Question

when living organisms originated they modified the early atmosphere

Answer 1

Initially, earth’s temperature was extremely high and it has no atmosphere.

Life began when the earth surface cooled down and an atmosphere formed commonly from gases.
The gases included hydrogen sulfide, methane and carbon dioxide.
The more cooling of earth leads to the formation.

Answer 2

Initially, earth’s temperature was very high and it has no atmosphere. Life began when the earth surface cooled down and an atmosphere was formed commonly from gases.

The gases included hydrogen sulfide, methane and carbon dioxide.

The more cooling of earth leads to the formation of living organisms by abiogenesis.