IGCSE Biology 0610/32 May/June 2025 Past Paper with Answers

Question 1

Photosynthesis occurs in the leaves of a plant. In which structure inside a plant cell does photosynthesis take place?

1. the chloroplast
2. the nucleus
3. the mitochondrion
4. the vacuole

Question 2

Photosynthesis takes place inside the chloroplasts of a leaf cell. What is the name of the green pigment found in these chloroplasts?

1. chlorophyll
2. haemoglobin
3. cellulose
4. glucose

Question 3

A student estimates the surface area of a leaf by drawing its outline on paper made of squares with sides of 1 cm, then counting 35 squares. What is the correct unit for this measurement of surface area?

1. cm² (square centimetres)
2. cm (centimetres)
3. cm³ (cubic centimetres)
4. mm (millimetres)

Question 4 · Answer A

Step 1: A large, flat surface gives more area for light to fall on. Step 2: More light absorbed by the chlorophyll means a faster rate of photosynthesis. Step 3: Losing water and reducing carbon dioxide entry would not help photosynthesis, and surface area does not protect against animals, so the benefit is greater light absorption.

Question 5 · Answer A

Step 1: The tall closely packed cells just below the upper surface are the palisade mesophyll, so part A is palisade mesophyll. Step 2: The single layer of cells on the lower surface is the lower epidermis, so part B is the lower epidermis. Step 3: The thin waxy layer on the upper surface is the cuticle, so part D is the cuticle.

Question 6 · Answer A

Step 1: A leaf vein carries water and dissolved substances through the leaf. Step 2: Water and mineral ions travel in the xylem, while dissolved sugars travel in the phloem. Step 3: So the vein is made of xylem and phloem; the other pairs are leaf cell layers or surface features, not transport tissues.

Question 7 · Answer A

Step 1: The lower surface of a leaf has small pores called stomata. Step 2: Each pore is surrounded by a pair of curved cells that open and close it, called guard cells. Step 3: Palisade cells are inside the leaf, root hair cells are in roots, and red blood cells are in animals, so the cells around the pore are guard cells.

Question 8 · Answer A

Step 1: Guard cells change shape to open and close the stomata. Step 2: When the stomata are open, carbon dioxide can diffuse into the leaf. Step 3: This carbon dioxide is a raw material for photosynthesis, so by opening the stomata the guard cells let in the gas the leaf needs; they do not make chlorophyll, carry water or store glucose.

Question 9 · Answer A

Step 1: Work out each range: carrot 22, corn 19, pea 20, pepper 17, tomato 14 °C. Step 2: The largest range is the carrot (22 °C) and the smallest is the tomato (14 °C). Step 3: Not all species germinate at 18 °C (peas only reach 24, but a pea germinates at 18; however tomato needs 21 so it would not), so the only correct pair is carrots largest and tomatoes smallest.

Question 10 · Answer A

Step 1: Germinating seeds need oxygen for respiration and water to start growth, as well as a suitable temperature. Step 2: Only tube D supplies both oxygen (the gas present) and water (the wet cotton wool). Step 3: Tubes A and C lack oxygen (they have carbon dioxide), and tube B lacks water (dry cotton wool), so only the seeds in tube D germinate.

Question 11 · Answer A

Step 1: Within the germination range, a higher temperature speeds up the chemical reactions and respiration in the seed. Step 2: Because 25 °C is warmer than 10 °C but still below 29 °C, the seeds germinate faster. Step 3: They will still germinate (25 °C is in range), so they do not stop or slow down, and the rate is not the same as at the cooler 10 °C.

Question 12 · Answer A

Step 1: A shoot grows towards light, a response called phototropism. Step 2: A root grows downwards towards gravity, a response called gravitropism. Step 3: Root hairs increase the surface for absorbing mineral ions and water, so the correct set is light; phototropism; gravity; gravitropism; mineral ions.

Question 13 · Answer A

Step 1: Gastric juice in the stomach contains hydrochloric acid. Step 2: This strong acid kills many of the pathogens that are taken in with food. Step 3: Gastric juice is acidic, not alkaline, and does not carry oxygen or feed pathogens, so its defence is that the acid kills the pathogens.

Question 14 · Answer A

Step 1: All the percentages must add up to 100 %. Step 2: The three named routes total 54 + 11 + 9 = 74 %. Step 3: So direct contact = 100 − 74 = 26 %.

Question 15 · Answer A

Step 1: Find 11 % of 300. Step 2: 11 % = 11/100, so 11/100 × 300 = 33. Step 3: Therefore 33 of the 300 people caught the virus from contaminated water.

