5.4 Cladistics

Understandings

A clade is a group of organisms that have evolved from a common ancestor

Evidence for which species are part of a clade can be obtained from the base sequences of a gene or the corresponding amino acid sequence of a protein.

Sequence differences accumulate gradually so there is a positive correlation between the number of differences between two species and the time since they diverged from a common ancestor.

Traits can be analogous or homologous.

Cladograms are tree diagrams that show the most probable sequence of divergence in clades.

Applications and skills

Cladograms including humans and other primates.

Reclassification of the figwort family using evidence from cladistics.

Analysis of cladograms to deduce evolutionary relationships.