Past-paper analysis
IB Biology HL past paper analysis
We tagged 269 questions worth 855 marks from 15 papers of the redesigned course, first examined in 2025. This page shows what each theme and topic is worth and which paper carries the marks. 78.9% of all marks sit in questions that join two or more topics.
- 269 questions
- 855 marks
- 15 papers
- New 2025 course
Written by Ejaz Ahmad. Published 18 October 2026. See how we analyse papers.
Marks by theme and topic
C · Interaction & interdependence (28.3%) and D · Continuity & change (26.3%) take the largest shares of marks. C4.1 Populations & communities (5.11%), C2.2 Neural signalling (4.05%) and A4.1 Evolution & speciation (4.04%) lead the table. The top five topics together carry 20.9% of all marks, and even the smallest of the 40 topics, A3.1 Diversity of organisms, holds 0.44%.
Share of marks by theme
| Theme | % of all marks |
|---|---|
| C · Interaction & interdependence | 28.3% |
| D · Continuity & change | 26.3% |
| B · Form & function | 25.6% |
| A · Unity & diversity | 19.8% |
Share of all 855 marks.
Share of marks by topic
| Topic | % of all marks |
|---|---|
| C4.1 Populations & communities | 5.11% |
| C2.2 Neural signalling | 4.05% |
| A4.1 Evolution & speciation | 4.04% |
| B3.3 Muscle & motility (HL) | 3.9% |
| C1.2 Cell respiration | 3.84% |
| C1.1 Enzymes & metabolism | 3.49% |
| D2.1 Cell & nuclear division | 3.39% |
| D1.2 Protein synthesis | 3.34% |
| A2.3 Viruses (HL) | 3.16% |
| B2.1 Membranes & transport | 3.14% |
| C1.3 Photosynthesis | 3.12% |
| B3.1 Gas exchange | 3.12% |
| B3.2 Transport | 3.12% |
| B1.2 Proteins | 2.87% |
| A3.2 Classification & cladistics | 2.83% |
| A1.2 Nucleic acids | 2.81% |
| D4.1 Natural selection | 2.81% |
| D3.3 Homeostasis | 2.73% |
| C3.2 Defence against disease | 2.71% |
| A4.2 Conservation of biodiversity | 2.58% |
| D1.3 Mutation & gene editing | 2.5% |
| B2.2 Organelles | 2.32% |
| C4.2 Energy & matter transfers | 2.27% |
| D4.2 Stability & change | 2.27% |
| B4.1 Adaptation to environment | 2.24% |
| A2.2 Cell structure | 2.18% |
| C3.1 Integration of body systems | 2.11% |
| B4.2 Ecological niches | 1.93% |
| B1.1 Carbohydrates & lipids | 1.73% |
| D3.2 Inheritance | 1.72% |
| D4.3 Climate change | 1.72% |
| C2.1 Chemical signalling (HL) | 1.63% |
| D1.1 DNA replication | 1.54% |
| D2.3 Water potential | 1.52% |
| D2.2 Gene expression (HL) | 1.41% |
| D3.1 Reproduction | 1.33% |
| B2.3 Cell specialization | 1.2% |
| A1.1 Water | 1.19% |
| A2.1 Origins of cells (HL) | 0.61% |
| A3.1 Diversity of organisms | 0.44% |
Share of all 855 marks. Marks from multi-topic questions are split equally between their tags.
Themes by level of organisation
The new Biology course crosses its four themes with four levels, from molecules up to ecosystems.
Marks by theme and level of organisation
| Theme | 1 · Molecules | 2 · Cells | 3 · Organisms | 4 · Ecosystems |
|---|---|---|---|---|
| A · Unity & diversity | 4% | 5.9% | 3.3% | 6.6% |
| B · Form & function | 4.6% | 6.7% | 10.1% | 4.2% |
| C · Interaction & interdependence | 10.4% | 5.7% | 4.8% | 7.4% |
| D · Continuity & change | 7.4% | 6.3% | 5.8% | 6.8% |
Each cell is a share of all marks; the grid adds up to 100%. Darker means more marks.
Paper 1A, Paper 1B and Paper 2
Marks attributed to each theme on each paper. Paper 2 (extended response) carries about 56% of the marks, Paper 1A (multiple choice) about 23% and Paper 1B (data / experimental) about 21%. Paper 1A is multiple choice, Paper 1B is data-based and experimental, Paper 2 is extended response.
Marks attributed to each theme, by paper
| Theme | Paper 1A (multiple choice) | Paper 1B (data / experimental) | Paper 2 (extended response) |
|---|---|---|---|
| A · Unity & diversity | 39.3 | 42.8 | 87.6 |
| B · Form & function | 45.1 | 54.2 | 119.2 |
| C · Interaction & interdependence | 56.5 | 46.5 | 139 |
| D · Continuity & change | 58.7 | 31.7 | 134 |
Marks after multi-topic questions are split among their tags.
How hard the questions are
Most questions are mid-level: 145 of 269 sit in the medium band.
Questions by difficulty rating
| Rating | Questions | Share |
|---|---|---|
| Accessible | 73 | 27.1% |
| Medium | 145 | 53.9% |
| Hard | 51 | 19% |
Rated by our team when each of the 269 questions was tagged.
What this means for your revision
- Start with the top five topics (C4.1 Populations & communities, C2.2 Neural signalling, A4.1 Evolution & speciation, B3.3 Muscle & motility (HL) and C1.2 Cell respiration). Together they carry 20.9% of marks.
- Expect mixed questions: 78.9% of marks sit in questions tagged with two or more topics. Practise linking topics, not only revising them one at a time.
- Bank the shorter marks on Paper 1A (multiple choice) and Paper 1B (data / experimental), then spend your long-answer time on Paper 2 (extended response), where most marks sit.
- Do not drop the small topics. The smallest, A3.1 Diversity of organisms, still holds 0.44% of marks.
Past frequency shows where marks have gone so far. It does not promise what a future paper will contain.
All courses
IB past paper analysis
The same analysis for every Maths, Physics, Chemistry and Biology course.
Method
We counted the 15 papers written for the redesigned course, first examined in 2025. Papers from the old course are left out because its topics and paper structure were different. Each question is read and tagged by topic. When a question carries more than one tag, its marks are split equally between them, so nothing is counted twice and the shares add up to 100%.
Tagging involves judgement, and these are counts of past marks, not a forecast. Read the full method.