Question 16 · Answer A

Step 1: Indirect transmission happens through contaminated water, food, surfaces and hands. Step 2: Washing hands, using clean water, cooking food and cleaning surfaces all remove or destroy the virus before it reaches a new person. Step 3: The other options either spread the virus (sharing bottles, raw food) or are irrelevant (antibiotics do not kill viruses; diet or exercise do not stop transmission).

Question 17 · Answer A

Step 1: The airways are lined with mucus made by goblet cells, and tiny hairs called cilia. Step 2: Mucus traps viruses and dust, and the cilia sweep the mucus away, stopping pathogens reaching the lungs. Step 3: Hydrochloric acid is made in the stomach, red blood cells carry oxygen, and insulin controls blood glucose, so none of these defends the airways.

Question 18 · Answer A

Step 1: The thick outer boundary around a bacterium is the cell wall, so part A is the cell wall. Step 2: The jelly-like material filling the cell is the cytoplasm, so part B is the cytoplasm. Step 3: The small separate circular loop of genetic material is a plasmid, so part C is a plasmid; bacteria have no true nucleus.

Question 19 · Answer A

Step 1: White blood cells both make antibodies and carry out phagocytosis. Step 2: Dissolved substances such as the hormone oestrogen are carried in the liquid plasma. Step 3: Red blood cells contain haemoglobin, which carries oxygen, so the correct matches are white blood cells (antibodies, phagocytosis), plasma (oestrogen) and red blood cells (oxygen).

Question 20 · Answer A

Step 1: Iron is needed to make haemoglobin in red blood cells. Step 2: Good dietary sources of iron include red meat and green leafy vegetables. Step 3: Lemons supply vitamin C, vegetable oil supplies fat, and yoghurt supplies calcium, so they are not the best iron sources.

Question 21 · Answer A

Step 1: When a blood vessel is cut, platelets help form a clot. Step 2: The clot seals the wound, which reduces the loss of blood. Step 3: The clot also forms a barrier that stops pathogens entering the body, so clotting reduces blood loss and prevents pathogen entry.

Question 22 · Answer A

Step 1: The largest artery leaving the heart carries blood to the whole body. Step 2: This vessel is the aorta. Step 3: The vena cava returns blood to the heart, the pulmonary artery goes to the lungs, and the pulmonary vein returns blood from the lungs, so the main body vessel is the aorta.

Question 23 · Answer A

Step 1: A curved bone of the rib cage is a rib. Step 2: A thin muscle running between two ribs is an intercostal muscle. Step 3: The large dome-shaped sheet of muscle across the base of the chest is the diaphragm, so the three structures are a rib, an intercostal muscle and the diaphragm.

Question 24 · Answer A

Step 1: Air flows from the trachea into the bronchi, which branch into smaller tubes. Step 2: These smallest tubes are the bronchioles, and they end in the air sacs called alveoli. Step 3: So the bronchioles are connected directly to the alveoli, while the larynx and trachea are higher up the airway.

Question 25 · Answer A

Step 1: Gas exchange happens in millions of tiny air sacs called alveoli. Step 2: These alveoli are found in the lungs. Step 3: The heart pumps blood, the liver processes substances, and the kidney filters blood, so the organ containing the alveoli is the lung.

Question 26 · Answer A

Step 1: Blood returning to the lungs carries waste carbon dioxide, so its concentration is higher in the capillary than in the air sac. Step 2: Carbon dioxide diffuses down its concentration gradient from the capillary into the alveolus. Step 3: From the alveolus it is breathed out, so the net movement of carbon dioxide is from the capillary into the alveolus, not the reverse.

Question 27 · Answer A

Step 1: A large surface area gives more space for gases to diffuse across. Step 2: Thin walls give a short distance for gases to diffuse. Step 3: A good blood supply keeps a steep concentration gradient, so a large surface area, thin walls and a good blood supply make the alveoli efficient.

Question 28 · Answer A

Step 1: Aerobic respiration uses glucose and oxygen as the reactants. Step 2: It releases energy and produces carbon dioxide and water as products. Step 3: So the equation is glucose + oxygen → carbon dioxide + water; the reverse is photosynthesis, and glucose → lactic acid is anaerobic respiration.

Question 29 · Answer A

Step 1: Aerobic respiration needs oxygen and releases energy from glucose. Step 2: This process happens mainly inside the mitochondria. Step 3: Chloroplasts carry out photosynthesis, the nucleus controls the cell, and the cell wall supports plant cells, so respiration occurs in the mitochondria.

Question 30 · Answer A

Step 1: Diffusion is the net movement from a region of higher concentration to a region of lower concentration, that is down a concentration gradient. Step 2: The energy comes from the kinetic energy of the molecules. Step 3: This movement of molecules is random, so the correct set is higher; lower; gradient; kinetic; random.

