Phylogeny
From Palaeos
Phylogeny or phylogenesis (from the Greek: phylon = tribe, race and genesis = birth) is the origin and evolution of a set of organisms, usually a set of species. Phylogenetics is the science of understanding phylogenetic relationships. This constitutes a major task of systematics, which is to determine the ancestral relationships among known species (both living and extinct).
Phylogeny describes the history or development of a race, species, or higher taxonomic grade of organisms, as opposed to ontogeny, which describeds the developmet of a single organism. It refers to the evolutionary relationships among organisms; the "family tree" of organisms as they evolve through geological time
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[edit] Phylogeny and Ontogeny
During the late 19th century, Ernst Haeckel's recapitulation theory, or biogenetic law, was widely accepted. This theory was often expressed as "ontogeny recapitulates phylogeny", i.e. the development of an organism exactly mirrors the evolutionary development of the species. The early version of this hypothesis has since been rejected as being oversimplified. However, most modern biologists recognize numerous connections between ontogeny and phylogeny, explain them using evolutionary theory, or view them as supporting evidence for that theory.
[edit] Phylogeny and Taxonomy
Phylogeny (the history of life) and Taxonomy (the classification of life) are not the same, although there is an overlap. Systematics is the application of phylogeny to taxonomy (and vice-versa)
[edit] Phylogeny and Cladistics
With cladistic revolution, phylogeny came to be interpeted as the pattern of lineage branching produced by the evolutionary history of the organisms considered.
However, according to O'Keefe & Sander (1999)
- A phylogeny is 'a diagram (not necessarily branching!) depicting the actual pattern of ancestry and descent among a series of taxa,' or a cladogram plus a time component and hypotheses of ancestor-descendant relationship.
Thus although cladistics is itself referred to as "phylogenetic systematics", a cladistic method and cladograms are an essential element in reconstructing any phylogeny, a cladogram itself is not the same as a phylogenetic tree. However in popular palaeo parlance, these trees are generally (if misleadingly) referred to as "cladograms". A more accurate term would be dendrogram, or an ascii phylogeny.
In Palaeos org, we make extensive use of such phylogenetic trees (some with timescales attached and others not) to chart the family history of life on Earth.
[edit] Credits
MAK061009
