GMAT PREP RC: More selective than most chemical pesticides..

[supratim7]

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?

(A) The blue butterfly's survival was indirectly dependent on sustaining a rabbit population of a particular size.
(B) The blue butterfly's survival was indirectly dependent on sustaining large amounts of vegetation in its habitat.
(C) The blue butterfly's survival was threatened when the ants began preying on its offspring.
(D) The blue butterfly was infected by the virus that had been intended to control rabbit populations.
(E) The blue butterfly was adversely affected by a biocontrol agent that competed with it for resources.

OA: ( A )

C: clearly wrong.
D: clearly wrong.
B: wrong. The virus reduced the amount of open ground i.e. increased ground cover i.e. increased the amount of vegetation. If The BBfly was dependent on large amt of vegetation then it wouldn't have gone extinct.

I was stuck between A & E

A: BBfly's survival was indeed indirectly dependent on sustaining rabbit population. sustaining rabbit pop = no virus introduction = no reduction in ant nests = no BBfly extinction

E: BBfly was indeed badly affected by the virus that competed with it for resources (ant nests).

Pls help. Thank you :)

[jnelson0612]

:-)

[kd17]

Hi Ron,

Sorry to open this up again, but I'm still confused about the answer.

[--- reference to mistaken posts that have since been deleted ---]

Thanks in advance!

[jlucero]

It looks like we have this posted somewhere else and since it's a GMAT Prep answer, we have to accept it as truth.

one-rc-question-needs-clarification-t13510.html

Here's my crack at A vs E:

virus was introduced // rabbit population went down // open ground went down (since rabbits were eating plants) // fewer ant nests // butterflies killed off

A) correct- this is the less specific of the two since it just equates two events- a butterfly's survival with having a certain population of rabbits (greater than what happened after the virus was introduced)

E) incorrect- the biocontrol agent COMPETED with the butterfly. This isn't stated- this is a case of causation rather than correlation.

[kd17]

Thanks for the explanation!

[RonPurewal]

For the sake of clarity, I've edited out a mistaken post that I made earlier in the thread, along with 1-2 replies to it.

If anyone has further questions about this problem, please post them in the thread linked above, not here.

Thanks all.

[RichaChampion]

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.

introduced to control rabbits is a participial phrase. "introduced " is not the action done by the virus, because it is participial not the main verb. Let's simplify the argument -

a virus _______ reduced the amount of open ground


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.

because large rabbit populations reduce the ground cover - This subordinate clause gives the reason how and why the ground was open.
They Eat grass, carrots and dig holes, Gotcha?

More simplified version -

Another example of indirect negative consequences occurred in England when a virus introduced to control rabbits reduced the amount of open ground, in turn reducing underground ant nests and triggering the extinction of a blue butterfly that had depended on the nests to shelter its offspring.

a virus introduced to control rabbits → reduced the amount of open ground → This, in turn, destroyed the holes, and thus, nest under them. These nests were created by Ants → Finally, triggering the extinction of a blue butterfly that had depended on the nests to shelter its offspring.


P.S. Do not worry how exactly the virus worked that it filled the holes or open ground that is not mentioned in the passage, and there can be N number of ways for that, but the passage has not given that information and neither wants us to know the inherent functioning of the virus.

[RonPurewal]

what are you trying to ask?

i'm sorry, but i have no idea what the point of that last post is... nor what/whom you're responding to.
(also, this discussion hasn't been active for 3 years.)