Which domain contains prokaryotes commonly living in extreme environments?

• A. Bacteria
• B. Archaea
• C. Eukaryotes
• D. Viruses

Answer: (B)

Extremophile prokaryotes belong to Archaea. These organisms thrive in conditions that most life cannot tolerate—extremely high or low temperatures, very saline environments, highly acidic or anaerobic settings. Archaea are prokaryotic, but they’re biochemically distinct from bacteria, with features like ether-linked membrane lipids and unique enzymes that support survival in these harsh habitats. While bacteria do include some extreme residents, the classic and most characteristic prokaryotes associated with extreme environments are Archaea. Eukaryotes are not prokaryotes, and viruses aren’t cellular organisms and don’t fit into the three-domain system, so Archaea are the best fit for this question.