Animal-like protists are the protozoans. These are organisms that have single cells. Because protozoans require damp environments, they like to live in watery places such as rivers and oceans. Some protozoans form symbiotic relationships with other organisms.
Kingdom Protista is made up of diverse groups of organisms. Some protists have the characteristics of plants, animals or fungi. Scientists have identified about 65,000 protozoa. Considered eukaryotic, protozoans as well as other protists have structures called organelles. When conditions become unfavorable for the survival of certain protozoans, they can retreat inside shells to await favorable conditions.
Protozoans fit into four categories – if they have flagella, they are called mastigotes, amoeba-like ones are called sarcodines, those that have cilia are called ciliates and types that rely on parasitizing other organisms are called apicomplexans.
Protozoans are like animals in that they are heterotrophic, which means they must consume other organisms to get energy. These animal-like creatures mostly consume bacteria, but they do eat other protists, as well as fungi.
Because protozoa are consumers, they need ways of moving around. Kinds with flagella whip these structures back and forth to move. The ciliates beat their hair-like projections to move, and sarcodines use the movement of their cytoplasm for transportation.