【OG20-P449-579题】The passage suggests which of the following about _OG16_-{$seo

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OG20官方指南，建议同学们刷3遍。第一遍做题了解题型和考点，第二遍精刷，第三遍集中解决疑难问题。建议考生第一遍刷题采用官方正版纸质书籍，若遇到疑难问题，欢迎在此专区查阅解析，提供解析，参与题目讨论，与所有考生一起解决疑难问题。

雷哥网GMAT>题库>OG16>阅读RC>9479

阅读RC-9479 (第4/4题) Time Cost00:00

该题平均耗时：1m13s，平均正确率：77.3%

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While the most abundant and dominant species within a particular ecosystem is often crucial in perpetuating the ecosystem, a "keystone" species, here defined as one whose effects are much larger than would be predicted from its abundance, can also play a vital role. But because complex species interactions may be involved, identifying a keystone species by removing the species and observing changes in the ecosystem is problematic. It might seem that certain traits would clearly define a species as a keystone species; for example, Pisaster ochraceus is often a keystone predator because it consumes and suppresses mussel populations, which in the absence of this starfish can be a dominant species. But such predation on a dominant or potentially dominant species occurs in systems that do as well as in systems that do not have species that play keystone roles. Moreover, whereas P. ochraceus occupies an unambiguous keystone role on wave-exposed rocky headlands, in more wave-sheltered habitats the impact of P. ochraceus predation is weak or nonexistent, and at certain sites sand burial is responsible for eliminating mussels. Keystone status appears to depend on context, whether of particular geography or of such factors as community diversity (for example, a reduction in species diversity may thrust more of the remaining species into keystone roles) and length of species interaction (since newly arrived species in particular may dramatically affect ecosystems).

【OG20-P449-579题】

The passage suggests which of the following about the identification of a species as a keystone species?

A

Such an identification depends primarily on the species’ relationship to the dominant species. 分析A选项
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B

Such an identification can best be made by removing the species from a particular ecosystem and observing changes that occur in the ecosystem. 分析B选项
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C

Such an identification is likely to be less reliable as an ecosystem becomes less diverse. 分析C选项
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D

Such an identification seems to depend on various factors within the ecosystem. 分析D选项
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E

Such an identification can best be made by observing predation behavior. 分析E选项
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当前版本由 ya**** 更新于2015-11-10 20:57:32 感谢由 ya**** 对此题目的解答所做出的贡献。

A错误，primarily带有明显标志
B错误，best带有明显标志
C错误，没有出现这个比较
D正确，文章后半部分开始讨论影响基石物种的各种因素
E错误，best使该选项带有明显标志

题目讨论（4条评论）

提交

851741xyf

美美全错，哎

0 0 回复 2021-10-17 10:28:42
853447wha

A项：But such predation on a dominant or potentially dominant species occurs in systems that do as well as in systems that do not have species that play keystone roles.

0 0 回复 2021-10-02 22:48:50
Zehnstein

Keystone status appears to depend on context

0 0 回复 2020-02-25 17:56:21
847716opn

B选项漏看了best

0 0 回复 2019-09-27 09:18:41

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