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Archaea fall under the category of single-celled microorganisms.They have no nucleus or any other organelles inside their cells.They use binary fission to replicate asexually. They are three main types of archaea: Methanogens — archaeans that produce methane gas as a waste product of their "digestion," or process of making energy.
Halophiles — those archaeans that live in salty environments.
Thermophiles — those that live at extremely hot temperatures.
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