Classification of living organisms: Linnaeus classified living things into kingdom, phylum, class, order, family, genus and species. Organisms are named by the binomial system of genus and species.

The idea

Linnaeus arranged living things into a hierarchy of seven groups: kingdom, phylum, class, order, family, genus and species. Each level contains fewer organisms with more shared features. For example, all animals are in the same kingdom, but dogs, wolves, coyotes and jackals share the genus Canis. The binomial system gives every species a two-part scientific name: the genus name followed by the species name. Human beings are Homo sapiens, where Homo is the genus and sapiens is the species. Scientific names are written in italics, with the genus starting with a capital letter and the species starting with a lower-case letter. This universal naming system avoids confusion caused by common names and allows scientists worldwide to communicate clearly.

What earns the marks

• The Linnaean hierarchy has seven levels: kingdom, phylum, class, order, family, genus and species.
• Each level down the hierarchy contains organisms with more shared characteristics.
• The binomial system names an organism using its genus and species.
• The genus name is written first and begins with a capital letter; the species name follows and begins with a lower-case letter.
• Scientific names are italicised or underlined.
• The binomial system provides a universal name for each species, avoiding confusion with common names.

Common mistakes and how to put them right

• Writing the species name with a capital letter.

  Put it right: Only the genus name starts with a capital letter.

• Reversing the order of genus and species.

  Put it right: Genus comes first, then species.

• Forgetting to italicise or underline scientific names.

  Put it right: Use italics in printed text or underline when handwriting.

Exam tips

• Memorise the hierarchy order using a mnemonic such as 'King Philip Came Over For Good Soup'.
• When writing a scientific name, check that the genus is capitalised and the species is lower case.
• If asked to name an organism using the binomial system, give both parts and format them correctly.