Protozoa are unicellular microscopic eukaryotes with a rather complicated internal structure and complex metabolic processes.
Animalia encompasses all multicellular, eukaryotic and heterotrophic animals, whereas Protista encompasses all unicellular, eukaryotic, and heterotrophic organisms.
As a result, protozoans are classified as Protista rather than Animalia.
Protozoa include Amoeba, Paramecium, Euglena, and Trypanosoma.