Practical skills

What you'll learn

• How GCSE Biology practical work is organised into Practical Activity Groups.
• How to plan a fair, safe investigation using variables and controls.
• How to collect reliable data, process it using means, rates and percentage change, and draw conclusions.
• How common PAG skills like microscopy, sampling, food tests, microbiology and osmosis appear in exam questions.

Why practical skills matter

In OCR Gateway Biology J247, practical work is not just something you do in the lab — it is also assessed in the written exams. Around 15% of the marks across the papers test practical skills, such as planning, measuring, analysing data and evaluating methods.

Your school must give you opportunities to complete at least eight practical activities, covering the required biology apparatus and techniques. OCR calls these PAGs, which stands for Practical Activity Groups. Your teacher may use OCR’s suggested practicals or suitable alternatives.

A good practical follows a logical route: plan, make it safe, collect data, process the data, then evaluate what the results mean.

Planning a fair investigation

Before you touch any apparatus, you need to know what you are testing.

For example, if you investigate how temperature affects enzyme activity, temperature is the independent variable. The rate of enzyme activity is the dependent variable. The pH, enzyme concentration and substrate concentration should be control variables.

Measuring carefully

Biology practicals often involve measuring length, area, mass, time, temperature, volume of liquids or gases, and pH.

Use apparatus with suitable resolution. For example, a balance reading to 0.01 g is better for potato-chip osmosis than a balance reading only to 1 g. When measuring liquids, read the bottom of the meniscus at eye level.

Processing data: rates and percentage change

A rate tells you how quickly something happens. In biology, you might calculate the rate of enzyme activity, photosynthesis, gas production, water uptake or colour change.

For example, in a photosynthesis practical using pondweed such as Cabomba, you might measure the volume of oxygen produced per minute.

Percentage change is useful when starting sizes are different, especially in osmosis practicals using potato chips.

$$percentage\; change=\frac{change}{original\; value}\times 100$$

Drawing graphs

Graphs help you spot patterns. Put the independent variable on the x-axis and the dependent variable on the y-axis.

Use a line graph when both variables are continuous, such as temperature and rate of enzyme activity. Use a bar chart when the independent variable is in categories, such as different food types or different antimicrobial discs.

Core practical skills in B7

Microscopy

In microscopy, you use microscopes to observe biological specimens and produce labelled scientific drawings.

Scientific drawings should be clear, large, drawn with single lines, and labelled with straight label lines. Avoid sketchy shading.

Testing for biological molecules

Food-test practicals use qualitative reagents, which are chemicals that show whether a substance is present by producing a colour change.

Typical tests include iodine solution for starch, Benedict’s solution for reducing sugars, Biuret reagent for protein, and the ethanol emulsion test for lipids. Benedict’s test needs safe heating, usually in a water bath rather than directly over a flame.

Sampling organisms

Sampling is used to estimate the distribution and abundance of organisms in an ecosystem.

A quadrat is a square frame used to count organisms in a known area. A transect is a line across a habitat used to study how organisms change with distance, such as from shade into sunlight.

You should consider biotic factors, which are living factors such as predators or competitors, and abiotic factors, which are non-living factors such as light intensity, temperature, pH or soil moisture.

Enzymes, photosynthesis and respiration

These practicals often measure a rate. You might measure gas production, oxygen bubbles, colour change of an indicator, uptake of water, pulse rate or ventilation rate.

For photosynthesis investigations, you must control factors such as temperature, carbon dioxide concentration and light intensity. For human physiology practicals, such as exercise and pulse rate, you must collect data safely and ethically.

Microbiological techniques

Microbiology practicals involve growing microorganisms such as bacteria on agar plates. Aseptic technique is used to reduce contamination.

For example, in an antimicrobial practical, bacteria may be spread onto agar to create a bacterial lawn. Discs containing antimicrobial substances are placed on the agar. A clear area around a disc is called a zone of inhibition, showing where bacterial growth has been prevented.

Plates are usually taped but not fully sealed, because fully sealed plates could encourage growth of harmful anaerobic bacteria.

Transport in and out of cells

Osmosis practicals often use potato chips placed in different concentrations of sugar or salt solution. You may measure change in mass or length.

The key skill is to control chip size, solution volume, temperature and time, then compare percentage change rather than only raw change.

Keeping a practical record

A contemporaneous record is a record made at the time you do the practical, not written from memory much later. It might include your method, results table, observations, calculations, graph and conclusion.

Your centre must confirm that practical opportunities have been provided, but for you as a student, the important point is this: practical skills can be tested even if the exact practical in the exam is unfamiliar.