An assemblage of eukaryotic organisms that includes the kingdoms containing all animals and fungi, plus certain flagellated protists, such as the DRIPs and choanoflagellates. Although the grouping is based chiefly on molecular systematics, members are characterized by having flagellated cells propelled by a single posterior flagellum, as in the sperm cells of mammals or the zoospores of chytrids (see chytridiomycota). This contrasts with the anterior flagella of flagellated cells in other eukaryotes.