LSAT 137 – Section 4 – Question 06

LSAT 137 - Section 4 - Question 06

October 2012

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Question
QuickView		 Type Tags Answer
Choices		 Curve Question
Difficulty		 Psg/Game/S
Difficulty		 Explanation
PT137 S4 Q06
+LR
Weaken +Weak
Link Assumption +LinkA
Lack of Support v. False Conclusion +LSvFC
A
76%
164
B
5%
158
C
10%
160
D
1%
157
E
7%
160
135
148
161
 +Medium 146.883 +SubsectionMedium

Columnist: Contrary to what many people believe, the number of species on Earth is probably not dwindling. Extinction is a natural process, and about as many species are likely to go extinct this year as went extinct in 1970. But the emergence of new species is also a natural process; 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.

Summarize Argument
The columnist concludes that the number of species on Earth is probably not decreasing. He supports this by saying that the extinction rate this year will likely be similar to 1970, and that new species are probably emerging at the same rate as in past centuries.

Notable Assumptions
In order for the number of species on Earth not to decrease, the columnist must assume that the extinction rate today and in 1970 is equal to or lower than the rate at which new species are emerging. If extinction is happening faster than new species are emerging, the number of species is decreasing.

A
In 1970 fewer new species emerged than went extinct.
This weakens the columnist’s conclusion by proving his key assumption is false. If fewer new species emerged than went extinct in 1970, the number of species decreased. So, since extinction and speciation rates are likely the same today, the number of species is decreasing.
B
The regions of the world where new species tend to emerge at the highest rate are also where species tend to go extinct at the highest rate.
It doesn’t matter where these species are emerging and going extinct. (B) doesn’t show that the rate of extinction, regardless of where it is happening, is higher than the rate of speciation, so it doesn’t weaken the columnist’s argument.
C
The vast majority of the species that have ever existed are now extinct.
While most species that have ever existed are now extinct, new species are still emerging. (C) doesn't give us any reason to believe that new species aren't replacing those that go extinct, so it doesn’t weaken the conclusion that the overall number of species is not decreasing.
D
There is no more concern now about extinction of species than there was in 1970.
People’s concern about extinction is irrelevant to the columnist’s argument. He is only addressing the actual rates of extinction and speciation, regardless of whether people care about it.
E
Scientists are now better able to identify species facing serious risk of extinction than they were in 1970.
Scientists may be more aware of endangered animals now, but this doesn’t change the fact that "about as many species are likely to go extinct this year as... in 1970." (C) doesn’t address the difference between extinction and speciation rates, so it doesn’t weaken the argument.

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LSAT PrepTest 137 Explanations

Section 1 - Reading Comprehension

Section 2 - Logical Reasoning

Section 3 - Logical Reasoning

Section 4 - Logical Reasoning

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