Protist

Protists Temporal range: Paleoproterozoic–present[1] Pha. Proterozoic Archean Had.
Examples of protists. Clockwise from top left: red algae, kelp, ciliate, golden alga, dinoflagellate, metamonad, amoeba, slime mold.
Scientific classification
Domain:	Eukaryota
Clades and phyla[2]
Amorphea Amoebozoa Obazoa (including animals and fungi) CRuMs Discoba Metamonada Malawimonadida Ancyromonadida Hemimastigophora Provora[3] Diaphoretickes Archaeplastida (including plants) Cryptista Haptista Telonemia SAR Stramenopiles Alveolata Rhizaria
Cladistically included but traditionally excluded taxa
Animalia Fungi Embryophyta (land plants)

A protist (/ˈproʊtɪst/ PROH-tist) or protoctist is any eukaryotic organism that is not an animal, plant, or fungus. Protists do not form a natural group, or clade, but are a paraphyletic grouping of all descendants of the last eukaryotic common ancestor excluding plants, animals, and fungi.

Protists were historically regarded as a separate taxonomic kingdom known as Protista or Protoctista. With the advent of phylogenetic analysis and electron microscopy studies, the use of Protista as a formal taxon was gradually abandoned. In modern classifications, protists are spread across several eukaryotic clades called supergroups, such as Archaeplastida (photoautotrophs that includes land plants), Sar, Obazoa (which includes fungi and animals), Amoebozoa and "Excavata".

Protists represent an extremely large genetic and ecological diversity in all environments, including extreme habitats. Their diversity, larger than for all other eukaryotes, has only been discovered in recent decades through the study of environmental DNA and is still in the process of being fully described. They are present in all ecosystems as important components of the biogeochemical cycles and trophic webs. They exist abundantly and ubiquitously in a variety of mostly unicellular forms that evolved multiple times independently, such as free-living algae, amoebae and slime moulds, or as important parasites. Together, they compose an amount of biomass that doubles that of animals. They exhibit varied types of nutrition (such as phototrophy, phagotrophy or osmotrophy), sometimes combining them (in mixotrophy). They present unique adaptations not present in multicellular animals, fungi or land plants. The study of protists is termed protistology.