Paper 12, worked through. Cambridge IGCSE Biology, May/June 2026: worked solutions

Forty questions, one mark each, 45 minutes: just over a minute a question. Most are won by knowing a definition or a diagram exactly, so read every option before you choose: the wrong ones are often true statements that answer a different question. If one is taking too long, put a mark beside it, guess, and come back at the end.

1. 1Which two characteristics of living things a plant shows when it grows towards light.[1]
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   1. Phototropism is a plant's response to the direction of light. Responding to a change in the surroundings is sensitivity.
   2. The plant responds by growing: the shoot grows towards the light. That is growth.

   AnswerB: growth and sensitivity.

   The light is used for nutrition later on, but phototropism itself is the response, not the feeding.

   Revise this: What living things do
2. 2What the binomial system is.[1]
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   1. "Binomial" means two names. Every species is given a name in two parts: the genus first, then the species, as in Homo sapiens.

   AnswerA: giving all organisms a genus name and a species name.

   The genus has a capital letter and the species does not. Kingdoms and keys are part of classifying organisms, but they are not the naming system.

   Revise this: Classifying and naming living things
3. 3The features that every mammal has.[1]
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   1. Mammals have hair or fur, and the females produce milk for their young.
   2. Mammals are vertebrates, so they all have a backbone made of vertebrae.

   AnswerA: all three features are present in all mammals.

   Having vertebrae is shared with fish, amphibians, reptiles and birds as well. The question asks what all mammals have, not what only mammals have.

   Revise this: The groups of living things
4. 4Identifying an organelle in a diagram of a plant cell.[1]
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   1. X is a small oval in the cytoplasm with a folded line drawn inside it. That is how a mitochondrion is shown: the folds are its inner membrane.
   2. Compare it with the others. The chloroplasts are the darker ovals with stripes, the nucleus is the round structure, and the vacuole is the large space in the middle of the cell.

   AnswerB: mitochondrion.

   When two kinds of oval organelle are drawn, there are usually several chloroplasts and they are shaded or striped. Mitochondria are where aerobic respiration happens.

   Revise this: Cell structure
5. 5Working out the magnification of a drawing.[1]
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   1. Magnification = size of the image ÷ actual size.
   2. Both sizes are in millimetres, so divide straight away: 36 ÷ 0.60 = 60.

   AnswerD: ×60

   The drawing is bigger than the real thing, so the answer must be more than 1. Dividing the wrong way round gives 0.017, and multiplying gives 21.6: both are options.

   Revise this: Magnification
6. 6The features of diffusion.[1]
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   1. Diffusion is the net movement of particles from where they are more concentrated to where they are less concentrated.
   2. It does not have to be across a cell membrane: a smell spreading across a room is diffusion.
   3. It needs no energy from respiration. The particles move because of their own random motion.

   AnswerA: high to low concentration, not always across a membrane, no energy from respiration.

   Movement from low to high concentration, using energy from respiration, is active transport.

   Revise this: Diffusion
7. 7The small molecules that cellulose is built from.[1]
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   1. Cellulose is a carbohydrate, like starch and glycogen. All three are long chains of glucose molecules.

   AnswerC: glucose.

   Proteins are made from amino acids. Fats and oils are made from fatty acids and glycerol.

   Revise this: Biological molecules and food tests
8. 8The test for protein and its result.[1]
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   1. The test for protein uses biuret solution. If protein is present, the blue solution turns purple.

   AnswerD: biuret, purple.

   Benedict's solution is for reducing sugars: heated, it goes from blue to brick-red. Iodine solution is for starch: it goes blue-black.

   Revise this: Biological molecules and food tests
9. 9The correct statement about enzymes.[1]
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   1. Enzymes are biological catalysts: proteins that speed up reactions without being changed by them.
   2. The reactions that keep an organism alive would be far too slow without them.

   AnswerB: they are catalysts that maintain the rate of the reactions needed to sustain life.

   Enzymes are denatured by high temperatures, not low ones. At low temperatures they only work slowly. And every living cell has enzymes, including bacteria and fungi.

   Revise this: Enzymes
10. 10Predicting how the air in three test-tubes changes when a water plant is given dim light, no light and bright light.[1]
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    1. Tube 2 is in a black bag, so the plant gets no light and cannot photosynthesise. It still respires, so it gives out carbon dioxide: the carbon dioxide goes up.
    2. Tube 3 has bright light. Photosynthesis is fast, so a lot of oxygen is released: a large increase in oxygen.
    3. Tube 1 has dim light. Photosynthesis is slow, so there is only a small increase in oxygen.

