Classification

This lesson covers the classification of living organisms — the system used to group and name species — as required by the Edexcel GCSE Combined Science specification (1SC0). You need to understand the Linnaean system, the three-domain system, binomial naming and how evolutionary trees show relationships between organisms.

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Why Do We Classify Organisms?

Classification is the process of sorting living organisms into groups based on their shared characteristics. Scientists classify organisms to:

• Organise the enormous diversity of life (over 8 million known species).
• Show evolutionary relationships between organisms.
• Make it easier to identify and study organisms.
• Allow scientists worldwide to use a universal system of naming.

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The Linnaean System

Carl Linnaeus (1735) developed the first widely accepted classification system. He grouped organisms into a hierarchy of increasingly specific categories:

Level	Example (Human)	Example (Domestic dog)
Kingdom	Animalia	Animalia
Phylum	Chordata	Chordata
Class	Mammalia	Mammalia
Order	Primates	Carnivora
Family	Hominidae	Canidae
Genus	Homo	Canis
Species	sapiens	familiaris