A-Level Biology Required Practicals – Complete All-Boards Guide
Every A-Level Biology required practical listed by board – AQA, Edexcel A, B and International, OCR PAGs and WJEC/Eduqas – how they’re assessed and how to revise.
Last updated: February 2026
Required Practicals: What They Are and Why They Matter
Practical work is not a side-show in A-Level Biology – it is examined directly in your written papers, and it is assessed separately as a practical endorsement that appears on your certificate. Students who treat the required practicals as “just lab lessons” are caught out every year, because at least 15% of the marks in your written exams are tied to practical skills: planning investigations, identifying variables, handling data, evaluating methods and spotting sources of error.
The good news is that practical questions are some of the most predictable and most answerable on the paper – if you understand how each practical works and what skills it’s testing. This page explains how practicals are assessed on every board (AQA, OCR, Edexcel A & B, Edexcel International, WJEC and Eduqas), lists what each board requires, and shows you exactly which skills to revise so you don’t lose easy marks.
How Practical Skills Are Assessed
Every UK board assesses practicals in two ways. Understanding both stops nasty surprises.
The Practical Skills Examiners Test (and How to Revise Them)
Whatever experiment a question is built around, it is really testing the same handful of transferable skills. Master these and you can answer a practical question on an experiment you’ve never seen.
AQA – The 12 Required Practicals
AQA specifies exactly 12 required practical activities, examined in the written papers and used for the endorsement.
| # | Required practical |
|---|---|
| 1 | Effect of a named variable on the rate of an enzyme-controlled reaction |
| 2 | Preparation of a stained root-tip squash to observe mitosis; calculate a mitotic index |
| 3 | Dilution series of a solute to produce a calibration curve (water potential of plant tissue) |
| 4 | Effect of a named variable on the permeability of cell-surface membranes |
| 5 | Dissection of an animal or plant gas exchange / mass transport system |
| 6 | Aseptic technique to investigate the effect of antimicrobial substances on microbial growth |
| 7 | Chromatography to separate photosynthetic pigments from leaves |
| 8 | Effect of a named factor on the rate of dehydrogenase activity in chloroplasts |
| 9 | Effect of a named variable on the rate of respiration of single-celled organisms |
| 10 | Effect of an environmental variable on animal movement (choice chamber or maze) |
| 11 | Dilution series of glucose + colorimetry to find glucose concentration in “urine” |
| 12 | Effect of an environmental factor on the distribution of a species (sampling/fieldwork) |
Edexcel – Core Practicals
Edexcel A (Salters-Nuffield, 9BN0) requires 18 core practicals; Edexcel B (9BI0) requires 16 core practicals. Both are examined in the written papers (a significant part of Paper 3) and underpin the endorsement.
Edexcel A (Salters-Nuffield) – the 18 core practicals
| # | Core practical |
|---|---|
| 1 | Investigate the effect of caffeine on Daphnia heart rate |
| 2 | Investigate the vitamin C content of food/drinks |
| 3 | Investigate membrane permeability using beetroot |
| 4 | Investigate the effect of enzyme concentration on the rate of reaction |
| 5 | Prepare and stain a root-tip squash to observe mitosis |
| 6 | Microscopy of plant stems (xylem/phloem) |
| 7 | Investigate plant mineral deficiencies |
| 8 | Determine the tensile strength of plant fibres |
| 9 | Investigate the antimicrobial properties of plants |
| 10 | Ecology investigation (distribution/abundance of a species) |
