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题库 / Prep2007E2-RC-7
More selective than most chemical pesticides in that they ordinarily destroy only unwanted species, biocontrol agents (such as insects, fungi, and viruses) eat, infect, or parasitize targeted plant or animal pests. However, biocontrol agents can negatively affect nontarget species by, for example, competing with them for resources: a biocontrol agent might reduce the benefits conferred by a desirable animal species by consuming a plant on which the animal prefers to lay its eggs. Another example of indirect negative consequences occurred in England when a virus introduced to control rabbits reduced the amount of open ground (because large rabbit populations reduce the ground cover), in turn reducing underground ant nests and triggering the extinction of a blue butterfly that had depended on the nests to shelter its offspring. The paucity of known extinctions or disruptions resulting from indirect interactions may reflect not the infrequency of such mishaps but rather the failure to look for or to detect them: most organisms likely to be adversely affected by indirect interactions are of little or no known commercial value and the events linking a biocontrol agent with an adverse effect are often unclear. Moreover, determining the potential risks of biocontrol agents before they are used is difficult, especially when a nonnative agent is introduced, because, unlike a chemical pesticide, a biocontrol agent may adapt in unpredictable ways, so that it can feed on or otherwise harm new hosts.
The passage suggests which of the following about the blue butterfly mentioned in the highlighted text?
The blue butterfly's survival was indirectly dependent on sustaining a rabbit population of a particular size.
The blue butterfly's survival was indirectly dependent on sustaining large amounts of vegetation in its habitat.
The blue butterfly's survival was threatened when the ants began preying on its offspring.
The blue butterfly was infected by the virus that had been intended to control rabbit populations.
The blue butterfly was adversely affected by a biocontrol agent that competed with it for resources.
题目分析：
题目释义：
细节题目
考点：
推断（Inference）
旨在考察我们对文章的深度理解，以及逻辑推断能力。
由于有高亮词的存在，这个题目通过题设即可以定位在高亮词出现的地方。
选项分析：
A选项：Correct. 蓝色蝴蝶的生存依赖于兔子的数量维持在一定的水平。原文说蓝蝶依靠蚂蚁的巢穴生存（保护后代）：一定数量的兔子=一定数量的蚂蚁巢穴（不会“reducing蚂蚁的巢穴”），所以这个选项是正确的。
B选项：蓝色蝴蝶的生存依赖于在其栖息地维持大量的植被。文中明确说明了蓝蝶的考兔子造的巢穴生存的。如果没有了兔子，植被再多也没法造巢穴。
C选项：蓝蝶的生存在蚂蚁开始捕食蓝蝶的后代时受到了威胁。文中没有提到蚂蚁和蓝蝶的关系。无法证明这个选项。
D选项：蓝蝶感染了用来控制兔子数量的病毒。文中没有提到蓝蝶感染病毒。这个选项属于无中生有。
E选项： 蓝蝶被生物控制说反作用的原因是这些生物占有了蓝蝶的资源。文中定位部分说的很清楚，蓝蝶是因为没有了兔子，才没有了哺育后代的地方。和生物是否与它们抢夺资源无关。
a virus introduced to control rabbits reduced the amount of open ground (because large rabbit populations reduce the ground cover), in turn reducing underground ant nests and triggering the extinction of a blue butterfly that had depended on the nests to shelter its offspring. open groud裸露地，不毛之地；ground cover地面植被
