In an experiment designed to show how life may have begun on Earth, scientists demonstrated that an electrical spark—...

First Name* on June 27, 2021

Do not understand

We are told in the stimulus that a reducing atmosphere is what the scientists have proposed to have been present at the time, and we are also told in the question stem to assume that they were correct. Why would we choose an answer choice that creates a reducing atmosphere that we are already told is present?

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Victoria on June 27, 2021

Hi @Lenny,

Happy to help!

I think you may have misread the stimulus a bit.

We learn that, in an experiment, scientists demonstrated that an electrical spark could produce amino acids. However, unless this spark occurs in a reducing atmosphere, amino acids do not readily form.

Amino acids form --> Reducing atmosphere
Not reducing atmosphere --> Amino acids do not form

What is a reducing atmosphere? One that has lots of hydrogen, but minimal oxygen.

Finally, we learn that scientists believe that, at the time life began, the atmosphere had lots of oxygen, but minimal nitrogen. This is not a reducing atmosphere; therefore, we need to find an answer choice which explains how amino acids could have formed when the Earth's atmosphere was not reducing.

Hope this helps! Please let us know if you have any further questions.