Systematics Vocab

systematics

the reconstruction and study of evolutionary relationships

outgroup

taxa that are closely related, but not direct members of the group being studied

clade

contains species that share a common ancestor

synapomorphy

a derived character shared by clade members

node

a point of divergence

principle of parsimony

the phylogeny that requires the fewest evolutionary events is considered to be the best hypothesis of the relationship between the taxa being studied

derived

similarity between species that is inherited from the most recent ancestor

ancestral

similarity that arose prior to the common ancestor is returned

homoplasy

refers to a shared character state that has not been inherited from a common ancestor - can result from convergent evolution or evolutionary reversal

classification

is the practice of placing species and groups of species into the taxonomic hierarchy

monophyletic group

includes the most recent common ancestor and all of its descendants

paraphyletic group

includes the most recent common ancestor but not ALL the descendants

polyphyletic group

does not contain the most recent common ancestor for all the members in the group

homologous structures

are derived from the same body part in a common ancestor

homoplastic structures

are derived from different ancestral sources

species richness

refers to the number of species per clade

convergent evolution

the independent development of similar traits in distantly related organisms, driven by adaptation to similar environments or ecological niches