P.S. Sorry, the PROKARYOTES were first. The Eukaryotes were second, having an internal engine (nucleus) which the PK's don't. A Eukaryote is a prokaryote with a booster engine.
They helped convert the atmosphere so further life could develop.
They are our God, but who created them?
The architects of the earth's atmosphere were primarily the cyanobacteria, which are prokaryotes.