Protozoa vs. Algae — What's the Difference?

Protozoa (also protozoan, plural protozoans) is an informal term for a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Historically, protozoans were regarded as "one-celled animals", because they often possess animal-like behaviours, such as motility and predation, and lack a cell wall, as found in plants and many algae.

Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades.

Any of numerous chiefly single-celled eukaryotic organisms, most of which move about freely and ingest food, including the amoebas, ciliates, flagellates, and apicomplexans. Protozoans along with certain algae, oomycetes, and some other groups make up the protists.

Any of numerous photosynthetic organisms of aquatic or moist habitats, ranging in size from single-celled diatoms to large seaweeds such as kelp, and characterized by a lack of complex organs and tissues. Once classified within the plant kingdom, the algae are now considered to include several unrelated groups belonging to different kingdoms.

Plural of protozoan

Algal organisms viewed collectively or as a mass; algal growth.

Plural of protozoon

(countable) A particular kind of algae.

The lowest of the grand divisions of the animal kingdom.

Plural of alga.

In some classifications considered a superphylum or a subkingdom; comprises flagellates; ciliates; sporozoans; amoebas; foraminifers

Primitive chlorophyll-containing mainly aquatic eukaryotic organisms lacking true stems and roots and leaves