OCR · A Level
OCR A Level Biology
OCR A Level Biology A (H420). What it covers, how it is assessed, a link to the official specification, and the free study material Marlbridge publishes for it.
- Syllabus
- H420
- Board
- OCR
- Qualification
- A Level
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Topics and resources
Each topic below is from the official OCR document for OCR A Level Biology A (H420), with its study guides, revision notes and practice questions together. Everything here is for OCR A Level Biology (H420) only.
- Learn with study guides
- Revise with revision notes
- Practise with practice questions
Searches topic names and resource titles for this course only.
No Biology (H420) resources match “”.
- Try one shorter word, or check the spelling.
- Try the wording the syllabus uses for the topic, as listed below once you clear the search.
- Some topics have no Marlbridge resource yet; they are still listed.
- Topic 1
Development of practical skills in biology
Covers Practical skills assessed in a written examination, Practical skills assessed in the practical endorsement
Study guides
Revision notes
- Topic 2
Foundations in biology
Covers Cell structure, Biological molecules, Nucleotides and nucleic acids
Study guides
- Cell structure, microscopy, prokaryotes and eukaryotes (H420) Read guide
- Nucleotides, ATP, DNA and replication (H420) Read guide
- Proteins, inorganic ions and biochemical tests (H420) Read guide
- The genetic code, transcription and translation (H420) Read guide
- Water, carbohydrates and lipids (H420) Read guide
- Foundations in Biology (H420) Read guide
Revision notes
- Cell structure, microscopy, prokaryotes and eukaryotes (H420) Revise topic
- Nucleotides, ATP, DNA and replication (H420) Revise topic
- Proteins, inorganic ions and biochemical tests (H420) Revise topic
- The genetic code, transcription and translation (H420) Revise topic
- Water, carbohydrates and lipids (H420) Revise topic
- Foundations in Biology Revise topic
Practice questions
- Cell structure, microscopy, prokaryotes and eukaryotes (H420) Try questions
- Nucleotides, ATP, DNA and replication (H420) Try questions
- Proteins, inorganic ions and biochemical tests (H420) Try questions
- The genetic code, transcription and translation (H420) Try questions
- Water, carbohydrates and lipids (H420) Try questions
- Foundations in Biology Try questions
- Topic 3
Exchange and transport
Study guides
Revision notes
No revision notes for this topic yet.
Practice questions
No practice questions for this topic yet.
- Topic 4
Biodiversity, evolution and disease
Study guides
- Classification and taxonomy (H420) Read guide
- Measuring biodiversity (H420) Read guide
- Pathogens, transmission and the first lines of defence (H420) Read guide
- Specific immunity, vaccination and medicines (H420) Read guide
- Threats to biodiversity and conservation (H420) Read guide
- Variation, adaptation and natural selection (H420) Read guide
Revision notes
- Classification and taxonomy (H420) Revise topic
- Measuring biodiversity (H420) Revise topic
- Pathogens, transmission and the first lines of defence (H420) Revise topic
- Specific immunity, vaccination and medicines (H420) Revise topic
- Threats to biodiversity and conservation (H420) Revise topic
- Variation, adaptation and natural selection (H420) Revise topic
Practice questions
- Classification and taxonomy (H420) Try questions
- Measuring biodiversity (H420) Try questions
- Pathogens, transmission and the first lines of defence (H420) Try questions
- Specific immunity, vaccination and medicines (H420) Try questions
- Threats to biodiversity and conservation (H420) Try questions
- Variation, adaptation and natural selection (H420) Try questions
- Topic 5
Communication, homeostasis and energy
Study guides
- Cell communication, homeostasis and the liver (H420) Read guide
- Chemiosmosis, anaerobic respiration and respiratory quotient (H420) Read guide
- Glycolysis, the link reaction and the Krebs cycle (H420) Read guide
- Hormonal communication and blood glucose control (H420) Read guide
- Nervous system, reflexes, heart control and muscle (H420) Read guide
- Neuronal communication (H420) Read guide
- Photosynthesis (H420) Read guide
- Plant responses and plant hormones (H420) Read guide
- The kidney, osmoregulation and renal failure (H420) Read guide
Revision notes
- Cell communication, homeostasis and the liver (H420) Revise topic
- Chemiosmosis, anaerobic respiration and respiratory quotient (H420) Revise topic
- Glycolysis, the link reaction and the Krebs cycle (H420) Revise topic
- Hormonal communication and blood glucose control (H420) Revise topic
- Nervous system, reflexes, heart control and muscle (H420) Revise topic
- Neuronal communication (H420) Revise topic
- Photosynthesis (H420) Revise topic
- Plant responses and plant hormones (H420) Revise topic
- The kidney, osmoregulation and renal failure (H420) Revise topic
Practice questions
- Cell communication, homeostasis and the liver (H420) Try questions
- Chemiosmosis, anaerobic respiration and respiratory quotient (H420) Try questions
- Glycolysis, the link reaction and the Krebs cycle (H420) Try questions
- Hormonal communication and blood glucose control (H420) Try questions
- Nervous system, reflexes, heart control and muscle (H420) Try questions
- Neuronal communication (H420) Try questions
- Photosynthesis (H420) Try questions
- Plant responses and plant hormones (H420) Try questions
- The kidney, osmoregulation and renal failure (H420) Try questions
- Topic 6
Genetics, evolution and ecosystems
Study guides
- DNA sequencing, profiling, PCR and electrophoresis (H420) Read guide
- Ecosystems, biomass transfer and succession (H420) Read guide
- Gene mutations and control of gene expression (H420) Read guide
- Genetic engineering and gene therapy (H420) Read guide
- Microorganisms in biotechnology and immobilised enzymes (H420) Read guide
- Natural and artificial cloning (H420) Read guide
- Populations, Hardy-Weinberg, speciation and artificial selection (H420) Read guide
- Populations, interactions and sustainable management (H420) Read guide
- Variation, genetic diagrams and chi-squared (H420) Read guide
Revision notes
- DNA sequencing, profiling, PCR and electrophoresis (H420) Revise topic
- Ecosystems, biomass transfer and succession (H420) Revise topic
- Gene mutations and control of gene expression (H420) Revise topic
- Genetic engineering and gene therapy (H420) Revise topic
- Microorganisms in biotechnology and immobilised enzymes (H420) Revise topic
- Natural and artificial cloning (H420) Revise topic
- Populations, Hardy-Weinberg, speciation and artificial selection (H420) Revise topic
- Populations, interactions and sustainable management (H420) Revise topic
- Variation, genetic diagrams and chi-squared (H420) Revise topic
Practice questions
- DNA sequencing, profiling, PCR and electrophoresis (H420) Try questions
- Ecosystems, biomass transfer and succession (H420) Try questions
- Gene mutations and control of gene expression (H420) Try questions
- Genetic engineering and gene therapy (H420) Try questions
- Microorganisms in biotechnology and immobilised enzymes (H420) Try questions
- Natural and artificial cloning (H420) Try questions
- Populations, Hardy-Weinberg, speciation and artificial selection (H420) Try questions
- Populations, interactions and sustainable management (H420) Try questions
- Variation, genetic diagrams and chi-squared (H420) Try questions
Covering more than one topic
Course guides, exam preparation and pages that span several topics.
