LSAT 136 – Section 4 – Question 10

LSAT 136 - Section 4 - Question 10

June 2012

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Question
QuickView		 Type Tags Answer
Choices		 Curve Question
Difficulty		 Psg/Game/S
Difficulty		 Explanation
PT136 S4 Q10
+LR
Resolve reconcile or explain +RRE
Causal Reasoning +CausR
A
78%
165
B
11%
161
C
5%
157
D
1%
154
E
5%
159
137
149
160
 +Medium 146.121 +SubsectionMedium

In an experiment designed to show how life may have begun on Earth, scientists demonstrated that an electrical spark—or lightning—could produce amino acids, the building blocks of Earth’s life. However, unless the spark occurs in a “reducing” atmosphere, that is, one rich in hydrogen and lean in oxygen, amino acids do not form readily and tend to break apart when they do form. Scientists now believe that Earth’s atmosphere was actually rich in oxygen and lean in nitrogen at the time life began.

"Surprising" Phenomenon
How could lightning have produced the first amino acids on Earth, even though Earth’s atmosphere at that time had a lot of oxygen, and amino acids break apart unless the spark that produced them occurs in an atmosphere that has a lot of hydrogen and not much oxygen (a “reducing” atmosphere)?

Objective
The correct answer should explain how there still could have been a “reducing” atmosphere necessary to allow the first amino acids to form and persist, even though Earth’s atmosphere had a lot of oxygen (and so was not a “reducing” atmosphere).

A
Meteorite impacts at the time life began on Earth temporarily created a reducing atmosphere around the impact site.
This raises the possibility that lightning could have produced amino acids around the impact sites of meteors, which temporarily had a reducing atmosphere.
B
A single amino acid could have been sufficient to begin the formation of life on Earth.
This doesn’t address how an amino acid could have formed and avoided breaking apart in an atmosphere that wasn’t reducing. If there was no reducing atmosphere, how would that single amino acid have come about?
C
Earth’s atmosphere has changed significantly since life first began.
The current atmosphere doesn’t matter, since the stimulus tells us Earth’s atmosphere “was” - meaning, at the time of the first amino acids - rich in oxygen. So, if the atmosphere wasn’t reducing, how could the amino acids form and avoid breaking apart?
D
Lightning was less common on Earth at the time life began than it is now.
But if there was lightning, however rare it was, how could that have produced amino acids in a non-reducing atmosphere? This doesn’t provide a theory about how this happened.
E
Asteroids contain amino acids, and some of these amino acids could survive an asteroid’s impact with Earth.
We’re interested in explaining how lightning could have produced the first amino acids. It doesn’t matter whether asteroids could have already had amino acids. Those aren’t amino acids produced by lightning on Earth.

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LSAT PrepTest 136 Explanations

Section 1 - Reading Comprehension

Section 2 - Logical Reasoning

Section 3 - Reading Comprehension

Section 4 - Logical Reasoning

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