Cladistics

cladisticcladistic analysiscladeapomorphsister groupcladisticallynode-based taxonphylogenetic analysissisterphylogenetic systematics
Cladistics (, from Greek κλάδος, kládos, "branch") is an approach to biological classification in which organisms are categorized in groups ("clades") based on the most recent common ancestor.wikipedia
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Paraphyly

paraphyleticembedded*
Many of these terms are normally used paraphyletically, outside of cladistics, e.g. as a 'grade'.
These terms were developed during the debates of the 1960s and 1970s accompanying the rise of cladistics.

Willi Hennig

HennigE. H. W. HennigEmil Hans Willi Hennig
The original methods used in cladistic analysis and the school of taxonomy derived from the work of the German entomologist Willi Hennig, who referred to it as phylogenetic systematics (also the title of his 1966 book); the terms "cladistics" and "clade" were popularized by other researchers.
Emil Hans Willi Hennig (April 20, 1913 – November 5, 1976) was a German biologist who is considered the founder of phylogenetic systematics, also known as cladistics.

Phylogenetics

phylogeneticphylogenetic analysisphylogenetically
Cladistics in the original sense refers to a particular set of methods used in phylogenetic analysis, although it is now sometimes used to refer to the whole field.
The degree to which taxonomies depend on phylogenies (or classification depends on evolutionary development) differs depending on the school of taxonomy: phenetics ignores phylogeny altogether, trying to represent the similarity between organisms instead; cladistics (phylogenetic systematics) tries to reproduce phylogeny in its classification without loss of information; evolutionary taxonomy tries to find a compromise between them.

Phenetics

pheneticpheneticallyphenetic analyses
From the time of his original formulation until the end of the 1970s, cladistics competed as an analytical and philosophical approach to systematics with phenetics and so-called evolutionary taxonomy.
Phenetics has largely been superseded by cladistics for research into evolutionary relationships among species.

Clade

cladesgroupcladistic
Cladistics (, from Greek κλάδος, kládos, "branch") is an approach to biological classification in which organisms are categorized in groups ("clades") based on the most recent common ancestor. The term "clade" was introduced in 1958 by Julian Huxley after having been coined by Lucien Cuénot in 1940, "cladogenesis" in 1958, "cladistic" by Cain and Harrison in 1960, "cladist" (for an adherent of Hennig's school) by Mayr in 1965, and "cladistics" in 1966.
German biologist Emil Hans Willi Hennig (1913 – 1976) is considered to be the founder of cladistics.

Lemur

lemursLemuroideaLemurs of Madagascar
The cladogram to the right represents the current universally accepted hypothesis that all primates, including strepsirrhines like the lemurs and lorises, had a common ancestor all of whose descendants were primates, and so form a clade; the name Primates is therefore recognized for this clade.
Like other strepsirrhine primates, such as lorises, pottos, and galagos, they share ancestral (or plesiomorphic) traits with early primates.

Arthur Cain

CainA.J. CainArthur James Cain
The term "clade" was introduced in 1958 by Julian Huxley after having been coined by Lucien Cuénot in 1940, "cladogenesis" in 1958, "cladistic" by Cain and Harrison in 1960, "cladist" (for an adherent of Hennig's school) by Mayr in 1965, and "cladistics" in 1966.
He made important contributions to the theory and practice of taxonomy, the problems of homology, phyletic weighting and taxonomic importance, on the status of the genus, and on the relevance of natural selection to our understanding of variation between taxonomic categories.

Monophyly

monophyleticmonophyletic groupnon-monophyletic
In cladistics, a monophyletic group, or clade, is a group of organisms that consists of all the descendants of a common ancestor (or more precisely ancestral population).

Julian Huxley

Sir Julian HuxleyJulian Sorell HuxleyJulian S. Huxley
The term "clade" was introduced in 1958 by Julian Huxley after having been coined by Lucien Cuénot in 1940, "cladogenesis" in 1958, "cladistic" by Cain and Harrison in 1960, "cladist" (for an adherent of Hennig's school) by Mayr in 1965, and "cladistics" in 1966.
Cladists, for example, were (and are) strongly against any suggestion that a group could be scientifically described as 'advanced' and others as 'primitive.' For them, and especially for the radical group of transformed cladists, there is no such thing as an advanced group, they are derived or apomorphic.

Primate

primatesnon-human primatesnon-human primate
The cladogram to the right represents the current universally accepted hypothesis that all primates, including strepsirrhines like the lemurs and lorises, had a common ancestor all of whose descendants were primates, and so form a clade; the name Primates is therefore recognized for this clade.
By modern cladistic reckoning, the order Primates is monophyletic.

