Describe how organisms are classified using the Linnaean taxonomic hierarchy, and explain why organisms in the same genus are more closely related than organisms that only share the same order.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (5 marks)
The Linnaean hierarchy is a system of named taxonomic groups.
1. Kingdom
2. Phylum
3. Class
4. Order
5. Family
6. Genus
7. Species
As you move down the ranks the groups become smaller and contain fewer organisms.
Organisms that share a genus have more characteristics in common than those that only share an order, because they are more closely related.
They also have a more recent common ancestor, which explains the greater similarity.
1. Kingdom
2. Phylum
3. Class
4. Order
5. Family
6. Genus
7. Species
As you move down the ranks the groups become smaller and contain fewer organisms.
Organisms that share a genus have more characteristics in common than those that only share an order, because they are more closely related.
They also have a more recent common ancestor, which explains the greater similarity.
Examiner tips
- Use the exact rank names in the correct order; a short list is enough.
- Show the hierarchy is nested – each lower rank is a subset of the one above.
- Explain that a shared genus means a more recent common ancestor and more shared traits.
Common mistakes
- Listing the ranks in the wrong order or omitting a rank.
- Confusing the number of ranks with the number of points to be awarded.
- Failing to mention the recent common ancestor as the reason for closer relatedness.
Mark scheme (5 marks)
- The Linnaean hierarchy consists of named taxonomic groups / taxa
- Correct sequence of at least four consecutive ranks stated in the correct order (e.g. kingdom → phylum → class → order → family → genus → species)
- As you move down the hierarchy the groups become smaller / contain fewer organisms
- Organisms in the same genus share more characteristics / features in common than those only sharing an order
- Organisms in the same genus have a more recent common ancestor than those only in the same order
Key terms in this question
Related
- All AQA A-Level Biology (7402) revision notes →
- How to answer a "Describe and Explain" question →
- Decode the mark scheme abbreviations →
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