LSAT 131 – Section 2 – Question 21

LSAT 131 - Section 2 - Question 21

December 2009

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Question
QuickView		 Type Tags Answer
Choices		 Curve Question
Difficulty		 Psg/Game/S
Difficulty		 Explanation
PT131 S2 Q21
+LR
Weaken +Weak
Causal Reasoning +CausR
Eliminating Options +ElimOpt
A
8%
161
B
2%
157
C
71%
166
D
12%
159
E
6%
157
148
156
165
 +Harder 147.936 +SubsectionMedium

J.Y.’s explanation

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Essayist: When the first prehistoric migrations of humans from Asia to North America took place, the small bands of new arrivals encountered many species of animals that would be extinct only 2,000 years later. Since it is implausible that hunting by these small bands of humans could have had such an effect, and since disease-causing microorganisms not native to North America were undoubtedly borne by the new arrivals as well as by the animals that followed them, these microorganisms were probably the crucial factor that accounts for the extinctions.

Summarize Argument
The essayist concludes that microorganisms brought to North America by prehistoric humans caused many species of native animals to go extinct within the next 2,000 years. This is because the prehistoric humans wouldn’t have been able to hunt those animals to extinction, and those same humans certainly brought microorganisms with them.

Notable Assumptions
Based on the fact that humans couldn’t have hunted the animals to extinction, the essayist concludes that it must’ve been microorganisms. This means the essayist doesn’t believe there’s any other means besides humans and microorganisms that could’ve caused the animals to go extinct. The essayist also believes that there was nothing common to the animals that went extinct that wasn’t common to those that didn’t go extinct—for example, perhaps those animals were sensitive to climate changes around that time.

A
Animals weakened by disease are not only less able to avoid hunters but are also less able to avoid their other predators.
This seems to strengthen the essayist’s argument. The diseased animals were susceptible to hunters and predators alike, giving yet another reason why they died out.
B
Human beings generally have a substantial degree of biological immunity to the diseases carried by other species.
We don’t care about the diseases humans are susceptible to. We need to know about the animals that went extinct.
C
Very few species of North American animals not hunted by the new arrivals from Asia were extinct 2,000 years after the first migrations.
Hunting by humans indeed made a difference. The vast majority of the species that went extinct were hunted, which provides us with an alternate hypothesis for how those animals went extinct.
D
Individual humans and animals can carry a disease-causing microorganism without themselves suffering from the disease.
Perhaps the animals that died out were ones that couldn’t carry the microorganisms without suffering from disease. We don’t know.
E
Some species of North American animals became extinct more than 2,000 years after the arrival in North America of the first prehistoric human migrants from Asia.
We care about the animals that became extinct within 2,000 years.

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LSAT PrepTest 131 Explanations

Section 1 - Logical Reasoning

Section 2 - Logical Reasoning

Section 3 - Logical Reasoning

Section 4 - Reading Comprehension

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