We inhale oxygen all the time otherwise we will died out in a few span of time in lack of oxygen. So question arises how the circumstances were be in the very past that makes possible that only oxygen can makes the survival of a being. Let’s get study about this👍👍👍. So in the beginning of our plant(just after millions of earth formation) there is a cyanobacteria which inhale carbon dioxide and exhale oxygen. By the fact I must tell you that at that time oxygen is poison for living beings. Cyanobacteria lives in ocean and replicate massively and exhale oxygen in very large amount in atmosphere. And the fact that oxygen is like a poison it created a Great Mass Extinction. Nearly 95% of living beings died out in this terrible time. But after that oxygen is such in that amount in atmosphere that it makes enable the upcoming creatures to inhale oxygen only(Because of large amount in atmosphere) and make the survival possible of life in earth.
This process is called-OXYGENATION CATASTROPHIC
Science Lover 