Editing Three-domain system (section)

===Domain Archaea===
The [[Archaea]] are [[prokaryotic]], with no nuclear membrane, but with biochemistry and RNA markers that are distinct from bacteria. The archaeans possess unique, ancient evolutionary history for which they are considered some of the oldest species of organisms on Earth, most notably their diverse, exotic metabolisms.

Some examples of archaeal organisms are:
* [[methanogen]]s – which produce the gas [[methane]]
* [[halophile]]s – which live in very salty water
* [[thermoacidophile]]s – which thrive in acidic high-temperature water