Answer to Question #101706 in Biology for Dylan

Question

What evidence is there that oxygen levels in the sea increased due to photosynthetic bacteria?

Answer 1

Banded iron formation (sedimentary layers of iron oxides) is one of the main evidence confirming that oxygen levels in the sea increased due to photosynthetic bacteria. Banded iron was formed mostly 2,400 million years ago. According to the hypothesis, the iron layers were formed in seawater due to the intensive production of oxygen by photosynthetic bacteria. The released oxygen combined with iron dissolved in seawater resulting in the formation of insoluble iron oxides. These complexes precipitated onto the sea bottom with certain cyclic variations leading to the formation of iron bends. As a result, banded iron formations reflect the rapid increase in oxygen concentration in seawater, which was associated with the active photosynthetic processes.