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OCR Biology A H020/H420: the route map

Checked against OCR Biology A H020/H420, version 4.1 (A), 4.0 (AS) (April 2026) on 19 August 2026. The table links each specification heading to the relevant InkBiology lesson and identifies partial or missing coverage. Use the awarding body’s current specification as the definitive source.

AS H020 examines modules 1 to 4; A-level H420 examines all six.

Start with the topic notes · questions by topic, with mark schemes · the practical work · where the real past papers are · the definitions · flashcards · a revision checklist.

1 Development of practical skills in biology

Ref	Specification heading	Taught in	Coverage
1.1	Practical skills assessed in a written examination	Variables and controls: what an experiment can show, Handling data: units, scales, rates and uncertainty, Averages, spread and the null hypothesis, Choosing, carrying out and concluding a statistical test	Covered
1.2	Practical skills assessed in the practical endorsement		An assessment arrangement rather than subject content

2 Foundations in biology

Ref	Specification heading	Taught in	Coverage
2.1.1	Cell structure	Eukaryotic cell structure and organelles, Microscopy, magnification and resolution, Prokaryotic cells and viruses, Cell specialisation and biological organisation, Optical microscopy and calibrated measurement, Preparing biological material: squashes, sections and mounts	Covered
2.1.2	Biological molecules	Water and inorganic ions, Carbohydrate structure and function, Lipids: triglycerides, phospholipids and ester bonds, Protein structure and function, Membrane structure and the fluid mosaic model, Diet, energy and how to read a health claim, Cholesterol, atheroma and what a risk factor means, Qualitative biochemical tests, and what they do not tell you, Colorimetry, dilution series and calibration curves, Chromatography and the separation of pigments	Covered
2.1.3	Nucleotides and nucleic acids	DNA and RNA structure, DNA replication, The genetic code and transcription, Translation and protein synthesis, Glycolysis, ATP and the link reaction, Extracting and precipitating DNA from tissue	Covered
2.1.4	Enzymes	Enzyme action and specificity, Factors affecting enzyme rate: temperature, pH and concentration, Enzyme inhibition and metabolic control, Cofactors, coenzymes and where enzymes work, Digestion and absorption in the human gut, Measuring the rate of an enzyme-controlled reaction	Covered
2.1.5	Biological membranes	Membrane structure and the fluid mosaic model, Diffusion and osmosis, Active transport, co-transport and bulk transport, Digestion and absorption in the human gut, Investigating membrane permeability, Water relations of plant tissue: osmosis and transpiration	Covered
2.1.6	Cell division, cell diversity and cellular organisation	The cell cycle and mitosis, Meiosis and the sources of genetic variation, Cell specialisation and biological organisation, Stem cells and cell potency, Xylem and the transpiration stream, Transpiration and stomatal control, Optical microscopy and calibrated measurement, Preparing biological material: squashes, sections and mounts	Covered

3 Exchange and transport

Ref	Specification heading	Taught in	Coverage
3.1.1	Exchange surfaces	Surface area to volume ratio: why size limits diffusion, Gas exchange in mammals: lungs and ventilation, Gas exchange in insects, fish and plants, Optical microscopy and calibrated measurement, Dissection and biological drawing	Covered
3.1.2	Transport in animals	The heart and cardiac cycle, Blood vessels, tissue fluid and lymph, Haemoglobin and oxygen dissociation curves, Dissection and biological drawing	Covered
3.1.3	Transport in plants	Xylem and the transpiration stream, Transpiration and stomatal control, Phloem translocation and the mass-flow hypothesis, Plan diagrams and tissue sections, Gas exchange in insects, fish and plants, Preparing biological material: squashes, sections and mounts, Water relations of plant tissue: osmosis and transpiration	Covered

4 Biodiversity, evolution and disease

Ref	Specification heading	Taught in	Coverage
4.1.1	Communicable diseases, disease prevention and the immune system	Pathogens and non-specific defences, The specific immune response, Antibodies, vaccination and the four kinds of immunity, Evidence for evolution, resistance and genetic drift, Enzyme inhibition and metabolic control, Infectious disease: transmission and control, Plant disease and plant defences, Plan diagrams and tissue sections, Conservation in situ and ex situ, Industrial biotechnology and fermentation, Genome analysis, genetic screening and gene therapy, Optical microscopy and calibrated measurement, Dissection and biological drawing	Covered
4.2.1	Biodiversity	Measuring biodiversity, Conservation in situ and ex situ, The carbon cycle and climate change, Field sampling, distribution and behavioural response	Covered
4.2.2	Classification and evolution	Classification, phylogeny and molecular evidence, Natural selection: variation, selection and allele frequency, Evidence for evolution, resistance and genetic drift, Averages, spread and the null hypothesis, Continuous and discontinuous variation, The five kingdoms, species concepts and viruses	Covered

