Taxonomy Vocabulary

taxon:the general term for any systematic category:
Domain Eukaryota
Kingdom Plantae
Division/Phylum -phyta
Class -ae
Order -ales
Family -aceae
Genus + specific-epithet = Binomial
Variety, etc.
incertae sedis:of uncertain position

biosystematics:study of variation and evolution at the species and infraspecific taxa
classification:assignment of plants to groups within a hierarchy of ranks based on structure, origins, and other characteristics
nomenclature:a system of names for the various taxa, especially including the species binomial
phylogeny:a reconstruction of evolutionary genealogy, descent from common ancestors
phylosystematics:study of phylogeny and classification at taxa of genus and above

apomorphic:derived character states
autapomorphic:character states exclusive to a particular taxon
plesiomorphic:old, patristic, or primitive character states
synapomorphic:shared derived character states

polarity:the understood direction from plesiomorphic state to apomorphic state often determined by stratigraphy (fossil analysis), ontogeny (recapitulates phylogeny), out-group comparison, etc.

parsimony:the simplest explanation, the shortest cladogram, the fewest steps in evolution, fewest homoplasies
homoplasy:independent evolution of identical character states
convergence:evolution of superficially similar features in unrelated taxa
parallelism:evolution of similar features in related taxa
reversal:loss of an apomorphic state, often reverting to a plesiomorphic state

anagenesis:divergence (growth) of branches in phylogeny
cladogenesis:formation of branches in phylogeny

cladistics:a method used to determine branching patterns in phylogeny involving study of synapomorphic character states
phenetics:a method used to determine natural relationships based on similarity of unweighted characters; numerical taxonomy

cladogram:a tree diagram expressing a hypothesis about branching in phylogeny
dendrogram:a tree-like diagram consisting of node and internodes
phylogram:a tree diagram expressing a hypothesis about branching and anagenesis in phylogeny

holophyletic=clade:all descendants from a common ancestor
monophyletic:descended from a single ancestor (natural assemblage)
paraphyletic:ancestral taxa
polyphyletic:a group having several different ancestors (unnatural assemblage)

This page © Ross E. Koning 1994.

The CBE citation style for this page would be: Koning, Ross E. 1994. "Taxonomy Vocabulary". Plant Physiology Website. (your visit date).

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