The Most-Tested Topics in A-Level Biology (CIE 9700)
Every 9700 past-paper question, tagged to its syllabus topic — ranked by how often each is tested (2009–2024).
AS Level (Papers 1–3)
117 papers analysed · top 15 of 51 topics
| # | Topic | % of all questions | Questions | Avg marks |
|---|---|---|---|---|
| 1 | Microscope resolution and magnification | 7.8% | 100 | 7.6 |
| 2 | Plant cell ultrastructure (chloroplast, cell wall, vacuole) | 7.8% | 100 | 6.2 |
| 3 | Animal cell ultrastructure and organelles | 7.3% | 93 | 2.5 |
| 4 | Xylem structure and water transport | 7% | 90 | 4.9 |
| 5 | Diffusion and facilitated diffusion | 5.7% | 73 | 2.7 |
| 6 | Stages of mitosis (prophase to telophase) | 5.7% | 73 | 2.5 |
| 7 | Protein structure (primary to quaternary) | 5.5% | 70 | 3.5 |
| 8 | Disaccharides and polysaccharides (starch, glycogen, cellulose) | 5.4% | 69 | 4.7 |
| 9 | Osmosis and water potential | 5.4% | 69 | 3.3 |
| 10 | Human gas exchange system (trachea, alveoli) | 5.4% | 69 | 2.9 |
| 11 | DNA structure (double helix, base pairing) | 5.3% | 68 | 2 |
| 12 | Phloem structure and translocation | 5.1% | 65 | 2.7 |
| 13 | Factors affecting enzyme activity (temp, pH, [S], [E]) | 4.8% | 61 | 7.9 |
| 14 | Transcription (DNA to mRNA) | 4.6% | 59 | 3.1 |
| 15 | Mode of enzyme action (lock-and-key, induced fit) | 4.3% | 55 | 4.6 |
A Level (A2 topics) (Papers 4–5)
117 papers analysed · top 15 of 47 topics
| # | Topic | % of all questions | Questions | Avg marks |
|---|---|---|---|---|
| 1 | Mitochondrial structure and function | 2.1% | 27 | 3.8 |
| 2 | Natural selection (directional, stabilising, disruptive) | 2% | 26 | 8.1 |
| 3 | Recombinant DNA technology | 2% | 25 | 9.4 |
| 4 | Species, habitat, niche, ecosystem | 1.6% | 21 | 10.2 |
| 5 | Chloroplast structure (thylakoid, stroma) | 1.6% | 20 | 7.9 |
| 6 | Action potential and nerve impulses | 1.6% | 20 | 8.1 |
| 7 | Conservation strategies | 1.5% | 19 | 9.6 |
| 8 | GMOs and applications | 1.5% | 19 | 10.1 |
| 9 | Variation (continuous vs discontinuous) | 1.4% | 18 | 10.6 |
| 10 | Light-dependent reactions (photolysis, ATP/NADPH) | 1.3% | 16 | 12.4 |
| 11 | Calvin cycle (light-independent reactions) | 1.3% | 16 | 11.3 |
| 12 | Limiting factors (light, CO2, temperature) | 1.2% | 15 | 10.7 |
| 13 | Homeostasis principles and negative feedback | 1.2% | 15 | 9.2 |
| 14 | Kidney structure (nephron) | 1.2% | 15 | 9.7 |
| 15 | ATP as energy currency | 1.1% | 14 | 5.1 |
How this was measured
Based on OwlsPrep's database of official CIE 9700 past papers (2009–2024), 1277 questions each tagged to its syllabus topic. “% of all questions” = the share of all tagged 9700 questions that test the topic. Because one question can test several topics, shares do not sum to 100%. AS and A2 are listed separately; A2 tends to use fewer, higher-mark questions. Figures are aggregate statistics from question metadata — no exam questions or mark schemes are reproduced.
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