Which best describes the first organisms on earth apex?

Evolutionary biologists theorize that the first living organisms on earth are single-celled prokaryotes. The two prokaryotic domains are archaea and bacteria. Bacteria varies from disease-causing pathogens to valuable photo synthesizers and symbionts while archaea are diverse, but not pathogenic and they have the characteristics to live in extreme environments. Moreover, the presence of prokaryotes is highly dominating for they can be found everywhere even inside our bodies but they are difficult to count, classify or detect.