OCR A-level Biology (H420): papers, marks and grade boundaries

OCR A-level Biology at a glance

OCR offers two A-level biology courses: Biology A (H420) and Biology B, Advancing Biology (H422). This guide covers Biology A. It is a linear qualification: all the exams are sat at the end of the course, in one May and June series, and a practical endorsement is reported separately.

The marks add up to 270. All components include synoptic assessment, extended response questions and stretch and challenge questions. For the endorsement, you must complete at least 12 assessed practical activities and show the competencies in OCR’s Common Practical Assessment Criteria.

What each paper covers

Paper 1: Biological processes

Section A is 15 marks of multiple choice and Section B is 85 marks of short answer questions (structured questions, problem solving, calculations, practical) and extended response. It examines module 2 (foundations: cell structure, biological molecules, nucleic acids, enzymes, membranes, cell division), module 3 (exchange surfaces, transport in animals and in plants) and module 5 (communication and homeostasis, excretion, neuronal and hormonal communication, photosynthesis and respiration), plus the practical skills of module 1.

Paper 2: Biological diversity

The same layout of 15 multiple choice marks and 85 written marks. It examines module 4 (communicable disease and the immune system, biodiversity, classification and evolution) and module 6 (cellular control, patterns of inheritance including Hardy-Weinberg, manipulating genomes, cloning and biotechnology, ecosystems, populations and sustainability), with modules 1 and 2.

Paper 3: Unified biology

One 70 mark paper that can use content from all six modules, with no multiple choice. It is made up of short answer and extended response questions, including practical ones, so expect to interpret an unfamiliar experiment or data set and connect topics that your teacher taught months apart.

Calculator and maths in OCR Biology

OCR permits a scientific or graphical calculator in components 01, 02 and 03, subject to the JCQ rules. The specification includes statistical tests (chi-squared among them), the Hardy-Weinberg principle and magnification calculations, so a reliable calculator routine matters. A calculator will not rescue a vague explanation: most marks are for biology, not arithmetic.

Worked examples in OCR style

Microscopy: calculating magnification

An electron micrograph shows a mitochondrion that measures 48 mm on the page. Its real length is 12 µm. Convert to the same unit first:

The usual lost mark is mixing millimetres and micrometres. Convert both to the same unit before dividing.

Inheritance: a chi-squared test

A cross is expected to give a 3 : 1 ratio. From 200 offspring you count 168 with the dominant phenotype and 32 with the recessive one. The expected numbers are 150 and 50.

There are 2 classes, so 1 degree of freedom. The critical value at p = 0.05 is 3.84. As 8.64 is greater than 3.84, the difference between the observed and expected numbers is significant, so you reject the null hypothesis that the cross gives 3 : 1 and look for another explanation, such as linkage or a lethal allele. If the value had been below 3.84 you would conclude that any difference is due to chance.

Populations: Hardy-Weinberg

A recessive condition affects 1 in 2500 people, so q² = 0.0004.

About 3.9% of the population are carriers. The model only holds for a large population where mating is random and nothing changes the allele frequencies: selection, mutation and migration are all absent. Be ready to list these if you are asked to evaluate it. Then try a genetics question in our course:

Grades and June 2026 grade boundaries

OCR adds your three paper marks into a total out of 270 and compares it with that series’ boundaries. The table is from OCR’s document published on 14 September 2026. Boundaries move each year, so treat them as a guide to the size of the target, not a promise.

Worked through: marks of 65, 58 and 40 give 163 out of 270, which is a B (150) and 13 marks below an A (176). The boundaries differ a lot between papers: Paper 1 needed 82 of 100 for an A*, while Paper 2 needed 71.

Using the daily paper as a short timed mock

Uni-Sine publishes a free daily paper on each A-level biology track, with a new one every day. It is a short timed paper of 8 questions worth 25 to 35 marks, marked instantly with worked answers. It is not a full OCR paper and OCR does not write it, so use it for quick, regular practice between full past papers.

• Biology Advanced 1 covers cell structure and microscopy, enzymes, gas exchange, nucleic acids and DNA replication, mass transport, genetic diversity and classification, the immune system, biological molecules, mitosis, membranes and protein synthesis. That matches Paper 1 and the early modules.
• Biology Advanced 2 covers photosynthesis, inheritance and Hardy-Weinberg, homeostasis and the kidney, respiration, gene expression, gene technology, muscle contraction, populations, energy in ecosystems, evolution and nervous coordination, which lines up with Paper 2 and parts of Paper 1.
• The daily papers do not rehearse the 70 mark synoptic style of Paper 3. Use full past papers for that. For advice on running mocks, see our A-level mocks guide and the A-level Biology guide.

Taking the WJEC Eduqas course instead? Read our Eduqas A-level Biology guide, which has its own papers and boundaries.

Exam answers

Uni-Sine does not publish official answers or mark schemes for OCR A-level Biology papers. The answers and a worked mark scheme for each question come with today’s paper once you have submitted it and it has been marked, so you can see where every mark was won or lost.

Common mistakes in OCR A-level Biology

• Describing instead of explaining. If a question asks why, finish the chain with a reason ("so the enzyme’s active site no longer fits the substrate").
• Mixing up units in microscopy. Convert to micrometres before calculating magnification.
• Stating "no difference" without the test. For chi-squared, put the calculated value beside the critical value and then say what that means for the null hypothesis.
• Naming the process without the structure. Link structure to function, such as the folded inner membrane of a mitochondrion and the area for respiration.
• Ignoring the context. Paper 3 rewards using information from the unfamiliar experiment in the stem.

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