gwd1 10,12 迷惑

tempture

我同意mike的说法

要作这道题应该看前文为什么会提到eruption。文中先说Straying rates remain relatively low when environmental conditions are stable, but can increase dramati- cally when streams suffer severe disturbance.  然后举的eruption的例子，它影响的应该是gene flow，而不是直接影响gene struture，这中间有一个gap。美国人的逻辑思维直接，所以我认为比较的应该是gene flow，而不是gene sturcture。

此外，comparation的确显示了这个例子的作用。should be measured也不一定非要是精确测量。可以是一个比较含糊的概念。

youpiao

Q10 我有跟TIANWAN 一样的疑惑：答案B是不是原文high straying rate 的取非？

ETS在INFER类的题里最爱考取非了！

当然我也同意D，但第二遍做时发现B没法否掉？

谁能告诉我B哪里错了？

concong

关于10：

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.

问题：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

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

完美的同意变换

如果说是取非的话：

原文：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.

问题：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

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

我觉得local adaptations和the adaptations of salomn population，不是同一个概念。

还有就是题目中问到的mechanism，原文中已经将一件事情定义为mechanism，可是没有将某种适应能力的消失或者保存定义为一种mechanism

如果想到取非的话是不是太复杂了

[此贴子已经被作者于2004-11-27 0:38:29编辑过]

concong

关于12：

原文  Although no one has quantified changes in the rate of straying as a result of the disturbances caused by humans, there is no  reason to suspect that the effect would be qualitatively different than what was seen in the aftermath of the Mount Saint Helens eruption.  Such a dramatic increase in straying from damaged areas to more pristine streams results in substantial gene flow, which can in turn lower the overall fitness of subsequent generations.

这一段是接上一段的，可以说是对上一段的总结，在讲人类的行为会对最终会引起多大的破坏，含有一种破坏程度意味。

B .indicate the extent to which the disturbance of salmon habitat by human activity in one stream might affect the genetic structure of salmon populations elsewhere

C. provide a standard of comparison against which the impact of human activity on the gene flow among salmon populations should be measured

C讲一个衡量的标准，上文只提到eruption造成迷失率由14％上升到16％，而第三段开头说了Although no one has quantified changes in the rate of straying as a result of the disturbances caused by humans

[此贴子已经被作者于2004-11-27 0:39:59编辑过]

youpiao

以下是引用concong在2004-11-27 0:32:00的发言：

关于10：

我觉得local adaptations和the adaptations of salomn population，不是同一个概念。

还有就是题目中问到的mechanism，原文中已经将一件事情定义为mechanism，可是没有将某种适应能力的消失或者保存定义为一种mechanism

偶被说服了，同意D。谢谢concong！！

tempture

以下是引用concong在2004-11-27 0:33:00的发言：

关于12：

原文  Although no one has quantified changes in the rate of straying as a result of the disturbances caused by humans, there is no  reason to suspect that the effect would be qualitatively different than what was seen in the aftermath of the Mount Saint Helens eruption.  Such a dramatic increase in straying from damaged areas to more pristine streams results in substantial gene flow, which can in turn lower the overall fitness of subsequent generations.

这一段是接上一段的，可以说是对上一段的总结，在讲人类的行为会对最终会引起多大的破坏，含有一种破坏程度意味。

B .indicate the extent to which the disturbance of salmon habitat by human activity in one stream might affect the genetic structure of salmon populations elsewhere

C. provide a standard of comparison against which the impact of human activity on the gene flow among salmon populations should be measured

C讲一个衡量的标准，上文只提到eruption造成迷失率由14％上升到16％，而第三段开头说了Although no one has quantified changes in the rate of straying as a result of the disturbances caused by humans

其实我没有看明白你最后选什么....

concong

12条我选B

tempture

为什么一定要纠缠与extent和standard of comparion呢，难道standard of compare就不一定是quantitative而不能是qualitative的么？

btw：是从16%到40％，当然这是个小问题。

魚子醬秋天

i choice E according to the article

:Strayingrates remain relatively low when environmental conditions are stable, but can increase dramati- cally when streams suffer severe disturbance

could anyone be kind to tell me why Ｅ　isn't correct  ?

leeon

12:B,原文火山爆发影响该鱼迷路，与其它地方的鱼杂交后产生了基因变异。说明了人的活动对溪流的干扰影响了该鱼在其它地方的基因结构。（同样都是由高的迷路率造成的结果）。