Chapter 18 terms

character

quantifiable, heritable characteristic or trait

clade

a group whose members share one or more defining derived traits

cladistics

method of making hypotheses about evolutionary relationships among clades

cladogram

evolutionary tree diagram that shows evolutionary relationships among clades

derived trait

a novel trait present in a clade but not in the clades ancestors

evolutionary tree

diagram showing evolutionary relationships

monophyletic group

an ancestor in which a derived trait evolved, together with all of its descendants

sister groups

the two lineages that emerge from a node on a cladogram

analogous structures

similar body structures that evolved separately in different lineages

homologous structures

body parts or structures that are similar in different lineages because they evolved in a common ancestor

morphological convergence

evolutionary pattern in which similar body parts evolve separately in different lineages

morphological divergence

evolutionary pattern in which a body part of an ancestor changes in its descendants

molecular clock

using molecular change to estimate how long ago two lineages diverged