QUESTION TEXT: Although some animals exhibit a mild skin…
QUESTION TYPE: Strengthen
CONCLUSION: Urushiol probably didn’t evolve in plants as a chemical defense.
REASONING: Some animals get mild skin troubles from urushiol, but only humans get painful rashes. Some animals such as wood rats even use poison oak branches in their nests. These branches have urushiol.
ANALYSIS: This sounds like a persuasive argument, but we really need to know more. For instance, the fact that the chemical defenses are weak doesn’t mean that isn’t why urushiol evolved. It might merely be a weak chemical protection. And maybe the mild skin reaction is enough to deter animals. After all there are many non rash-inducing plants. We can strengthen the argument by showing urushiol really isn’t a deterrent for most animals. We only really know about wood rats.
The author also ignores the fact that humans are a major source of ecosystem disruption. It’s possible the plant evolved mainly to defend against us. So, eliminating that possibility would help.
___________
- This weakens the argument. Maybe the live poison oak branches would hurt the rats.
- CORRECT. This strengthens the argument quite a lot. A poison defense is not very effective if a wide variety of animals can ignore it. Sometimes a single type of species can evolve to ignore a poison entirely (i.e. rats), but having a variety of animals eat poison oak suggests urushiol really isn’t a chemical defense.
- This mildly weakens the argument. If chemical defenses are common, then maybe urushiol is a type of chemical defense. The argument would be stronger if chemical defenses were rare.
- This just reaffirms that plants such as poison ivy are annoying to humans. But it doesn’t tell us why urushiol evolved.
- This mildly weakens the argument. It suggests that urushiol is an effective chemical defense against us. But we’re trying to prove that it’s not a chemical defense.
Recap: The question begins with “Although some animals exhibit a mild skin”. It is a Strengthen question. To practice more Strengthen questions, have a look at the LSAT Questions by Type page.
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