LR Question 20 Explanation, by LSATHacks
QUESTION TEXT: Amphibian populations are declining in numbers worldwide…
QUESTION TYPE: Strengthen – Exception
CONCLUSION: The depletion of the ozone layer is the primary cause of the declining amphibian population.
REASONING: Ozone blocks UV-B. Amphibians and amphibian eggs are particularly vulnerable to UVB because they lack hair, hide or feathers and their eggs lack leathery or hard shells.
ANALYSIS: The main point is that lack of ozone has been harmful. The wrong answer focuses specifically on UV-B. Lack of ozone does cause harmful UV-B to get through but the argument doesn’t rule out the possibility that ozone has other harmful effects.
___________
- CORRECT. This doesn’t help. If lack of ozone was letting other dangerous things through then the argument would be even stronger.
- This supports the argument by showing that UV-B may be a cause.
- This shows that the proposed cause (ozone depletion) is occurring everywhere amphibians live.
- This rules out habitat loss as an alternative explanation.
- The ozone layer has also been declined continuously. If the amphibian population had an unsteady rate of decline then some other factor might have been the cause.
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I still cannot get the answer. I am rereading the stimulus 20 times and I cannot understand. Answer A says that UV-B is the only type that can damage genes and that this type of radiation, together with other types, is being blocked by atmospheric ozone. So if UV-B is being blocked by ozone, it means that in the last 50 years UV-B was let through and was damaging genes, particularly, amphibian genes. So it supports the conclusion that the primary cause of declining amphibian population is the depletion of the ozone layer ( because UV-B gets through because of this depletion.) So how is it not strengthening the stimulus???
This question asks us to strengthen the connection between the depletion of the ozone layer and the declining amphibian population. (A) is correct because all it’s doing is comparing the effect of UVB to that of the other types of radiation blocked by atmospheric ozone. It’s not telling us anything new about how UVB (i.e. the depletion of the ozone layer) is harmful to amphibians. What does it matter if it’s the only type of radiation that can damage genes? For this answer to be incorrect, it would need to–for example–specify how these other types of radiation are harmful to the health of the amphibian population. Then, it would be bolstering and contributing something new to the argument.