#10 - In an experiment designed to show how life may have

[Administrator]

Complete Question Explanation

Resolve the Paradox. The correct answer choice is (A)

The stimulus contains a fact set. Do not let the hard science topic discourage you: this is actually a relatively easy question, once you simplify the language in the stimulus.

Scientists observed that lightning could produce amino acids, the building blocks of life, but only in a “reducing atmosphere” (i.e. one rich in hydrogen and lean in oxygen):

• Lightning produce amino acids Reducing atmosphere

Surprisingly, Earth’s atmosphere at the time life began was rich in oxygen and lean in nitrogen. In other words, it was the opposite of a “reducing atmosphere.” The correct answer choice must explain how lightning could have produced the first amino acids on Earth despite the lack of reducing atmosphere. Note that the correct answer must explain how the situation came into being without questioning either the scientists’ current belief, or the atmospheric conditions on Earth at that time.

Answer choice (A): This is the correct answer choice. If meteorite impacts at the time life began temporarily created a reducing atmosphere around the impact site, then it is possible that lightning produced the first amino acids at the site of such impacts. This answer choice is consistent with the proposition that Earth’s atmosphere was not a reducing atmosphere at that time, and it also allows the scientists’ current belief to be correct.

Answer choice (B): Even if a single amino acid could have been sufficient to begin the formation of life on Earth, it is still unclear how that amino acid was produced in the first place. The fact remains that there was no reducing atmosphere at that time, which—according to the stimulus—is a necessary condition for lightning to produce amino acids.

Answer choice (C): Whether Earth’s atmosphere has changed since life first began is entirely irrelevant and does not explain the paradox described in the stimulus. Even if a reducing atmosphere were present at a later time, this would not explain how lightning produced the first amino acids on Earth.

Answer choice (D): The relative frequency of lightning at the time life began has no bearing on the paradox described in the stimulus.

Answer choice (E): This may seem like an attractive answer choice, because it suggests one possible way for life to have begun on Earth: the first amino acids were brought in by asteroids from outer space. Recall, however, that your job is to explain not how life began on Earth, but how lightning could have produced the first amino acids. This is a typical Shell Game answer, explaining a different paradox than the described by the author.

[15veries]

Hello,

I'm not sure why C is wrong...
Is it because it only states a fact, not reason why? So it actually does not explain anything?

[Emily Haney-Caron]

Hi 15veries,

Remember for Resolve the Paradox questions (and really most LR questions!!) you want to make sure you come up with a strong prephrase so you're less likely to get led astray by incorrect answer choices that sound tempting. Here's what we have in the stimulus:

To create amino acids (and, therefore, possibly life), a spark has to happen in a reducing atmosphere.
When life began, the earth's atmosphere was not a reducing atmosphere.

How can we explain that?? We need some answer choice that tells us how amino acids could have formed from lighting anyway.

C doesn't explain the paradox; even if the atmosphere is significantly different now, the stimulus tells us the earth's atmosphere was not a reducing atmosphere when life was formed.

If you had a solid prephrase for this one, that would help you quickly discard C. Does that help?

[15veries]

yes thanks Emily

[willmcchez]

I'm struggling with this one. I don't understand how A is correct.

- A states that meteorite impacts created a temporary reducing atmosphere.
- The stimulus states that amino acids tend to break apart when they do form in non-reducing atmospheres.

So, if the reducing atmosphere was temporary, wouldn't the amino acids have broken apart when it returned to non-reducing?

I went with B. I found the language to be open and not precluding the possibility of a single amino acid existing in a non-reducing atmosphere. The stimulus states that "amino acids do not form readily" (not that they flatly do NOT form, meaning they COULD form) and they "tend to break apart when they do form" (not that they always break apart). Thus, I was thinking that the stimulus left open the possibility that aminos COULD form, but it would be unlikely. In my view, B could totally be correct.

[willmcchez]

I'm struggling with this one. I don't understand how A is correct.

- A states that meteorite impacts created a temporary reducing atmosphere.
- The stimulus states that amino acids tend to break apart when they do form in non-reducing atmospheres.

So, if the reducing atmosphere was temporary, wouldn't the amino acids have broken apart when it returned to non-reducing?

I went with B. I found the language to be open and not precluding the possibility of a single amino acid existing in a non-reducing atmosphere. The stimulus states that "amino acids do not form readily" (not that they flatly do NOT form, meaning they COULD form) and they "tend to break apart when they do form" (not that they always break apart). Thus, I was thinking that the stimulus left open the possibility that aminos COULD form, but it would be unlikely. In my view, B could totally be correct.

Bumping this. I know the forum was down for a bit, but I could use some clarity.

[Adam Tyson]

Good thinking, willmcchez! I like your analysis here. However, answer B should still leave us wondering how that one amino acid managed to not only form (against the odds) but then also stick together (still further against the odds). It's a bit of a stretch, isn't it? Sure, it tells us that "maybe one amino acid beat the odds somehow", but it doesn't really explain how the lightning could have produced it, just that it somehow did produce it.

Answer A gives us a how situation - a sort of safe zone in which the conditions could have been just right. Since the stem asked us to explain how lightning could have created the amino acids, this is the better answer.

I'm with you, worrying about that temporary status, and what happened after that temporary situation went away. This answer still leaves a lot to be desired. However, I am not going to reject A because of it, because of a few things. 1) I don't know how long "temporary" is. An hour? A week? A century?; 2) I don't know at what point an amino acid becomes strong enough not to break down, or evolves into something that doesn't break down, in a reducing atmosphere, so maybe the "temporary" period is enough to get it there?; 3) neither 1 nor 2 matters, because this answer is still the best answer of those we were given, because it is the only one that addresses the how aspect of the question stem. Not "how did life manage to form despite the odds against it," but rather "how did lightning manage to form the amino acids that led to the formation of life".

Not completely satisfactory, in my opinion, but enough to make me pretty confident that A is the credited response! I hope you feel that way about it, now, too!