| 11 | Investigate photosynthesis using isolated chloroplasts (the Hill reaction) |
| 12 | Investigate the effect of temperature on the rate of an enzyme reaction (or membrane permeability) |
| 13a | Investigate the rate of growth of seedlings |
| 13b | Investigate factors affecting brine-shrimp hatching |
| 14 | Gel electrophoresis (separating DNA fragments / amino acids) |
| 15 | Investigate the effects of antibiotics on microbial growth |
| 16 | Investigate the rate of respiration using a respirometer |
| 17 | Investigate and interpret spirometer traces |
| 18 | Investigate habituation to a stimulus (e.g. in a snail) |
Edexcel B (9BI0) – the 16 core practicals
| # | Core practical |
|---|---|
| 1 | Investigate the rate of an enzyme-controlled reaction |
| 2 | Use of the light microscope (and calibration) |
| 3 | Prepare a root-tip squash to observe mitosis |
| 4 | Investigate pollen-tube growth |
| 5 | Investigate membrane permeability using beetroot |
| 6 | Determine the water potential of plant tissue |
| 7 | Dissection of a gas exchange system |
| 8 | Investigate water uptake by a plant (transpiration / potometer) |
| 9 | Investigate the rate of respiration using a respirometer |
| 10 | Investigate the rate of photosynthesis |
| 11 | Separate chloroplast pigments by chromatography |
| 12 | Investigate bacterial growth |
| 13 | Aseptic technique – streak plating |
| 14 | Starch-agar assay (investigating enzyme/antimicrobial action) |
| 15 | Sampling methods to estimate abundance |
| 16a/16b | Investigate the distribution and morphology of a species |
Edexcel International A-Level (YBI11) – the 18 core practicals
Edexcel International assesses practical skills through dedicated written examination units (Unit 3 and Unit 6) rather than a teacher endorsement – so for International students the practical skills are examined even more directly. Here are the core practical activities named in the specification:
| CP | Core practical |
|---|---|
| 1 | Semi-quantitative Benedict’s and iodine tests to estimate reducing sugar and starch concentrations |
| 2 | Investigate the vitamin C content of food and drink |
| 3 | Effect of alcohol and temperature on membrane permeability |
| 4 | Effect of temperature, pH, enzyme and substrate concentration on the initial rate of enzyme reactions |
| 5 | Light microscope observations and drawings of animal cells; using a graticule and scale |
| 6 | Prepare and stain a root-tip squash to observe mitosis |
| 7 | Microscopy and plan diagrams of T.S. roots, stems and leaves (xylem, phloem, sclerenchyma) |
| 8 | Determine the tensile strength of plant fibres |
| 9 | Antimicrobial properties of plants, using aseptic technique |
| 10 | Effects of light intensity, wavelength, temperature and CO2 on the rate of photosynthesis |
| 11 | Ecology of a habitat using quadrats and transects, with abiotic factors |
| 12 | Effect of temperature on development (seedling growth or brine-shrimp hatch rate) |
| 13 | DNA technology / gel electrophoresis to separate DNA fragments |
| 14 | Effect of different antibiotics on bacteria |
| 15 | Use an artificial hydrogen carrier (redox indicator) to investigate respiration in yeast |
| 16 | Use a respirometer to determine the rate of respiration and RQ |
| 17 | Effects of exercise on tidal volume, breathing rate and oxygen consumption (spirometer traces) |
| 18 | Investigate the production of amylase in germinating cereal grains |
OCR A & OCR B – Practical Activity Groups (PAGs)
OCR A and OCR B don’t prescribe a numbered list of student experiments in the same way. Instead they group required practical skills into twelve Practical Activity Groups (PAG 1–12) for the endorsement, and assess practical skills throughout the written papers.
