Paper 42, worked through. Cambridge IGCSE Biology, May/June 2026: worked solutions

Eighty marks in an hour and a quarter. The number of marks tells you how many separate points to make: a four-mark "explain" needs four things said, not one thing said at length. Where a mark scheme says "any four from", there are more creditable points than marks, so the answers here give a full set to choose from.

1. 1(a)(i)Working out a rate from a distance and a time.[1]
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   1. The other rows of the table show how the rate was found: distance moved by the bubble ÷ time. For example, 12 ÷ 300 = 0.04.
   2. For a wind speed of 10 m/s: 135 ÷ 300 = 0.45 mm per second.

   Answer0.45

   Match the other values in the column: they are all given to two decimal places.

   Revise this: Transpiration
2. 1(a)(ii)Describing how the rate of transpiration changes as the wind gets faster.[2]
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   1. The overall pattern: as wind speed increases, the rate of transpiration increases.
   2. Now look at how it increases. From 0 to 6 m/s it creeps up, from 0.01 to 0.12. Between 6 and 8 m/s it jumps from 0.12 to 0.38. So the rise is not steady: it is much bigger at higher wind speeds.

   AnswerThe rate increases as wind speed increases, and the increase is not even: it is much greater at the higher wind speeds.

   "Describe" with two marks wants the trend and then something more precise about it. Quoting figures from the table is the easy way to show the second point.

   Revise this: Transpiration
3. 1(a)(iii)Why the rate of transpiration and the rate of water uptake are not quite the same thing.[1]
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   1. The apparatus measures the water the shoot takes up. Most of that water is lost from the leaves as vapour, but not all of it.
   2. The plant keeps some: it is used in photosynthesis, and it keeps the cells turgid.

   AnswerNot all the water taken up is lost by transpiration; some is used by the plant, for example in photosynthesis.

   Naming a use scores. Don't say the water is used in respiration: respiration produces water, and the mark scheme rejects it.

   Revise this: Transpiration
4. 1(a)(iv)Two other conditions that change how fast a shoot loses water.[2]
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   1. Temperature: warmer air makes water evaporate faster and the vapour diffuse faster.
   2. Humidity: when the air is already full of water vapour, less diffuses out of the leaf.

   AnswerTemperature and humidity. (Light intensity is accepted too.)

   The question says other, so wind speed is out. It says environmental as well, so it is about the surroundings, not the plant: leaf size or number of stomata would not count.

   Revise this: Transpiration
5. 1(b)How losing water from the leaves pulls water up the xylem.[4]
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   1. Water evaporates from the surfaces of the mesophyll cells into the air spaces of the leaf, and the vapour diffuses out through the stomata.
   2. Losing water lowers the water potential of the leaf cells, so water moves into them from the xylem.
   3. That pulls on the water in the xylem. This is the transpiration pull.
   4. Water molecules are held to each other by forces of attraction, so the water in the xylem is one unbroken column. Pulling at the top draws the whole column up, from the roots to the leaves.

   AnswerWater evaporates from mesophyll cells and diffuses out through the stomata. This lowers the water potential in the leaf and creates a transpiration pull. The water molecules are held together by forces of attraction, so a continuous column of water is drawn up the xylem.

   Four marks from eight possible points. The ones most often left out are the forces holding the water molecules together and the unbroken column. Use the term "transpiration pull": it is a mark by itself.

   Revise this: Transpiration
6. 2(a)What makes a resource sustainable.[2]
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   1. A sustainable resource is one that is produced as fast as it is removed from the environment.
   2. Because it is replaced as quickly as it is used, it does not run out.

   AnswerA resource that is produced as rapidly as it is removed, so that it does not run out.

   Both ideas are needed for two marks. "It can be reused" or "it can be regrown" is not the definition and is ignored.

   Revise this: Conservation
7. 2(b)Why fish that eat producers grow better in a sunny pond.[3]
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   1. Light is the energy source for photosynthesis. More light means the producers in the pond, the algae and water plants, photosynthesise more.
   2. Light energy is converted into chemical energy in glucose, so the producers grow and there are more of them.
   3. That is more food, and more energy, for the tilapia, which feed on producers. With more food they make more new cells and grow faster.

   AnswerMore light means more photosynthesis by the producers, so more of them grow. That gives the tilapia more food and energy, so the fish grow more.

   Follow the energy in order: light, producers, fish. The fish don't use the light themselves. Photosynthesis also releases oxygen, which the fish need for respiration: that is credited as an extra point.

   Revise this: Food chains, food webs and energy
8. 2(c)(i)The mineral ion that supplies an element found in every protein.[1]
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   1. Proteins are made of amino acids, and every amino acid contains nitrogen.
   2. Plants and algae take in nitrogen as nitrate ions.

   AnswerNitrate ions.

