specification overview
OCR A-Level Biology A (H420) is a two-year linear qualification structured around six modules, from foundations in biology through to genetics, evolution and ecosystems. Students sit three written papers at the end of year 13, plus a separate Practical Endorsement (Pass/Fail) covering 12 practical activity groups (PAGs). All papers are synoptic.
subject content
1. Development of practical skills in biology
All papers- Practical skills assessed in written examinations
- Practical skills assessed in the Practical Endorsement
2. Foundations in biology
Components 01 and 02- Cell structure
- Biological molecules; nucleotides and nucleic acids
- Enzymes
- Biological membranes
- Cell division, cell diversity and cellular organisation
3. Exchange and transport
Component 01- Exchange surfaces
- Transport in animals
- Transport in plants
4. Biodiversity, evolution and disease
Component 02- Communicable diseases, disease prevention and the immune system
- Biodiversity
- Classification and evolution
5. Communication, homeostasis and energy
Component 01- Communication and homeostasis
- Excretion as an example of homeostatic control
- Neuronal and hormonal communication
- Plant and animal responses
- Photosynthesis and respiration
6. Genetics, evolution and ecosystems
Component 02- Cellular control and patterns of inheritance
- Manipulating genomes
- Cloning and biotechnology
- Ecosystems, populations and sustainability
assessment structure
| Paper | What's assessed | Length | Marks | Weight | Question types |
|---|---|---|---|---|---|
| Component 01 (Biological Processes) | Modules 1, 2, 3 and 5 | 2h 15m | 100 | 37% | Structured questions and extended-response questions, including synoptic content |
| Component 02 (Biological Diversity) | Modules 1, 2, 4 and 6 | 2h 15m | 100 | 37% | Structured questions and extended-response questions, including synoptic content |
| Component 03 (Unified Biology) | All six modules | 1h 30m | 70 | 26% | Synoptic questions drawing content from across the whole specification |
All three components include synoptic assessment. Component 04 is the Practical Endorsement, a non-exam assessment reported separately (Pass/Fail) alongside the A-Level grade.
assessment objectives
| AO | What it means | Overall |
|---|---|---|
| AO1 | Demonstrate knowledge and understanding of scientific ideas, processes, techniques and procedures. | 31-34% |
| AO2 | Apply knowledge and understanding of scientific ideas, processes, techniques and procedures, in theoretical and practical contexts and when handling data. | 40-43% |
| AO3 | Analyse, interpret and evaluate scientific information, ideas and evidence to make judgements, reach conclusions and refine practical design and procedures. | 25-28% |
required practicals
| Practical | What it involves |
|---|---|
| PAG1 Microscopy | Use of light microscopy, staining, drawing and estimating scale. |
| PAG2 Dissection | Dissection of animal or plant material to observe structure. |
| PAG3 Sampling techniques | Sampling of biodiversity in a habitat using quadrats, transects and other techniques. |
| PAG4 Rates of enzyme-controlled reactions | Investigate factors affecting the rate of an enzyme-controlled reaction. |
| PAG5 Colorimeter or potometer | Use of a colorimeter or potometer to measure a physiological rate. |
| PAG6 Chromatography or electrophoresis | Separation of biological molecules using chromatography or electrophoresis. |
| PAG7 Microbiological techniques | Aseptic techniques to culture and investigate microorganisms. |
| PAG8 Transport in and out of cells | Investigate diffusion, osmosis and active transport, including factors affecting membrane permeability. |
| PAG9 Qualitative testing | Qualitative reagent tests for carbohydrates, proteins and lipids. |
| PAG10 Investigation using data-logger or computer modelling | Use of ICT to record and process experimental data. |
| PAG11 Investigation into the measurement of plant or animal responses | Safe and ethical use of organisms to measure plant or animal responses and physiological functions. |
| PAG12 Research skills | Apply investigative approaches, use online and offline research skills, and correctly cite sources of information. |
key tips for success
Learn the module → component mapping
Component 01 covers Modules 1, 2, 3 and 5. Component 02 covers Modules 1, 2, 4 and 6. Component 03 (Unified Biology) covers everything. Knowing which module lands in which paper helps focused revision.
Take Component 03 seriously
The Unified Biology paper is 26% of the A Level and pulls synoptic content across all six modules. Practise linking topics from Component 01 and 02 material rather than treating them as separate blocks.
Master the 12 PAGs
The Practical Activity Groups feed into both written-paper questions (all three papers include practical-context questions) and the Practical Endorsement (Pass/Fail). Learn method, apparatus, expected results for each.
Build maths fluency
AO2 is 40-43% of the qualification and includes handling numerical data. Practise Simpson's Index, chi-squared, Hardy-Weinberg, standard deviation, colorimetry calculations and Rf values so they're automatic.
Track your Practical Endorsement progress
Your teacher assesses your competence across the 12 PAGs through the year. Some university science courses require a Pass, so check in regularly to make sure you're on track.
Practise extended-response questions
Components 01 and 02 both include extended-response questions worth 6+ marks. Structure your answer with clear scientific vocabulary, worked reasoning and a linked conclusion.
Where to next
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