5.4  Cladistics

big ninja

Essential Idea:

The ancestry of groups of species can be deduced

by comparing their base or amino acid sequences


  • A clade is a group of organisms that have evolved from a common ancestor
  • Cladograms are tree diagrams that show the most probable sequence of divergence in clades
  • Evidence for which species are part of a clade can be obtained from the base sequence 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
  • Evidence from cladistics has shown that classification of some groups based on structure did not correspond with the evolutionary origins of a group or species


  • Cladograms including humans and other primates
  • Reclassification of the figwort family using evidence from cladistics


  • Analysis of cladograms to deduce evolutionary relationships