Question

Why are iron oxides in rocks evidence for prehistoric photosynthesis?(1 point)
Responses

Iron oxides form when oxygen, a product of photosynthesis, is in the atmosphere.
Iron oxides form when oxygen, a product of photosynthesis, is in the atmosphere.

Iron oxides form when cyanobacteria use carbon dioxide for photosynthesis.
Iron oxides form when cyanobacteria use carbon dioxide for photosynthesis.

Iron oxides form when carbon dioxide, a reactant 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.

Answer 1

Iron oxides form when oxygen, a product of photosynthesis, is in the atmosphere.

Explanation: As photosynthetic organisms (like cyanobacteria) released O2, dissolved iron in seawater oxidized and precipitated as iron oxides, leaving banded iron formations in ancient rocks.