The Kingdom Protista

This kingdom, sometimes called Protoctista, consists of single-celled microorganisms and simple multicelled organisms.

Phylum Protozoa

The protozoans. Single-celled; solitary or in colonies. Aquatic, terrestrial, or parasitic. Examples: amoeba, globigerina, paramecium.

Phylum Chrysophyta

Golden-brown algae, or diatoms, and yellow-green algae. Most are single-celled. Marine and freshwater. Contain chlorophyll.

Phylum Pyrrophyta, or Dinoflagellata

Fire algae, or dinoflagellates. Most are single-celled; marine. Contain chlorophyll.

Phylum Euglenophyta

Most are single-celled flagellates containing chlorophyll. Freshwater, marine, or parasitic. Example: euglena.

Phylum Phaeophyta

Brown algae. Multicelled; marine. Contain chlorophyll. Example: kelp.

Phylum Rhodophyta

Red algae. Multicelled; most are marine. Contain chlorophyll. Example: Irish moss.

Phylum Chlorophyta

Green algae. Single- and multicelled; most are freshwater. Contain chlorophyll.

Phylum Myxomycota

The plasmodial slime molds. Body is a thin, flat mass of protoplasm with many nuclei. Certain kinds parasitic.

Phylum Acrasiomycota

The cellular slime molds. Body is multicelled and sluglike.

Phylum Chytridiomycota

The chytrids. Single-celled. Parasitic or absorb dead organic matter.

Phylum Oomycota

White rusts, downy mildews, and water molds. Parasitic or absorb dead organic matter. Some of these organisms have caused serious plant diseases, such as the potato blight in 19th-century Ireland.