Describe how the work of Carl Woese led to a new system of classification, and explain why other scientists were reluctant to accept his ideas at first.

AQA GCSE Biology (8461) — 4.6.3 The development of understanding of genetics and evolution · Describe · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Woese developed a three‑domain system of classification.
The three domains are Archaea, Bacteria and Eukaryota.
He used molecular evidence – the base sequences of ribosomal RNA – to group organisms.
Other scientists were reluctant to accept his ideas because it conflicted with the long‑standing Linnaean system.

Examiner tips

  • Use the exact terminology: three‑domain system, Archaea, Bacteria, Eukaryota, ribosomal RNA.
  • Show the link between molecular evidence and the new classification.
  • Mention the conflict with the traditional Linnaean system.
  • Keep the answer concise – 4 marks, one point each.

Common mistakes

  • Using ‘DNA’ instead of ‘ribosomal RNA’ as the evidence.
  • Failing to name all three domains.
  • Claiming the new system was ‘better’ without noting the initial reluctance.

Mark scheme (4 marks)

  1. Woese developed the three-domain system of classification
  2. The three domains are Archaea, Bacteria and Eukaryota
  3. Woese used molecular evidence / RNA or DNA base sequences to group organisms
  4. Scientists were reluctant to accept his ideas because it conflicted with / challenged the accepted Linnaean system that had been used for a long time

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