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A protist (/ ˈ p r oʊ t ɪ s t / PROH-tist) or protoctist is any eukaryotic organism that is not an animal, land plant, or fungus.Protists do not form a natural group, or clade, but are a polyphyletic grouping of several independent clades that evolved from the last eukaryotic common ancestor.
A protist (/ ˈ p r oʊ t ɪ s t /) is any eukaryotic organism (one with cells containing a nucleus) that is not an animal, plant, or fungus.The protists do not form a natural group, or clade, since they exclude certain eukaryotes with whom they share a common ancestor; [a] but, like algae or invertebrates, the grouping is used for convenience.
Haeckel's original (1866) conception of the three kingdoms of life, including the new kingdom Protista. Notice the inclusion of the cyanobacterium Nostoc with plants. In 1674, Antonie van Leeuwenhoek, often called the "father of microscopy", sent the Royal Society of London a copy of his first observations of microscopic single-celled organisms ...
Protists have been described as a taxonomic grab bag of misfits where anything that does not fit into one of the main biological kingdoms can be placed. [8] Some modern authors prefer to exclude multicellular organisms from the traditional definition of a protist, restricting protists to unicellular organisms.
A variety of multi-kingdom systems were proposed, and the Kingdoms Protista and Protoctista became established in biology texts and curricula. [ 22 ] [ 23 ] [ 24 ] By 1954, Protozoa were classified as "unicellular animals", as distinct from the "Protophyta", single-celled photosynthetic algae, which were considered primitive plants. [ 25 ]
Kingdom Protista (or Protoctista) is included in the traditional five- or six-kingdom model, where it can be defined as containing all eukaryotes that are not plants, animals, or fungi. [ 16 ] : 120 Protista is a paraphyletic taxon, [ 47 ] which is less acceptable to present-day biologists than in the past.
In 1818, the German biologist Georg A. Goldfuss coined the word Protozoa to refer to organisms such as ciliates, [57] and this group was expanded until Ernst Haeckel made it a kingdom encompassing all single-celled eukaryotes, the Protista, in 1866. [58] [59] [60] The eukaryotes thus came to be seen as four kingdoms: Kingdom Protista; Kingdom ...
The Protist kingdom contains species that have been categorized due to the simplicity of their structure and being unicellular. These include protozoa , algae and slime molds . In marine ecosystems, macroalgae and microalgae make up a large portion of the photosynthetic organisms found.