<P> Historically , the Protozoa were classified as `` unicellular animals '' , as distinct from the Protophyta , single - celled photosynthetic organisms ( algae ) which were considered primitive plants . Both groups were commonly given the rank of phylum , under the kingdom Protista . In older systems of classification , the phylum Protozoa was commonly divided into several sub-groups , reflecting the means of locomotion : Classification schemes differed , but throughout much of the 20th century the major groups of Protozoa included : </P>
<P> Historically , the Protozoa were classified as `` unicellular animals '' , as distinct from the Protophyta , single - celled photosynthetic organisms ( algae ) which were considered primitive plants . Both groups were commonly given the rank of phylum , under the kingdom Protista . In older systems of classification , the phylum Protozoa was commonly divided into several sub-groups , reflecting the means of locomotion : Classification schemes differed , but throughout much of the 20th century the major groups of Protozoa included : </P>
protozoan classification used to be based on their means of
protozoan classification used to be based on their means of
locomotion
locomotion