    AnswerC: carbon dioxide rises in 2, oxygen rises a lot in 3 and a little in 1.

    Plants respire all the time and photosynthesise only in the light. In the dark, respiration is the only one of the two that is happening.

    Revise this: Photosynthesis
11. 11What nectar is for.[1]
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    1. Nectar is a sugary liquid made at the base of the petals. Insects visit the flower to feed on it.
    2. As they feed, they pick up pollen and carry it to the next flower.

    AnswerA: to attract insects for pollination.

    Revise this: Reproduction in flowering plants
12. 12Naming four labelled parts in a section through a leaf.[1]
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    1. P is the thin layer on the outside of the top of the leaf: the waxy cuticle.
    2. Q points into the vascular bundle, the cluster of small cells in the middle. Xylem is in the upper part of the bundle.
    3. R points to one of the small bodies inside a mesophyll cell: a chloroplast.
    4. S is the gap between two guard cells in the lower surface: a stoma.

    AnswerB: cuticle, xylem, chloroplast, stoma.

    P alone decides it, since only one row starts with cuticle. Check one more label to be sure, then move on.

    Revise this: Leaf structure
13. 13Comparing two kinds of milk from a table of nutrients.[1]
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    1. Check each statement against the numbers.
    2. Fat: 17.0 against 8.5. R has double, which is 100% more, not 50% more.
    3. Protein: 16.5 against 3.3. The difference is 13.2, and 13.2 ÷ 3.3 = 4, so R has 400% more.
    4. Milk S has less protein, so fewer amino acids, and less of everything, so less energy.

    AnswerB: milk R contains 400% more protein than milk S.

    "More than" in percentages means the difference divided by the smaller amount. Five times as much is 400% more, not 500% more.

    Revise this: A balanced diet
14. 14Where starch is digested.[1]
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    1. Starch is digested by amylase. Amylase is in saliva, so digestion starts in the mouth.
    2. More amylase is made by the pancreas and released into the duodenum, where starch digestion continues.
    3. The stomach makes a protease and its contents are acidic, so no starch is digested there.

    AnswerA: 1 and 3 (the duodenum and the mouth).

    Learn where each enzyme works: amylase in the mouth and duodenum, protease in the stomach and duodenum, lipase in the duodenum.

    Revise this: Chemical digestion
15. 15Which tissue a red stain shows up in a celery stem.[1]
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    1. The stain is dissolved in water, and the stem takes up water through its xylem vessels.
    2. So after some hours it is the xylem that is coloured red, as a pattern of dots across the cut end.

    AnswerD: xylem.

    Xylem carries water and mineral ions up from the roots. Phloem carries sugars and amino acids, and would not take up the stain.

    Revise this: Transport in plants
16. 16The list in which all three vessels carry oxygenated blood.[1]
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    1. The aorta carries oxygenated blood from the heart to the body.
    2. The pulmonary vein carries oxygenated blood from the lungs back to the heart.
    3. The renal artery is a branch off the aorta going to a kidney, so it is oxygenated too.

    AnswerB: aorta, pulmonary vein, renal artery.

    The pulmonary vessels break the usual rule. Arteries carry oxygenated blood except the pulmonary artery; veins carry deoxygenated blood except the pulmonary vein.

    Revise this: Blood vessels
17. 17The part of the blood that carries out phagocytosis.[1]
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    1. Phagocytosis is the engulfing and digesting of pathogens. It is done by white blood cells.

    AnswerD: white blood cells.

    Red blood cells carry oxygen, platelets help the blood clot, and plasma carries dissolved substances.

    Revise this: Blood
18. 18An example of personal hygiene in the kitchen.[1]
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    1. Personal hygiene is about keeping your own body clean. Washing your hands removes pathogens before they get onto the food.
    2. The other three are good practice too, but they are about the food and the waste, not the person.

    AnswerD: washing hands before preparing food.

    All four options help to control the spread of disease. Only one is personal, and that is the word the question hangs on.

    Revise this: Disease and immunity
19. 19What the body makes to defend itself against pathogens.[1]
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    1. Mucus traps pathogens in the nose and airways. It is one of the body's barriers, and the body makes it.
    2. Antibiotics are medicines. The body does not make them.
    3. Red blood cells are made by the body, but their job is carrying oxygen, not defence.

