There is little agreement among taxonomists on how to classify the protists, but they may be conveniently divided into seven general groups that share certain characteristics of locomotion, nutrition, and reproduction. The following list exhibits the general groupings:

• Sarcodinas: Amoebas and related organisms that have no permanent locomotive structure
• Algae: Single-celled and multicellular organisms that are photosynthetic
• Diatoms: Photosynthetic organisms with hard shells formed of silica
• Flagellates: Organisms that propel themselves through water with flagella
• Sporozoans: Nonmotile parasites that spread by forming spores
• Ciliates: Organisms that have many short, hairlike structures on their cell surface associated with locomotion
• Molds: Heterotrophs with restricted mobility that have cell walls composed of carbohydrates