原有生物链：兔子多--》植被少--〉裸露地多--》地下蚁穴多--〉蓝蝶产卵的地方多--》蓝蝶多
病毒引入后：兔子少--〉植被多--》裸露地少--〉地下蚁穴少--》蓝蝶没地儿产卵--〉蓝蝶灭绝
open ground 是指失去了groud cover, 即没有vegetation(植被)的地方
没有完全理解文中该段话的逻辑关系
D. The blue butterfly was infected by the virus蓝蝶感染了用来控制兔子数量的病毒，错误
a virus introduced to control rabbits reduced the amount of open ground (because large rabbit populations reduce the ground cover), in turn reducing underground ant nests and triggering the extinction of a blue butterfly that had depended on the nests to shelter its offspring. open groud裸露地，不毛之地；ground cover地面植被
原有生物链：兔子多--》植被少--〉裸露地多--》地下蚁穴多--〉蓝蝶产卵的地方多--》蓝蝶多
病毒引入后：兔子少--〉植被多--》裸露地少--〉地下蚁穴少--》蓝蝶没地儿产卵--〉蓝蝶灭绝
主要是open ground 和 ground cover 没有分清楚
large rabbit populations reduce the ground cover——reduce open ground——reduce nests——reduce shelter for butterfly offspring
所以rabbit populations是会影响butterfly的
考察inference，错选D，文章没有说蓝蝶感染了病毒，只是说引入病毒后，蓝蝶灭绝了。正确A，原文逻辑链：病毒引入后：兔子少--〉植被多--》裸露地少--〉地下蚁穴少--》蓝蝶没地儿产卵--〉蓝蝶灭绝，可以推出A选项 蓝色蝴蝶的生存依赖于兔子的数量维持在一定的水平。
还是要搞明白阅读题干是考inference还是supporting data，这道题是考inference。
A选项：Correct. 蓝色蝴蝶的生存依赖于兔子的数量维持在一定的水平。原文说蓝蝶依靠蚂蚁的巢穴生存（保护后代）：一定数量的兔子=一定数量的蚂蚁巢穴（不会“reducing蚂蚁的巢穴”），所以这个选项是正确的。
病毒和蝴蝶无关
只有保持一定的兔子数量—>open ground面积大，植被少—>蚂蚁多蚁穴多—>蝴蝶有地方产卵；植被多了反而不利于蝴蝶的生存
infected感染
virus-> rabbits->open ground-> ants-> butterfly
virus用来控制兔子，导致了地下蚂蚁巢穴减少，最终导致了依赖蚂蚁巢穴保护offspring的蓝蝴蝶的灭绝
virus 控制兔子-->增加了植被-->导致了open ground减少-->ant nests 减少-->blue butterfly 灭绝
open ground 是指失去了groud cover, 即没有vegetation(植被)的地方
所以B 说的恰好相反
通过有关无关性可以排除B,C,D,E→但我为什么错选了D呢？没有仔细分析原文内容以及选项所表达的意思。
定位原文：a virus introduced to control rabbits reduced the amount of open ground (because large rabbit populations reduce the ground cover), in turn reducing underground ant nests and triggering the extinction of a blue butterfly that had depended on the nests to shelter its offspring.→这说明了两层关系：①virus影响兔子的数量；②virus同时也影响蚂蚁巢→进而影响蓝色蝴蝶，这说明对兔子的数量的影响在逻辑链上等同于对蚂蚁巢的影响，所以A正确。
GMAT难就难在光简单读懂表面意思还不够，还得要理清各个内容、观点之间的逻辑关系才能做对题。这个平时要多注意多训练。
病毒是降低兔子数量保护ground cover，under ground越来越多，open ground就少了，所以后面连锁反应，这个要看出来。。。所以选a，b不对在稳定的大量植被，不应该是大量！
A indirectly
原文：biocontrol agents can negatively affect nontarget species by, for example, competing with them for resources。。。Another example of indirect negative consequences occurred in England when a virus introduced to control rabbits。。。
两个并列的例子说明destroy unwanted species。
兔子太多影响地表植被数量，引入一种病毒控制兔子的数量，但是同时导致地下蚂蚁巢数量减少，导致蝴蝶灭绝。
因此是蝴蝶间接依赖于维持一定数量的兔子群体
B：蝴蝶的生存依赖于很多蔬菜（文中没提到蔬菜）
C：蚂蚁开始吃蝴蝶后代，文中没提到过
D（错误选项）：蝴蝶被病毒感染（间接导致灭绝，不是直接感染）
E：蝴蝶跟生物控制的媒介（这里指病毒）分享资源（文中不是这个意思）
Another example of indirect negative consequences occurred in England when a virus introduced to control rabbits reduced the amount of open ground 感觉这句话的分词用的不大对啊。如果introduced是谓语动词，introduced前面少了一个be动词。redeced和rabbits也够不成被动关系。如果reduced是从句谓语动词，a virus introdeced to control做什么成分呢？
when引起的是原因状语从句啊， introduced to control rabbits是过去分词短语，做定语修饰virus，意思是，被引入去控制兔子数量的病毒减少了open ground的数量。
*时间状语从句
occurred是谓语动词
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