Question

What evidence is there that oxygen levels in the sea increased due to photosynthetic bacteria?(1 point)
Responses

decreases in anaerobic organisms
decreases in anaerobic organisms

rust deposits in the ancient ocean
rust deposits in the ancient ocean

rust deposits in today’s ocean
rust deposits in today’s ocean

global cooling

Answer 1

The most relevant evidence that oxygen levels in the sea increased due to photosynthetic bacteria is **rust deposits in the ancient ocean**. These deposits indicate that free oxygen was present in significant amounts, which would have resulted from photosynthetic processes carried out by cyanobacteria. As these microorganisms produced oxygen as a byproduct of photosynthesis, it led to the oxidation of iron and the formation of rust (iron oxides) in the ocean and subsequently in sediments.