   Magnesium is the other ion the syllabus names, and it is for making chlorophyll, not protein.

   Revise this: Photosynthesis
9. 2(c)(ii)Why we need protein in what we eat.[1]
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   1. Protein supplies the amino acids the body uses to build new cells and tissues.

   AnswerFor growth (or for the repair of tissues).

   Don't say "for energy": the mark scheme ignores it. Carbohydrates and fats are the energy foods.

   Revise this: A balanced diet
10. 2(c)(iii)What too much added organic material can cause in a pond.[1]
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    1. The extra material supplies nutrients such as nitrate. Algae grow fast and cover the water, the plants beneath die for lack of light, and the bacteria that decompose them use up the dissolved oxygen, so fish die.
    2. The name of the whole process is eutrophication.

    AnswerEutrophication.

    "Algal bloom" is one stage of it, and is not accepted as the name of the process.

    Revise this: Pollution
11. 2(d)How a rule about the size of the holes in fishing nets protects fish stocks.[4]
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    1. The holes have to be large enough.
    2. Small, young fish swim through the holes and escape. Only the larger, older fish are caught.
    3. The young fish that escape can grow until they are old enough to breed.
    4. They reproduce, so new fish replace the ones that were caught, and the population does not fall.

    AnswerThe holes must be large, so small, young fish escape and only large fish are caught. The young fish grow to breeding age and reproduce, which keeps the population up.

    Carry the argument through to the end. Many answers stop at "small fish escape" and collect two marks of the four. The point of letting them go is that they live to breed.

    Revise this: Conservation
12. 2(e)The reasons species become endangered.[6]
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    1. Climate change: conditions change faster than a species can adapt.
    2. Habitat destruction, with examples: forests are cleared for farming and building, so there is less food, shelter and space.
    3. Hunting, and overharvesting, such as overfishing: individuals are removed faster than they are replaced.
    4. Pollution, with examples: pesticides, plastics, untreated sewage and oil spills kill organisms or poison their food.
    5. Introduced species: a new predator, or a competitor that takes the food of the native species.
    6. Whatever the cause, the population gets smaller. A small population has less genetic variation and its members find it harder to meet a mate, so it recovers slowly and a disease can wipe it out.

    AnswerClimate change; habitat destruction such as deforestation; hunting and overharvesting; pollution such as pesticides or plastics; and introduced species that compete with or prey on native ones. Each reduces the population, and a small population has less genetic variation and is less able to adapt.

    Six marks means six separate points. Naming examples earns extra marks: two kinds of habitat destruction or two pollutants count as two points each time. Finish by saying what happens to the population, since that link is a mark as well.

    Revise this: Conservation
13. 2(f)Describing artificial insemination and in vitro fertilisation.[5]
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    1. Artificial insemination: semen is collected from a male. It is placed in the female's vagina or uterus, at the time when she is releasing an egg. Fertilisation then happens inside her body.
    2. In vitro fertilisation: eggs are collected from a female and sperm from a male. They are mixed in a dish in a laboratory, so fertilisation happens outside the body. An embryo that develops is then placed in the uterus of a female.
    3. Points that apply to both: the female can be given fertility drugs so that she releases eggs, and sperm can be frozen and stored, or brought from an animal that is far away.

    AnswerAI: semen is collected from a male and inserted into the female's vagina or uterus around ovulation. IVF: eggs and sperm are collected, fertilisation takes place in a dish outside the body, and the embryo is put into a uterus.

    The difference to bring out is where fertilisation happens: inside the female in AI, in a dish in IVF. "In vitro" means "in glass". Be careful with eggs: they are collected in IVF but not in AI.

    Revise this: Conservation
14. 3(a)Completing a table of the parts of the male reproductive system: name, letter and job.[5]
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    1. E is the sperm duct. It carries sperm from the testis towards the urethra.
    2. The prostate gland is D. It makes the fluid that sperm swim in.
    3. F is the scrotum, the sac that holds the testes outside the body.
    4. The tube that both urine and sperm pass through is the urethra, G.
    5. The penis is H. It passes semen into the vagina, and it is also how urine leaves the body.

    AnswerE: sperm duct, carries sperm. Prostate gland: D, makes fluid for the sperm. F: scrotum, holds the testes. Urethra: G. Penis: H, passes sperm into the vagina.

    One mark for each complete row, so a row with one wrong entry scores nothing. For the sperm duct, write sperm and not urine: only the urethra carries both.

    Revise this: Human reproduction
15. 3(b)Why it matters that meiosis happens in the testes.[4]
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    1. J is a testis. Meiosis there produces the male gametes, the sperm, for sexual reproduction.
    2. Meiosis is a reduction division: it halves the chromosome number, so sperm are haploid, with 23 chromosomes where body cells have 46.
    3. When a haploid sperm fertilises a haploid egg, the zygote is diploid again. The chromosome number stays the same from one generation to the next, and does not double each time.
    4. Meiosis also makes the sperm genetically different from one another, which gives variation in the offspring.

