prokaryotes
22.1 | Prokaryotic Diversity By the end of this section, you will be able to: Describe the evolutionary history of prokaryotes Discuss the distinguishing features of extremophiles Explain why it is difficult to culture prokaryotes Prokaryotes are ubiquitous. They cover every imaginable surface where there is sufficient moisture, and they live on and inside of other living things. In the typical human body, prokaryotic cells outnumber human body cells by about ten to one. They comprise the majority of living things in all ecosystems. Some prokaryotes thrive in environments that are inhospitable for most living things. Prokaryotes recycle nutrientsessential substances such as carbon and nitrogen and they drive the evolution of new ecosystems, some of which are natural and others man-made. Prokaryotes have been on Earth since long before multicellular life appeared.