The Most-Tested Topics in IB Biology HL
Every IB Biology HL past-paper question, mapped to the current syllabus and ranked by how often each topic is tested (2016–2025).
All topics (HL) ()
42 papers analysed · top 15 of 28 topics
| # | Topic | % of all HL questions | Questions | Avg marks |
|---|---|---|---|---|
| 1 | Gas exchange and transport in humans | 14.6% | 144 | 4 |
| 2 | Cell structure | 14.5% | 143 | 2.3 |
| 3 | Adaptation and speciation | 11.6% | 114 | 4 |
| 4 | Mutation and gene technology | 11.5% | 113 | 4.4 |
| 5 | Ecosystems and carbon cycling | 10.4% | 102 | 4.4 |
| 6 | Inheritance | 9.7% | 95 | 2.4 |
| 7 | Hormones, homeostasis and reproduction | 9.1% | 90 | 2.9 |
| 8 | Nucleic acids | 8.4% | 83 | 2.3 |
| 9 | Cell and nuclear division | 8.1% | 80 | 3.1 |
| 10 | Proteins | 7.1% | 70 | 2.5 |
| 11 | Population dynamics | 6.3% | 62 | 5.1 |
| 12 | Translation and gene expression | 6.1% | 60 | 2.3 |
| 13 | Neural signalling | 5.9% | 58 | 4.1 |
| 14 | Cell membranes and transport | 5.7% | 56 | 2.6 |
| 15 | Enzymes and metabolism | 5.3% | 52 | 3.8 |
How this was measured
Based on OwlsPrep's database of IB Biology HL past papers (2016–2025), 984 questions each tagged to its syllabus topic and mapped to the current IB syllabus via our topic crosswalk. “% of all HL questions” = the share of all tagged IB Biology HL 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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