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taxa
(singular, taxon)
named groups of organisms
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phylogeny
- a diagram of evolutionary history that superficially resembles a cladogram
- has an absolute time axis
- instead of at the top, taxa are ordered vertically to indicate when they lived
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phylogenetic systematics or
cladistic analysis
- Hennig's method for ascertaining genealogies
- Each dichotomy marks the splitting and disappearance of an ancestral species and the formation of two daughter species
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clade
- monophyletic group
- (an ancestral species and all of its descendants)
- all of the taxa that possess a given synapomorphy, but not other taxa
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cladogram
- THIS IS AN HYPOTHESIS
- a branching diagram where all of the taxa under study are listed at the top, with intersecting lines, or branches, beneath them to illustrate their common ancestry relationships
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character states
- a feature that is an observable part or attribute of an organism, in it's different forms or appearances
- coded by assigning a number: 0, 1...
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plesiomorphy
an "ancestral", "less specialized", or "primitive" character
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apomorphy
a "derived", "specialized", or "advanced" character
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outgroup comparison
a means of determining which character in a transformation series is a plesiomorphy and which is an apomorphy
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outgroup
- the plesiomorphic character state
- the most closely related taxon to, but not the ancestor of, the set of taxa under study
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ingroup
the taxon under study
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synapomorphy
- shared derived character
- an apomorphy that occurs in two or more taxa
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autapomorphy
- an apomorphy that occurs in only one taxon
- demonstrate the uniqueness of taxa, but they don't help identify clades
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paraphyletic group
- consists of an ancestor and some of its descendants
- an incomplete clade, defined by the absence of at least one character
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polyphyletic groups
- two or more taxa, but not the common ancestor of those taxa
- defined by at least one similar character that evolved independently (by convergent or parallel evolution)
- they share some superficial similarity, not because they're closely related to one another
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phylogenetic trees
- are hypotheses about the evolutionary relationships among a group of organisms
- we develop these hypotheses by observing shared and/or unique traits (characters) in the taxa to be studied
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parsimony
- the shorter tree or the one with the fewest changes
- this one wins
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node
most recent common ancestor of 2 lineages
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homoplasy
anything that makes your tree more complicated, or adds a step; like convergent evolution or losing a trait
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