gwd1 10,12 迷惑

chang2301

Q10 The answer should be B, not D

In the context, if the fish disappear-->repopulated

And in D, if the strewam recover-->recolonized

Since repopulated=repopulated while if the fish disappear is contrary to if the strewam recover, answer D

cannot be the correct answer.(different perspective cannot lead to the same consequence)

Therefore, the answer should be B as Tianwan has claimed in the previous page and his logic is right.

Furthermore, this question is an inference question, which means it asks for the indirect answer that is

not specifically stated in the passage or that is simply the rephrase of the sentence. Choice D is

obviously trying to confuse us with a closing rephrase structure.

jcjc0602

Q9:

The primary purpose of the passage is to

             

1. argue against a conventional explanation for the extinction of certain salmon populations and suggest an alternative

2. correct a common misunderstanding about the behavior of salmon in response to environmental degradation caused by human activity

3. compare the effects of human activity on salmon populations with the effects of natural disturbances on salmon populations

4. differentiate the particular effects of various human activities on salmon habitats

5. describe how environmental degradation can cause changes in salmon populations that extend beyond a numerical reduction

我觉得第九题应该选c，因为阅读全文之后，第一段说人类的活动不仅造成了马哈鱼数量的减少而且减少了其基因的多样化，然后第二段说large-scale-disturbution also have potential to alter the genetic structure of population.最后一段说人类活动的影响没有自然disturbution的影响大，所以整篇文章不是应该在说二者的对比吗？

apoab

1-9~12题对我来是最难的是10，12题大家都讨论那么多了，表示B、C都有可选之处，但讨论10的人反而不多，感觉大家都会的样子，让我有点汗颜…原因是我一直想不明白原文的某些的地方，就在刚刚，A-HA灵机一动突然想通了，分享给大家，有点长，如果大家都会了也可以看看小弟的思考是不是跟大家一样，有问题也请指正。

 

10. 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

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

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

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

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

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

Ans：D

原文定位应该是这里：

(35) Low levels of straying are crucial, since the process provides a source of novel genes and a mechanism by which a location can be (40)  repopulated should the fish there disappear. Yet high rates of straying can be problematic because misdirected fish may interbreed with the existing stock (45) to such a degree that any local adaptations that are present become diluted.

这两句话如果要做note的话应该是：

Low level straying：crucial, provide a mechanism, a location can be repopulated if the fish disappear.
            

High level straying：problematic, misdirected fish may interbreed the existing fish à diluted local adaptations.

Straying：指的是迷路(的鱼)

从crucial跟problematic我们可知，作者认为Low level是正面的，High level是负面的，这一点没问题。但Low level的为何会好呢?? 因为它提供了一个机制(mechanism)吗? 那这个机制又是如何运作的呢?? a location指的是原来鱼群的栖息地还是迷失的鱼群存在的新地方呢? the fish disappear 的the fish只的是原来的鱼群消失还是迷失的鱼群消失呢? 又是哪一群鱼在repopulate呢?最重要的一点是，为何Low level的机制可以提供repopulate 的好处，High level时反而不能提供呢?? 不都是把鱼分成两群吗?? 相较于High level那一句话的清楚明了，说实话我在模考时对Low level整句话心中就是浮现这么多的疑问的。原因就在于我没有真正了解作者对straying rate态度。后来我反而是从第10题的答案中反推才想通的。

 

我推测是这样子：作者对straying rate的态度是，完全没有straying:负面à Low level straying：正面àHigh level straying：负面，为什么Low level straying会比完全没有straying好，因为它能把鱼分成两群，一群回到原产地，一群迷路到新的河流，如果原产地的河流遭到环境的污染，原来那群鱼通通死光了(should the fish disappear)，要是完全没有straying那么这整个鱼群就绝种了，unique genes 也通通lost了，可是如果有另一小群鱼迷失在别的河流而存活下来，那么至少可以将这一鱼群特有的gene特殊性保存下来，也许，等到这一群鱼或是这一群鱼的后代明年再从海里游回家 (鲑鱼每年10月会都从海里回去产卵)，它们其中有些会回到原来被污染的河流，而那时也许河流已恢复，那这原来品种的鱼又可以在原来的河流重新繁衍下去了(a location can be repopulated)，这就是整个(mechanism)实际运作的方法(a location can be repopulated should the fish disappear by this mechanism)。用一句老话来形容这个机制就是 ”不把全部的鸡蛋放在同一个蒌子里。”

 

到这边其实可以解释为何第10题选D了，题目为the occasional failure of some salmon to return to their natal streams就是问Low-leveling straying 的mechanism。把上一段的红色部分拿来跟D选项对照一下an environmentally degraded stream(如果原产地的河流遭到环境的污染)could be recolonized(repopulated) by new salmon populations should the stream recover(而那时也许河流已恢复)，如果大家能够同意我上一段的推论，那选D当答案应该是说得通的。

 

