Protozoa are classified as single-celled organisms called eukaryotes, which belong to the subkingdom Protista. Individual types of protozoa within this subkingdom are typically identified by observing their form of movement.
The types of protozoa include ciliates, flagellates, sporozoa and amoebae. Flagellates and ciliates move through liquids by waving hair-like extensions of their cytoskeleton. Amoebae move by using wider extensions called pseudopodia, which allow them to move across solid surfaces. Sporozoa form as sedentary organisms and do not exhibit movement once grown, although it is theorized that they have a gliding method of movement during their prespore stages. Some protozoa consume other microorganisms for sustenance, while others perform photosynthesis to survive and reproduce.