Organisms known as protozoa include a wide range of organisms, most of which are free-living single-celled eukaryotes. Therefore, protozoa fit into the Domain Eukarya. Although the different phyla of the kingdom Protista are not closely related, they are nonetheless classified together because of their large differences from the other kingdoms of plants, animals and fungi. The name “protozoa” has a dynamic history, at one time including only the “animal-like” unicellular forms of life. Today, these heterotrophic protozoa are lumped together with the autotrophic algae and other simple forms of life into the Kingdom Protista. While all protozoa are eukaryotes,...