1. Animal-like Protists At one time animal-like protists were called protozoa, which means “first animals,” and were classified separately from more plant-like protists. Like animals these organisms are all heterotrophs. Unlike animals they are all made of only one cell. The four phyla of animal-like protists are classified based on their method of movement. For example, ciliates move using cilia, or hair-like projections. Flagellates move using flagella, or whip-like projections. Sacrodines move using extensions of their cytoplasm, and sporozoans do not move at all.

2. Plant-like Protists Many protist contain the green pigment chlorophyll and carry out photosynthesis. Many of these organisms are highly motile, or able to move about freely. Despite this, the fact that they perform photosynthesis is so important that we group these protists in a separate category, the plant-like protists. Plant-like protists are called “algae.” Algae may be unicellular or multicellular, and many have cell walls like plants. Unlike plants they do not have roots, stems and leaves. Examples of algae range from unicellular euglena to multicellular brown algae, more commonly called seaweed.

3. Fungus-like Protists If you were to talk a walk through a forest after a long rain, you may see patches of what looks like brightly colored mold. Fungus-like protists grow in damp or moist environments and have sometimes been classified as fungi even though their cellular structure more closely resembles that of the protists. Like fungi, the fungus-like protists are heterotrophs that feed from dead or decaying organic matter. But, unlike fungi, fungus-like protists lack chitin cells walls of true fungi. The fungus-like protists include the cellular slime molds, acellular slime molds and the water molds.