In short
IGCSE Biology is marked by the exam board against a mark scheme that lists the points worth credit, usually one mark per correct point. Cambridge 0610 combines three papers (30%, 50% and 20%) into a grade from A* to G. Edexcel 4BI1 adds two papers (110 + 70 marks) into a total out of 180 and awards grades 9 to 1.
Every IGCSE Biology paper is marked by the exam board, not your school, using a mark scheme. The mark scheme lists the marking points that earn credit, and in most written questions each correct point earns one mark, up to the marks shown. Your paper marks are then combined and turned into a grade using grade boundaries set for that exam series.
This guide covers both boards: Cambridge IGCSE Biology 0610 (and Combined Science 0653) and Pearson Edexcel International GCSE Biology 4BI1. The paper facts come from the official specifications. Our free notes are on the Cambridge IGCSE Biology and Edexcel IGCSE Biology course pages.
How Cambridge IGCSE Biology 0610 is marked
All 0610 candidates take three papers, all externally assessed. Core candidates sit Papers 1, 3 and 5 or 6, and can get grades C to G. Extended candidates sit Papers 2, 4 and 5 or 6, and can get grades A* to G.
| Paper | Time | Marks | Weighting | What it tests |
|---|---|---|---|---|
| Paper 1 (Core) or Paper 2 (Extended): Multiple Choice | 45 minutes | 40 | 30% | 40 four-option questions; AO1 and AO2 |
| Paper 3 (Core) or Paper 4 (Extended): Theory | 1 hour 15 minutes | 80 | 50% | Short-answer and structured questions; AO1 and AO2 |
| Paper 5: Practical Test | 1 hour 15 minutes | 40 | 20% | Experiments in a laboratory; AO3 only |
| Paper 6: Alternative to Practical | 1 hour | 40 | 20% | Written questions about experiments; AO3 only |
Across the whole IGCSE, 50% of the marks are for AO1 (knowledge with understanding), 30% for AO2 (handling information and problem-solving) and 20% for AO3 (experimental skills and investigations). The practical papers are entirely AO3, and the other papers have no AO3 marks. So recall is only half the qualification.
The multiple-choice paper has one mark per question and a blank scores nothing, so always choose an answer. Papers 5 and 6 are the same for Core and Extended candidates. Our IGCSE Biology Paper 6 guide covers the practical paper in detail.
Cambridge IGCSE Combined Science 0653
0653 uses the same pattern: multiple choice (40 marks, 30%), theory (80 marks, 50%) and Paper 5 or 6 (40 marks, 20%), with the same Core and Extended routes and grade ranges. The difference is that each paper covers biology, chemistry and physics, so biology is only part of each paper. See our Cambridge IGCSE Combined Science course.
How Edexcel IGCSE Biology 4BI1 is marked
Edexcel 4BI1 is untiered: everyone sits the same two papers in the same series, set and marked by Pearson. There is no practical exam or coursework; practical skills are tested in the written papers.
| Paper | Time | Marks | Weighting | Content |
|---|---|---|---|---|
| Paper 1 (4BI1/1B) | 2 hours | 110 | 61.1% | All content not in bold (no 'B' statements) |
| Paper 2 (4BI1/2B) | 1 hour 15 minutes | 70 | 38.9% | All content, including the bold 'B' statements |
The specification says the total is 180 marks, made by adding Paper 1 (out of 110) and Paper 2 (out of 70), and that "the marks for the papers are not scaled". Your grade, from 9 (highest) to 1, is based on that total. Both papers mix multiple-choice, short-answer, calculation and extended open-response questions. AO1 (knowledge) and AO2 (application and analysis) are each 38 to 42% of the marks, and AO3 (experimental skills) is 19 to 21%.
Science (Double Award) 4SD0 students sit the same Biology Paper 1 as 4BI1 students, alongside chemistry and physics papers, and get a grade on a 9-9 to 1-1 scale. See our Edexcel IGCSE Double Award course, and our Cambridge vs Edexcel IGCSE Biology guide for a full comparison of the boards.
How an IGCSE Biology mark scheme works
Both boards publish mark schemes with their past papers, and they work in a similar way. The mark scheme usually lists more acceptable points than there are marks, and you get one mark per correct point, up to the maximum. A 3-mark question needs three separate ideas, not one idea written three ways.
