From Sciencedaily, if you know anything about life’s progression(for a lack of a better way of saying it) bacteria came first. Then multi-cellular organisms. So that the rest of life’s diversity evolved in about 1 billion years(in a ~3.8 billion year span for the whole of life).

Bacteria shares DNA through the use of plasmids. Some viruses use can use reverse transcriptase to integrate into the DNA of its host to make new copies of itself. It is believed that this transfer of DNA can speed the rate of evolution.