| PAG | Skill area | Example practicals OCR provides |
|---|---|---|
| 1 | Microscopy | Light microscope to study mitosis; drawing cells in blood smears; examining lung tissue |
| 2 | Dissection | Dissection of the mammalian heart; stem dissection; chicken-wing dissection |
| 3 | Sampling techniques | Calculating species diversity; distribution & abundance of plants; correlation with a biotic/abiotic factor |
| 4 | Rates of enzyme-controlled reactions | Effect of substrate conc, enzyme conc and temperature on enzyme activity |
| 5 | Colorimeter or potometer | Effect of temperature on membrane permeability; determining glucose concentration; potometer |
| 6 | Chromatography or electrophoresis | Paper chromatography of amino acids; electrophoresis; TLC of photosynthetic pigments |
| 7 | Microbiological techniques | Effect of antibiotics on microbial growth; dilution plating; bacterial transformation |
| 8 | Transport in/out of cells | Water potential of potato; osmosis in an artificial cell; rate of diffusion through a membrane |
| 9 | Qualitative testing | Tests for proteins, lipids and reducing sugars |
| 10 | Data logger / computer modelling | DNA modelling (RasMol); turbidity; yoghurt pH |
| 11 | Plant or animal responses | Exercise & pulse rate; Daphnia heart rate; phototropism; effect of plant hormones |
| 12 | Research skills | Respiration rate of yeast; fruit-fly crosses & analysis; oxygen production by pondweed |
WJEC & Eduqas – Specified Practical Work
WJEC and Eduqas share the same content and specify the same specified practical work throughout the course, examined in the written papers. WJEC is distinctive: its Unit 5 includes internally assessed practical tasks – an Experimental Task and a Practical Analysis Task – which do contribute to the A-Level grade (unlike the pass/fail endorsement on other boards). The full list of specified practicals is set out in the WJEC/Eduqas lab book.
AS specified practical work (Units 1–2 / Components AS)
| # | Specified practical |
|---|---|
| 1 | Food tests |
| 2 | Calibration of the light microscope |
| 3 | Preparation and scientific drawing of a slide of living cells |
| 4 | Determination of water potential by measuring changes in mass or length |
| 5 | Determination of solute potential (degree of incipient plasmolysis) |
| 6 | Investigation into the permeability of cell membranes using beetroot |
| 7 | Effect of temperature or pH on enzyme activity |
| 8 | Effect of enzyme or substrate concentration on enzyme activity |
| 9 | Simple extraction of DNA from living material |
| 10 | Scientific drawing of root-tip cells to show stages of mitosis |
| 11 | Scientific drawing of developing anthers to show stages of meiosis |
| 12 | Investigation into biodiversity in a habitat |
| 13 | Investigation into stomatal numbers in leaves |
| 14 | Dissection of a fish head to show the gas-exchange system |
| 15 | Scientific drawing of a low-power plan of a T.S. leaf |
A2 specified practical work (Units 3–5 / Components A2)
| # | Specified practical |
|---|---|
| 1 | Investigation into transpiration using a simple potometer |
| 2 | Scientific drawing of a low-power plan of a T.S. artery and vein |
| 3 | Dissection of the mammalian heart |
| 4 | Investigation of dehydrogenase activity using artificial hydrogen acceptors |
| 5 | Factors affecting the rate of respiration in yeast |
| 6 | Separation of chloroplast pigments by chromatography |
| 7 | Factors affecting the rate of photosynthesis |
| 8 | Role of nitrogen and magnesium in plant growth |
| 9 | Investigation into the numbers of bacteria in fermented milk |
| 10 | Abundance and distribution of organisms in a habitat |
| 11 | Dissection of the kidney |
| 12 | Digestion of starch agar using germinating seeds |
| 13 | Dissection of wind- and insect-pollinated flowers |
| 14 | Scientific drawing of an anther (with actual size and magnification) |
| 15 | Gene segregation, including the chi-squared test |
| 16 | Continuous variation in a species, including the Student’s t-test |
Exam Board Comparison – Practical Requirements at a Glance
| Feature | AQA | OCR A/B | Edexcel A | Edexcel B | Edexcel Intl | WJEC / Eduqas |
|---|---|---|---|---|---|---|
| Set practical list | 12 required | 12 PAGs | 18 core | 16 core | 18 core | Specified work |
| Skills examined in written papers | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ |
| Teacher endorsement (pass/fail) | ✔ | ✔ | ✔ | ✔ | ❌ (exam units) | ✔ (Eduqas) |
| Practical counts towards grade | Via papers | Via papers | Via papers | Via papers | Units 3 & 6 | WJEC Unit 5 tasks |
| Dedicated practical paper | ❌ | OCR B: ✔ | ❌ | ❌ | ✔ | WJEC Unit 5 |
