A genus of protists (see also protozoa) formerly placed in the phylum Rhizopoda but now, on the basis of molecular systematics, classified as amoebozoans. Amoeba spp. have lobe-shaped pseudopodia, which are used for locomotion and feeding and result in a constantly changing body shape (see amoeboid movement). Most species are free-living in soil, mud, or water, where they feed on smaller protists and other single-celled organisms, but a few are parasitic. The best-known species is the much studied A. proteus.