AQA GCSE Biology Paper 2: what to revise, in what order, right now

AQA Paper 2 pulls from three units. Not every topic is equally likely to be tested at length. The ones below come up most often, carry the most marks, and have very predictable answer structures. Hit these before anything else.

• Unit 5 high yield: negative feedback loops, blood glucose regulation (insulin and glucagon), kidney function and ADH, reflex arc sequence, menstrual cycle hormones in order, plant hormones (auxin).
• Unit 6 high yield: natural selection (five-step chain), Punnett squares for monohybrid inheritance, dominant vs recessive, sex determination, meiosis vs mitosis, antibiotic-resistant bacteria, selective breeding vs genetic engineering.
• Unit 7 high yield: carbon cycle with named processes, quadrats and transects method, biomass transfer efficiency, biodiversity and human impact, food security trade-offs.
• Across all units: required practical questions — variables, repeats, means, reliability, validity. These appear on every paper and follow exactly the same pattern.

Homeostasis questions look like Biology questions but they are mostly vocabulary tests in disguise. AQA marks on specific language, not general understanding.

• Blood glucose high: pancreas releases insulin → liver and muscle cells convert glucose to glycogen → blood glucose falls.
• Blood glucose low: pancreas releases glucagon → liver converts glycogen back to glucose → blood glucose rises.
• Glycogen is the storage molecule. Insulin and glucagon are the hormones. Mixing these up is the most common Unit 5 mistake.
• ADH: released when blood water content is too low → kidneys reabsorb more water → small volume of concentrated urine produced.
• Reflex arc order: stimulus → receptor → sensory neurone → relay neurone → motor neurone → effector → response. Reflexes are fast because they bypass the brain.
• Menstrual cycle: FSH (matures egg, stimulates oestrogen) → oestrogen (rebuilds uterus lining, triggers LH) → LH (triggers ovulation) → progesterone (maintains lining). Learn by job, not just name.
• Auxin: moves to shaded side of shoot → cells on that side elongate more → shoot bends towards light. In roots, auxin inhibits elongation, so the direction reverses.

On Bare Bones Biology, open the hub and select Homeostasis and response. The mastery session will ask you to recall these sequences from scratch — not recognise them. That is the difference between answering the exam question and just feeling like you know it.

Genetics questions look hard because the vocabulary is unfamiliar, but the underlying logic is repeatable. Once you know the method, most questions are variations on the same few patterns.

• DNA vocabulary in order of scale: DNA → gene (a section of DNA that codes for a protein) → chromosome (a long coiled molecule of DNA) → allele (a version of a gene) → genotype (the combination of alleles) → phenotype (the characteristic shown).
• Mitosis: two genetically identical cells, same chromosome number, used for growth and repair.
• Meiosis: four genetically different cells, half the chromosome number, used to make gametes.
• Punnett square method: state the letter you are using, write parent genotypes, separate into gametes, complete the grid, state the ratio of genotypes and phenotypes, give probability in the exact form the question asks (fraction, percentage, ratio, or decimal).
• Natural selection five steps: variation exists in the population → some individuals have an allele that gives an advantage in that environment → they are more likely to survive and reproduce → the advantageous allele is inherited by offspring → over generations its frequency in the population increases.
• Antibiotic resistance uses the same five-step chain. The variation is random mutation. The selective pressure is the antibiotic. The surviving bacteria reproduce and pass on the resistant allele.
• Selective breeding: choose parents with desired characteristics, breed over many generations. Genetic engineering: use enzymes to cut and insert a gene into another organism using a vector. Same goal, different method, very different exam wording needed.

In the hub, Unit 6 mastery sessions will test you on DNA vocabulary, inheritance diagrams, and natural selection explanations separately. Work through whichever turns up amber or red first.

Ecology questions always look approachable, and students always lose more marks than they expect. The fix is treating ecology like a practical subject with method steps and named processes, not general environmental knowledge.

• Carbon cycle named processes: photosynthesis (CO₂ removed from atmosphere) → feeding (carbon passes along food chain) → respiration (CO₂ returned to atmosphere) → decomposition (decomposers break down dead matter, releasing CO₂ and returning minerals) → combustion (burning fossil fuels or wood releases stored carbon).
• Quadrat method in full: place quadrats at random coordinates (use random numbers to reduce bias) → count organisms or estimate percentage cover → repeat many times → calculate a mean → use the sample mean to estimate population size across the whole habitat.
• Transects: used when distribution changes across an environmental gradient (e.g. distance from a path, shoreline, light source). Place quadrats at regular intervals along the line.
• Biomass transfer efficiency: (biomass transferred to next level ÷ biomass available at current level) × 100. Only about 10% transfers at each stage — the rest is lost through respiration, movement, keeping warm, and waste.
• Abiotic factors are non-living: temperature, light intensity, moisture, soil pH, wind speed, oxygen concentration. Biotic factors are living: predation, competition, disease, food availability.
• Biodiversity answers need specific actions: breeding programmes, wildlife corridors, protecting peat bogs, reducing deforestation, setting fishing quotas, seed banks.

Required practical questions follow a near-identical structure every year. The topic changes; the underlying questions rarely do. If you know this vocabulary cold, you can pick up marks even on a practical you have never seen before.

• Independent variable: the factor you deliberately change.
• Dependent variable: the factor you measure.
• Control variable: everything else you keep the same, so results can be attributed to the independent variable alone.
• Reliability: improved by repeating measurements and calculating a mean, which smooths out anomalies.
• Validity: the test measures what it is supposed to measure. Controls are what make a test valid.
• Accuracy: how close a measurement is to the true value. A calibrated instrument or a more sensitive measuring tool improves accuracy.

Paper 2 practicals most likely to appear: reaction time (ruler drop, nervous system), plant responses (seedling growth towards light, auxin), field investigations (quadrats, transects, sampling), and decay (effect of temperature or moisture on decomposition rate).

You do not need to panic about the maths, but you do need to be ready for a few specific calculations that AQA sets reliably.

• Percentage change: ((new value − original value) ÷ original value) × 100. Always show the working.
• Biomass transfer efficiency: (biomass at next level ÷ biomass at previous level) × 100.
• Mean: add all values, divide by the number of values. Exclude anomalies before calculating.
• Rate: amount ÷ time. Check the unit the question asks for.
• Magnification (if it appears): image size ÷ actual size. Or rearrange for actual size.
• Describing a graph: quote the specific values ("from 20°C to 37°C, the rate increases from 2 cm³/min to 8 cm³/min"), then add the explanation. Data first, biology second.

Bare Bones Biology is built around free recall — the same process as the exam. Instead of rereading notes, the mastery sessions ask you to retrieve the content with nothing in front of you, so you find out immediately whether it is actually in your head.

• Start with the Starting Point Check. It asks you a short set of diagnostic questions across all three Paper 2 units and shows you exactly where the gaps are — so you spend your time on the topics that actually need work, not the ones you are already comfortable with.
• Open the hub and pick the weakest topic the Starting Point Check flagged. Each topic runs as a mastery session: a question appears, you type your answer from memory, then compare it side by side with the mark-scheme answer.
• Mark yourself honestly. Missed a key term? Amber. Missed the whole idea? Red. The site tracks this across every topic so you always know what still needs attention.
• Work through red and amber topics until they turn green. Green means you retrieved it correctly from memory — not that you recognised it when you saw it written out. That distinction is exactly what the exam tests.