Chapter 18 Flashcards
Phylogeny
hereditary relationships of any group of organisms
Taxonomy (Taxa)
classification; any taxonomic group including species, genus, family, etc
Systematics
way of understanding organisms evolutionary lines; system of names: nomenclature
Cladistics
the study of phylogeny centered on examining the similarity of one species to others; proportion of common characteristics
Cladogram
a branching diagram showing the phylogenic relationships of several or many taxa
Clade
any ancestor (any node) and all of the branches that lead from it
Plesiomorphy (ancestral condition)
characters that were present in a group’s ancestors; ancestral or derived trait
Symplesiomorphy
ancestral characters shared by two or more modern groups; shared primitive traits; not usually helpful in analyzing primitive traits
Apomorphy
derived characters; new characters that were not present in ancestors
Synapomorphy
are shared derived characters; they are derived characters that occur in two or more modern groups because those groups are closely related; they share a recent ancestor that had this character and they have inherited it
Homoplasy (analogous)
the result of convergent evolution; characters that appear to be the same in two or more groups but in fact they did not evolve from the same ancestral character
Monophyletic
includes a group of organisms descended from a single ancestor
Paraphyletic
a group that does not contain all the descendants of the most recent common ancestor
Polyphyletic
composed of unrelated organisms descended from more than one ancestor.
Principle of Parsimony
the concept of minimum complexity; the simplest hypothesis that explains several observations is the most parsimonious; in cladistics, a cladogram with the least number of steps is the most parsimonious