8 Common Mistakes in Practical Questions
| # | The mistake | The correction |
|---|---|---|
| 1 | “To make it a fair test” | A GCSE phrase. Name the specific control variable and explain why controlling it matters. |
| 2 | Confusing reliability and validity | Reliability = repeatable/consistent results; validity = actually measuring what you intended. |
| 3 | Mixing up independent and dependent variables | Independent = what you change; dependent = what you measure. |
| 4 | Forgetting units in tables/calculations | Every column heading and every calculated answer needs the correct units. |
| 5 | Wrong significant figures | Match the precision of your data and the resolution of your apparatus. |
| 6 | “Do more repeats” as a catch-all improvement | Say what the repeats achieve (identify anomalies, calculate a reliable mean) – and suggest method-specific improvements too. |
| 7 | Not using the data in evaluation questions | Quote specific values and anomalies from the results table – don’t answer in general terms. |
| 8 | Ignoring practical questions in revision | 15%+ of marks are practical-skills based. Practise practical questions specifically, not just content. |
Losing Marks on Practical Questions?
Practical skills are worth at least 15% of your marks – and they’re some of the most learnable. As a former examiner I know exactly how practical questions are marked and where students slip up on variables, validity, uncertainty and data analysis. Tutoring will turn practicals from a worry into easy marks.
Tyrone John • CBiol MRSB • Former WJEC/Eduqas & Edexcel Examiner • 25+ Years Teaching A-Level Biology
Book a Free ConsultationFrequently Asked Questions – Required Practicals
Do the required practicals count towards my A-Level grade?
There are two separate things. The practical endorsement, assessed by your teacher, is a separate pass/fail result reported on your certificate and does not count towards your A to E grade. However, questions about the practicals and the skills behind them appear in your written papers and do count – at least 15% of the marks across the papers assess practical skills. So you must complete the practicals for the endorsement, and you must revise them because they are examined in the written papers.
How many required practicals are there for each exam board?
It varies. AQA specifies 12 required practical activities. OCR A and OCR B group the skills into 12 Practical Activity Groups (PAGs). Edexcel A (Salters-Nuffield) and Edexcel International have 18 core practicals, and Edexcel B has 16 core practicals. WJEC and Eduqas embed specified practical work throughout the course, with WJEC additionally having internally assessed practical tasks in Unit 5. Whatever the number, the underlying skills tested are very similar across all boards.
What is the difference between reliability and validity?
Reliability is about consistency: a reliable result is one you get repeatedly if you do the experiment again, which is why repeating readings and calculating a mean improves reliability. Validity is about whether you are actually measuring what you intended to measure, which depends on controlling other variables so they don’t affect your dependent variable. An experiment can be reliable but not valid (consistently wrong) or valid but unreliable. Examiners often award marks specifically for using these terms correctly.
What practical skills do the written papers test?
The written papers test transferable practical skills rather than just whether you did a particular experiment. These include identifying independent, dependent and control variables; explaining controls and validity; improving methods; assessing reliability through repeats; calculating uncertainty and percentage error; tabulating and graphing data with correct units and significant figures; calculating rates; and choosing and interpreting statistical tests such as the chi-squared test, t-test and correlation coefficient. Crucially, you must be able to apply these skills to unfamiliar experiments you have never seen.
What happens if I miss a required practical?
For the endorsement, your teacher needs to assess your competence on at least 12 occasions and to confirm you have used each required apparatus and technique. If you miss a practical that is the only one covering a particular technique, your teacher will arrange another suitable practical so that technique is still covered. For the written papers, you simply need to learn the method, results and evaluation of the missed practical from notes or a textbook, just as you would revise any other content – you don’t need to have physically done it to answer questions on it.