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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, 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.
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]
Many protists have protective shells or tests, [139] usually made from calcium carbonate (chalk) or silica (glass). Protists are mostly single-celled and microscopic. Their shells are often tough mineralised forms that resist degradation, and can survive the death of the protist as a microfossil. Although protists are very small, they are ...
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 ]
Ciliates are an important group of protists, common almost anywhere there is water—in lakes, ponds, oceans, rivers, and soils, including anoxic and oxygen-depleted habitats. [2] About 4,500 unique free-living species have been described, and the potential number of extant species is estimated at 27,000–40,000. [ 3 ]
When the function of these ion channels is disrupted, the coccolithophores stop the calcification process to avoid acidosis, thus forming a feedback loop. [104] Low ocean alkalinity , impairs ion channel function and therefore places evolutionary selective pressure on coccolithophores and makes them (and other ocean calcifiers) vulnerable to ...
Foraminifera (/ f ə ˌ r æ m ə ˈ n ɪ f ə r ə / fə-RAM-ə-NIH-fə-rə; Latin for "hole bearers"; informally called "forams") are single-celled organisms, members of a phylum or class of Rhizarian protists characterized by streaming granular ectoplasm for catching food and other uses; and commonly an external shell (called a "test") of diverse forms and materials.
Amoebozoa is a major taxonomic group containing about 2,400 described species of amoeboid protists, [8] often possessing blunt, fingerlike, lobose pseudopods and tubular mitochondrial cristae. [ 7 ] [ 9 ] In traditional classification schemes, Amoebozoa is usually ranked as a phylum within either the kingdom Protista [ 10 ] or the kingdom ...