Protozoa are a diverse group of unicellular eukaryotic (complex cells with a nucleus and organelles) organisms. Historically, protozoa were defined as single-celled organisms with animal-like behaviors, such as motility and predation.
Protozoa are mainly microscopic organisms, ranging in size from 10 to 52 micrometers, although some are significantly larger. Free-living forms are restricted to moist environments, such as soils, mosses and aquatic habitats, although many form resting cysts which enable them to survive drying. Many protozoan species are symbiontic, some are parasites, and some are predators of bacteria, algae and other protists.
(m3pr.protozoa) Blepharisma japonicum, A ciliated protozoan
Photo Credit: Frank Fox
