How to Answer IGCSE Biology 0610 Paper 4 Describe and Explain Questions

In Cambridge IGCSE Biology 0610 Paper 4, "describe" asks you to state the points or main features of something, and "explain" asks you to give reasons, saying why or how. A describe answer earns one mark per separate observation. An explain answer earns marks for each linked step in the reasoning, usually one step per mark.

Paper 4 is the Extended theory paper: 1 hour 15 minutes, 80 marks and 50% of the qualification. The syllabus says Papers 3 and 4 test knowledge with understanding (63% of the marks) and handling information and problem-solving (37%). Most of the long answers on the paper start with one of two words, describe or explain, and students lose marks by answering the wrong one. The examples below come from the June 2026 paper 0610/42, which is in the PapaMarks past papers library with its mark scheme.

What Cambridge means by describe and explain

The command-word table in the current 0610 syllabus (version 3, published August 2026) gives these meanings:

In practice, describe asks "what" and explain asks "why" or "how". If a question says "describe and explain", it wants both, and the mark scheme usually splits the marks between them. Our general guide to IGCSE command words covers the rest of the table.

Describe: a worked example from 0610/42, June 2026

Question 4(c) shows a graph of blood glucose concentration for six hours after a meal, for a person with diabetes and a person without. It asks: "Describe the differences between the blood glucose concentrations of the person without diabetes and the person with diabetes." It is worth 3 marks.

The published mark scheme gives four marking points and awards any three. For the person without diabetes, blood glucose:

1. is always lower
   The reverse statement (higher with diabetes) is also accepted.
2. rises more slowly, or by a smaller amount
   This is the shape of the curve, put into words.
3. falls back to its starting level faster
   The scheme accepts a return in 2.5 hours without diabetes against 5, 5.5 or 6 hours with it.
4. a comparative data quote
   A pair of readings from the graph. The scheme says units must be stated at least once for both variables, so write "mg per 100 cm³" and "hours".

None of the four points mentions insulin. The question asks what the graph shows, so an answer that explains why the person with diabetes has high glucose earns nothing for that sentence, however correct the biology is. A full-mark answer could read: "Without diabetes, blood glucose is lower throughout and rises less after the meal. It returns to its starting concentration after about 2.5 hours, while with diabetes it takes about 5 hours." Each sentence lands on a different marking point.

The same pattern shows up in older papers. In the PapaMarks question bank, 0610 November 2010 Paper 2 (variant 2) question 2(b) asks students to "Describe two external features that occur in insects but do not occur in other arthropods." The mark scheme wants two features: three pairs of legs, and three body regions (head, thorax and abdomen). Describing a feature means naming it precisely. "Six legs" is the feature; "insects can walk" is not.

Explain: two worked examples from the same paper

Question 2(d), 4 marks

"One way of conserving wild fish stocks is to regulate the size of the holes in the nets that are used to catch the fish. Explain how this helps to conserve fish stocks."

The mark scheme reads as a chain. Any four of these five points score:

1. The holes should be large
   The scheme ignores "nets are large", so name the holes.
2. Small or young fish escape
   Or: only large, older fish are caught.
3. The escaped fish grow to sexual maturity
   "Reach breeding age" is also accepted.
4. They can reproduce
   This is the step most students leave out.
5. The population size is maintained
   The end of the chain, linked back to the question.

A student who writes "larger holes let small fish escape so there are more fish" has made two points and jumped to the end. The marks sit in the middle of the chain, in why escaping fish matter: they grow up and breed. That is what "say why and/or how" means in the syllabus definition.

Question 5(a), 6 marks

Onion cells were placed in two salt solutions, A and B, and photographed. The question asks: "Explain the appearance of the plant cells shown in Figure 5.1." There are ten marking points and the scheme caps the answer at six. They include a reference to osmosis, water moving across a partially permeable membrane, solution A being less concentrated than B, water moving into the cells in A, the vacuole getting larger, solution A having a higher water potential than the cells, the membrane pushing on the cell wall (turgor pressure), and in B the membrane coming away from the wall.

Two lessons come out of this one question. First, an explain answer to a picture still has to say what you see (the vacuole is bigger, the membrane has pulled away), and then give the reason. Second, the scheme ignores "water concentration" for the water potential point. The syllabus wording is "water potential", and in a 6-mark question the keyword is worth a mark on its own. Our osmosis guide for 0610 covers that wording in full.

A method for any describe or explain question

1. Circle the command word and the mark in brackets
   The mark tells you how many points the examiner is looking for. For [4], plan four separate points.
2. For describe, write what changes and by how much
   Compare, give the trend, then quote two readings from the graph with units. Leave reasons out unless the question asks for them.
3. For explain, build a chain with "so" or "because"
   Write each link as its own sentence. If two ideas are joined only by "and", one of them is probably not a reason.
4. Use the syllabus term
   Water potential, partially permeable membrane, haploid, sexual maturity. The mark scheme is written in syllabus language.
5. Mark it against the published scheme
   Award a point only when your words match it. Our self-marking guide sets out the routine.

Question 3(b) on the same paper is a good test of the method: "Explain the importance of meiosis occurring in structure J" (the testis), for 4 marks. The mark scheme credits any four of: it produces sperm; for sexual reproduction; it halves the chromosome number to make haploid cells; so the sperm can fertilise an egg; the zygote is diploid; it allows genetic variation; and the sperm determines the sex of the offspring. Try writing a four-link answer before you look.

For more practice, the 0610 past papers library holds 62 Paper 4 question papers from 2016 to 2026, each with its own mark scheme. If you are aiming for the top grade, our 0610 A* guide shows where Paper 4 sits in the total.

FAQ

Sources

• Cambridge International, Cambridge IGCSE Biology 0610 syllabus for 2026, 2027 and 2028, version 3, August 2026: command words, assessment overview and assessment objective weightings.
• Cambridge IGCSE Biology 0610/42, Paper 4 Theory (Extended), May/June 2026, question paper and published mark scheme, questions 2(d), 3(b), 4(c) and 5(a), and the science-specific marking principles. Held in the PapaMarks library.
• Cambridge IGCSE Biology 0610, November 2010, Paper 2 variant 2, question 2(b), and its mark scheme, as held in the PapaMarks question bank.