Explain how convergent evolution can complicate the classification of organisms and how cladistics addresses this problem.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Convergent evolution is the independent evolution of similar traits in unrelated lineages because of similar selection pressures.
These analogous (homoplastic) similarities can mislead traditional classification that relies on overall physical appearance or morphology, causing unrelated organisms to be grouped together.
Cladistics solves this by using shared derived characters (synapomorphies) that are inherited from a common ancestor, rather than overall similarity.
Because cladistics often employs molecular sequence data (DNA or protein), which are less prone to convergent evolution, it can more reliably determine true evolutionary relationships.
These analogous (homoplastic) similarities can mislead traditional classification that relies on overall physical appearance or morphology, causing unrelated organisms to be grouped together.
Cladistics solves this by using shared derived characters (synapomorphies) that are inherited from a common ancestor, rather than overall similarity.
Because cladistics often employs molecular sequence data (DNA or protein), which are less prone to convergent evolution, it can more reliably determine true evolutionary relationships.
Examiner tips
- Use the definition of convergent evolution first; then explain its effect on morphology-based classification; mention synapomorphies and molecular data; keep answer concise and use exam terminology.
Common mistakes
- Confusing homology with homoplasy; over‑emphasising morphology without linking to classification; not mentioning molecular data as a tool to avoid convergence.
Mark scheme (4 marks)
- Convergent evolution is the independent evolution of similar traits in unrelated lineages due to similar selection pressures.
- These analogous (homoplastic) similarities can lead to organisms being incorrectly grouped together in traditional classification based on physical appearance/morphology.
- Cladistics uses shared derived characters (synapomorphies) inherited from a common ancestor, rather than overall similarity, to group organisms.
- Molecular sequence data (e.g. DNA or protein sequences) used in cladistics are less likely to be affected by convergent evolution, allowing more reliable determination of true evolutionary relationships.
Key terms in this question
convergent evolution · cladistics
Related
- All IB DP Biology Standard Level (2023 syllabus) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
More Classification and cladistics questions
- Explain how cladistics differs from traditional Linnaean classification in the w…
- Explain the evidence from ribosomal RNA (rRNA) sequence comparisons that led to …
- Explain how the construction of a cladogram uses shared derived characters (syna…
- Explain why viruses are not classified within any of the recognised domains of l…
- Explain how molecular sequence data, such as base sequences of DNA or amino acid…
- Explain how the binomial system of nomenclature and the hierarchical classificat…