Mark schemes also tell examiners how to treat answers that are close but not exact. Wording varies by board, but you will typically see conventions like these:
| Convention | What it means | What to do |
|---|---|---|
| Allow / accept, AW (alternative wording) | Another answer or wording that also gets the mark | Use the scientific term where you can; you do not need the exact mark scheme words |
| Ignore | Extra words that neither gain nor lose the mark | Do not pad answers: ignored words waste time |
| Reject / do not accept | An answer that does not get the mark, often a common misconception | Avoid vague or wrong terms, such as enzymes being 'killed' |
| ORA (or reverse argument) | The opposite statement is also credited, for example 'smaller' instead of 'larger' when comparing the other way round | Make your comparison clear and consistent |
| Max | A limit on how many marks one group of points can score | Cover different ideas, not just one area |
| Error carried forward | In multi-step calculations, a wrong earlier value can still earn credit for later steps done correctly | Always show your working |
Writing a correct point and a wrong point that contradicts it. Examiners mark what you write, and a contradiction can cancel the mark. If you are unsure between two answers, choose one.
Mark your own answers against real mark schemes: our Cambridge IGCSE past papers and Edexcel IGCSE past papers pages link to the official papers, mark schemes and examiner reports.
Command words and how they map to marks
The command word tells you what kind of point earns the mark. Both boards publish their own list, and the definitions differ slightly, so learn the one for your board.
| Command word | Cambridge 0610 meaning | Edexcel 4BI1 meaning | What earns marks |
|---|---|---|---|
| State / Give | "express in clear terms" / "produce an answer from a given source or recall/memory" | Give, State and Name are treated as synonyms that require recall | A short, correct fact |
| Describe | "state the points of a topic / give characteristics and main features" | Give an account; statements developed but need not include a reason | What happens, with values quoted |
| Explain | "set out purposes or reasons / make the relationships between things clear / say why and/or how and support with relevant evidence" | Must contain some element of reasoning or justification | A reason for each point ('because', 'so') |
| Suggest | Apply knowledge to situations where there are "a range of valid responses" | Propose a solution to a problem in a novel context | Any sensible biological answer that fits |
| Calculate | "work out from given facts, figures or information" | Obtain a numerical answer, showing relevant working | Working and a correct answer with its unit |
| Evaluate | "judge or calculate the quality, importance, amount, or value of something" | Weigh strengths and weaknesses and reach a supported judgement | Points on both sides and a conclusion |
Edexcel's list also includes Comment on, Deduce, Determine (the answer must include a quantitative element), Discuss, Justify, Plot and Sketch. The 0610 list also defines Compare, Define, Identify, Outline, Predict and Sketch, and the 0653 list is longer. Look up any term you meet in the Cambridge IGCSE glossary or the Edexcel IGCSE glossary.
"Describe" questions about a graph or table want the pattern and numbers from the data. "Explain" questions want the biology behind the pattern. Many questions ask for both, so do both.
Calculations and units
A calculation often has a mark for the working and a mark for the answer, so clear working can still score if the answer is wrong. The Cambridge syllabus says "a measurement or calculated quantity must be accompanied by a correct unit, where appropriate", and both boards expect a sensible number of significant figures. Expect percentages, percentage change, means, rates, gradients and (for Cambridge) magnification.
Rate of an enzyme reaction
Our practice question: In an amylase experiment, the starch was fully broken down after 50 s. Calculate the rate of reaction as 1 ÷ time. Give your answer with its unit. [2]
- Write the method: rate = 1 ÷ time = 1 ÷ 50 s. This earns the working mark.
- = 0.02
- The unit of 1 ÷ time in seconds is s⁻¹ (per second).
Answer: 0.02 s⁻¹ (one mark for 1 ÷ 50, one mark for 0.02 with the unit)
Use the units given in the question. The Cambridge syllabus says you should not convert to other units unless the question asks, and that cubic decimetres (dm³) are used instead of litres.
How extended answers are marked
Edexcel 4BI1 papers include "extended open-response questions", but the specification does not set a fixed mark value for them, so check the format in Pearson's sample assessment materials and past mark schemes. Cambridge theory papers use "short-answer and structured questions", where a long question is usually broken into parts. On both boards, a longer answer is still marked point by point, so plan one clear, separate point for each mark.
