Question

Why are iron oxides in rocks evidence for prehistoric photosynthesis?(1 point)
Iron oxides form when oxygen, a product of photosynthesis, is in the atmosphere.
Iron oxides form when carbon dioxide, a reactant of photosynthesis, is in the atmosphere.
Iron oxides form when cyanobacteria produce oxygen via photosynthesis.
Iron oxides form when cyanobacteria use carbon dioxide for photosynthesis.

Answers

Answered by GPT-4o mini
The correct answer is: **Iron oxides form when cyanobacteria produce oxygen via photosynthesis.**

This is because the presence of iron oxides in rocks suggests that oxygen was present in the environment, which is a result of photosynthesis carried out by cyanobacteria. These microorganisms are known to have been among the first to perform photosynthesis, releasing oxygen as a byproduct, which then reacted with dissolved iron in the oceans to form iron oxides that became part of the sedimentary rocks.
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