If you've left GCSE biology required practicals revision near the bottom of your list, you're not alone, and you're also leaving some of the easiest marks on the table. The required practicals are the experiments your exam board says you have to do, which means examiners are allowed to ask about them directly. They show up as "describe the method", "name the independent variable", "why was a water bath used", "how could this be improved", and the answers barely change from one year to the next. Lock them down and you've banked a reliable chunk of marks before the paper even reaches the harder application questions.
Why required practicals revision is some of your most reliable marks
Most of the biology paper asks you to apply knowledge to something you've never seen before. The practical questions are different: the experiments are fixed, they're listed on your specification, and the question types repeat. You're not guessing what might come up. You already know the experiments, so you can prepare the exact answers in advance. That's rare in an exam, and it's exactly why these marks are worth protecting.
One thing to check first: each exam board sets its own list of required practicals, so revise your board's set rather than a generic one off the internet. Combined Science and separate Biology don't always share the same list either. Get the right list in front of you before you start: there's no point perfecting an experiment your paper can't ask about.
The four things to nail for every single practical
You don't need to memorise every practical as a paragraph. For each one, you need four things, and if you can say them out loud without looking, you've covered most of what gets asked:
The independent variable: the one thing you deliberately change. The dependent variable: the one thing you measure. The control variables: everything you keep the same so it's a fair test, plus why each one matters. And one improvement: how you'd make the results more accurate or more repeatable. Change, measure, keep the same, improve. Four prompts, every practical, no exceptions.
Worked example: osmosis in potato
Change: the concentration of the sugar or salt solution. Measure: the change in mass of the potato chips. Keep the same: same potato, same size and number of chips, same time in the solution, same temperature. The method marks people miss here are the small ones: blotting the chips dry before weighing (so you're measuring water moved by osmosis, not water clinging to the surface), and calculating percentage change in mass rather than raw grams (so chips that started at slightly different masses can still be compared fairly). Improvement: test more concentrations and repeat each one to take a mean. That's a full-mark answer hiding in a five-line method.
Worked example: the effect of pH on enzymes
The classic is amylase breaking down starch, tested with iodine. Change: the pH (set with a buffer). Measure: the time taken for the starch to disappear. You sample the mixture onto iodine at intervals and the moment it stops turning blue-black, the starch is gone. Keep the same: temperature (this is why the water bath is there), the concentration and volume of amylase, and the amount of starch. The precision mark is usually the continuous-sampling detail and naming the water bath's job as keeping temperature constant. Improvement: use narrower pH intervals around the optimum and repeat for a mean. Examiners reward the method and precision here, not a memorised number.
Worked example: using a light microscope
Not every practical is a "change one thing, measure another" investigation, and the microscope one trips people up because it's really about technique. Know the order of steps (lowest-power objective first, coarse focus then fine focus), the rules for a good biological drawing (sharp pencil, clear unbroken lines, no shading, label lines that don't cross), and the magnification calculation: magnification = image size ÷ actual size. The marks that slip away are units and rearranging that equation when they give you magnification and ask for the real size instead. Practise the rearrange three times and it stops being scary.
Worked example: light and the rate of photosynthesis
Pondweed in water, a lamp moved to different distances, and you count the bubbles of oxygen given off, or measure the volume collected. Change: the distance of the lamp (which controls light intensity). Measure: the rate of bubbling, or volume of gas, in a set time. Keep the same: the temperature (the lamp gives off heat, so a beaker of water acts as a heat shield to stop that becoming a second variable), the same piece of pondweed, and the same length of time. The precision marks are explaining the heat shield and using the inverse-square idea: that intensity drops sharply as the lamp moves further away. Improvement: repeat each distance and take a mean, and leave the pondweed to settle before counting. Notice the pattern by now: it's always change, measure, keep the same, improve.
How to revise them with the days you've got left
Don't rewrite whole methods from scratch. That feels productive but mostly tests your handwriting. Instead, recall-test: cover your notes, and for each practical say the four things out loud: change, measure, keep the same, improve. Where you stall is exactly where your revision time should go. Then take one past-paper practical question, mark your answer hard against the mark scheme, and tally what you actually missed. Nine times out of ten it's the same handful of method or precision points, and once you've seen them you stop dropping them.
This is where doing it on your own board's spec pays off. GCSE Boss maps the required practicals in your actual exam board's specification, so you're revising the ones that can genuinely come up on your paper (not a generic list), and you can see at a glance which ones you've still got shaky. In the final week, that's the difference between revising everything thinly and revising the right things properly.
Pick three practicals tonight. Say the four things for each. Mark one question against the scheme. That's a real evening's work on some of the most bankable marks in the paper, and it beats reading the whole topic again and hoping.