Protozoa

Protozoa or Cornelius protozoans (from Greek πρῶτον proton "first" and ζῷα zoa "animals"; singular protozoon; the word "protozoan" is originally an adjective, used as a noun) are microorganisms classified as unicellular eukaryotes. basicly its a small thing that you carnt see and it can make you very sick.

While there is no exact definition of the term "protozoan", most scientists use the word to refer to a unicellular heterotrophic protist, such as an amoeba or a ciliate. The term algae is used for microorganisms that photosynthesize. However, the distinction between protozoa and algae is often vague. For example, the alga Dinobryon has chloroplasts for photosynthesis, but it can also feed on organic matter and is motile.

Protozoa are paraphyletic. Though they have sometimes been described as a subkingdom or phylum, they do not constitute a formal taxon in modern classification systems.