (C) Both the deep sea and the Amazon basin have not experienced dramatic changes in climate or physical conditions.

  (D) A dependable supply of water to the Amazon basin and the deep sea has moderated the rate of extinction in both habitats.

  (E) The rate of speciation in the Amazon basin is equivalent to the rate of speciation in the deep sea.

  16. The author of the passage would most likely agree with which one of the following statements about Haffer’s hypothesis?

  (A) It provides an intriguing and complete explanation for the high rate of species diversity in the Amazon basin.

  (B) It is partially correct in that a number of climatic disturbances account for species diversity in the Amazon basin.

  (C) It has not yet been verified, but it has had an influential effect on current research on species diversity in the Amazon basin.

  (D) It is better than Sanders’ theory in accounting for the low rate of species extinction in the Amazon basin.

  (E) It provides a compelling explanation for the distribution of species in the Amazon basin but does not account for the high species diversity.

  17. According to the passage, lowlands in the Amazon basin currently differ from uplands in which one of the following respects?

  (A) Lowlands are desertlike, whereas uplands are lush.

  (B) Lowlands are less vulnerable to glaciation during the ice ages than are uplands.

  (C) Uplands support a greater diversity of species than do lowlands.

  (D) Uplands are wetter than are lowlands.

  (E) Uplands are more densely populated than are lowlands.

  18. Which one of the following best describes the organization of the passage?

  (A) A hypothesis is discussed, evidence that undercuts that hypothesis is presented and a new hypothesis that may account for the evidence is described.

  (B) A recently observed phenomenon is described, an explanation for that phenomenon is discussed, and the explanation is evaluated in light of previous research findings.

  (C) Several hypotheses that may account for a puzzling phenomenon are described and discounted, and a more promising hypothesis is presented.

  (D) A hypothesis and the assumptions on which it is based are described, and evidence is provided to suggest that the hypothesis is only partially correct.

  (E) Two alternative explanations for a phenomenon are presented and compared, and experiments designed to test each theory are described.

  19. The author of the passage mentions the number of ice ages in the third paragraph most probably in order to

  (A) provide proof that cooler and drier temperatures are primarily responsible for the distribution of species in the Amazon

  (B) explain how populations of species were protected from extinction in the Amazon basin

  (C) explain how most existing species were able to survive periodic climatic disturbances in the Amazon basin

  (D) suggest that certain kinds of climatic disturbances cause more species diversity than do other kinds of climatic disturbances

  (E) suggest that geographic isolation may have occurred often enough to cause high species diversity in the Amazon basin

  20. The passage suggests that which one of the following is true of Sanders’ hypothesis?

  (A) He underestimated the effects of winter and glaciation in the Amazon basin on the tropical rain forest.

  (B) He failed to recognize the similarity in physical conditions of the Amazon lowlands and the Amazon uplands.

  (C) He failed to take into a count the relatively high rate of extinction during the ice ages in the Amazon basin.

  (D) He overestimated the length of time that species have survived in the Amazon basin.

  (E) He failed to account for the distribution of species in the Amazon basin.

  21. Which one of the following is evidence that would contribute to the “proof” mentioned in line 54?

  (A) Accurately dated sediment cores from a freshwater lake in the Amazon indicate that the lake’s water level rose significantly during the last ice age.

  (B) Data based on radiocarbon dating of fossils suggest that the Amazon uplands were too cold to support rain forests during the last ice age.

  (C) Computer models of climate during global ice ages predict only insignificant reductions of monsoon rains in tropical areas such as the Amazon.

  (D) Fossils preserved in the Amazon uplands during the last ice age are found together with minerals that are the products of an arid landscape.

  (E) Fossilized pollen from the Amazon lowlands indicates that during the last ice age the Amazon lowlands supported vegetation that needs little water rather than the rain forests they support today.

新东方网托福官方微信:新东方托福 (微信号:xdftoefl

最新考试资讯、托福预测、托福解析,请扫一扫二维码,关注我们的官方微信! 

新东方留学考试辅导专区

班级名称 上课地点 上课时间 费用 详细

焦点推荐

版权及免责声明

凡本网注明"稿件来源:新东方"的所有文字、图片和音视频稿件,版权均属新东方教育科技集团(含本网和新东方网) 所有,任何媒体、网站或个人未经本网协议授权不得转载、链接、转贴或以其他任何方式复制、发表。已经本网协议授权的媒体、网站,在下载使用时必须注明"稿件来源:新东方",违者本网将依法追究法律责任。

本网未注明"稿件来源:新东方"的文/图等稿件均为转载稿,本网转载仅基于传递更多信息之目的,并不意味着赞同转载稿的观点或证实其内容的真实性。如其他媒体、网站或个人从本网下载使用,必须保留本网注明的"稿件来源",并自负版权等法律责任。如擅自篡改为"稿件来源:新东方",本网将依法追究法律责任。

如本网转载稿涉及版权等问题,请作者见稿后在两周内速来电与新东方网联系,电话:010-60908555。