These cells obtained their energy by oxidising the organic molecules being produced by the cyanobacteria. Earths crust solidified at aprox 4600 million years before present. The origin of prokaryotic cells occurred after this with the first fossils found in 3500 my old rocks. 2-3000 mya prokaryotes split into Bacteria and Archaea. 2500 mya, cyanobacteria create an aerobic atmosphere with an ozone layer, therefore UV-Radiation was reduced significantly.
Some prokaryotes diversify into using oxygen to metabolise organic molecules.
1700 mya, first eukaryotic fossils were found. 3 - Precambriam. Cells containing them both could respire aerobically and use the energy from the sun to make their own food. Plants, Fungi and Animals arose from unicellular eukaryotes. Plants from green algae and fungi and animals from heterotrophic unicellular eukaryotes.