GMAT考试资料：GWD试题合集（一）.

以下将为正在备战GMAT考试的同学们整理一些经典的GMAT阅读试题，并分多个合集推出，希望能够为正在备考GMAT考试的考生提供或多或少的帮助。

1. GWD-1-Q9 to Q12环境退化导致鲑鱼数量下降

Over the last 150 years, large

stretches of salmon habitat have

been eliminated by human activity:

Line mining, livestock grazing, timber

(5) harvesting, and agriculture as well

as recreational and urban devel-

opment. The numerical fect is

obvious: there are fewer salmon

in degraded regions than in pris-

(10) tine 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

(15)populations. Indeed, most

analysts believe that some kind

of environmental degradation

underlies the demise of many

extinct salmon populations.

(20)Although some rivers have

been recolonized, the unique

genes of the original populations

have been lost. 提出现象：数量减少，基因多样性下降，因为环境问题

Large-scale disturbances in

(25)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

(30)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

(35) 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

(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. Straying

rates remain relatively low when

environmental conditions are

(50)stable, but can increase dramati-

cally when streams suffer severe

disturbance. The 1980 volcanic

eruption of Mount Saint Helens,

for example, sent mud and debris

(55)into several tributaries of the

Columbia River. For the next

couple of years, steelhead trout

(a species included among the

salmonids) returning from the

(60)sea to spawn were forced to

find alternative streams. As

a consequence, their rates of

straying, initially 16 percent,

rose to more than 40 percent

(65)overall.另外后果及原因:干扰同样导致基因结构变化，因为洄游路线频率上升

Although no one has quantified

changes in the rate of straying

as a result of the disturbances

caused by humans, there is no

(75) matic 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.最终结果：后代适应性变差

结论解释

逻辑简图：

1P:samlon habitat eliminated by… fect obvious: fewer; however, reduce genetic diversity

2P: also alter genetic structure. Low crucial; yet high, problematic.

3P: although, no reason to suspect…. Increase result in, in turn lower the …..

以上就是本期GMAT试题的所有内容，考生可以此为据并进行针对性的练习，逐步掌握GMAT阅读的解题规律及技巧，以达到迅速提高GMAT考试成绩的目的。

相关链接：

1.浅析GMAT阅读的提升技巧

2.GMAT备考经验分享：不要忽视阅读和逻辑(一)

3.GMAT阅读解题技巧：抽象词速度法

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