    AnswerMeiosis in the testes produces sperm that are haploid. At fertilisation the zygote is therefore diploid, so the chromosome number is kept the same in each generation. It also produces genetic variation.

    Explain the reason for halving. "It halves the chromosomes" is one mark; saying what that achieves at fertilisation is another. Mitosis would give cells with the full number, and the number would double every generation.

    Revise this: Mitosis and meiosis
16. 4(a)The elements in every carbohydrate.[1]
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    1. The name gives it away: carbo- is carbon, and -hydrate is water, which is hydrogen and oxygen.

    AnswerCarbon, hydrogen and oxygen.

    All three are needed for the one mark. Proteins contain these three and nitrogen as well.

    Revise this: Biological molecules and food tests
17. 4(b)(i)Picking out, by letter, the organ that makes urea and the organ that makes pepsin.[2]
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    1. Urea is made in the liver, from amino acids the body does not need. The liver is Q.
    2. Pepsin is the protease in gastric juice, made by the stomach. The stomach is L.

    AnswerUrea: Q. Pepsin: L.

    The kidneys remove urea from the blood. They do not make it.

    Revise this: Excretion and the kidneys
18. 4(b)(ii)Naming the hormone from the pancreas that raises blood glucose, and saying how it works.[3]
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    1. Structure M is the pancreas. When blood glucose falls too low, it releases glucagon.
    2. Glucagon travels in the blood to the liver.
    3. It makes the liver cells break down their stored glycogen into glucose, which passes into the blood.

    AnswerGlucagon. It causes the liver to convert glycogen into glucose, which is released into the blood.

    Three words that look alike: glucagon is the hormone, glycogen is the store, glucose is the sugar. Insulin does the opposite, lowering blood glucose by having glucose stored as glycogen.

    Revise this: Homeostasis
19. 4(b)(iii)Another hormone that raises blood glucose.[1]
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    1. Adrenaline, released in "fight or flight" situations, increases the concentration of glucose in the blood so that muscles have more to respire.

    AnswerAdrenaline.

    Revise this: Hormones
20. 4(c)Comparing two lines on a graph of blood glucose after a meal.[3]
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    1. Level: the person without diabetes is lower all the way through. They start at 90 mg per 100 cm³; the person with diabetes starts at about 120.
    2. Rise: both peak one hour after the meal, but the person without diabetes rises only to 140 mg per 100 cm³, while the person with diabetes reaches 200.
    3. Recovery: the person without diabetes is back at the starting level by about 2.5 hours. The person with diabetes takes until about 5 hours or later.

    AnswerWithout diabetes, the concentration is always lower, it rises by less (to 140 against 200 mg per 100 cm³ at 1 hour), and it returns to its starting level much sooner (2.5 hours against more than 5).

    "Describe" means say what the graph shows, not why. Make each point a comparison, and quote one pair of figures with their units: that is a mark in itself.

    Revise this: Homeostasis
21. 4(d)How type 1 diabetes is treated.[3]
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    1. In type 1 diabetes the pancreas does not make insulin, so insulin is given: by injection, or by a pump.
    2. Blood glucose is tested regularly, to judge how much insulin is needed.
    3. The diet is managed: the amount of carbohydrate eaten is counted and matched to the insulin dose and to how active the person is.

    AnswerInsulin injections, regular testing of blood glucose, and controlling the amount of carbohydrate in the diet.

    Say how the insulin gets in: "insulin" alone is not credited. It cannot be swallowed, because it is a protein and would be digested.

    Revise this: Homeostasis
22. 5(a)Explaining why onion cells look different after an hour in two salt solutions.[6]
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    1. Water moves by osmosis, through the partially permeable cell membrane, from a higher water potential to a lower one.
    2. Solution A is the more dilute of the two. It has a higher water potential than the cell contents, so water moves into the cells.
    3. The vacuole swells and takes up more of the cell. It pushes the cytoplasm against the cell wall: the cell is turgid. The cell wall stops the cell from bursting.
    4. Solution B is more concentrated than the cell contents. It has a lower water potential, so water moves out of the cells.
    5. The vacuole shrinks, so the coloured contents take up less space and look darker. The cell membrane pulls away from the cell wall: the cell is plasmolysed.

    AnswerWater moves by osmosis through the partially permeable membrane. Solution A has a higher water potential than the cells, so water enters, the vacuoles swell and the contents press on the cell walls. Solution B has a lower water potential than the cells, so water leaves, the vacuoles shrink and the membranes pull away from the walls.

