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Some insects

by akhpad » Mon Jul 05, 2010 6:49 am
Some insects are able to feed on the leaves of milkweed, a toxic plant, by first cutting and draining the vein that secretes the toxin. This method of detoxification guarantees that some insects will always be able to eat milkweed, because the plant could never evolve to produce a toxin that is lethal in the trace amounts left after the vein is cut.

The argument depends on which of the following assumptions?
A. The insects that successfully detoxify milkweed are not able to undergo the evolutionary changes necessary to allow them to detoxify other plants.
B. Unlike milkweed, other kinds of toxic plants would be able to overcome their vulnerabilities to predators through evolutionary changes.
C. The toxin-carrying veins of the mildewed plant can never evolve in such a way that insects cannot cut through.
D. The method of detoxification used by insect predators of mildewed would not successfully detoxify other kinds of toxic plants.
E. There are insects that use means other than draining the toxin in order to feed on toxic plants.

OA: C

I am having trouble in understanding stimulus. So I could not find Assumption.
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by prepgmat09 » Mon Jul 05, 2010 7:32 am
Premise : Some insects can feed on a toxic plant called milkweed by cutting and draining some part of the plant that is responsible for secreting the toxin. After the vein is cut and drained, the plant can never produce toxins.

Conclusion: As a result of this method of detoxication. some insects will always be able to eat milkweed.

A. All we know is about some insects that detoxify Milkweed. We do not know anything about detoxication of other plants by these insects. May be these insects are able to detoxify other plants as well. So, this is out.

B. Out of scope. All we know is about Milkweed. Other plants will be able to overcome vulnerabilities is too much to assume. So, this is out.

C. This appears to be a correct answer. If we negate the choice, it reads, "The toxin-carrying veins of the mildewed plant can sometimes evolve in such a way that insects cannot cut through". Clearly, if this is true, the conclusion falls apart.
However, the only reservation I have with this answer choice is its language "....evolve in such a way that insects cannot cut through". The argument talks about "some" insects. Here we are talking about insects in general. But I would keep this small reservation for second cut elimination if need be.

D. No information in argument assumes that the insects cannot use the same method on other plants.

E. May be. But no information in argument assumes that the insects use means other than draining the toxin.

So, IMO C.
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by paes » Mon Jul 05, 2010 8:20 am
IMO C

good explanation above.
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by paddle_sweep » Mon Jul 05, 2010 8:07 pm
Hi Akhilesh, Could you pls quote the source of this qn?
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by akhpad » Mon Jul 05, 2010 9:12 pm
paddle_sweep wrote:Hi Akhilesh, Could you pls quote the source of this qn?
Source: LSAT

I am solving those problems, which come under GMAT syllabus.
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by dream700 » Tue Jul 06, 2010 11:10 pm
for me the catch was " some insects will always be able..... "

this shows that insects will always be feeding on such plants by the method of detoxification...and the plant won't eveolve to avoid that...

Deutsch750
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