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In phylogenetics, a plesiomorphy ("near form") and symplesiomorphy are synonyms for an ancestral character shared by all members of a clade, which does not distinguish the clade from other clades. Plesiomorphy, symplesiomorphy, apomorphy, and synapomorphy all mean a trait shared between species because they share an ancestral species.
A plesiomorphy ("close form") or ancestral state is a character state that a taxon has retained from its ancestors. When two or more taxa that are not nested within each other share a plesiomorphy, it is a symplesiomorphy (from syn-, "together"). Symplesiomorphies do not mean that the taxa that exhibit that character state are necessarily ...
Pseudoplesiomorphy – a trait that cannot be identified as either a plesiomorphy or an apomorphy that is a reversal. [15] Reversal – a loss of derived trait present in ancestor and the reestablishment of a plesiomorphic trait. Convergence – independent evolution of a similar trait in two or more taxa. Apomorphy – a derived trait.
The terms "plesiomorphy" and "apomorphy" are typically used in the technical literature: for example, when a plesiomorphic trait is shared by more than one member of a clade, the trait is called a symplesiomorphy, that is, a shared primitive trait; a shared derived trait is a synapomorphy.
The publication of Darwin's theory of evolution in 1859 gave this view increasing weight. In 1876 Thomas Henry Huxley , an early advocate of evolutionary theory, proposed a revised taxonomy based on a concept strongly resembling clades, [ 7 ] although the term clade itself would not be coined until 1957 by his grandson, Julian Huxley .
Taxonomy (Greek language τάξις, taxis = 'order', 'arrangement' + νόμος, nomos = 'law' or 'science') is the classification, identification and naming of organisms. . It is usually richly informed by phylogenetics, but remains a methodologically and logically distinct discipline.
Texas executed Death Row inmate Richard Lee Tabler on Thursday, 20 years after he fatally shot four people in what he described as a fit of rage.. Texas used a lethal injection of pentobarbital to ...
A phylogenetic tree, phylogeny or evolutionary tree is a graphical representation which shows the evolutionary history between a set of species or taxa during a specific time. [ 1 ] [ 2 ] In other words, it is a branching diagram or a tree showing the evolutionary relationships among various biological species or other entities based upon ...