    Six marks: aim for three points on each solution, and use the terms osmosis, partially permeable membrane and water potential. Writing "water concentration" does not earn the water potential mark.

    Revise this: Osmosis
23. 5(b)(i)What mitosis does in a root.[3]
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    1. Mitosis produces new cells that are genetically identical.
    2. The new cells make the root grow longer.
    3. They also replace cells that are worn away, and repair damaged tissue.

    AnswerIt produces new cells for growth of the root, for the replacement of cells, and for the repair of damaged tissue.

    Write "repair of tissues" and "replacement of cells". "Repair cells" is not credited: a damaged cell is replaced, not mended.

    Revise this: Mitosis and meiosis
24. 5(b)(ii)What stem cells are for in a root.[1]
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    1. Stem cells are unspecialised. They divide by mitosis, and the cells they produce can become specialised for particular jobs.

    AnswerThey divide to produce cells that can become specialised, such as root hair cells or xylem.

    Revise this: Mitosis and meiosis
25. 5(b)(iii)The substance in a leaf cell that contains magnesium.[1]
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    1. Magnesium ions are needed to make chlorophyll, the green pigment that absorbs light for photosynthesis.

    AnswerChlorophyll.

    Chloroplast is where the chlorophyll is kept. It is a structure, not a substance, and the mark scheme ignores it.

    Revise this: Photosynthesis
26. 5(b)(iv)How roots take in mineral ions.[3]
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    1. Mineral ions are absorbed by active transport, into the root hair cells.
    2. They are moved from a lower concentration in the soil water to a higher concentration inside the cell: against the concentration gradient.
    3. That takes energy from respiration, and it is done by protein carriers in the cell membrane.

    AnswerBy active transport into root hair cells: ions are moved across the cell membrane by protein carriers, against the concentration gradient, using energy from respiration.

    Water enters by osmosis and mineral ions by active transport: keep the two apart. Diffusion only counts if you say the ions are more concentrated outside the root.

    Revise this: Active transport
27. 6(a)(i)Naming three parts of the heart from a diagram.[3]
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    1. Q is a valve between an atrium and a ventricle: an atrioventricular valve.
    2. R is a valve at the way out of a ventricle, where the artery begins: a semilunar valve.
    3. S is the lower chamber on the right-hand side of the diagram. The heart is drawn as if it is facing you, so that is its left side: the left ventricle.

    AnswerQ: atrioventricular valve. R: semilunar valve. S: left ventricle.

    Left and right are the heart's own, not yours, which is why the left ventricle is on the right of the page. It has the thicker wall of the two ventricles, because it pumps blood all the way round the body.

    Revise this: Circulation and the heart
28. 6(a)(ii)The part of the heart that keeps oxygenated and deoxygenated blood apart.[1]
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    1. The wall of muscle down the middle of the heart is the septum. It separates the right side, with deoxygenated blood, from the left side, with oxygenated blood.

    AnswerT

    The question asks for the letter. Writing "septum" without the letter does not answer it.

    Revise this: Circulation and the heart
29. 6(a)(iii)The vessel the drainage tubes are attached to.[1]
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    1. The tubes take blood out of the body before it reaches the heart. Blood returning from the body arrives at the right atrium in the vena cava.

    AnswerThe vena cava.

    Revise this: Circulation and the heart
30. 6(a)(iv)The organ that the oxygenator stands in for.[1]
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    1. The oxygenator adds oxygen to the blood and takes carbon dioxide out. In the body that gas exchange happens in the lungs.

    AnswerThe lungs.

    The pump in the machine does the job of the heart. Between them, the two parts explain the machine's name.

    Revise this: Circulation and the heart
31. 6(b)The arteries that supply the heart's own muscle.[1]
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    1. The heart muscle gets its oxygen from the coronary arteries, which run over the surface of the heart.

    AnswerThe coronary arteries.

    When one of these is blocked, part of the heart muscle is starved of oxygen: that is coronary heart disease.

    Revise this: Circulation and the heart
32. 6(c)Filling four gaps in a description of the human circulation.[4]
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    1. Blood goes through the heart twice on each complete circuit: once on the way to the lungs and once on the way to the rest of the body.
    2. That makes it a double circulation.
    3. Because the blood returns to the heart after the lungs and is pumped again, it travels round the body at high pressure.
    4. So oxygen reaches the cells quickly, for aerobic respiration, which releases energy.

    Answertwice; double; high; respiration

    A fish has a single circulation: the blood passes through its heart once per circuit and loses pressure in the gills.

    Revise this: Circulation and the heart

These explanations are Papermunch’s own, written to teach the method. The answers have been checked against the exam board’s mark scheme, which has the final say: open it above. The question paper and mark scheme belong toCambridge University Press & Assessment: each question shown here is drawn from the paper itself as you read, and is not kept on this site.