Numerical taxonomy

numerical taxonomiststaxonometric
Phenetics was championed at this time by the numerical taxonomists Peter Sneath and Robert Sokal, and evolutionary taxonomy by Ernst Mayr.
They divided the field into phenetics in which classifications are formed based on the patterns of overall similarities and cladistics in which classifications are based on the branching patterns of the estimated evolutionary history of the taxa.

Transformed cladistics

Transformed cladistics arose in the late 1970s in an attempt to resolve some of these problems by removing phylogeny from cladistic analysis, but it has remained unpopular.
Transformed cladistics, also known as pattern cladistics is an epistemological approach to the cladistic method of phylogenetic inference and classification that makes no a priori assumptions about common ancestry.

Cladogram

cladogramscladistic analysiscladistic interpretation
The outcome of a cladistic analysis is a cladogram – a tree-shaped diagram (dendrogram) that is interpreted to represent the best hypothesis of phylogenetic relationships.
A cladogram (from Greek clados "branch" and gramma "character") is a diagram used in cladistics to show relations among organisms.

Phylogenetic nomenclature

stem-based taxonphylogenetic taxonomyphylogenetic classification
(See phylogenetic nomenclature.)
It spread together with the methods for discovering clades (cladistics) and is an integral part of phylogenetic systematics (see above).

Tetrapod

tetrapodsTetrapodaland vertebrates
Newer taxonomy is frequently based on cladistics instead, giving a variable number of major "branches" (clades) of the tetrapod family tree.

Homology (biology)

homologoushomologyhomolog
Decisions as to whether particular character states are homologous, a precondition of their being synapomorphies, have been challenged as involving circular reasoning and subjective judgements.
As implied in this definition, many cladists consider secondary homology to be synonymous with synapomorphy, a shared derived character or trait state that distinguishes a clade from other organisms.

Patrocladogram

A patrocladogram is a cladistic branching pattern that has been precisely modified by use of patristic distances (i.e., divergences between lineages); a type of phylogram.

Synapomorphy and apomorphy

derivedsynapomorphiessynapomorphy
Hypothesized relationships are typically based on shared derived characteristics (synapomorphies) that can be traced to the most recent common ancestor and are not present in more distant groups and ancestors.
So the concept can be understood as well in terms of "a character newer than" (autapomorphy) and "a character older than" (plesiomorphy) the apomorphy: mammary glands are evolutionarily newer than vertebral column, so mammary glands are an autapomorphy if vertebral column is an apomorphy, but if mammary glands are the apomorphy being considered then vertebral column is a plesiomorphy.

Computational phylogenetics

computational phylogeneticphylogenetic inferenceBayesian
Although traditionally such cladograms were generated largely on the basis of morphological characters and originally calculated by hand, genetic sequencing data and computational phylogenetics are now commonly used in phylogenetic analyses, and the parsimony criterion has been abandoned by many phylogeneticists in favor of more "sophisticated" but less parsimonious evolutionary models of character state transformation. This is similar to the traditional comparative method of historical linguistics, but is more explicit in its use of parsimony and allows much faster analysis of large datasets (computational phylogenetics).

Taxonomy (biology)

taxonomictaxonomytaxonomist
Cladistics (, from Greek κλάδος, kládos, "branch") is an approach to biological classification in which organisms are categorized in groups ("clades") based on the most recent common ancestor.
With the advent of such fields of study as phylogenetics, cladistics, and systematics, the Linnaean system has progressed to a system of modern biological classification based on the evolutionary relationships between organisms, both living and extinct.

Molecular phylogenetics

molecular phylogeneticmolecularmolecular phylogeny
Datasets are tables consisting of molecular, morphological, ethological and/or other characters and a list of operational taxonomic units (OTUs), which may be genes, individuals, populations, species, or larger taxa that are presumed to be monophyletic and therefore to form, all together, one large clade; phylogenetic analysis infers the branching pattern within that clade.
Molecular systematics is an essentially cladistic approach: it assumes that classification must correspond to phylogenetic descent, and that all valid taxa must be monophyletic.

Occam's razor

parsimonyparsimoniousOckham's razor
This is similar to the traditional comparative method of historical linguistics, but is more explicit in its use of parsimony and allows much faster analysis of large datasets (computational phylogenetics).
Cladograms are branching, tree-like structures used to represent hypotheses of relative degree of relationship, based on shared, derived character states.

Polytomy

polytomouspolytomiespentatomy
It is also possible that multiple surviving lineages are generated while interbreeding is still significantly occurring (polytomy).