    AnswerB: mucus only.

    Antibodies and antibiotics sound alike. Antibodies are made by white blood cells; antibiotics come from a pharmacy.

    Revise this: Disease and immunity
20. 20The route an oxygen molecule takes from the air into the blood.[1]
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    1. Air passes the larynx, goes down the trachea, along a bronchus and into the bronchioles.
    2. The bronchioles end in alveoli. Oxygen diffuses through the wall of an alveolus and into a capillary.

    AnswerC: larynx → bronchiole → alveolus wall → capillary.

    Only two of the sequences start in the right place, and only one ends with the blood.

    Revise this: Breathing and gas exchange
21. 21What is needed and what is produced in aerobic respiration.[1]
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    1. Glucose + oxygen → carbon dioxide + water, with energy released.
    2. So oxygen is required, and carbon dioxide and water are produced. Like all the reactions in cells, it is controlled by enzymes.

    AnswerA: all four are correct.

    Revise this: Aerobic respiration
22. 22Naming a part of the excretory system from a diagram.[1]
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    1. The two bean-shaped organs at the top are the kidneys. A tube, a ureter, runs down from each one.
    2. X is the bag that the two ureters empty into. It stores urine: the bladder.

    AnswerA: bladder.

    Ureter and urethra are easy to swap. There are two ureters, from the kidneys to the bladder, and one urethra, from the bladder to the outside.

    Revise this: Excretion and the kidneys
23. 23What makes up the central nervous system.[1]
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    1. The central nervous system is the brain and the spinal cord. The nerves that run out to the rest of the body are the peripheral nervous system.

    AnswerD: both the brain and the spinal cord.

    Revise this: Nerves and reflexes
24. 24What happens at a labelled part of the eye.[1]
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    1. W is the clear, rounded structure just behind the pupil: the lens.
    2. The lens focuses light onto the retina.

    AnswerB: light is focused onto the retina.

    The other statements describe other parts: the optic nerve carries impulses to the brain, the retina holds the light receptors, and the pupil changes diameter.

    Revise this: The eye
25. 25Matching a labelled gland to its hormone.[1]
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    1. X is the long gland lying across the body below the stomach: the pancreas. It secretes insulin.
    2. Z are the two small glands sitting on top of the kidneys: the adrenal glands. Y are low in the body, on either side of the uterus: the ovaries.

    AnswerA: X is the pancreas and secretes insulin.

    In each wrong option the hormone does match the gland that is named, but the letter points to a different gland. Check the letter against the diagram first.

    Revise this: Hormones
26. 26The responses shown by a bean plant grown in the dark.[1]
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    1. There is no light, so nothing can be a response to light. That rules out phototropism for both parts.
    2. The root has grown downwards and the shoot upwards. Both are responses to gravity: gravitropism.

    AnswerA: gravitropism in the root and in the shoot.

    Roots grow towards the pull of gravity and shoots grow away from it. Both are gravitropism.

    Revise this: Plant responses
27. 27Why antibiotics only work on some infections.[1]
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    1. Antibiotics kill bacteria.
    2. They do not affect viruses, so they are no use against a viral infection such as a cold.
    3. Some bacteria are resistant to an antibiotic and are not killed by it.

    AnswerC: they kill bacteria, but not viruses and not resistant bacteria.

    Revise this: Drugs and antibiotics
28. 28The two parts of a stamen.[1]
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    1. The stamen is the male part of a flower. It is made of the anther, which produces the pollen, and the filament, the stalk that holds the anther up.

    AnswerA: anther and filament.

    The stigma, style and ovary make up the carpel, the female part.

    Revise this: Reproduction in flowering plants
29. 29Comparing sperm cells with egg cells.[1]
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    1. A sperm cell is much smaller than an egg cell.
    2. It can swim, using its flagellum. An egg cell cannot move by itself.
    3. Millions of sperm are produced, against one egg released each month.

    AnswerD: smaller, more motile and greater in number.

    Revise this: Human reproduction
30. 30The meaning of phenotype.[1]
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    1. The phenotype is the set of features of an organism that you can observe.
    2. The genotype is its genetic make-up: the alleles it has.

    AnswerD: the observable features.

    "Combination of alleles" and "genetic make-up" both describe the genotype, which is why they cannot be the answer here.