Study guides
No study guide for this course yet.
Revision notes
No revision notes for this course yet.
Practice questions
Source: OCR – official A Level Biology A (H420) specification PDF, Version 4.1, April 2026 — Version 4.1 (April 2026), for first assessment in 2025. Verified 2026-09-02. Subtopics are shown where Marlbridge has entered them; a topic may have more in the official document. A topic listed here is part of the syllabus; it does not mean Marlbridge has published material for it. Always check the current syllabus for your examination year.
About this course
- Qualification
- OCR A Level Biology
- Spec code
- H420
- Does Marlbridge teach it?
- Yes, one-to-one only (Rs 6,000 per class; other currencies) — request a free trial class
- Who teaches it?
- Saad Zai · Harris Zaman · Hina Mogul
- Are resources available?
- Yes — 101 published
- Is enrolment open?
- Enquire to join — no online enrolment yet
- Official specification
- OCR specification
- Topic checklist
- Printable H420 checklist
- Where was this verified?
- 2026-08-18, official OCR specification
Compiled and maintained by the Marlbridge Academic Team, checked against the official OCR specification on 2026-08-18.
Spotted something wrong on this page? Report an error — see the corrections policy.
The qualification
OCR A Level Biology A (H420)
Marlbridge's summary of the course
Our A Level in Biology A allows students to develop relevant practical skills alongside essential knowledge and understanding of a range of biological concepts and scientific methods. Biological mathematics and problem-solving skills can be fully integrated into teaching and learning.
The board's own description is on the official OCR syllabus page.
Qualification number 601/4260/1.
Specifications change between examination series. Always confirm the current syllabus and assessment structure on the OCR syllabus page for your examination year.
Assessment structure
Linear qualification
| Component | Duration | Marks | Weighting | Type |
|---|---|---|---|---|
| H420/01: Paper 1: Biological processes | 2h 15m | 100 | 37% | Written exam |
| H420/02: Paper 2: Biological diversity | 2h 15m | 100 | 37% | Written exam |
| H420/03: Paper 3: Unified Biology | 1h 30m | 70 | 26% | Written exam |
Source: official OCR specification, verified 2026-08-28. Directly confirmed against OCR's own official A Level Biology A (H420) "Assessment story: exploring our question papers" guide (2026-08-28). Three examined components: Paper 1 "Biological processes" and Paper 2 "Biological diversity" are each 100 marks/2h15/37%; Paper 3 "Unified Biology" (all modules, synoptic) is 70 marks/1h30/26%. Total 270 marks across the three papers determines the overall A*-E grade. A separate Practical Endorsement (non-exam assessment, minimum 12 practical activities, internally assessed) is reported separately as Pass/Not Classified and does not contribute marks to the 270-mark grade; it is not listed as a component in the table because it carries no marks towards the 270-mark total.
Questions about this course
How is OCR Biology (H420) assessed?
OCR Biology (H420) is assessed through: H420/01 (Paper 1: Biological processes) — 2h 15m, 100 marks, 37% of the qualification; H420/02 (Paper 2: Biological diversity) — 2h 15m, 100 marks, 37% of the qualification; H420/03 (Paper 3: Unified Biology) — 1h 30m, 70 marks, 26% of the qualification. It is a linear qualification. Source: official OCR specification, verified 2026-08-28.
What topics does OCR A Level Biology (H420) cover?
6 topics in the current syllabus: Development of practical skills in biology; Foundations in biology; Exchange and transport; Biodiversity, evolution and disease; Communication, homeostasis and energy; Genetics, evolution and ecosystems. The printable topic checklist lists every topic and subtopic on one page.
Can I get a tutor for OCR A Level Biology (H420)?
Yes. Marlbridge teaches OCR A Level Biology (H420) live online, one-to-one only, taught by a named subject teacher from its academy in Lahore, Pakistan. The first trial class is free.
Are there free OCR A Level Biology (H420) revision notes and practice questions?
Yes. Marlbridge has published 101 free resources for this course (study guides, practice questions, revision notes, exam preparation guides), free to read with no sign-up.
The subject
Biology teaching and study resources, organised by level and topic.
Biology at other qualifications
These are separate qualifications with different syllabuses and assessments — not different names for the same course. Check which one your school enters you for.
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