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TPO46托福阅读文本及答案解析(Ecosystem Diversity and Stability)

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发表于 2018-11-6 11:47:15 | 显示全部楼层 |阅读模式
1. The word "significant" in the passage is closest in meaning to 【词汇题】
  A direct
  B important
  C long-term
  D surprising
  答案:B
  解析:significant的语境含义为”重要的“。B选项的important的意思是”重要的“,与语境吻合,故为正确答案。
  direct 直接的。 long-term长期的。 surprising令人惊讶的。

2. According to paragraph 1, why has the extinction of species been a concern for conservation biologists? 【事实信息题】
  A When ecosystems lose just one species, they undergo permanent change.
  B The extinction of a particular predator species could cause an overpopulation of certain prey species.
  C The loss of one or more species could cause the decline of a whole ecosystem.
  D The extinction of a single species is evidence that plant-food sources are in danger of disappearing.
  答案:C
  解析:根据原文An ecosystem could survive the loss of some species, but if… would be severely damaged…. dramatically change an entire ecosystem.故C选项正确。

 3. According to paragraph 1, what was the result of the removal of Pacific sea otters? 【事实信息题】
  A The kelp and sea urchins were destroyed by new predators.
  B The uncontrolled population of sea urchins ate most of the kelp plants.
  C Without sea otters, the kelp beds soon became overgrown.
  D Macroalgae remained as the primary population in the ecosystem.
  答案:B
  解析:根据原文信息The kelp beds were practically obliterated too because in the absence of sea otter predation, sea urchin populations exploded and consumed most of the kelp and other macroalgae.可知B选项正确。题干的removal对应这里的absence。选项中的uncontrolled对应这里的exploded. Ate对应句中的consumed.

  4. The word “redundancy” in the passage is closest in meaning to 【词汇题】
  A duplication
  B variety
  C requirements
  D flexibility
  答案:A
  解析:redundancy的语境含义为“复制”。A选项的含义为“复制、副本”,与语境吻合,故为正确答案。
  variety多样性。 requirements要求。 flexibility灵活性。

  5. What is the function of paragraph 2 in the passage? 【修辞目的题】
  A To present a hypothesis about ecosystem diversity and some reasons why it might be true
  B To give examples of types of ecosystems that have the greatest diversity
  C To contradict a previous belief about the stability of species-rich ecosystems
  D To contrast species-rich and species-poor ecosystems
  答案:A
  解析:第二段先给出了一个hypothesis: It is usually claimed that species-rich ecosystems tend to be more stable than species-poor ecosystems. 之后对这个hypothesis为什么正确给予了三种解释,故A选项正确。

 6. According to paragraph 2, which of the following increases the stability of an ecosystem? 【事实信息题】
  A Species in which producers outnumber predators
  B New or exotic species that increase ecosystem diversity
  C Heavily populated species that are free of disease
  D Species that are diverse but have similar nutritional roles
  答案:D
  解析:根据原文First, if… greater redundancy among species in terms of their nutritional roles. Second, diverse ecosystems may be less likely to be invaded…可知D选项正确。

7. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information. 【句子简化题】
  A In any ecosystem, as the number of individuals in the same species increases, the rate of disease transmission slows down.
  B Ecosystems that have a small number of different species tend to be disease-free, because the species’ habitats are at a safe distance from each other.
  C In ecosystems with many species, diseases spread more slowly because there are fewer individuals in a species and, as a result, the individuals are more widely scattered.
  D The average distance between individuals in a species-rich ecosystem increases, so diseases are prevented from being communicated between species.
  答案:C
  解析:原句的逻辑为因果逻辑,因为句中出现了because. 句子的核心为: diseases may spread more slowly, thus increasing distance and hampering disease transmission. C选项的核心与原句吻合,且逻辑关系一致,故C为正确选项。

 8. The phrase ”compensating for" in the passage Is closest in meaning to 【词汇题】
  A working against
  B leaving out
  C making up for
  D spreading over
  答案:C
  解析:compensating for的语境含义为”弥补“, C选项的making up for意为”弥补“,与语境吻合,为正确选项。
  working against 反对。 leaving out省略。 spreading over 遍布于。

