Question

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

Answer 1

Cyanobacteria

Step-by-step explanation:

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

Answer 2

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.

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