    Revise this: Inheritance
31. 31The diagram that shows how sex is inherited.[1]
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    1. A mother has two X chromosomes, XX. A father has an X and a Y, XY.
    2. Every egg carries an X. Half the sperm carry an X and half carry a Y.
    3. X from the mother with X from the father gives XX, a girl. X with Y gives XY, a boy. So the children are half girls and half boys.

    AnswerC: the father is XY, the mother is XX, and the children are XX, XX, XY and XY.

    Start with the parents. Any diagram that gives the mother a Y, or the father two of the same chromosome, can be crossed out without reading further.

    Revise this: Inheritance
32. 32What continuous variation is.[1]
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    1. Continuous variation gives a range of phenotypes between two extremes, with every value in between possible. Height is an example.
    2. Discontinuous variation gives a limited number of distinct phenotypes with nothing in between, such as blood group.

    AnswerD: a range of phenotypes between two extremes.

    Revise this: Variation and mutation
33. 33Finding the secondary consumer in a food chain.[1]
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    1. The chain is grass → rabbit → fox → flea.
    2. Grass is the producer. The rabbit eats the producer, so it is the primary consumer. The fox eats the primary consumer, so it is the secondary consumer.

    AnswerC: fox.

    Count from the first animal: primary, secondary, tertiary. The flea, feeding on the fox, is the tertiary consumer.

    Revise this: Food chains, food webs and energy
34. 34Counting the organisms that feed at the fourth trophic level in a food web.[1]
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    1. Level one is the producer, grass. Level two is whatever eats grass: ant, mouse and grasshopper.
    2. Level three is whatever eats those. The mouse is here as well, because it also eats ants. So are the frog and the bird, which eat grasshoppers, and the owl and hawk, which eat mice.
    3. Level four is whatever eats a level-three animal. The owl and the hawk eat the mouse that ate an ant. The owl also eats the frog. The snake eats the frog and the bird.
    4. That is three organisms: owl, hawk and snake.

    AnswerB: 3

    An animal can be in more than one trophic level, depending on which chain you follow. Trace every route and count the animals, not the routes.

    Revise this: Food chains, food webs and energy
35. 35Naming two processes in the carbon cycle from the direction of their arrows.[1]
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    1. Arrow X goes from carbon dioxide in the air to green plants. Plants take in carbon dioxide for photosynthesis.
    2. Arrow Y goes from the breakdown of dead organic material to carbon dioxide in the air. Decomposers release carbon dioxide as they break the material down: decomposition.

    AnswerD: X is photosynthesis and Y is decomposition.

    Look at which way each arrow points. Photosynthesis is the only process in the cycle that takes carbon dioxide out of the air. Everything else puts it back.

    Revise this: The carbon cycle
36. 36The meaning of a community.[1]
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    1. A population is all the organisms of one species in an area.
    2. A community is all the populations of the different species living in the same ecosystem.

    AnswerC: all populations of different species in an ecosystem.

    Add the non-living environment to the community and you have an ecosystem. The option about one species describes a population.

    Revise this: Populations
37. 37Reading from a population graph when births outnumber deaths.[1]
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    1. A population grows when the birth rate is greater than the death rate.
    2. In section 1 the line rises, so the population is growing.
    3. In section 2 the line is level: births and deaths are equal. In section 3 it falls: the death rate is greater.

    AnswerC: section 1 only.

    Revise this: Populations
38. 38Choosing the area with the highest biodiversity from four pie charts.[1]
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    1. Biodiversity is the number of different species that live in an area.
    2. Each colour in a chart is one species, so count the slices. One chart has eight slices and the others have four or five.

    AnswerB

    More slices means more species. The area whose chart has the most slices, with none of them taking up most of the circle, has the highest biodiversity.

    Revise this: Conservation
39. 39Working out the total cut in methane from a herd of cows.[1]
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    1. One cow: 35% of 50 kg = 0.35 × 50 = 17.5 kg less each year.
    2. Ninety cows: 17.5 × 90 = 1575 kg.

    AnswerC: 1575 kg

    17.5 kg is the saving for one cow, and it is option A. The question asks about 90 of them. 4500 kg is all the methane the herd makes with no additive.

    Revise this: Pollution
40. 40The name for putting a gene into a crop plant.[1]
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    1. Changing the genetic material of an organism by inserting genes into it is genetic modification.

    AnswerB: genetic modification.

    Selective breeding also changes crops, but by choosing which plants to breed from over many generations. No gene is inserted.

    Revise this: Genetic modification

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.