British Biology Olympiad · United Kingdom
The British Biology Olympiad is the first stage of the UK team selection for the International Biology Olympiad, run by UK Biology Competitions. It is open to students in their final two years of school and is sat in school. High scorers are invited to further theoretical and practical assessment, from which a team of four is chosen.
Pathway: BBO → further UK training and assessment → team of 4 → IBO
Weightings are the indicative proportions of the theory paper. Read them as where to spend your time, not as a promise about one year’s questions.
| Subject area | Share | What is actually asked |
|---|---|---|
| Animal anatomy and physiology | ~25% | The heaviest section. Comparative physiology across systems — circulation, gas exchange, osmoregulation, neural and endocrine control — asked at mechanism level rather than as labelled diagrams. |
| Cell biology | ~20% | Membranes and transport, bioenergetics, the cell cycle, signalling and molecular genetics. Where most students start, and where Campbell alone runs out first. |
| Genetics and evolution | ~20% | Mendelian and molecular genetics, linkage and mapping, population genetics and evolutionary mechanisms. The most problem-solving-heavy section on the paper. |
| Plant anatomy and physiology | ~15% | Tissue organisation, transport, photosynthesis in real depth, growth regulators and reproduction. Consistently the most under-prepared section. |
| Ecology | ~10% | Population and community dynamics, energy flow, nutrient cycling, and biodiversity. Quantitative more often than students expect. |
| Ethology | ~5% | Behavioural mechanisms, learning, and the evolutionary logic of behaviour. Small, tractable, and frequently left until it is too late. |
| Biosystematics | ~5% | Classification, phylogeny and the reasoning behind tree construction. Reward per hour is high because the scope is genuinely narrow. |
BBO does not publish a topic-by-topic syllabus with weightings. It is deliberately written to reward reading beyond the A-Level specification, and it maps onto the IBO subject areas. Prepare against the breakdown above and treat your A-Level content as the floor rather than the ceiling.
A-Level Biology is the starting point, not the preparation. BBO exists precisely to reward students who have read past it.
Campbell is the bridge. Work through it alongside your A-Level course rather than treating it as a separate project.
Plant physiology and biosystematics get far less A-Level attention than they carry in olympiad papers. That asymmetry is an opportunity.
Practise under time. The multiple-choice format rewards decisiveness, and students who know the biology still lose marks to hesitation.
If you progress past BBO, the practical component becomes real. Start thinking about technique and data handling early.
Tell us the class and the last biology score and we will say which of the seven sections is actually costing marks, and whether this season is realistic.
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