which organisms were the first to add oxygen to the atmosphere"?

Question

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Answer 1

It is widely believed that the earliest life forms were prokaryotes, such as bacteria and Cyanobacteria.

Answer 2

This is the formed planet. Cyano means green breath of
nonorganic. The earlier periods were inclusive of the atomic
age the original in terms of recognizable shapes, resources,
rocks, and cores. These gave off valence 4 the lava flow
mineral very near to oxygen, though not for use of life. Then
the neophase periods were making dead mineral, these went
on for several hundred billion years in some planet layers to
become the largest and most common resource the inorganic
shell data of the core, the minerals and the moltens. Today
these still provide some important breathable chemistry oxygen. Still all these early periods of formation simple were in
lifeless environments. Technically neophytes like fleas, shrimps, and maggots were
the first destroyed data chemical and mineral.

Answer 3

algae

wait that guy is right cynobacteria