Cladistics tests whether traditional taxa match evolutionary relationships, revealing when similar morphology results from convergence rather than shared ancestry alone.
Coverage 2018–2018 · Updated 15 Jul 2026
A classification is stronger when morphology, molecular sequences, fossils and geography support the same branching pattern.
Researchers compare competing trees, identify conflicts and ask whether differences reflect sampling, convergent traits, gene transfer or different evolutionary histories. Agreement increases confidence but does not remove uncertainty.
Test correspondence by:
If a morphology tree and several gene trees place two taxa together, the relationship is better supported than if only one superficial trait does.
One matching feature cannot override a broad, well-sampled conflict without explaining why.
This objective is assessed through multiple choice.
Build the answer around this relationship: Cladistics can test whether traditional taxa reflect evolutionary ancestry.
Representative question
The figwort family is a large one consisting of many flowering plants that look similar. For what reason have some members of the family been reclassified into a new family?
Cladistic analysis shows the differences in flower structure to be fewer than the shared similarities.
DNA analysis shows the similarities in flower shape to be a product of convergent evolution.
DNA analysis shows some of the families to have suffered recent mutations in only one gene.
DNA analysis shows the similarities between the seed dispersal strategies to be a product of divergent evolution.
A3.2 exam answers are strongest when they sound like evidence arguments. Classification organizes diversity, but fixed ranks and morphology can mislead. Evolutionary classification should match phylogeny using monophyletic clades supported by synapomorphies. Molecular clocks estimate divergence time from calibrated sequence differences. Cladograms are built from aligned sequence data and interpreted by nodes, not tip positions. Cladistics can reclassify old taxa, and rRNA evidence supports the three-domain system.
