Phylogeny is the evolutionary history of related groups of organisms. organisms are grouped into taxa based on homologous characteristics, shared traits that result from common ancestry. which statement is true? a. the term 'monophyletic' refers to a taxon that includes an ancestral species and all of its descendants. b. homologous structures look the same and serve the same function, but they differ in evolutionary origin and structure. c. ancestral traits are always simpler than derived traits.