The Most-Tested Topics in IB Biology SL
Every IB Biology SL past-paper question, mapped to the current syllabus and ranked by how often each topic is tested (2016–2025).
All topics (SL) ()
42 papers analysed · top 15 of 27 topics
| # | Topic | % of all SL questions | Questions | Avg marks |
|---|---|---|---|---|
| 1 | Cell structure | 17% | 129 | 3.1 |
| 2 | Gas exchange and transport in humans | 13.9% | 105 | 3 |
| 3 | Ecosystems and carbon cycling | 13.3% | 101 | 4.2 |
| 4 | Mutation and gene technology | 9.6% | 73 | 3.6 |
| 5 | Inheritance | 9.2% | 70 | 3.1 |
| 6 | Adaptation and speciation | 8.9% | 67 | 3 |
| 7 | Proteins | 8.1% | 61 | 2.4 |
| 8 | Population dynamics | 7.9% | 60 | 3.8 |
| 9 | Neural signalling | 7.8% | 59 | 4.2 |
| 10 | Classification and biodiversity | 7.7% | 58 | 3.5 |
| 11 | Cell and nuclear division | 7.3% | 55 | 3.9 |
| 12 | Cell membranes and transport | 7.1% | 54 | 3.1 |
| 13 | Carbohydrates and lipids | 6.9% | 52 | 3 |
| 14 | Nucleic acids | 6.5% | 49 | 2.9 |
| 15 | Hormones, homeostasis and reproduction | 6.3% | 48 | 3.4 |
How this was measured
Based on OwlsPrep's database of IB Biology SL past papers (2016–2025), 757 questions each tagged to its syllabus topic and mapped to the current IB syllabus via our topic crosswalk. “% of all SL questions” = the share of all tagged IB Biology SL questions that test the topic. Topics no longer in the current syllabus are excluded; because one question can test several topics, shares do not sum to 100%. Figures are aggregate statistics from question metadata — no exam questions or mark schemes are reproduced.
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