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- Sun Jan 20, 2013 12:00 am
#25837
Complete Question Explanation
Weaken—#%. The correct answer choice is (A)
This stimulus begins with the conclusion, which is focused on numbers. When LSAC introduces numerical concepts into Logical Reasoning questions, it does so to confuse and frustrate you. Typically, there will be some flaw in how the data is used in support of the conclusion. You can turn the tables on LSAC by focusing your prephrase on the numbers idea so that you can shine a spotlight on the gap in the argument.
Here, the columnist disagrees with the belief held by many that the number of species on Earth is dwindling. The columnist supports his view by drawing a comparison between the number of species going extinct and the number of new species emerging. However, this comparison is flawed.
Regarding extinction, the columnist says that about as many species are likely to go extinct this year as went extinct in 1970. But, he points out, there is no reason to doubt that new species are emerging at about the same rate as they have been for the last several centuries. From this evidence, the columnist concludes that the number of species on Earth is probably not dwindling.
The are multiple problems with this line of reasoning. But, focusing on the numerical flaw, we do not know how many species went extinct in 1970. Nor do we know how that number compares to the rate at which new species have been emerging for the last several centuries. For example, it may be the case that one new species per year has emerged on average over the last several centuries, but there were one hundred species that went extinct in 1970.
Without some hard numbers to put the premises in context, the conclusion that the number of species on Earth is probably not dwindling is unsupported. So, your prephrase in this Weaken question is that the correct answer will likely exploit this weakness to undermine the conclusion.
Answer choice (A): This is the correct answer choice. This choice provides some context to help us understand the relationship between the rate at which species have emerged and the number that went extinct in 1970. The author makes the claim that "the number of species on Earth is probably not dwindling," and continues on to state that "about as many species are likely to go extinct this year as went extinct in 1970." That, in connection with the statement that "new species are emerging at about the same rate as they have been for the last several centuries," suggests that extinction and emergence numbers are fairly balanced, and have been for a while. But, this answer tells us that in 1970, overall there was a net loss of species (more went extinct than emerged), and so if that's the case, the author's statements would actually suggest that the number of species on earth may be dwindling.
Answer choice (B): This choice is irrelevant to the conclusion, because it provides information about where species emerge and go extinct, rather than the numbers involved.
Answer choice (C): This choice does not help put the current rates of species emergence and decline into perspective, so it has no impact on the conclusion.
Answer choice (D): This choice uses “concern” as a proxy for real numbers, implying that since there is no more concern now about extinction than there was in 1970, then the number of species is not dwindling. However, nothing in the stimulus supports this suggested connection between concern and the actual numbers, so this choice has no effect on the conclusion.
Answer choice (E): The increased ability to identify species facing serious risk of extinction does not tell you about the current rates of extinction and emergence, and so this answer choice is irrelevant to the conclusion.
Weaken—#%. The correct answer choice is (A)
This stimulus begins with the conclusion, which is focused on numbers. When LSAC introduces numerical concepts into Logical Reasoning questions, it does so to confuse and frustrate you. Typically, there will be some flaw in how the data is used in support of the conclusion. You can turn the tables on LSAC by focusing your prephrase on the numbers idea so that you can shine a spotlight on the gap in the argument.
Here, the columnist disagrees with the belief held by many that the number of species on Earth is dwindling. The columnist supports his view by drawing a comparison between the number of species going extinct and the number of new species emerging. However, this comparison is flawed.
Regarding extinction, the columnist says that about as many species are likely to go extinct this year as went extinct in 1970. But, he points out, there is no reason to doubt that new species are emerging at about the same rate as they have been for the last several centuries. From this evidence, the columnist concludes that the number of species on Earth is probably not dwindling.
The are multiple problems with this line of reasoning. But, focusing on the numerical flaw, we do not know how many species went extinct in 1970. Nor do we know how that number compares to the rate at which new species have been emerging for the last several centuries. For example, it may be the case that one new species per year has emerged on average over the last several centuries, but there were one hundred species that went extinct in 1970.
Without some hard numbers to put the premises in context, the conclusion that the number of species on Earth is probably not dwindling is unsupported. So, your prephrase in this Weaken question is that the correct answer will likely exploit this weakness to undermine the conclusion.
Answer choice (A): This is the correct answer choice. This choice provides some context to help us understand the relationship between the rate at which species have emerged and the number that went extinct in 1970. The author makes the claim that "the number of species on Earth is probably not dwindling," and continues on to state that "about as many species are likely to go extinct this year as went extinct in 1970." That, in connection with the statement that "new species are emerging at about the same rate as they have been for the last several centuries," suggests that extinction and emergence numbers are fairly balanced, and have been for a while. But, this answer tells us that in 1970, overall there was a net loss of species (more went extinct than emerged), and so if that's the case, the author's statements would actually suggest that the number of species on earth may be dwindling.
Answer choice (B): This choice is irrelevant to the conclusion, because it provides information about where species emerge and go extinct, rather than the numbers involved.
Answer choice (C): This choice does not help put the current rates of species emergence and decline into perspective, so it has no impact on the conclusion.
Answer choice (D): This choice uses “concern” as a proxy for real numbers, implying that since there is no more concern now about extinction than there was in 1970, then the number of species is not dwindling. However, nothing in the stimulus supports this suggested connection between concern and the actual numbers, so this choice has no effect on the conclusion.
Answer choice (E): The increased ability to identify species facing serious risk of extinction does not tell you about the current rates of extinction and emergence, and so this answer choice is irrelevant to the conclusion.
