IB Biology: syllabus, the Individual Investigation IA and exam strategy
A guide to IB Biology: the syllabus organisation, HL vs SL, the three exam papers, the Individual Investigation IA and the skills that separate a 5 from a 7.
IB Biology is a group 4 science whose difficulty is less about hard concepts than about sheer volume: individually the ideas are approachable, but the breadth is heavy. Success in the Diploma Programme comes from mapping the syllabus to command terms and starting the Internal Assessment early. This guide covers the syllabus, exam papers, the IA and exam strategy. For one-to-one support see IB Biology tutoring.
Syllabus structure
The current IB Biology syllabus is built around unifying themes — unity and diversity, form and function, interaction and interdependence, and continuity and change — examined at the molecular, cellular, organism and ecosystem levels. HL students cover the same themes with additional depth. A practical-skills strand on experimental design and data handling runs throughout and is assessed.
HL vs SL
HL and SL share the thematic core; HL adds extra content and an additional paper's worth of material, with more demanding data-analysis expectations. Because Biology is content-dense, HL's main challenge is retention and synthesis across topics rather than a single hard concept.
The exam papers
- Paper 1: multiple-choice plus a data-based section testing breadth and interpretation.
- Paper 2: short-answer and extended-response questions where synthesis across topics is rewarded.
- HL depth: the higher tier examines the additional content and expects deeper data analysis.
The Individual Investigation (IA)
The Biology IA is a student-designed investigation worth 20% of the grade. Its particular challenge is biological variation: living samples vary, so replication and controlled variables matter more than in physics or chemistry. A strong IA uses at least five levels of the independent variable with multiple repeats, a measurable dependent variable and careful attention to the IB's ethical guidelines for living organisms and human participants.
What separates a 5 from a 7
- Command-term discipline: "outline", "explain" and "evaluate" demand different depths; matching them precisely protects easy marks.
- Data-based questions: interpreting graphs and drawing evidence-based conclusions is a distinct, trainable skill.
- Active recall over re-reading: in a content-heavy subject, retrieval practice beats passive review.
- Early IA: living materials need lead time, so drafting the IA in the DP1 summer has a high payoff.