why are organisms placed into the domain of eukarya
Domain (biology) In biological taxonomy, a domain (Latin: regio[1]), also superkingdom or empire,[2] is the highest taxonomic rank of organisms in the three-domain system of taxonomy designed by Carl Woese, an American microbiologist and biophysicist. According to the Woese system, introduced in 1990, the tree of life consists of three domains: Archaea, Bacteria, and Eukarya.[1] The first two are all prokaryotic microorganisms, or single-celled organisms whose cells have no nucleus. All life that has a nucleus and membrane-bound organelles, and multicellular organisms, is included in the Eukarya. Stefan Luketa in 2012 proposed a five "dominion" system, adding two more to the above.[3]
Flagellum A flagellum (/fləˈdʒɛləm/; plural: flagella) is a lash-like appendage that protrudes from the cell body of certain bacterial and eukaryotic cells. The primary role of the flagellum is locomotion, but it also often has function as a sensory organelle, being sensitive to chemicals and temperatures outside the cell.[1][2][3][4] The similar structure in the archaea functions in the same way but is structurally different and has been termed the archaellum.[5]