Plants use the process called photosynthesis to make food usingsunlight. Protists are primarily unicellular organisms that are notplants, fungus or animals, and are classified based onhow they obtain their nutrition, and whether or not they areable to move.Animal and fungus-like protists are heterotrophs, which meansthat they do not make their own food and must obtain it fromoutside sources.Plant-like protists, such as algae, are autotrophs, whichindicates that they produce their own food. The must usesunlight.