Vertebrate Biology Chapter 1

Phylogeny

Hypothesis about evolutionary relationships among groups

Cladogram

Diagram to depict phylogenetic relationships

Apomorphy/Derived Trait

Novel feature that evolved once and is shared ONLY by the descendants of the ancestral species in which it first evolved

Synapomorphies

Shared derived traits

Plesiomorphies

Ancestral characters

Symplesiomorphies

Shared ancestral characters

Characters

Discrete

Qualitative character condition

Continuous

Quantitative character condition

Binary

When there is only two states that a character state can be in

Multistate

When there is multiple states that a character state can be in

Parsimonious

Requires the fewest evolutionary steps (least changes)

Sister Group

Most closely related taxon to a taxon

Paraphyletic Group

Organisms grouped together, but does not include all the descendants from most recent common ancestor

Polytomy

Polyphyletic Group

Organisms that are grouped together, but do not share an immediate common ancestor

Monophyletic Group

Everything in the group is traced back to one node

Homologous Structures

Convergent Evolution

Natural selection causes body forms to converge on each other

Reversal

In determining phylogenetic relationships, convergent evolution where forms will reverse back to previous forms