Answer the task being asked

From a command to a useful answer

Start with the question’s context and command. Use evidence when you describe a pattern, a mechanism when you explain it, and a judgement supported by evidence when you evaluate a claim.

Apply this to a case study

Describe and explain use different parts of your knowledge

Describe the enzyme data

The measured rate rises from 0.12 µmol min⁻¹ at 0.5 mmol dm⁻³ substrate to 0.50 at 4, then increases only to 0.52 at 8.

Explain a plausible reason for the plateau

With a fixed enzyme amount, active sites can become highly occupied. Additional substrate then has little effect because catalytic capacity limits the rate under this interpretation.

The first answer identifies the pattern and numerical evidence. The second links it to a possible mechanism. A question that asks for both needs both kinds of response.

Practical guidance for common commands

Calculate

Use the supplied values and an appropriate relationship. Show substitutions and retain the units and reference quantity.

Case example: In the osmosis case, divide the mass difference by initial mass before multiplying by 100.

Describe

Report what the supplied data or structure shows. Use relevant values and identify a change, exception or comparison.

Case example: The enzyme rate rises from 0.12 to 0.50 µmol min⁻¹ between 0.5 and 4 mmol dm⁻³ substrate, then changes little.

Explain

Give a biological reason and connect the mechanism to the observation being asked about.

Case example: At high substrate concentration, many active sites can be occupied, so the fixed enzyme amount limits further rate increase.

Compare

Relate the items directly using the same quantity or feature. Quantify a difference when the evidence permits.

Case example: The corrected respiration displacement rates are 0.35 and 0.70 mm min⁻¹; the second is twice the first.

Suggest

Apply relevant knowledge to the given context. Make the reasoning and any assumption behind a plausible proposal clear.

Case example: More independent random quadrats could improve evidence about spatial variation in the field.

Evaluate

Assess how the evidence supports a claim, identify relevant limits or alternatives, then give a justified conclusion.

Case example: A non-significant chi-squared result does not reject the stated model at that threshold; it does not prove the model.

Justify

Support a choice with reasons tied to the question and the information supplied.

Case example: Random quadrats suit a whole-field abundance estimate because they reduce deliberate placement bias across that sampling area.

Estimate / predict

Use an appropriate model or the supplied pattern, and state where an assumption limits the result.

Case example: Linear interpolation in the osmosis data estimates zero mass change at 0.30 mol dm⁻³; it is not an exact measurement of every cell’s solute content.

Make an evaluation specific

Identify the actual claim and the observation that supports it. Explain why a named limitation matters, consider a plausible alternative and state the conclusion the evidence permits. “It was unreliable” without a reason or a useful improvement leaves the judgement unsupported.

This is original revision advice using the site’s case studies. Question wording, context and official mark schemes determine what is credited in a real examination; there is no universal rule that one self-check point equals one mark.

Try the enzyme case · Evaluate field evidence · Official papers and mark schemes

Assessment context: AQA assessment objectives · OCR A official assessment resources.