- Count the marks and plan that many points, plus one spare.
- Follow the command word: for "explain", every point needs a reason.
- Use specification terms, such as "active site" and "denatured", and quote any data given, with units.
How drawings and graphs are marked
Drawings and graphs are marked against fixed rules, set out in the 0610 syllabus: drawings in sharp pencil, large, unshaded, with ruled label lines that touch the feature; graphs with axes labelled quantity / unit, scales using more than half the grid, accurate points and one thin, smooth best-fit line. Edexcel's definition of Plot asks for accurate points, a line of best fit, and a suitable scale and labelled axes if they are not given. The full rules are in our Paper 6 guide.
Each of those rules can be a separate mark, which makes them some of the easiest marks on the paper. Practise them with our notes on biological drawings and graphs and charts.
Worked example: a mark scheme in action
This is our practice question, written to match Cambridge 0610 Supplement point 5.1.8 (an Extended topic) and Edexcel 4BI1 point 2.11. The marking points are our own, written in the style of a real mark scheme.
Explain the effect of temperature on enzyme activity [4]
Our practice question: A student measured the rate of an enzyme-controlled reaction at different temperatures. The rate increased from 10 °C to a maximum at 40 °C, then fell to zero at 60 °C. Explain these results. [4]
- Point 1: as temperature rises to 40 °C, molecules gain kinetic energy.
- Point 2: more frequent effective collisions, so more enzyme-substrate complexes form. Allow 'substrate fits the active site more often'.
- Point 3: 40 °C is the optimum temperature. Ignore 'works best' without 'optimum'.
- Point 4: above 40 °C the enzyme is denatured, as the active site changes shape. Reject 'the enzyme is killed'.
- Point 5: the substrate no longer fits, so fewer enzyme-substrate complexes form and the rate reaches zero at 60 °C.
- Any four points (max 4).
Answer: As the temperature rises from 10 °C to 40 °C, the enzyme and substrate molecules gain kinetic energy [1], so they collide more often and more enzyme-substrate complexes form [1]. 40 °C is the optimum temperature [1]. Above 40 °C the enzyme is denatured: the bonds holding it in shape break and the active site changes shape [1], so the substrate no longer fits and no enzyme-substrate complexes form by 60 °C [1]. (5 creditworthy points, 4 marks awarded)
A weaker answer, "The rate goes up because it gets hotter, then the enzyme gets killed so it stops working", would score little or nothing: it gives no reason for the rise and uses "killed". Revise this in our temperature and enzymes notes for Cambridge and Edexcel, and the practical sheets for Cambridge and Edexcel.
Common ways students lose marks
- Not matching the command word: describing when the question says explain, or explaining at length for a 1-mark "state".
- Too few points for the marks: three marks need three separate ideas.
- Vague words: "it", "the amount" or "it changes colour" instead of naming the quantity or the start and end colours.
- No data quoted when a question gives a graph or table.
- Missing units or working in calculations.
- Breaking drawing and graph rules: shading, arrowheads on label lines, small scales, dot-to-dot lines.
- Misconceptions that mark schemes reject, such as enzymes being killed.
How to use mark schemes to revise
- Learn the content topic by topic from the Cambridge or Edexcel course page, and tick it off on the Cambridge specification checklist or Edexcel specification checklist.
- Answer questions under timed conditions, using our Cambridge IGCSE exam questions, Edexcel IGCSE exam questions or all exam questions. For enzymes, try the Cambridge enzymes questions or the Edexcel biological molecules and enzymes questions.
- Mark your answers against the mark scheme, tick each point you made, then rewrite weak answers so each mark has its own clear point.
- Practise practical questions with the Cambridge practicals, Edexcel practicals or the main practicals page.
- Finish with full, timed past papers from the official boards.
If you want help turning what you know into marks, we offer 1-to-1 biology tutoring online and in Dubai.
Sources: Cambridge IGCSE Biology 0610 syllabus 2026 to 2028, Cambridge IGCSE Combined Science 0653 syllabus 2025 to 2027 and the Pearson Edexcel International GCSE Biology 4BI1 specification.