Compare the Linnaean system of classification with the three-domain system developed by Carl Woese.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
The Linnaean system classifies organisms into a hierarchy of kingdom, phylum, class, order, family, genus and species. It groups all bacteria and archaea together within the kingdom Bacteria, so it does not recognise a separate domain for archaea.
The three‑domain system, developed by Carl Woese, divides life into three domains: Archaea, Bacteria and Eukaryota. It separates archaea from other bacteria.
The Linnaean system is based on observable physical characteristics, while the three‑domain system was developed using molecular and genetic evidence such as DNA and RNA analysis.
The three‑domain system, developed by Carl Woese, divides life into three domains: Archaea, Bacteria and Eukaryota. It separates archaea from other bacteria.
The Linnaean system is based on observable physical characteristics, while the three‑domain system was developed using molecular and genetic evidence such as DNA and RNA analysis.
Examiner tips
- Use the word ‘hierarchy’ to show the Linnaean levels; mention the three domains explicitly; contrast the basis of classification (physical vs. genetic).
- Include the key difference that archaea are not separated in Linnaean but are in the three‑domain system.
Mark scheme (4 marks)
- The Linnaean system organises organisms into kingdom, phylum, class, order, family, genus and species
- The three-domain system groups all organisms into three domains: Archaea, Bacteria and Eukaryota
- The Linnaean system does not separate Archaea from other bacteria / treats Archaea and Bacteria as the same group, whereas the three-domain system separates them
- The three-domain system was developed using molecular / genetic evidence (e.g. DNA / RNA analysis), whereas the Linnaean system was based on physical characteristics / observable features
Key terms in this question
Linnaean system · three-domain system
Related
- Revision notes: Classification of living organisms →
- How to answer a "Compare" question →
- Decode the mark scheme abbreviations →
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