Protists may be plants, animals or fungi: amoeba, protozoa and giardia are all examples. Despite falling into the same class of protists, the organisms that comprise this class vary significantly in appearance and biological composition. They live in different areas around the world, including Arctic environments, tropical locales, rain forests and can be found on land and in water.
Animal-like protists are among the most common. These organisms consist of single cells and share commonalities of heterotrophic feeding mechanisms and the ability to move. Protozoa are consumers and feed by taking in other organisms, which are digested using special enzymes. Some protozoa are predators and may prey upon other single-celled organisms, such as bacteria, which keeps their populations in check. Protozoa may be benign or malignant; the human disease of malaria is generated by a virulent species of protozoa. These organisms are classified based on their patterns of movement. Of all protists, only sporozoa lack the ability to move at all. Algae are other types of protists and resemble plants in shape and color. They are considered plant-like because they contain chloroplasts and produce food via photosynthesis. Algae protists primarily take the form of diatoms and seaweed. Lastly, fungal protists include various types of mold, and they reproduce with spores.