Question

Until The Early _______ There Were Only Negligible Amounts Of Free Oxygen In The Atmosphere

Answer 1

Until The Early _______ There Were Only Negligible Amounts Of Free Oxygen In The Atmosphere. The answer is Proterozoic.

Answer 2

Until the early proterozoic there were only negligible amount of free oxygen in the atmosphere. During the proterozoic period, oxygen build up in the atmosphere occurred and this make it possible for explosion of eukaryotic form of animals to occur while many of the existing bacterial organisms were wiped out.