LSAT Explanation PT 29, S4, Q20: Amphibian populations are declining in numbers

LSAT Question Stem

Each of the following, if true, would strengthen the argument EXCEPT: 

Logical Reasoning Question Type

This is a Strengthen question. 

Correct Answer

The correct answer to this question is A. 

LSAT Question Complete Explanation

Let's first summarize and analyze the argument in the passage. The argument states that amphibian populations are declining worldwide, and the primary cause of this decline is the depletion of the earth's ozone layer. The ozone layer blocks UV-B radiation, which can damage genes, and amphibians are particularly vulnerable to this type of radiation due to their lack of natural protection. The structure of the argument is as follows:

1. Premise: Amphibian populations are declining worldwide.

2. Premise: The ozone layer has been continuously depleted throughout the last 50 years.

3. Premise: The ozone layer blocks UV-B radiation, which can damage genes.

4. Premise: Amphibians are particularly vulnerable to UV-B radiation.

5. Conclusion: The primary cause of the declining amphibian population is the depletion of the ozone layer.

Now, let's come up with an "Evaluate" question about the argument: "Is there a direct correlation between the depletion of the ozone layer and the declining amphibian populations?"

The question type for this problem is Strengthen, and we are asked to find the answer choice that does NOT strengthen the argument.

a) This answer choice does not strengthen the argument because it does not provide any additional information about the connection between the depletion of the ozone layer and the declining amphibian populations. The fact that UV-B is the only damaging type of radiation blocked by ozone is irrelevant to the argument.

b) This answer choice strengthens the argument by showing that when the cause (ozone depletion) is absent in nonamphibian populations, the effect (population decline) does not occur. This supports the conclusion that the depletion of the ozone layer is the primary cause of the declining amphibian population.

c) This answer strengthens the argument by showing that the areas of ozone depletion and amphibian decline match each other, thereby affirming the data used to make the conclusion.

d) This answer choice strengthens the argument by eliminating an alternate cause for the effect (habitat shrinkage). By eliminating the possibility of habitat shrinkage, the stated cause in the argument (ozone depletion) is strengthened.

e) This answer strengthens the argument by showing that the decline of the amphibians has mirrored the decline of the ozone layer, thereby affirming the data used to make the conclusion.

In conclusion, the correct answer is (a) because it does not strengthen the argument, while the other four answer choices do strengthen the argument in various ways.