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OG18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。
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该题平均耗时:4m10s,平均正确率:59.7%

建议使用官方纸质指南,查看对照完整题目

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-P448-576题】

The passage mentions which of the following as a factor that affects the role of P. ochraceus as a keystone species within different habitats?

  • 分析A选项
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  • 分析B选项
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  • 分析C选项
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  • 分析D选项
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  • 分析E选项
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该题目由网友PHNAOhBu提供。更多GMAT题目请
暂无雷哥网文字解析
当前版本由 ya**** 更新于2015-11-10 20:58:38 感谢由 ya**** 对此题目的解答所做出的贡献。
从文中可知,P物种的基石物种的地位跟地点有关
A正确,符合文中意思
B错误,没有谈及地点
C错误,同上
D错误,与“种群大小”无关
E错误,与“种群的多样性”无关

题目讨论 3条评论)

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  • 用户头像

    Sunnie22

    注意题目是:affects——影响P占主导地位的因素
    文中的比较点是wave-exposed 和 wave-sheltered这个环境因素的不同
    0 0 回复 2018-10-19 09:19:48
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    Better vivi

    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,
    就是这句话,做错的原因是把问题想复杂了。。。。对A项有戒备心。。。。
    0 0 回复 2018-05-17 20:57:49
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    xiaoyi

    within different habitats
    0 0 回复 2017-02-06 21:36:06
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