How to Answer Describe, Explain and Evaluate Questions

Describe: say what the evidence shows

A description reports an observable feature, pattern or sequence. It does not need the biological reason unless the question also asks for one. For a graph or table, begin with the overall trend: does the value increase, decrease, remain stable, reach a peak or level off? Then support that statement with carefully chosen figures and units.

When two conditions are present, make a direct comparison. ‘Plant A produced 14 bubbles and Plant B produced 9’ lists data; ‘Plant A produced 5 more bubbles per minute than Plant B’ compares it. If the pattern changes across the range, divide it into stages. Mention an anomaly only when it is genuinely outside the pattern and relevant to the requested description.

• State the overall pattern before quoting detail.
• Select start, end, peak or turning-point values rather than copying the table.
• Include units and identify the conditions attached to each value.
• Use comparative words explicitly when the question says compare.

Explain: connect cause and effect

An explanation adds the biological reason. A useful structure is cause, mechanism and outcome. Name what changes, identify the process or structure involved and show how it produces the effect in the question. The answer should form a chain rather than a collection of correct but disconnected facts.

For example, explaining why vigorous exercise raises breathing rate might connect increased muscle contraction to greater energy demand, a higher rate of respiration, increased oxygen requirement and carbon dioxide production, followed by faster ventilation. The final link matters: it demonstrates why the response is useful rather than merely naming respiration.

• Avoid merely repeating the observation.
• Use precise names for structures and processes.
• Build a linked chain when more than one step is required.
• Check that the final link answers the original question.

Compare: write about both items in the same point

A comparison needs a relationship between the two items. Writing a paragraph about A followed by a paragraph about B leaves the reader to do the comparison. Pair the features instead: ‘A has a thicker wall than B’, or ‘Both contain DNA, but only A has a membrane-bound nucleus’. Use ‘whereas’, ‘both’, ‘higher than’ and ‘in contrast’ to make the relationship clear.

For numerical comparisons, quote paired data and calculate a difference, ratio or percentage only when it helps answer the question. Check that the values come from equivalent points. Comparing the maximum of one curve with the starting value of another may be meaningless unless the question specifically requires it.

Suggest and predict: use evidence plus biological knowledge

‘Suggest’ signals that the exact answer may not have been taught in that form. The response still needs evidence. Look for clues in the stem, graph, diagram or experimental design, then combine them with a relevant biological principle. Use cautious wording when more than one explanation is possible, but make the proposed mechanism clear.

A prediction states what is expected to happen, usually beyond the measured range or after a change in conditions. Give the direction of change and, when asked, a reason. Do not extend a straight-line trend indefinitely if a limiting factor, optimum or biological boundary is likely to alter it.

Calculate and determine: make the method visible

A correct number is strongest when the working can be followed. Write the relationship first, substitute values, keep full calculator precision during the working and round only the final answer. Include the unit and check whether the question specifies significant figures or decimal places. For percentage change, subtract the original value, divide by the original value and multiply by 100.

‘Determine’ may require reading a graph, combining data or reaching a value from several steps. Mark the coordinates used and show conversions. If the answer seems biologically impossible, check the scale and units before moving on. A quick estimate is often enough to catch an error by a factor of ten or one hundred.

Evaluate: weigh evidence before judging

Evaluation is more than listing a strength and a weakness. Identify what the evidence allows you to conclude, how secure that conclusion is and what limits it. In an investigation, consider the range and spacing of the independent variable, repeats, sample size, control of relevant variables, measurement quality, anomalies and whether the method actually tests the stated hypothesis.

Link every comment to the material provided. ‘The sample is small’ becomes useful when you explain that a small sample may not represent the wider population and makes the conclusion less secure. ‘Repeat it’ becomes useful when you state which measurements should be repeated, that a mean should be calculated and that anomalous results can then be identified.

Finish with a qualified judgement. Phrases such as ‘the results support the hypothesis within the tested range, although…’ show both the conclusion and its limitation. Avoid claiming that evidence proves a broad biological statement when the study measured one species, one concentration range or a short time period.

• Use a strength or limitation that is visible in the evidence.
• Explain how it affects confidence in the conclusion.
• Propose a specific improvement when the question requests one.
• End with a judgement that matches the quality and scope of the data.

Build answers around the mark allocation

The command word sets the type of answer; the mark allocation suggests its depth. A two-mark explanation may need a cause and an effect, while a longer response may need several linked stages. Briefly plan longer answers with key terms before writing. This reduces repetition and helps maintain the correct biological order.

After answering, reread the question rather than only your response. Check that every part has been addressed, that pronouns clearly refer to named structures, and that data include units. Command words are practical instructions. Treating them that way makes answers shorter, more relevant and easier for the examiner to credit.