The Protista is an heterogeneous group of eukaryotic organisms. That is, the nucleus is surrounded by a nuclear envelope, and they contain organized plastids and mitochondria. Most protists are unicellular, but there are some relatively simple multicellular forms. This group is extremely diverse, and includes such organisms as algae, slime, molds, and protozoa. They include both autotrophic and heterotrophic forms.

Reproduction is both sexual (in some forms) and asexual. Locomotion (in non-sessile forms) is by pseudopodia, or by flagella or cilia which show the typical 9+2 microtubular arrangement.

The KINGDOM PROTISTA is subdivided as follows:

Algal protists, including green algae, diatoms, and brown algae; and Slime molds.

Animal-like protists (protozoa) shown on the right: