This guide covers IGCSE Biology classification and identification keys. You will revise dichotomous keys (using and constructing), binomial naming (Genus species), and how to identify organisms from features.

Key concepts to revise

• Dichotomous key – Pairs of yes/no questions that lead to identification. Each step divides organisms into two groups.
• Using a key – Follow each step; write the organism name exactly as in the key.
• Constructing a key – Use clear, visible features; one feature per step; same type of feature in each pair (e.g. has wings vs no wings).
• Binomial naming – Genus (capital) and species (lowercase); italic or underlined (e.g. Homo sapiens).

Exam tips and command words

• Use the key – Follow each step in order; write the final name exactly as given.
• Construct a key – Use 4–5 organisms; write pairs of statements; avoid vague or overlapping choices.
• State – The genus and species of an organism from a key.
• Explain – Why binomial naming is used (universal; avoids confusion; shows relationships).

Common mistakes

• Using vague choices in a key (e.g. big vs small without a clear divide).
• Writing both genus and species with capital letters, or not italicising/underlining.
• Overlapping choices (e.g. green and yellow in one step; organism is both).

Revision checklist

• Use a dichotomous key to identify an organism from a list of features.
• Construct a simple dichotomous key from 4–5 organisms.
• Write a binomial name correctly (Genus species; italics or underline).
• State why binomial naming is used (universal; shows relationships).

Next steps

Book a free trial with an IGCSE Biology tutor to practise keys and classification, or explore Tutopiya’s learning portal for more revision resources.