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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.
Systematists today do not treat Protista as a formal taxon, but the term "protist" is still commonly used for convenience in two ways. [22] The most popular contemporary definition is a phylogenetic one, that identifies a paraphyletic group: [23] a protist is any eukaryote that is not an animal, (land) plant, or (true) fungus; this definition [24] excludes many unicellular groups, like the ...
The resulting five-kingdom system, proposed in 1969 by Whittaker, has become a popular standard and with some refinement is still used in many works and forms the basis for new multi-kingdom systems. It is based mainly upon differences in nutrition ; his Plantae were mostly multicellular autotrophs , his Animalia multicellular heterotrophs ...
The earliest evidence for life on Earth includes: 3.8 billion-year-old biogenic hematite in a banded iron formation of the Nuvvuagittuq Greenstone Belt in Canada; [30] graphite in 3.7 billion-year-old metasedimentary rocks in western Greenland; [31] and microbial mat fossils in 3.48 billion-year-old sandstone in Western Australia.
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.
In 1818, the German biologist Georg A. Goldfuss coined the word Protozoa to refer to organisms such as ciliates, [56] and this group was expanded until Ernst Haeckel made it a kingdom encompassing all single-celled eukaryotes, the Protista, in 1866. [57] [58] [59] The eukaryotes thus came to be seen as four kingdoms: Kingdom Protista; Kingdom ...
The initial targets of Cavalier-Smith's classification, the protozoa were classified as members of the animal kingdom, [12] and many algae were regarded as part of the plant kingdom. With growing awareness that the animals and plants embraced unrelated taxa, the use of the two kingdom system was rejected by specialists.
Protistology is a scientific discipline devoted to the study of protists, a highly diverse group of eukaryotic organisms. All eukaryotes apart from animals, plants and fungi are considered protists. [1]