Revision notes · Inheritance, variation and evolution
Classification of living organisms
Classification of living organisms4.6.4
Definition: Classification is the organisation of living organisms into groups based on their structures and characteristics.
Organisms are categorised using the traditional Linnaean system and the modern three-domain system to reflect evolutionary relationships.
- •Carl Linnaeus classified organisms into a hierarchy: Kingdom, Phylum, Class, Order, Family, Genus, and Species.
- •Organisms are named internationally using the binomial system, which combines the genus (capitalised) and species (lowercase).
- •Carl Woese introduced the three-domain system based on chemical analysis of RNA and cellular biochemistry.
- •Evolutionary trees are created using classification and fossil data to map out shared common ancestors and relationships between species.
| Domain | Description |
|---|---|
| Archaea | Primitive bacteria, usually found in extreme conditions |
| Bacteria | True bacteria |
| Eukaryota | Protists, fungi, plants and animals |
⚠️ Common mistake: Capitalising the species name in binomial titles, or confusing Archaea with true Bacteria.
🧠 Remember: King Philip Came Over For Good Soup (Kingdom, Phylum, Class, Order, Family, Genus, Species).
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