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#7 - Although some animals exhibit a mild skin reaction to

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Complete Question Explanation

Stengthen. The correct answer choice is (B)

This argument claims that urushiol probably did not evolve in plants as a chemical defense based on the premises that (1) only humans develop painful rashes from touching it and (2) some animals use parts of plants that produce urushiol to build nests. In evaluating the structure of this argument, you may note that we are presented with a straightforward situation in which some support is offered for a conclusion, but this support is by no means sufficient to establish the validity of this conclusion. Indeed, since you are looking for what will most support the conclusion, we need not find anything that will establish beyond the shadow of a doubt that this conclusion is sound. Instead, given the lack of other major structural fallacies in the reasoning of this argument, we will likely anticipate a "supporter" answer choice: something that will give significant and new support for the contention that urushiol did not develop as an evolutionary defense.

Consider possible existing gaps in the evidence offered. So far we know that animals use urushiol-producing plants for housing. For the best support, we will look for some new and different evidence that would illustrate that the urushiol does not provide any defense mechanism against animal or environmental threats.

Answer choice (A): This answer choice actually weakens the conclusion by adding evidence that the urushiol-producing plant parts the animals use are dead, desiccated portions of the plants. If so, the urushiol may retain a defensive purpose that no longer applies once the plant is already dead.

Answer choice (B): This is the correct answer choice. This choice adds additional information that shows that in addition to animals' using parts of urushiol-producing plants to build nests, some animals also consume urushiol-producing plants for food. This provides new, significant evidence that the urushiol does not provide an evolutionary defense mechanism since the plants are also eaten.

Answer choice (C): If anything, this choice weakens the conclusion that urushiol did not develop as an evolutionary defense mechanism. If such defense mechanisms are common in other plants, it stands to reason that urushiol may be a similar such defense.

Answer choice (D): This factually accurate statement might be of some interest to those who suffer from an allergy to poison ivy but does nothing to bolster the claim that urushiol did not develop as an evolutionary defense mechanism.

Answer choice (E): This choice follows the common model of inviting test-takers to introduce multiple assumptions of their own to try to make a square peg fit in a round hole. Test-takers might be tempted to speculate that "if the fact that urushiol-producing plants do well in response to human modification of their environment, then maybe the presence of urushiol is just some insignificant feature of these plants unrelated to evolutionary adaptation." In fact, if anything such a train of thought would weaken the conclusion since one could reason that the success of urushiol-producing plants might be because of their resistance to humans in environments that humans have already impacted. Either way, this answer choice just leads you down the primrose path and is incorrect.
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Hi! I know this question was in 1-10 and was supposed to be easier but the "chemical defense" line thrown in at the conclusion confused me because it wasn't mentioned anywhere else. My prephrase was something along the lines of "humans developed a chemical defense to the oil" since we do not know for fact that the rash humans get means that they developed a chemical defense. I chose C because I thought it was saying that it is possible for plants to develop chemical defenses and thus the fact that nothing happened and they use those branches daily without reaction proves that they did not. Am I over thinking this? I see how B strengthens but doesn't it require the assumption that the rash humans developed was a "chemical defense". Thanks!
Claire Horan
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Hi 180Please,

No, you are not overthinking this question. I think the problem is more that you aren't reading carefully. Read the last sentence slowly and you'll see that the conclusion states that urushiol probably did not as a chemical defense FOR THE PLANTS. In other words, this chemical didn't evolve in plants because it protected the plants. This conclusion has nothing to do with humans developing a defense to urushiol. In order to strengthen the argument, you'll want to first determine any obvious weaknesses in the argument. The most obvious weakness in the stimulus argument is that an animal need not break out in a rash to react to a the chemical. What if they are harmed in some other way? B strengthens the argument because it explains that a lot of animals also eat these plants. The idea is that the chemical must not defend the plant very well if animals still eat them despite the chemical!

I hope this helps!