They are believed to be a part of the microbial world as they are unicellular and microscopic. Protozoa are divided into four major groups based on the structure and the part involved in the locomotion: 1. It was first coined in the 1800s. Protozoa. Protozoan, organism, usually single-celled and heterotrophic (using organic carbon as a source of energy), belonging to any of the major lineages of protists and, like most protists, typically microscopic. Protozoa is a single cell animal that we can find in every possible habitat on earth. Protozoa are single-celled organisms without cell walls. See more. There is a great deal to know about their classification, characteristics and more. The word protozoa comes from the word protos, which was Greek for "first," and zoia which meant "animal." Protozoa definition, a major grouping or superphylum of the kingdom Protista, comprising the protozoans. Protozoa are non-phototrophic, unicellular, eukaryotic microorganisms with no … They have flagella for locomotion Moreover, they are herbivores, carnivores, and omnivores. In some newer schemes, however, most algae are classified in the kingdoms Plantae and Chromista , and in such cases the remaining forms may be classified as a kingdom Protozoa. It is a loose assemblage of different groups of unicellular organisms and they do not belong to a monophyletic Unease, probably shares a member of polyphyletic lineases. Protozoa [pro″to-zo´ah] a subkingdom (formerly a phylum) comprising the unicellular eukaryotic organisms; most are free-living, but some lead commensalistic, mutualistic, or parasitic existences. Protozoa is a phylum having unicellular heterotrophs. The group of organisms known as 'protozoa' are defined by a few of their shared characteristics. Definition: Unicellular or acellular, eukaryotic and com­monly motile heterotrophic organisms are called Protozoa. Furthermore, the scientist has described more than 50 thousand species of Protozoa. Protozoa. All protozoans are eukaryotes and therefore possess a “true,” or membrane-bound, nucleus. They live in a wide variety of moist habitats including fresh water, marine environments and the soil. Before then, the microscopic protozoa, defined by their organelles, were unable to be fully appreciated. Learn more about it. home >> biology >> definition They belong among the eukaryotes , and are often grouped in the kingdom Protista together with the plant-like algae . They come in many different shapes and sizes ranging from an Amoeba which can change its shape to Paramecium with its fixed shape and complex structure. Mastigophora or Flagellates: They are parasites or free-living. Protozoa are single celled organisms. Protozoa (meaning "first animals") are heterotrophic, single-celled or colonial eukaryotes. Protozoa Classification and Examples. It comes under Kingdom Protista. 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