Explain how the binomial nomenclature system used in the classification of organisms reflects evolutionary relationships between species within the same genus.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Binomial nomenclature gives each species a two‑part Latin name: the genus followed by the species epithet.
Species that share the same genus name are grouped together because they share a more recent common ancestor with each other than with species in other genera.
Thus the shared genus name signals a closer evolutionary or phylogenetic relationship (greater homology) between species within that genus compared to species in different genera.
Modern taxonomy uses a phylogenetic/cladistic approach, so the genus grouping is based on molecular and/or morphological evidence of shared derived characters (synapomorphies) rather than superficial similarity alone.
Species that share the same genus name are grouped together because they share a more recent common ancestor with each other than with species in other genera.
Thus the shared genus name signals a closer evolutionary or phylogenetic relationship (greater homology) between species within that genus compared to species in different genera.
Modern taxonomy uses a phylogenetic/cladistic approach, so the genus grouping is based on molecular and/or morphological evidence of shared derived characters (synapomorphies) rather than superficial similarity alone.
Examiner tips
- Use the exact phrase "binomial nomenclature" and "genus". Show that shared genus means a more recent common ancestor. Mention phylogenetic/cladistic evidence. Keep answer concise to fit 4 marks.
Common mistakes
- Confusing species epithet with genus. Assuming binomial names are arbitrary. Ignoring the evolutionary basis of the genus grouping.
Mark scheme (4 marks)
- Binomial nomenclature assigns each species a two-part Latin (or Latinised) name consisting of the genus name followed by the species name/epithet.
- Species sharing the same genus name are placed in the same genus because they share a more recent common ancestor with each other than with species in other genera.
- The shared genus name therefore indicates a closer evolutionary/phylogenetic relationship (greater homology) between species within that genus compared to species in different genera.
- Modern taxonomy (phylogenetic/cladistic approach) aims to ensure classification reflects evolutionary history, so the genus grouping is based on molecular and/or morphological evidence of shared derived characters (synapomorphies) rather than superficial appearance alone.
Key terms in this question
Related
- All IB DP Biology Higher Level (2023 syllabus) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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