Question

What organisims allowed for the build up of oxygen in the atmosphere?

Answer 1

Answer:

The answer is tiny organisms known as cyanobacteria, or blue-green algae. These microbes conduct photosynthesis: using sunshine, water and carbon dioxide to produce carbohydrates and, yes, oxygen.

:-))

Answer 2

Answer:

Cyanobacteria

Explanation:

The answer is tiny organisms known as cyanobacteria, or blue-green algae.