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Protozoa (sg.: protozoan or protozoon; alternative plural: protozoans) are a polyphyletic group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic debris. [1] [2] Historically, protozoans were regarded as "one-celled animals".
Later, in 1845, Carl Theodor von Siebold was the first to establish Protozoa as a phylum of exclusively unicellular animals consisting of two classes: Infusoria (ciliates) and Rhizopoda (amoebae, foraminifera). [188]
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.
The term phylum was coined in 1866 by Ernst Haeckel from the Greek phylon (φῦλον, "race, stock"), related to phyle (φυλή, "tribe, clan"). [4] [5] Haeckel noted that species constantly evolved into new species that seemed to retain few consistent features among themselves and therefore few features that distinguished them as a group ("a self-contained unity"): "perhaps such a real and ...
Apicomplexa – parasitic and secondary non-photosynthetic protozoa that lack axonemal locomotive structures except in gametes The Acavomonidia and Colponemidia were previously grouped together as colponemids, a taxon now split because each has a distinctive organization or ultrastructural identity .
Feeding techniques vary considerably, however. Some ciliates are mouthless and feed by absorption , while others are predatory and feed on other protozoa and in particular on other ciliates. Some ciliates parasitize animals, although only one species, Balantidium coli, is known to cause disease in humans. [21]
The phylum Cercozoa includes many of the most abundant and ecologically significant protozoa in soil, marine and freshwater ecosystems. [ 8 ] Soil-dwelling cercozoans are one of the dominant groups of free-living eukaryotic microorganisms found in temperate soils, accounting for around 30% of identifiable protozoan DNA in arid or semi-arid ...
The following is a list of the classes in each phylum of the kingdom Animalia. There are 107 classes of animals in 33 phyla in this list. However, different sources give different numbers of classes and phyla. For example, Protura, Diplura, and Collembola are often considered to be the three orders in the class Entognatha. This list should by ...