5 Communication, homeostasis and energy (A-level only)

Ref	Specification heading	Taught in	Coverage
5.1.1	Communication and homeostasis	Hormonal communication and negative feedback, Receptors: transduction and the reflex arc, The synapse: transmission, and why it runs one way, Thermoregulation in endotherms and ectotherms	Covered
5.1.2	Excretion as an example of homeostatic control	Osmoregulation and kidney function, Regulation of blood glucose and diabetes mellitus, Antibodies, vaccination and the four kinds of immunity, The liver: detoxification, deamination and the making of urea, Preparing biological material: squashes, sections and mounts, Dissection and biological drawing	Covered
5.1.3	Neuronal communication	Receptors: transduction and the reflex arc, The action potential and its propagation, The synapse: transmission, and why it runs one way, Organisation of the nervous system	Covered
5.1.4	Hormonal communication	Hormonal communication and negative feedback, Regulation of blood glucose and diabetes mellitus, Recombinant DNA technology, Stem cells and cell potency, Optical microscopy and calibrated measurement, Preparing biological material: squashes, sections and mounts	Covered
5.1.5	Plant and animal responses	Plant responses: tropisms, auxins and the classic experiments, Receptors: transduction and the reflex arc, The synapse: transmission, and why it runs one way, Muscles and movement: the sliding-filament model, The heart and cardiac cycle, Hormonal communication and negative feedback, Organisation of the nervous system, Plant disease and plant defences, Optical microscopy and calibrated measurement, Preparing biological material: squashes, sections and mounts	Covered
5.2.1	Photosynthesis	Chloroplast structure and the light-dependent reactions, The Calvin cycle, Limiting factors and primary productivity, Chromatography and the separation of pigments, Measuring respiration and photosynthesis rates	Covered
5.2.2	Respiration	Glycolysis, ATP and the link reaction, The Krebs cycle and oxidative phosphorylation, Anaerobic respiration and the respiratory quotient, Measuring respiration and photosynthesis rates	Covered

6 Genetics, evolution and ecosystems (A-level only)

Ref	Specification heading	Taught in	Coverage
6.1.1	Cellular control	Control of gene expression, Mutation, gene expression and cancer, The cell cycle and mitosis, Hormonal communication and negative feedback, Homeobox genes, Hox genes and apoptosis, The genetic code and transcription	Covered
6.1.2	Patterns of inheritance	Meiosis and the sources of genetic variation, Monohybrid inheritance and genetic diagrams, Dihybrid inheritance, linkage, epistasis and the chi-squared test, Population genetics and Hardy-Weinberg equilibrium, Natural selection: variation, selection and allele frequency, Evidence for evolution, resistance and genetic drift, Speciation and reproductive isolation, Artificial selection and selective breeding	Covered
6.1.3	Manipulating genomes	Genome analysis, genetic screening and gene therapy, Recombinant DNA technology, Pharming, recombinant medicines and synthetic biology	Covered
6.2.1	Cloning and biotechnology	Enzyme inhibition and metabolic control, Populations and their limits, Stem cells and cell potency, Cloning in plants and animals, Industrial biotechnology and fermentation, Aseptic technique and the effect of antimicrobials	Covered
6.3.1	Ecosystems	Populations and their limits, Limiting factors and primary productivity, Nutrient cycles: nitrogen, phosphorus and eutrophication, Succession and environmental change, Measuring biodiversity, The carbon cycle and climate change, Field sampling, distribution and behavioural response	Covered
6.3.2	Populations and sustainability	Populations and their limits, Conservation in situ and ex situ, Succession and environmental change, Measuring biodiversity, Managing ecosystems sustainably	Covered

What each paper is, how long it runs and where OCR publishes it: H420 past papers.

Found a mismatch between this map and a lesson? Report it from the relevant lesson page.