LSAT 134 – Section 1 – Question 22

LSAT 134 - Section 1 - Question 22

October 2011

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Question
QuickView		 Type Tags Answer
Choices		 Curve Question
Difficulty		 Psg/Game/S
Difficulty		 Explanation
PT134 S1 Q22
+LR
Strengthen +Streng
Causal Reasoning +CausR
A
9%
162
B
67%
166
C
8%
158
D
14%
160
E
1%
157
148
157
167
 +Harder 147.067 +SubsectionMedium

Microbiologist: Because heavy metals are normally concentrated in sewage sludge during the sewage treatment process, the bacteria that survive in the sludge have evolved the unusual ability to resist heavy-metal poisoning. The same bacteria also show a strong resistance to antibiotics. This suggests that the bacteria’s exposure to the heavy metals in the sewage sludge has somehow promoted their resistance to antibiotics.

Summarize Argument: Phenomenon-Hypothesis
The microbiologist hypothesizes that the bacteria’s exposure to heavy metals in sewage sludge caused them to develop antibiotic resistance. He supports this by saying that since heavy metals are concentrated in the sludge, bacteria that survive there have evolved to resist heavy-metal poisoning, and these same bacteria are resistant to antibiotics.

Notable Assumptions
The microbiologist assumes that heavy metal exposure can promote antibiotic resistance in certain bacteria. He also assumes that there are no alternative hypotheses to explain the observed correlation— that is, he assumes that there is not a third factor that causes both antibiotic resistance and heavy-metal poisoning resistance. He also assumes that the causal relationship is not reversed— that is, that antibiotic resistance does not cause heavy-metal poisoning resistance.

A
Most bacteria that are not resistant to antibiotics are not resistant to heavy-metal poisoning either.
The microbiologist is only addressing those bacteria that are resistant to both heavy-metal poisoning and antibiotics. Even if (A) is true, it wouldn’t impact his conclusion that heavy-metal exposure causes antibiotic resistance in certain bacteria.
B
Bacteria that live in sewage sludge that is free of heavy metals, but is in other respects similar to normal sewage, are generally resistant to neither heavy-metal poisoning nor antibiotics.
This strengthens the hypothesis by providing a control group. If bacteria in sludge without heavy metals aren’t resistant to heavy-metal poisoning or antibiotics, it’s more likely that the heavy-metal exposure did cause antibiotic resistance in the bacteria in the other sludge.
C
Antibiotic resistance of bacteria that survive in sewage sludge in which heavy metals are concentrated contributes to their resistance to heavy-metal poisoning.
This weakens the microbiologist’s hypothesis by suggesting that the causal relationship is reversed. That is, (C) suggests that antibiotic resistance causes heavy-metal poisoning resistance, rather than the other way around.
D
Sewage sludge that contains high concentrations of heavy metals almost always contains significant concentrations of antibiotics.
This weakens the hypothesis by providing a plausible alternative explanation. If sludge that contains heavy metals also contains significant amounts of antibiotics, it’s likely that the antibiotics cause antibiotic resistance in the bacteria, not the heavy-metal exposure.
E
Many kinds of bacteria that do not live in sewage sludge are resistant to both heavy-metal poisoning and antibiotics.
This doesn’t strengthen the hypothesis that heavy-metal exposure caused antibiotic resistance in the bacteria. We don’t know if the bacteria described in (E) were exposed to heavy metals or not.

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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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