taxa (singular, taxon) named groups of organisms 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 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 clade monophyletic group (an ancestral species and all of its descendants) all of the taxa that possess a given synapomorphy, but not other taxa 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 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... plesiomorphy an "ancestral", "less specialized", or "primitive" character apomorphy a "derived", "specialized", or "advanced" character outgroup comparison a means of determining which character in a transformation series is a plesiomorphy and which is an apomorphy outgroup the plesiomorphic character state the most closely related taxon to, but not the ancestor of, the set of taxa under study ingroup the taxon under study synapomorphy shared derived character an apomorphy that occurs in two or more taxa autapomorphy an apomorphy that occurs in only one taxon demonstrate the uniqueness of taxa, but they don't help identify clades paraphyletic group consists of an ancestor and some of its descendants an incomplete clade, defined by the absence of at least one character 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 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 parsimony the shorter tree or the one with the fewest changes this one wins node most recent common ancestor of 2 lineages homoplasy anything that makes your tree more complicated, or adds a step; like convergent evolution or losing a trait