Past-paper analysis
IB Biology SL past paper analysis
We tagged 207 questions worth 605 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. 74.9% of all marks sit in questions that join two or more topics.
- 207 questions
- 605 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 (28.8%) and D · Continuity & change (28.2%) take the largest shares of marks. C1.1 Enzymes & metabolism (5.37%), C4.2 Energy & matter transfers (5.07%) and B1.1 Carbohydrates & lipids (4.5%) lead the table. The top five topics together carry 23.8% of all marks, and even the smallest of the 35 topics, A3.2 Classification & cladistics, holds 0.5%.
Share of marks by theme
| Theme | % of all marks |
|---|---|
| C · Interaction & interdependence | 28.8% |
| D · Continuity & change | 28.2% |
| B · Form & function | 25.8% |
| A · Unity & diversity | 17.2% |
Share of all 605 marks.
Share of marks by topic
| Topic | % of all marks |
|---|---|
| C1.1 Enzymes & metabolism | 5.37% |
| C4.2 Energy & matter transfers | 5.07% |
| B1.1 Carbohydrates & lipids | 4.5% |
| B2.1 Membranes & transport | 4.45% |
| C1.2 Cell respiration | 4.4% |
| D2.1 Cell & nuclear division | 4.33% |
| C2.2 Neural signalling | 4.17% |
| C4.1 Populations & communities | 4.13% |
| A2.2 Cell structure | 3.97% |
| B3.2 Transport | 3.8% |
| A4.2 Conservation of biodiversity | 3.64% |
| D3.2 Inheritance | 3.56% |
| D3.1 Reproduction | 3.31% |
| B3.1 Gas exchange | 3.2% |
| A4.1 Evolution & speciation | 3.04% |
| C3.2 Defence against disease | 2.95% |
| A1.1 Water | 2.95% |
| D4.3 Climate change | 2.82% |
| B4.1 Adaptation to environment | 2.73% |
| D2.3 Water potential | 2.73% |
| B4.2 Ecological niches | 2.62% |
| D1.2 Protein synthesis | 2.59% |
| D4.1 Natural selection | 2.46% |
| D1.1 DNA replication | 2.24% |
| A1.2 Nucleic acids | 1.68% |
| B2.2 Organelles | 1.63% |
| C3.1 Integration of body systems | 1.63% |
| D3.3 Homeostasis | 1.63% |
| B1.2 Proteins | 1.57% |
| D1.3 Mutation & gene editing | 1.46% |
| A3.1 Diversity of organisms | 1.43% |
| B2.3 Cell specialization | 1.32% |
| C1.3 Photosynthesis | 1.07% |
| D4.2 Stability & change | 1.07% |
| A3.2 Classification & cladistics | 0.5% |
Share of all 605 marks. Marks from multi-topic questions are split equally between their tags.
Paper 1A, Paper 1B and Paper 2
Marks attributed to each theme on each paper. Paper 2 (extended response) carries about 55% of the marks, Paper 1A (multiple choice) about 25% 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 | 23.5 | 22.2 | 58.4 |
| B · Form & function | 40.5 | 22.9 | 92.7 |
| C · Interaction & interdependence | 48 | 45.3 | 80.8 |
| D · Continuity & change | 37.9 | 34.6 | 97.9 |
Marks after multi-topic questions are split among their tags.
How hard the questions are
Most questions are mid-level: 112 of 207 sit in the medium band.
Questions by difficulty rating
| Rating | Questions | Share |
|---|---|---|
| Accessible | 72 | 34.8% |
| Medium | 112 | 54.1% |
| Hard | 23 | 11.1% |
Rated by our team when each of the 207 questions was tagged.
What this means for your revision
- Start with the top five topics (C1.1 Enzymes & metabolism, C4.2 Energy & matter transfers, B1.1 Carbohydrates & lipids, B2.1 Membranes & transport and C1.2 Cell respiration). Together they carry 23.8% of marks.
- Expect mixed questions: 74.9% 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, A3.2 Classification & cladistics, still holds 0.5% 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 from the two real sittings of the new course so far, May 2025 and November 2025. No specimen paper is included. 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.