hikarugaara 发表于 2010-7-14 16:03
q12为什么说是细节就错，这题又不是主题题对于C，文中并没有comparison啊，我觉得就是举例volcanica erupti ...
我分析了这篇文章好久,感觉是看明白了,可是题目错了一大片.请NN帮忙指导我该怎样去分析这篇文章和题目.现在被阅读困扰得直想撞墙.原来我的阅读这么差!!!我急切需要指导走出这个困境.
提前感谢回帖的NN们.致敬!!!
Over the last 150 years, large stretches of salmon habitat have been eliminated by human activity: mining, livestock grazing, timber harvesting, and agriculture as well as recreational and urban development. The numerical effect is obvious: there are fewer salmon in degraded regions than in pristine ones; however, habitat loss also has the potential to reduce genetic diversity. This is most evident in cases where it results in the extinction of entire salmon populations. Indeed, most analysts believe that some kind of environmental degradation underlies the demise of many extinct salmon populations. Although some rivers have been recolonized, the unique genes of the original populations have been lost.
Large-scale disturbances in one locale also have the potential to alter the genetic structure of populations in neighboring areas, even if those areas have pristine habitats. Why? Although the homing instinct of salmon to their natal stream is strong, a fraction of the fish returning from the sea (rarely more than 15 percent) stray and spawn in nearby streams. 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. The 1980 volcanic eruption of Mount Saint Helens, for example, sent mud and debris into several tributaries of the
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
GWD1-Q9:
The primary purpose of the passage is to
A. argue against a conventional explanation for the extinction of certain salmon populations and suggest an alternative
B. correct a common misunderstanding about the behavior of salmon in response to environmental degradation caused by human activity
C. compare the effects of human activity on salmon populations with the effects of natural disturbances on salmon populations
D. differentiate the particular effects of various human activities on salmon habitats
E. describe how environmental degradation can cause changes in salmon populations that extend beyond a numerical reduction
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GWD1-Q10:
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
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GWD1-Q11:
According to the passage, human activity has had which of the following effects on salmon populations?
A. An increase in the size of salmon populations in some previously polluted rivers
B. A decline in the number of salmon in some rivers
C. A decrease in the number straying salmon in some rivers
D. A decrease in the gene flow between salmon populations that spawn in polluted streams and populations that spawn in pristine streams
E. A decline in the vulnerability of some salmon populations to the effects of naturally occurring habitat destruction
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GWD1-Q12:
The author mentions the “aftermath of the
A. provide an example of the process that allows the repopulation of rivers whose indigenous salmon population has become extinct
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
D. show how salmons’ homing instinct can be impaired as a result of severe environmental degradation of their natal streams
E. show why straying rates in salmon populations remain generally low except when spawning streams suffer severe environmental disturbance
ＴＮ２４里给的Ｑ１２的答案是Ｃ，但是ＧＷＤ－ＲＣ 解题里给的答案是Ｂ
简单看下文章逻：
1：鱼的聚集地因为人类活动而减少，从而导致了基因多样性的减少
2：环境波动影响周边地区的基因多样性 - 原因：环境 影响洄游偏移， 洄游偏移影响基因多样性 例子：火山
3：再次强调人类活动对基因的影响不可忽视
文章主要：介绍鱼数量减少，趋于灭绝的原因及过程。看下题目
GWD1-Q9:
The primary purpose of the passage is to 文章目的不是反对，纠正，比较，区分，而是大篇幅描述了环境变化对鱼的影响过程
A. argue against a conventional explanation for the extinction of certain salmon populations and suggest an alternative
B. correct a common misunderstanding about the behavior of salmon in response to environmental degradation caused by human activity
C.D. differentiate the particular effects of various human activities on salmon habitats
E. describe how environmental degradation can cause changes in salmon populations that extend beyond a numerical reduction
GWD1-Q10:
It can be inferred from the passage that the occasional failure（low level of spaying) of some salmon to return to their natal streams in order to spawn provides a mechanism by which回游的时候迷路了会出现什么问题呢？
定位：low level of spraying, mechanism
文中说了since the process provides a source of novel genes and a mechanism by which a location can be repopulated should the fish there disappear.提供了这种体系：即使水体中的鱼消失了仍然可以再次发展壮大 - 同义变换选项D:an environmentally degraded stream could be recolonized by new salmon populations should the stream recover一个被污染的水体（鱼可能都死了）当恢复后可以重新被鱼们占据生长
这道题目其他选项你观察下pristine streams ；adaptations ；pristine habitats ； the extinction of the salmon populations 都没有在定位点提到
注：should the stream recover：虚拟语气 相当于 if the stram should recover如果溪水回复正常
GWD1-Q11: 选B
According to the passage, human activity has had which of the following effects on salmon populations?
定位human activity/ effect
The numerical effect is obvious: there are fewer salmon in degraded regions than in pristine ones.
GWD1-Q12:
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
:人类的影响下，火山过后的结果也是会不一样的，其实作者态度就是人类对鱼基因的影响是存在不可以忽视的，选C, 通过比较，突出人类影响
其他的都没有反映这个意思。D中的n one stream ，elsewhere一看都是细节，错
我觉得文章主要3点：文章的结构 - 作者想说什么 - 定位点映像
做题3点：定位 - 同义变换 - 错选原因（细节，其他内容等）做多了就好啦，别灰心，GWD比较难得
搜到了这篇的解释,阅读一下子豁然开朗了很多,忍不住顶一下,nn的解释就是不一样...
hikarugaara 发表于 2010-7-14 16:03
q12为什么说是细节就错，这题又不是主题题对于C，文中并没有comparison啊，我觉得就是举例volcanica erupti ...
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