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 楼主| 发表于 2018-11-6 11:47:36 | 显示全部楼层
 9. What is the main importance of the study discussed in paragraph 3? 【修辞目的题】
  A It examines the response of certain grassland plants to a drought.
  B It contains an index of plants that survived well in times of drought.
  C It provides scientific evidence that diversity helps to make ecosystems stable.
  D It shows that ecosystems contain both resistant species and less tolerant ones.
 答案:C
  解析:第三段的中心句为段落最后一句:Apparently, species-rich plots were likely to contain… 段落前面主要讲了相关的research,故正确答案为C。

  10. Select the TWO answer choices that, according to paragraph 4, are conclusions that can be drawn from the study by Tilman and Downing. To receive credit you must select TWO answer choices. 【双选题】
  A A diverse ecosystem will have species that respond differently to a variety of conditions.
  B Species within a species-rich ecosystem are more likely to have competitors.
  C An ecosystem is more likely to develop diverse and stable species when it is exposed to extreme conditions.
  D Species with similar ecological functions will perform the function of a lost species.
  答案:AD
  解析:根据原文a species-rich ecosystem may be more stable because it is more likely to have species with a wide array of responses to variable conditions such as droughts. 可知,A选项正确。
  根据原文Furthermore, a species-rich ecosystem is more likely to have species with similar ecological functions,so that if a species is lost from an ecosystem, another species, probably a competitor, is likely to flourish and occupy its functional role.可知,D选项正确。

  11. The word “detect” in the passage is closest in meaning to 【词汇题】
  A repeat
  B alter
  C find
  D emphasize
  答案:C
  解析:detect的语境含义为“探测,发现。”C选项的意思为“发现”,与语境吻合,故为正确答案。
  repeat重复。 alter 改变。 emphasize强调。

 12. According to paragraph 5, which of the following is true about Tilman and Downing’s findings? 【事实信息题】
  A General patterns of diversity and stability have been established as a result of the findings.
  B Questions about the findings have been refuted by computer models.
  C The findings have been tested in a broad spectrum of ecosystems with similar results.
  D The findings are not sufficient to prove a definite link between diversity and stability in ecosystems.
  答案:D
  解析:根据原文However, its findings have been questioned…have not always fund a positive relationship between diversity and stability.可知,D选项正确。

  13. Look at the four squares [■] that indicate where the following sentence could be added to the passage. 【句子插入题】
  It seems clear that there is room for a great deal more research, although some work has been done.
  Where would the sentence best fit? Click on a square [■] to add the sentence to the passage.
 答案:A
  解析:插入句的意思是:尽管一些工作已经完成了,但似乎有余地来做更多的研究。说明插入的句子之前已经叙述了相关work,插入句之后会谈到更多的research. 插入点A处前面的句子说明了已经有一些scientific evidence了,也就是已经进行了一些工作。插入点A处后面的句子中有one of the first studies说明进行了research,所以插入A处是合适的。故正确选项为A。

14. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points. 【概要小结题】
  Drag your answer choices to the spaces where they belong To remove an answer choice, click on it
  To review the passage, click VIEW TEXT
  Biologists have long been worried about the possible effect of the extinction of species on whole ecosystems.
  Answer Choices
  Conservation biology studies Indicate that the loss of a single important species may bring temporary change to an ecosystem but it seldom results in lasting damage.
  Ecosystems having species with similar functions but different responses to adverse conditions can survive environmental disturbances.
  The Minnesota grassland study by Tilman and Downing presented evidence that the greater the diversity of species in an ecosystem, the more stable the ecosystem.
  The absence of sea otter predation in a Pacific kelp bed ecosystem dramatically changed the entire ecosystem by stabilizing the total kelp population.
  The findings of the Minnesota grassland study by Tilman and Downing indicated an equal number of drought-resistant and drought-tolerant plant species in species-rich plots.
  More research is needed on the relationship between species diversity and ecosystem stability, though a simple explanation is unlikely.
  答案:BCF
  解析:A选项中temporary的说法与原文的would be severely damaged 的说法不一致,故该选项错误。
  B选项的说法与第4段Both of these, variability in responses and functional redundancy, could be thought of as insurance against disturbances. 对应, 正确。
  C 选项与原文species-rich ecosystem may be more stable because it is more likely to have species with a wide array of responses to variable conditions such as droughts.对应,正确。
  D选项的dramatically changed the entire ecosystem的说法原文没有提及,错误。
  E选项的说法在文中没有依据,错误。
  F选项对应原文Clearly, this is a complex issue that requires further field research with a broad spectrum of ecosystems and species.故该选项为正确选项。

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