How common are prokaryotes on earth?
Prokaryotes are extremely common. They’re everywhere. Most bacteria are prokaryotes. “Prokaryotes are found in nearly all environments on earth. Archaea in particular seem to thrive in harsh conditions, such as high temperatures, thermophiles, or salinity, halophiles. Organisms such as these are referred to as extremophiles. Many prokaryotes live in or on the bodies of other organisms, including humans” http://en.wikipedia.
