AQA Biology exam technique

One asks 'What is happening?', the other asks 'Why is it happening?'

Answer: 'Describe' requires you to state what the data shows (the trends or patterns), whereas 'Explain' requires you to provide the biological reasoning behind why those trends occur.

For a graph, 'describe' asks you to report the pattern shown by the data, using values where useful. 'Explain' asks for biological reasoning that accounts for the pattern. If you only explain when the task asks for description, you may omit the observations that carry the available marks.

Evaluation requires a balanced argument. Look at both sides of the coin.

Answer: You must discuss evidence from the data that supports the conclusion, evidence that contradicts it, and identify limitations of the methodology or statistical analysis.

Exam Technique (AO3). 'Evaluate' questions require a critical appraisal. You must look for data supporting the claim, data refuting it, and flaws in the study (e.g., small sample size, no statistical test, correlation vs. causation, animal models vs. humans).

'Suggest' means taking a core biological principle you *do* know and applying it to a situation you *don't* know.

Answer: Apply your general knowledge of protein structure to this novel scenario: state that excess $H^+$ ions disrupt ionic and hydrogen bonds, altering the tertiary structure and active site.

Exam Technique. The 'Suggest' command word is used for novel contexts (AO2 application). You aren't expected to have memorised the specific example, but you are expected to apply general biological principles (like enzyme denaturation) to it.

Describing the steps of the cycle is just factual recall. *Why* does the organism need this cycle to stay alive?

Answer: By stating that the cycle produces reduced NAD and FAD, which provide electrons for oxidative phosphorylation, ultimately producing the ATP essential for survival processes like active transport.

Essay Technique. Detail (depth) is required, but it must be linked to the 'importance' to hit the top marking bands. The importance of the Krebs cycle is not the cycle itself, but the products it generates that fuel ATP synthesis to keep the organism alive.

Think about the 'lock and key' concept applied to proteins in the blood.

Answer: The variable region of an antibody has a highly specific tertiary structure that is exactly complementary to a specific pathogen's antigen, allowing agglutination and targeted phagocytosis.

Essay Synoptic Link. The specific tertiary structure of proteins is the core of 'shapes fitting together'. Applying this to antigen-antibody complexes demonstrates a strong understanding of how molecular shape dictates systemic immune function.

Two things rising at the same time does not mean one is pushing the other up.

Answer: The graph shows an association, but observational correlation alone does not establish that smoking caused the difference; confounding factors and other causal explanations must be considered.

Correlation shows that two variables vary together. By itself it does not establish causation, because confounding variables, selection effects or other causal structures may contribute to the association. Strong causal conclusions require evidence beyond the correlation alone.

What two opposing forces push fluid out and pull fluid back into the blood?

Answer: By describing how a hydrostatic pressure gradient forces fluid out of capillaries, and a water potential gradient (caused by plasma proteins) draws water back in, facilitating nutrient exchange.

Essay Synoptic Link. Gradients aren't just for ions or concentrations. The formation and return of tissue fluid relies on competing physical gradients (hydrostatic pressure vs. oncotic/water potential pressure), making it a high-level synoptic example.

You need a balance: enough topics to show wide knowledge, but few enough that you can still go into deep detail.

Answer: 4 or 5 distinct topics drawn from different sections of the A-level syllabus (e.g., linking molecular, cellular, physiological, and ecological concepts).

Essay Technique. The 'sweet spot' for breadth and depth is 4-5 well-developed paragraphs, each covering a different syllabus topic related to the title. AS topics are perfectly valid and highly encouraged to show synoptic understanding.