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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-P448-577题】
Which of the following hypothetical experiments most clearly exemplifies the method of identifying species, roles that the author considers problematic?
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类比题，需要选择一个同样也要移除某个物种的实验
A错误，与“某个种群的数量”无关
B错误，该选项没有谈及“移除某个物种”
C正确
D错误，没有提及“物种被移除”
E错误，与“物种灭绝”无关
定位：identifying a keystone species by removing the species and observing changes in the ecosystem is problematic
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2019-10-09 10:05:47
定位在第三行
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2019-08-22 09:55:12
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