LSAT 153 – Section 3 – Question 14

LSAT 153 - Section 3 - Question 14

June 2019

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Question QuickView	Type	Tags	Answer Choices	Curve	Question Difficulty	Psg/Game/S Difficulty	Explanation
PT153 S3 Q14	+LR	Strengthen +Streng Causal Reasoning +CausR	A 55% 164 B 4% 156 C 25% 159 D 8% 156 E 9% 156	151 160 169	+Hardest	146.755 +SubsectionMedium

Guam has 40 times more spiders than nearby islands have. Biologists argue that this is a consequence of the accidental 1940s introduction into Guam of the brown tree snake, which by the 1980s had eliminated ten of twelve native bird species. The biologists attribute the spider population’s increase to the loss of bird species, because many birds prey on spiders and some use spiderwebs in constructing nests.

Summarize Argument: Phenomenon-Hypothesis

The biologists hypothesize that the spider population’s increase is a result of the introduction of the brown tree snake. This is based on the fact that the brown tree snake eliminated native bird species, and on the subsidiary conclusion that this loss of bird species caused the spider population to increase. This sub-conclusion is based on the fact that many birds prey on spiders and use spiderwebs to construct nests.

Notable Assumptions

The author assumes that there’s no other explanation for the increase in spider population on Guam besides the decrease in bird species. The author also assumes that there was a decrease in overall bird population (as opposed to simply a decrease in the number of species, which doesn’t automatically indicate a decrease in population).

Birds compete with spiders for insect prey.

This strengthens by providing another causal mechanism that could show bird populations can affect spider populations. If birds and spiders compete for food, a decrease in birds would mean spiders have less competition for food. This could help spiders survive and thrive.

The biologists counted spiderwebs as a means of estimating the spider population.

This has no clear impact on the hypothesis. So, we estimated the spider population increase based on an increase in the number of spiderwebs. Does the spider population have anything to do with a decline in birds? (B) is silent on this.

Spiderwebs are more prevalent on Guam than on nearby islands.

This doesn’t help connect the increase in spiders with the bird population decline. The issue is the cause of the spider population increase, not whether the spider population has increased. We already know Guam has more spiders than other nearby islands.

The two bird species remaining on Guam have proliferated since the arrival of the brown tree snakes.

This undermines the argument by pointing out that overall number of birds might have increased even if the number of species has gone down.

Brown tree snakes have proven difficult to eradicate on Guam.

This has nothing to do with whether the snakes caused the bird population to decline and whether the bird population decline caused an increase in spider population. We care about the effect of the snakes. Not how easy it is to remove the snakes.

LSAT 153 – Section 3 – Question 14

LSAT 153 - Section 3 - Question 14

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Review Results

LSAT PrepTest 153 Explanations

Section 1 - Reading Comprehension

Section 2 - Logical Reasoning

Section 3 - Logical Reasoning

Section 4 - Reading Comprehension

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