A-Level Biology exam technique: where students lose marks

Most marks lost in A-Level Biology are not lost because a student does not know the content. They are lost because the answer is close but not quite what the mark scheme credits. The good news is that these slips are predictable, which means you can train them out.

Read the command word before anything else

The command word tells you what kind of answer earns marks. Two answers with identical biology can score very differently.

• Describe means say what happens. For a graph, that is the trend, with figures read off the axes and their units.
• Explain means say why it happens. Each step of the reasoning is usually a separate mark point.
• Suggest means apply what you know to an unfamiliar context. There is rarely one right answer, but there is a right kind of answer: a plausible biological reason.
• Compare means give similarities or differences side by side. A sentence about one thing followed by a sentence about the other is not a comparison until you link them with "whereas" or "both".

If a question says "describe and explain", split your answer into those two halves. It stops you running out of description and drifting into explanation without noticing.

For more on this, see our guide to command words in A-Level science.

Where students trip up most often

Enzymes: "complementary", not "the same shape"

An enzyme's active site is complementary to its substrate. Saying the substrate is "the same shape" as the active site is a classic way to drop a mark. When an enzyme denatures, say what actually happens: the hydrogen bonds and ionic bonds holding the tertiary structure break, the active site changes shape, and fewer enzyme-substrate complexes form.

Practise this on proteins and enzymes questions.

Water potential, not "water concentration"

Water moves by osmosis from a region of higher water potential to lower water potential (less negative to more negative) across a partially permeable membrane. Answers that talk about "water concentration" or say water moves "to where there is more solute" are usually not credited, even though the idea behind them is right.

Energy is released, ATP is produced

Respiration releases energy and produces ATP. It does not "make energy" or "produce energy". The same goes for photosynthesis: light energy is converted to chemical energy, it is not created.

Try this wording on respiration questions.

Graphs: trend, figures, units

"It goes up" earns nothing. A full description gives the direction of the trend, any change in that trend, and quotes values with units, for example "the rate increases to a maximum of 4.2 cm³ per minute at 40 °C, then falls". If there is an anomaly, name it.

Calculations: show the working, match the data

Write the working even when you can do it in your head. A wrong final answer with correct working often still earns a mark, while a wrong answer on its own earns none. Give your answer to the same number of significant figures as the data, and check the units the question asks for.

Use the marks as a guide to length

The number of marks is the number of separate creditable points the examiner is looking for. A 4-mark explain question wants four distinct ideas, not one idea written four ways. Before you write, jot down the points in the margin and count them.

Train it with real practice

Knowing these traps is not the same as avoiding them under time pressure. The only way that sticks is answering questions, then checking your answer against the mark scheme point by point and noticing which wording you missed.

That is exactly how ExamKata's questions work: answer first, reveal the full mark scheme, and tick only the points you actually made. Your stats page then shows the mark points you keep missing, so you know which habits to fix.