Protists are unicellular eukaryotic organisms that can be categorized into three main groups: animal-like protists, plant-like protists, and fungus-like protists. Animal-like protists include protozoans that can move on their own and feed as heterotrophs, with examples being amoebas, paramecium, and sporozoans. Plant-like protists include algae, which can be unicellular or multicellular, produce their own food via photosynthesis, and account for 70% of the Earth's oxygen production. Fungus-like protists have cell walls and reproduce via spores, with examples being water molds and slime molds