LR Question 10 Explanation, by LSATHacks
QUESTION TEXT: In an experiment designed to show how…
QUESTION TYPE: Paradox
PARADOX: Lighting could create amino acids. Without a reducing atmosphere, amino acids break apart and can’t form life.
At the time life formed, Earth did not have a reducing atmosphere.
ANALYSIS: First, it’s important to read the scientific words carefully.
Reducing atmosphere: Has much hydrogen and little oxygen.
Earth’s atmosphere when life formed: rich in oxygen and low in nitrogen.
So when life formed, Earth did not have a reducing atmosphere. This means amino acids could not have stuck together and formed life.
The right answer explains this by saying that a local reducing atmosphere protected the amino acids.
___________
- CORRECT. This shows that there was a local reducing atmosphere in the area where life began.
- This doesn’t explain how the amino acids formed life in a reducing atmosphere.
- This doesn’t explain how life formed billions of years ago, when Earth had a reducing atmosphere.
- The lighting isn’t the issue. We need to explain the reducing atmosphere. Though fewer lightning strikes make it less likely for life to form.
- That’s nice. But once the amino acids survived the impact, they would encounter Earth’s non-reducing atmosphere, and they would break apart.
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I think another valuable way to discredit answer choice E is that the question stem asks for how “lightning” could have created amino acids. AC (E) tells us another source of these amino acids (i.e. meteorites) this does not satisfy what the stem is asking for and is therefore not a viable answer choice.
I have a question with respect to the difference between answer choices A and E. For answer E, I understand that the acids would encounter Earth’s non-reducing atmosphere. But isn’t that the same as choice A because the reducing atmosphere was created temporarily?
Even though the atmosphere would be temporary, (A) would explain how life could begin. It’s important to remember that we don’t know (given what’s contained in the stimulus that is) if that reducing atmosphere needs to continue to be present in order for life to continue to develop. So, given the information we have, (A) could explain how lightning might produce the first amino acids.
(E) doesn’t allow for any possibility of a reducing atmosphere–temporary or not. So, unlike (B), (E) lacks one of the required conditions for the beginnings of life.
The question is about HOW LIGHTNING created the amino acids. So anything that proves otherwise (a method wherein lightning doesn’t creat AA) will be automatically wrong.