Kingdom Protista includes unicellular eukaryotic organisms that are not classified as animals, plants, or fungi. It is divided into three types: animal-like protists which are heterotrophic and include protozoans like amoebas and ciliates; plant-like protists which are photosynthetic and include algae; and fungus-like protists which are decomposers and include slime molds. Protists play important ecological roles as primary producers, decomposers, and parasites.