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Emil Hans Willi Hennig (20 April 1913 – 5 November 1976) was a German biologist and zoologist who is considered the founder of phylogenetic systematics, otherwise known as cladistics. [ 1 ] [ 2 ] [ 3 ] In 1945 as a prisoner of war , Hennig began work on his theory of cladistics, which he published in German in 1950, with a substantially ...
Cladistics (/ k l ə ˈ d ɪ s t ɪ k s / klə-DIST-iks; from Ancient Greek κλάδος kládos 'branch') [1] is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry.
A cladogram (from Greek clados "branch" and gramma "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to descendants, nor does it show how much they have changed, so many differing evolutionary trees can be ...
This is largely what is meant by the term 'Linnaean taxonomy' when used in a modern context. In cladistics, originating in the work of Willi Hennig, 1950 onwards, each taxon is grouped so as to include the common ancestor of the group's members (and thus to avoid phylogeny).
A simple cladogram showing the evolutionary relationships between four species: A, B, C, and D. Here, Species A is the outgroup, and Species B, C, and D form the ingroup. In cladistics or phylogenetics, an outgroup [1] is a more distantly related group of organisms that serves as a reference group when determining the evolutionary relationships of the ingroup, the set of organisms under study ...
Gauthier is the son of Edward Paul Gauthier and Patricia Marie Grogan. [citation needed] He received a B.S. degree in zoology at San Diego State University in 1973, a master's in biological science at the same institute in 1980, and a PhD in paleontology from the University of California, Berkeley, in 1984. [1]
The Willi Hennig Society was founded on a philosophical division among systematic biologists in the late 1970s. A debate created the rift between pheneticists who advocated for statistical or numerical methods that grouped taxa by overall similarity in taxonomy and systematic biologists who adopted a strict cladistic approach to taxonomy, recognizing groups by shared, derived characters alone.
The term sister group is used in phylogenetic analysis, however, only groups identified in the analysis are labeled as "sister groups".. An example is birds, whose commonly cited living sister group is the crocodiles, but that is true only when discussing extant organisms; [3] [4] when other, extinct groups are considered, the relationship between birds and crocodiles appears distant.