Five kingdoms and three domainsSpec 4.7
In short
Organisms were traditionally classified into five kingdoms: animals, plants, fungi, protists and prokaryotes. Improved genetic analysis showed that the prokaryotes are not all closely related, so a system of three domains was introduced above the kingdoms. The three domains are Archaea, Bacteria and Eukarya, which includes all organisms with a nucleus.
Living things were traditionally sorted into five kingdoms: animals, plants, fungi, protists and prokaryotes. This was based on the structure and features of organisms that could be observed.
Improved methods of genetic analysis (comparing the genetic material of different organisms) showed that the prokaryotes are not all closely related. This led to a new system of three domains, which sits above the kingdoms.
| Domain | Organisms |
|---|---|
| Archaea | Prokaryotes that are genetically very different from bacteria |
| Bacteria | 'True' bacteria (prokaryotes) |
| Eukarya | Organisms with a nucleus: protists, fungi, plants and animals |
Explain the change using the key idea: genetic analysis revealed differences that observation of structure could not, so the prokaryotes were split into two domains.
Quick check
Which is older, Ardi or Lucy?
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Ardi (4.4 million years ago; Lucy is 3.2 million years ago).
How are stone tools dated from their environment?
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By finding the age of the rock layer, or materials found with them, in which they were buried.
Name the five kingdoms.
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Animals, plants, fungi, protists and prokaryotes.
What are the three domains?
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Archaea, Bacteria and Eukarya.
Written and checked against the Edexcel GCSE Combined Science (1SC0) specification · Updated October 2026