LSAT 134 – Section 1 – Question 08

LSAT 134 - Section 1 - Question 08

October 2011

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Question
QuickView		 Type Tags Answer
Choices		 Curve Question
Difficulty		 Psg/Game/S
Difficulty		 Explanation
PT134 S1 Q08
+LR
Weaken +Weak
Causal Reasoning +CausR
Math +Math
A
1%
156
B
89%
165
C
3%
158
D
3%
155
E
4%
157
130
141
152
 +Easier 147.067 +SubsectionMedium

According to the “bottom-up” theory of how ecosystems are structured, the availability of edible plants is what primarily determines an ecosystem’s characteristics since it determines how many herbivores the ecosystem can support, which in turn determines how many predators it can support. This theory also holds that a reduction in the number of predators will have little impact on the rest of the ecosystem.

Summarize Argument
The bottom-up theory claims that ecosystems are determined by how many edible plants they can support. This is because edible plants support herbivores, which in turn support predators. Everything depends on edible plants.

Notable Assumptions
While the bottom-up theory holds that the population of predators has little effect on ecosystems, the theory doesn’t account for the population of herbivores. Given that the bottom-up theory states that edible plants determine the characteristics of an ecosystem, this means the bottom-up theory assumes that an influx of herbivores also wouldn’t cause any changes. Nothing besides the availability of edible plants can have a deterministic effect on ecosystems.

A
In an effort to build up the population of a rare species of monkey on Vahique Island, monkeys were bred in zoos and released into the wild. However, the effort failed because the trees on which the monkeys fed were also nearly extinct.
This seems to support the bottom-up theory: edible plants determine an ecosystem. We need something that challenges the theory.
B
After hunting virtually eliminated predators on Rigu Island, the population of many herbivore species increased more than tenfold, causing the density of plants to be dramatically reduced.
Rather than plants determining how many herbivores an ecosystem can support, the number of herbivores determines the availability of plants. Thus, we have a deterministic factor that isn’t edible plants.
C
After many of the trees on Jaevix Island were cleared, the island’s leaf-cutter ants, which require a forested ecosystem, experienced a substantial decrease in population, as did the island’s anteaters.
Supposing those trees are edible plants, this supports the bottom-up theory. We need something that challenges it.
D
After a new species of fern was introduced to Lisdok Island, native ferns were almost eliminated. However, this did not affect the population of the herbivores that had eaten the native ferns, since they also thrived on a diet of the new fern.
Edible plants are plentiful here. This doesn’t challenge the bottom-up theory.
E
Plants that are a dietary staple of wild pigs on Sedif Island have flourished over the last three decades, and the population of the pigs has not changed much in spite of extensive hunting.
Nothing here challenges the claim that edible plants determine the characteristics of an ecosystem. Not even hunting local herbivores makes a difference.

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LSAT PrepTest 134 Explanations

Section 1 - Logical Reasoning

Section 2 - Logical Reasoning

Section 3 - Logical Reasoning

Section 4 - Reading Comprehension

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