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标题: GWD1-Q10 [打印本页]

作者: rearn    时间: 2009-8-31 07:01     标题: GWD1-Q10

Low levels of straying are crucial, since the process provides a source of novel genes and a mechanism by which a location can be repopulated should the fish there disappear.  Yet high rates of straying can be problematic because misdirected fish may interbreed with the existing stock to such a degree that any local adaptations that are present become diluted.  Straying rates remain relatively low when environmental conditions are stable, but can increase dramatically when streams suffer severe disturbance。

 

It can be inferred from the passage that the occasional failure of some salmon to return to their natal streams in order to spawn provides a mechanism by which

 

A.      pristine streams that are near polluted streams become polluted themselves

 

B.       the particular adaptations of a polluted stream’s salmon population can be preserved without dilution

 

C.      the number of salmon in pristine habitats decreases relative to the number in polluted streams

 

D.      an environmentally degraded stream could be recolonized by new salmon populations should the stream recover

 

E.       the extinction of the salmon populations that spawn in polluted streams is accelerated

请问答案确实是d吗?为什么?b哪里错了?

什么叫should the stream recover????

万分感谢!!!


作者: grassgreen    时间: 2009-8-31 19:55

should the stream recover=if the stream recovers
我做這題時也不決定, 最後用"換字(repopulated=>reconlonized)"選對...

我對adaptation的理解不是很清楚
I **guess**文中說的dilution是local adaptations而不是the particular adaptations of a polluted stream’s salmon population

等NN來解釋

作者: vincentwh    时间: 2009-9-1 06:22

这里should =if
作者: heilongh    时间: 2009-9-2 06:39

我也选的B,哈。这篇文章做题时没怎么看懂,狂错。

反思一下,我觉得这道题用定位的方法其实不懂也可以做对。题干可以定位到原文"low levels of straying are crucial, since the process provides a source of novel genes and a mechanism by which a location can be repopulated should the fish there disappear".所以mechanism的关键是degraded river流失了一小批鱼,但是又能重新繁殖充裕起来。所有答案里只有D选项有reclonize=repopulize


作者: Avantasia    时间: 2009-9-3 06:43

定位就是这句话Low levels of straying are crucial, since the process provides a source of novel genes and a mechanism by which a location can be repopulated should the fish there disappear. 个人理解,should the fish there disappear等同于if the fish there were to disappear,是虚拟语气的倒装,想表达的意思就是低水平的迷路是很重要的,因为这样的过程可以产生新的基因和机制——即一旦那里的鱼消失了还可以(游过来新的鱼)通过这样的机制来重新repopulate这个区域。D选项是正确的。D的意思是说,一个环境质量下降的河流可以重新被recolonize(=repopulate)一旦河流恢复(污染程度)。D也用了同样的虚拟语气should the stream recover=if the stream were to recover.我对这个虚拟语气的同意改写没有必然的把握,但是解释应该是这样子的。如果我的虚拟语气同义改写大家有不同意见,请多指教:)




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