Question 31 · Answer A

Step 1: Starch is a carbohydrate, made of many glucose units joined together. Step 2: Carbohydrates contain only the elements carbon, hydrogen and oxygen. Step 3: Nitrogen and sulfur are found in proteins, not carbohydrates, so starch is made of carbon, hydrogen and oxygen.

Question 32 · Answer A

Step 1: Glucose is a small sugar that plant cells can build into larger carbohydrates. Step 2: As well as starch, plants make cellulose (for the cell wall) and sucrose (for transport) from glucose. Step 3: Proteins are built from amino acids, fats from fatty acids and glycerol, and water is not made from glucose, so cellulose is the correct answer.

Question 33 · Answer A

Step 1: Dialysis tubing lets small molecules through but holds back large ones, so it is partially permeable. Step 2: The part of a cell that controls what enters and leaves in this way is the partially permeable cell membrane. Step 3: The nucleus, cytoplasm and chloroplast do not act as the partially permeable boundary, so the tubing represents the cell membrane.

Question 34 · Answer A

Step 1: Dialysis tubing is partially permeable, letting only small molecules through. Step 2: Glucose is a small molecule, so it diffuses out into the water, which is why glucose is detected outside. Step 3: Starch is a large molecule that cannot pass through the tubing, so none is found outside, explaining the results.

Question 35 · Answer A

Step 1: Starch is a carbohydrate that must be digested into smaller sugars. Step 2: The enzyme that breaks starch down into reducing sugars (maltose/glucose) is amylase. Step 3: Protease digests proteins, lipase digests fats, and catalase breaks down hydrogen peroxide, so the enzyme for starch is amylase.

Question 36 · Answer A

Step 1: In the binomial system the first word is the genus and the second is the species. Step 2: In Elephas maximus the first word, Elephas, is the genus name. Step 3: maximus is the species name, the full two-word name is the binomial name, and "elephant" is the common name, so the genus is Elephas.

Question 37 · Answer A

Step 1: Mammals have several features, including hair (fur) and external ears (pinnae). Step 2: Hair on the body is a visible mammal feature that the elephant shows. Step 3: Feathers belong to birds, dry scales to reptiles, and moist bare skin to amphibians, so hair identifies the elephant as a mammal.

Question 38 · Answer A

Step 1: A herbivore eats plants and a carnivore eats animals, so an organism that is both eats plants and animals. Step 2: The bearded pig feeds on the jackfruit tree (a plant) and on the stick insect (an animal), so it is both a herbivore and a carnivore. Step 3: The tiger and python eat only animals, and the fig tree is a producer, so the answer is the bearded pig.

Question 39 · Answer A

Step 1: A producer is followed by the primary consumer, then the secondary consumer, then the tertiary consumer. Step 2: Here the jackfruit tree is the producer, the orangutan the primary consumer, the bearded pig the secondary consumer, and the tiger the tertiary consumer. Step 3: So the tertiary consumer is the tiger, not the producer or the earlier consumers.

Question 40 · Answer A

Step 1: A producer makes its own food by photosynthesis, usually a green plant. Step 2: The fig tree and jackfruit tree are green plants that photosynthesise, so they are producers. Step 3: The orangutan, tiger and bearded pig are all consumers that feed on other organisms, so the producer is the fig tree.

Question 41 · Answer A

Step 1: Arthropods have an exoskeleton and jointed legs; insects are one group of arthropods. Step 2: A stick insect is an insect, so it is an arthropod. Step 3: The tiger and orangutan are mammals and the python is a reptile, all with internal skeletons, so the arthropod is the stick insect.

Question 42 · Answer A

Step 1: In a food chain each arrow points from the food to the organism that eats it. Step 2: The jackfruit tree (producer) is eaten by the orangutan, so the first arrow goes from the tree to the orangutan. Step 3: The orangutan is then eaten by the tiger, so the chain is jackfruit tree → orangutan → tiger.

Question 43 · Answer A

Step 1: An ecosystem is more than just the organisms; it includes their surroundings. Step 2: It is a unit made up of the community of organisms together with the non-living environment. Step 3: These living and non-living parts interact, so the best description is the community of organisms and their environment interacting; one species alone is a population, not an ecosystem.

Question 44 · Answer A

Step 1: The number falls from 1850 in 2010 to 1500 by 2015, a decrease of 350 elephants. Step 2: From 2015 to 2016 the number stays at 1500, so the population is then stable. Step 3: So the population decreases by 350 and then levels off, rather than increasing or staying the same throughout.

Question 45 · Answer A

Step 1: Organisms become endangered when their numbers fall towards extinction. Step 2: Habitat loss from deforestation, hunting and pollution all reduce a species’ numbers. Step 3: The other options describe conservation measures or improved conditions, which help a species recover rather than endanger it.