Topics: Phylogenetics, Evolution, Phylogenetic tree Pages: 4 (1129 words) Published: March 12, 2013


In biology, phylogenetics is the study of evolutionary relationships among groups of organisms (e.g. species,populations), which are discovered through molecular sequencing data and morphological data matrices. The term phylogenetics derives from the Greek terms phylé and phylon , denoting "tribe", "clan", "race"] and the adjectival form, genetikós of the word genesis "origin", "source", "birth".The result of phylogenetic studies is a hypothesis about the evolutionary history of taxonomic groups: their phylogeny. Monophyletic

In common cladistic usage, a monophyletic group is a taxon (group of organisms) which forms a clade, meaning that it consists of a species and all its descendants. The term is synonymous with the uncommon termholophyly. Monophyletic groups are typically characterized by shared derived characteristics (synapomorphies). Monophyly is contrasted with the terms paraphyly and polyphyly, which are most easily understood from the second diagram in this article. In current usage, a paraphyletic group consists of all of the descendants of a possibly hypothetical closest common ancestor minus one or more monophyletic groups (most usually one). A paraphyletic group is thus 'nearly' monophyletic (consistent with the meaning of the prefix 'para', namely 'near' or 'alongside'.) A polyphyletic group is any group other than a monophyletic group or a paraphyletic group, which like a paraphyletic group contains only some of the descendants of their closest common ancestor, but unlike a paraphyletic group is not characterized by the missing descendants forming one (or more) monophyletic groups.


A polyphyletic (Greek for "of many races") group is one characterized by one or more homoplasies: character states which have converged or reverted so as to appear to be the same but which have not been inherited from common ancestors.For example, the group consisting of warm-blooded animals is polyphyletic, because it contains...
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