Protist

Protists (IPA: /ˈprəʊ.tɪst/ (RP); /ˈproʊ.tɪst/ (GenAm)), Greek protiston -a meaning the (most) first of all ones, are a diverse group of organisms, comprising those eukaryotes that can not be classified in any of the other kingdoms as fungi, animals, or plants. They are usually treated as the kingdom Protista or Protoctista. The protists are a paraphyletic grade, rather than a natural (monophyletic) group, and do not have much in common besides a relatively simple organization (unicellular, or multicellular without highly specialized tissues). Essentially, the Kingdom Protista is comprised of organisms which cannot be classified into any other kingdom. The term protista was coined by Ernst Haeckel in 1866.

Protists were traditionally subdivided into several groups based on similarities to the higher kingdoms: the animal-like protozoa, the plant-like algae, and the fungus-like slime molds and water molds. These groups often overlap, and have been replaced by phylogenetic classifications. However, they are still useful as informal groups for describing the morphology and ecology of protists.

At one time, bacteria were also considered protists, under the three-kingdom system of Animalia (corresponding closely to the modern kingdom), Plantae (which included Fungi as well as plants), and Protista (everything else). See kingdom. However, most recent texts treat bacteria separately.