The first organisms to inhabit the Earth were prokaryotes which include Bacteria and Archaea. And because prokaryotes have adapted so muchthroughout history means that they have considerable genetic variation due to rapid reproduction and mutation. Another factor that contributes to genetic variation is genetic recombination. This is the combining of DNA from twosources. Also, transformation can occur to maximize genetic variation. This is when the genotype and sometimes the phenotype of a prokaryotic cell is altered by gaining foreign DNA from the cells surroundings.
“There are no obvious precursor structures known among prokaryotes from which such attributes [eukaryotic flagella, Golgi, endoplasmic reticulum, etc.] could be derived, and no intermediate cell types known that would guide a gradual evolutionary inference between the prokaryotic and eukaryotic state. Accordingly, thoughts on the topic are diverse, and new suggestions appearfaster than old ones can be tested.(Purdom 2006)” So basically, scientists have concluded that there is no known common ancestor of prokaryotes.
A difference in evolutionary history as the Archaea has evolved is the presence of lipids in shales from 2.7 billion years ago from the start of their existence 3.5 billion years ago. Also, bacteria have evolved throughout their life. An example of this is how bacteria have evolved is because they have becomeresistant to bacteriophages. As well as becoming resistant to antibiotics which is very important for the medical world to understand.
Scientists argued that the Bacteria, Archaea, and Eukaryotes represent separate lines of descent that separated early on from an “ancestral” colony of organisms. However, a few biologists argue that the Archaea and Eukaryota came from a group of bacteria.Also, some scientists think that viruses and Archaea began relationships approximately two billion years ago, and that co- evolution may have been occurring between members of these groups. Biologists think that it is possible that the last common ancestor of theBacteria and Archaea was a thermophile, which raises the possibility that lower temperatures are "extreme environments" in Archaeal terms, and organisms that live in cooler environments appeared only later.