Which set lists the three domains recognized in the three-domain system?

• A. Bacteria, Archaea, Eukarya
• B. Archaea, Protista, Fungi
• C. Bacteria, Eukarya, Protista
• D. Eukarya, Protista, Fungi

Answer: (A)

Grouping life into three domains uses genetic evidence to separate major lineages. Bacteria and Archaea are both prokaryotes—organisms without a true nucleus—but they represent very distinct lineages with different genetic and biochemical features. Eukarya includes organisms with true nuclei and membrane-bound organelles, spanning complex kingdoms like plants, animals, fungi, and many protists. This division, based on ribosomal RNA comparisons, shows deep evolutionary relationships that purified the domains into Bacteria, Archaea, and Eukarya.

Protista is not a domain; it’s a traditional kingdom grouping many single-celled eukaryotes, while Fungi is one of the kingdoms within Eukarya. Therefore, the set that lists the three domains correctly names Bacteria, Archaea, and Eukarya.