Common Command Word Mistakes in Biology

A right idea in the wrong command-word shape still loses marks

Command words such as describe, state, explain, compare, discuss, suggest and calculate each set a specific kind of response, and a mark scheme is written to match that specific shape. Correct biological content written in the wrong shape for the command word used, reasons given where only a description was asked, one point given where a paired comparison was required, regularly loses marks that have nothing to do with whether the underlying biology is understood.

These are not content errors; they are matching errors between what the question asked for and what was written, and they are common enough to be worth checking for deliberately rather than assumed away.

Common mistakes by command word

The two mistakes that cost the most marks

Explaining under a "describe" command word is the most common way that time is lost without any matching gain in marks, the reasoning added is often correct biology, but the mark scheme for a "describe" question credits the description itself, not the reason behind it, so the extra sentences use up time that could go toward another question. The reverse also loses marks: answering "explain" with only an observation, leaving out the reason, misses exactly the point the question was built to test.

Comparison questions lose marks in a similarly specific way, giving one difference on its own ("Plant A has broad leaves") without stating what the other item does instead ("...while Plant B has narrow leaves") often earns nothing, because a comparison mark usually requires both halves of the contrast in the same point. Describing each item's features in two separate paragraphs, without ever placing them side by side, has the same effect even when every individual fact stated is correct.

Compound command words that get half-answered

Some questions use two command words together, such as "state and explain" or "describe and label", and each half usually carries its own marks. Answering only the second instruction, explaining without first clearly stating what is being explained, or describing a diagram without labelling it, leaves the marks tied to the first instruction unclaimed even when the second half is done well.

The safest habit is treating each command word in a compound instruction as a separate mini-task with its own marks, answering both in the order they appear, rather than reading the whole instruction as one general request.

How can you tell 'describe' and 'explain' apart at a glance?

The quickest test is to ask what the mark scheme would reward. If a point earns credit for saying what happens or what is seen, the command word is 'describe'; if it earns credit only when a reason is attached, the word is 'explain'.

Reading the command word this way, as a signal of what kind of point scores, is faster than recalling a definition of each term under time pressure.

Take transpiration as a worked contrast. 'Describe how water moves up the stem' rewards the sequence, water is lost from the leaves, this pulls the column of water upward through the xylem, and more water is drawn in at the roots.

'Explain why water moves up the stem' rewards the cause behind each step, evaporation from the mesophyll lowers the water potential in the leaf, so water is pulled up a continuous column held together by cohesion. Same topic, two different shapes of answer, decided entirely by the command word.

Which command words carry the most marks in the Paper 2 essay sections?

The extended-writing questions in Paper 2 reward command words differently from the short structured items. Section C in particular sets essay-style questions where 'explain', 'describe' and 'discuss' each expect sustained, ordered points rather than a single line, and marks are shared between the biological content and the way it is organised.

Because these questions carry a fixed block of marks, treating the command word as a plan for the whole answer, not just the first sentence, is what turns knowledge into marks. An 'explain' essay needs a reason attached to each stated fact throughout; a 'discuss' essay needs more than one factor weighed before a closing judgement.

• Paper 2 is worth 100 marks over 2 hours 30 minutes.
• Section B is worth 20 marks, and Section C is worth 20 marks.
• Section A carries 60 marks across 8 questions (answer all).

What does the command word tell you about how much to write?

A command word is also a rough guide to length. 'State' and 'name' expect a word or a short phrase, so a full sentence wastes time another question could use.

'Describe' expects an ordered set of points with no reasons; 'explain' expects each point paired with its cause, which roughly doubles the writing per mark.

'Discuss' asks for the most: more than one factor or viewpoint, set out in turn, before a short judgement that ties them together. Matching the amount written to what the command word expects keeps the pace steady and stops a single early question from eating the time needed later in the paper.

A quick check before moving to the next question

Frequently asked questions