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The kingdom-level classification of life is still widely employed as a useful way of grouping organisms, notwithstanding some problems with this approach: Kingdoms such as Protozoa represent grades rather than clades , and so are rejected by phylogenetic classification systems.
The basic ranks are species and genus. When an organism is given a species name it is assigned to a genus, and the genus name is part of the species name. The species name is also called a binomial, that is, a two-term name. For example, the zoological name for the human species is Homo sapiens. This is usually italicized in print or underlined ...
Linnaeus 1735 [1] Haeckel 1866 [2] Chatton 1925 [3] Copeland 1938 [4] Whittaker 1969 [5] Woese et al. 1990 [6] Cavalier-Smith 1998, [7] 2015 [8] 2 kingdoms 3 kingdoms 2 empires: 4 kingdoms: 5 kingdoms
1938 [5] [6] Whittaker 1969 [7] Woese et al. 1977 [8] [9] Woese et al. 1990 [10] Cavalier-Smith 1993 [11] [12] [13] Cavalier-Smith 1998 [14] [15] [16] Ruggiero et al. 2015 [17] — — 2 empires: 2 empires: 2 empires: 2 empires: 3 domains: 3 superkingdoms 2 empires: 2 superkingdoms: 2 kingdoms 3 kingdoms — 4 kingdoms: 5 kingdoms: 6 kingdoms ...
The science of classification, in biology the arrangement of organisms into a classification [4] "The science of classification as applied to living organisms, including the study of means of formation of species, etc." [5] "The analysis of an organism's characteristics for the purpose of classification" [6]
In 1987, Cavalier-Smith introduced a classification divided into two superkingdoms (Prokaryota and Eukaryota) and seven kingdoms, two prokaryotic kingdoms (Eubacteria and Archaebacteria) and five eukaryotic kingdoms (Protozoa, Chromista, Fungi, Plantae and Animalia). [48]
Halophiles (organisms that thrive in highly salty environments) and hyperthermophiles (organisms that thrive in extremely hot environments) are examples of Archaea. [1] Archaea are relatively small. They range from 0.1 μm to 15 μm diameter and up to 200 μm long, about the size of bacteria and the mitochondria found in eukaryotic cells.
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 ...