Logical ReasoningDifficulty: Medium

PT136 S4 Q10 Explanation

In an experiment designed

A free, expert breakdown of this official LSAT Logical Reasoning question.

TopicsParadox

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Stimulus

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 actually rich in oxygen and lean in nitrogen at the time life began.

What this question is testing

Paradox

Your task

Break the argument into its conclusion and evidence, then do exactly what the question stem asks with that structure.

Common trap

Answers that sound relevant to the topic but don't connect to the argument's actual reasoning.

Winning move

Predict what a right answer must do, then test each choice against the conclusion-evidence gap.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question
10.

Assuming that the scientists' current belief about Earth's atmosphere at the time life began is correct, which one of the following, if true, would most help to explain

Answer choices

  1. Correct77% picked this

    Meteorite impacts at the time life began on Earth temporarily created a reducing atmosphere around

    Why this is right

    This allows for their to be "hotspots" of the reducing atmosphere, even though the Earth's atmosphere was different. If there were temporary bubbles of high hydrogen / low oxygen, then a lightning strike there could have triggered amino acids. (Can you imagine the double-whammy for that spot on Earth? You get hit by a meteorite, and then before the gases from the impact have even had time to disperse, you get hit by lightning. On the other hand, you did give birth to the building block of all life as we know it.)

    Skill tested: Paradox · how this choice captures the argument's function is the move to repeat next time.

  2. Doesn't Explain Origin10% picked this

    A single amino acid could have been sufficient to begin the formation of

    This tells us about what a single amino acid could do, if it existed. But we're trying to figure out how it existed in the first place. How could lightning make that first single amino acid, if the environment was wrong? This answer doesn't say.

  3. No Impact5% picked this

    Earth's atmosphere has changed significantly since life

    I'm sure the atmosphere has changed, (C), but we are only talking about one specific version of Earth's atmosphere --- one that was high oxy / low nitrogen, and we're wondering how lightning could have made an amino acid within this environment. You're not telling us how lightning was able to cause an amino acid, in this one particular ill-suited environment.

  4. No Impact / Opposite1% picked this

    Lightning was less common on Earth at the time life began than

    The relative frequency of lightning is pretty out of scope. If there was barely any lightning and the atmosphere was wrong, then I would be even more confused about how lightning could have sparked an amino acid. But even if lightning happened all the time way back when, this still wouldn't address the paradox, which is that the atmospheric composition isn't a good match for the conditions lightning needs to make an amino acid.

  5. Unrelated to Goal7% picked this

    Asteroids contain amino acids, and some of these amino acids could survive an asteroid's

    We need to explain how lightning could have caused amino acids, not just how did amino acids get on Earth?

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