Q14 - Caffeine can kill or inhibit

[tamwaiman]

OA is (E) and I choose (C), I wonder why (C) is incorrect, thank you.

[ManhattanPrepLSAT2]

Here's a simple analogy- please let me know if you would like more detailed explanation and I'll be happy to provide it --

Notice the conclusion is one of causation -- an analogous one could be:

The item mildewed because it was left in the rain.

Does these mean that we need to assume that whenever there is rain anywhere, there has to be mildew? No, of course not.

The conclusion is about some plants evolving to have a little caffeine as a defense. In order to prove this, do we need to know that wherever there is a threat, plants must have developed this defense? No, and that's essentially what (C) states.

[tamwaiman]

Hi Mike.Kim

One reason I keep an eye on (C) is when negating it, it SEEMS to weaken the stimulus:

caffeine-producing plants NEVER grow wherever insect larvae pose a major threat to indigenous plants NOR once posed a major threat to the ancestors of those plants

Whether the crux is "A MAJOR THREAT"?

[dylancox_12]

Well I think your problem is the negation/opposite of "grow wherever insect larvae ..." is not "never grow where insect larvae ...". Instead the negation/opposite would be "don't grow everywhere insect larvae ..."

To put it more simply, the negation of ALWAYS is not NEVER. It's "NOT ALWAYS"

So the statement would read "caffeine-producting plants don't grow everywhere insect larvae pose a major threat to indigenous plants or where they once posed a major threat to the ancestors of those plants".

This statement doesn't destroy the argument, as was essentially said by Mike above. We don't need to know that wherever there is a threat, that plants MUST have developed this defence.

[coco.wu1993]

I chose B for this one. My reasoning is, if the concentration of caffeines in the plants is lower than what in the preparation, it may be effectively kill the larvae, thus it cannot function as a defense for the plants. The negation of B destroys the argument. Why am I wrong?

[maryadkins]

Our core is:

caffeine can kill some insect larvae including tobacco hornworm larvae

-->

caffeine in plants evolved as a defense against insects

What's the assumption?

That there wasn't another reason the plants have caffeine in them.

(A) is irrelevant.

(B) doesn't have to be true. Maybe less caffeine than what the larvae in the experiment were fed still would have killed them. We don't know.

(C) doesn't need to be true. There could be places where there are a lot of threatening insects and no plants at all. The point is that where the PLANTS with caffeine are, there are or were insects at some point, not the other way around.

(D) is tempting but we don't know that the tobacco plant is one of the ones that has the non-negligible quantities of caffeine. Maybe it only has negligible caffeine levels.

(E) must be true. If we negate it and say neither the plants nor their ancestors were ever exposed to caffeine-sensitive creatures, there's no way the two are linked.

[WaltGrace1983]

So, if my initial thought is correct, (D) is wrong because the tobacco hornworm larvae do not necessarily feed on the tobacco plant? We are given this example about the tobacco hornworm, saying that it dies when it eats tea leaves. However, we know nothing about the tobacco plant - maybe this plant isn't fed on or maybe it simply didn't build up any defense or maybe it DID build up a defense but for a different reason.

The point is that we know nothing about the tobacco plant from the stimulus and thus we don't need to assume anything about it. This was probably a trap answer for people reading into the "tobacco hornworm" too closely.

In addition, (C) would be right if it said "at least one caffeine-producing plant grows where insect larvae post a major threat to it," right? If this is not true, and there aren't any plants that grow where larvae pose a threat, then these plants could not have developed a defense against the larvae that weren't present.

[maryadkins]

Yes, and yes!

[rpcuhk]

In addition, (C) would be right if it said "at least one caffeine-producing plant grows where insect larvae post a major threat to it," right? If this is not true, and there aren't any plants that grow where larvae pose a threat, then these plants could not have developed a defense against the larvae that weren't present.

I think your version of (C) is still a bit strong, the insect larvae do not need to be a major threat.