接下来的思考只是为了更了解作者的本意：照上面的推论，不管迷路的鱼群是少还是多(Low or High level straying)，只要能把鱼分成两群，都能够提供这样一个机制，所以我之前的疑问可以解答了，High level的straying同样也能提供这样一个正面的机制，甚至应该更好，因为更多的鱼留下来，原来鱼群绝种的机会就更少了。最后的问题来了，为什么作者对High level的straying抱持着跟Low level相反的负面态度呢? 再看一次原文：because misdirected fish may interbreed with the existing stock (45) to such a degree that any local adaptations that are present become diluted.，原来是因为迷路的鱼若太多，跟本来当地的鱼杂交机率也会变高，到某一个程度之后，会冲淡它们的后代身上可以适应原产地的特性，一旦被充淡后代的鱼出生，原来在新河流里另外一个鱼群，就会如第一段L10~15所说的reduce genetic diversity 导致 the extinction of entire salmon populations, 要注意一点就是所谓的any local adaptations become diluted 是双方面互相影响的，不仅影响原来跟迷路的鱼同样一个族群的鱼，就连那些跟迷路鱼杂交当地的另一个族群的鱼也被影响了，两个族群的genetic diversity都减少了。所以，结论就是High-level straying同样能提供Low level所能提供的机制，但是过多的鱼迷路却会让这个本来正面的机制不但有原来的效果还产生非预期外的负面效果，而作者认为负面效果掩盖了正面，所以说它problematic。

来否定一下其它的选项吧~

1. pristine streams that are near polluted streams become polluted themselves 错，迷路的鱼群并不会污染干净的河流

2. the particular adaptations of a polluted stream’s salmon population can be preserved without dilution 唯一有可能的干扰选项，但依据上面的推论，文中只说High level会dilute，low level所提供的mechanism跟dilute可一点关系没有，本题问的是”Low level”的mechanism，依照原文来看如果把without dilution给拿掉，B就对了。
               

3. the number of salmon in pristine habitats decreases relative to the number in polluted streams 错，在mechanism下迷路的鱼群游到另一条干净的河流并不会影响当地的鱼群数量，High level除了mechanism外还多了会diluted local adaptation, 本题问的是Low level，就算是问High level也不可能对。

E .the extinction of the salmon populations that spawn in polluted streams is accelerated 错，low level straying不但不会加速在原来污染河流里的鱼群绝种，反而会因为mechanism运作而更不会绝种。

 

看之前的讨论，大部份人好像都是用同义代换才选到D，但就如chang2301所说的，完全用代换法的话，选项D其实是不太正确的，但我想考试大部分人应该没时间想那么多了吧~~^__^。

wangwei8581

不是c 就是 b！

我是说选 b

d_sheep

103楼说的已经很详细了,我认为就是这么回事,10就是D了,

raikey

以下是引用dreaminger在2006-7-17 14:49:00的发言：

文章最后一段：人类的侵扰和大自然的改变对结论不会有太大出入。最后一句话：用大自然中火山爆发影响基因的例子来说明，人类的侵扰会造成相似的后果。所以答案C正确。

同意上述论据,但不同意上述结论. 因为文章没有明确说"人类的侵扰会造成相似的后果", 没明确说的就叫做"indicate". 而standard必须是十分明确的东东.
支持12题答案为B

定位:

Although no one has quantified

changes in the rate of straying

as a result of the disturbances

caused by humans, there is no

 (70)      reason to suspect that the effect

would be qualitatively different

than what was seen in the

aftermath of the Mount Saint
Helens eruption.

 

该句说"没证据能证明人类是最愧祸首,但火山爆发造成的后果很明显,"  这样的句子,出现在一篇讲述"人类造成危害"的文章里,不就是指桑骂槐吗? B选项"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"正有此意.  而C中的standard极其成问题,

jasoncz1

" Although no one has quantified changes in the rate of straying as a result of the disturbances caused by humans" 是在讲鱼儿迷路的频率的改变, 文章说了这后果是人类造成的, 没有疑问.   C 和 B 都有对和错的地方.  因为这一段都是在讲这后果对鱼儿迷路有多大影响, 用了MSH来做个估计, 其实是来show the extent that human activity can affect the rate of stray in salmon respawning and affect the gene flow of the overall populations.  Gene structure 这点是挑小毛病而已. 

罗马青年

看的真痛快，超级N的讨论帖！看了3个小时，值！！！

收获非常多，简直可以编成一本告诉大家“如何做好阅读”的教材了。将如何理解文章结构、定位、理解作者的本意（106楼“指桑骂槐”很绝，呵呵！）、ETS的出题伎俩 都谈得非常到位，看完不仅仅是理解了一道题，而是对GMAT 阅读有了新的认识！！！

感谢LS所有前辈“不见面”的指导！谢谢了！

ssl507

10题支持B

以下引用（如果原产地的河流遭到环境的污染，原来那群鱼通通死光了(should the fish disappear)，要是完全没有straying那么这整个鱼群就绝种了，unique genes 也通通lost了，可是如果有另一小群鱼迷失在别的河流而存活下来，那么至少可以将这一鱼群特有的gene特殊性保存下来。）

既然河流已污染，迷失的鱼怎么可能在这里存活下来？

ssl507

12题还是支持B

可以想像，作者的目的就是给你提供一个人为破坏的严重程度，而不是在于比较。