IGCSE Biology 0610/43 October/November 2025 Past Paper with Answers

Question 1

In the binomial system every species is given a two-part scientific name. Which option correctly names the two parts of a scientific name in the binomial system?

1. the genus and the species
2. the kingdom and the phylum
3. the genus and the kingdom
4. the family and the variety

Question 2

A newly discovered species is multicellular, has cell walls that are not made of cellulose, and feeds by releasing digestive enzymes onto its surroundings and then absorbing the digested nutrients. To which kingdom does this species belong?

1. the fungus kingdom
2. the plant kingdom
3. the animal kingdom
4. the prokaryote kingdom

Question 3

Two species belong to the plant kingdom. Which pair of structures are both found in plant cells but are not found in animal cells?

1. a cellulose cell wall and chloroplasts
2. a nucleus and mitochondria
3. a cell membrane and ribosomes
4. a flagellum and a contractile vacuole

Question 4 · Answer A

Step 1: Plant X has fronds and reproduces by spores, which are features of ferns. Step 2: Plant Y is a flowering plant with long narrow leaves and parallel veins, which are features of a monocotyledon. Step 3: Dicotyledons have broad leaves with net-like veins, and ferns do not have flowers or seeds, so only the first option matches both plants.

Question 5 · Answer A

Step 1: The base sequences in the DNA of organisms can be compared to study how closely they are related. Step 2: Species that share a more recent common ancestor have more similar base sequences. Step 3: Height, flower colour and soil type are affected by the environment and do not reliably show evolutionary relationships, so comparing DNA base sequences is the best method.

Question 6 · Answer A

Step 1: The change in mass is 4090 − 775 = 3315 g. Step 2: Percentage change = (change ÷ original) × 100 = (3315 ÷ 775) × 100 = 427.742…%. Step 3: Rounded to three significant figures this is 428%.

Question 7 · Answer A

Step 1: Chickens that mature faster reach a saleable size and begin producing eggs at a younger age. Step 2: This means the farmer can sell meat or collect eggs sooner. Step 3: Selling sooner, and over more cycles, increases the farmer's profit, so the first option gives the genuine advantages.

Question 8 · Answer A

Step 1: The farmer chooses the chickens with the largest body mass and breeds them together. Step 2: From their offspring, the farmer again selects those with the largest body mass to breed. Step 3: Repeating this selection over many generations gradually increases the body mass of the chickens.

Question 9 · Answer A

Step 1: The chicken faeces wash into the lake and add nitrate ions, a process called eutrophication. Step 2: The extra nitrate causes rapid growth of producers such as algae; when these die in large numbers, decomposers break them down. Step 3: The decomposers respire aerobically and use up the dissolved oxygen in the water, so aquatic organisms that need oxygen, such as fish, die and the habitat is destroyed.

Question 10 · Answer A

Step 1: Excess amino acids cannot be stored, so they are broken down in the liver by deamination. Step 2: Deamination removes the nitrogen-containing part of each amino acid. Step 3: This nitrogen-containing part is converted into urea, which is then carried in the blood to the kidneys to be excreted.

Question 11 · Answer A

Step 1: Water from the soil first enters a root hair cell by osmosis. Step 2: It then moves across the cells of the root cortex. Step 3: Finally it reaches the xylem, which carries it up the plant, so the first pathway is correct.

Question 12 · Answer A

Step 1: The mass lost is 135.7 − 118.3 = 17.4 g. Step 2: This loss happened over three hours, so the rate is 17.4 ÷ 3. Step 3: 17.4 ÷ 3 = 5.8 g per hour.

Question 13 · Answer A

Step 1: The plant at 25 °C had a higher transpiration rate (3.1 g per hour) than the plant at 15 °C (0.9 g per hour), so it lost water faster. Step 2: At the higher temperature the water molecules have more kinetic energy, so more water evaporates from the surfaces of the mesophyll cells inside the leaf. Step 3: This increases the diffusion of water vapour out through the stomata, so the transpiration rate is higher.

Question 14 · Answer A

Step 1: Lower humidity means the air around the leaf contains less water vapour. Step 2: This makes a steeper concentration gradient of water vapour between the inside of the leaf and the air outside. Step 3: A steeper gradient means water vapour diffuses out through the stomata faster, so the transpiration rate increases.

Question 15 · Answer A

Step 1: The xylem transports water and mineral ions, and its cells form a long continuous tube with walls strengthened by lignin. Step 2: Water moves upwards because of transpiration pull. Step 3: This pull draws up a continuous column of water molecules, which are held together by forces of attraction (cohesion) between the water molecules.

Question 16 · Answer A

Step 1: On a hot dry day water is lost by transpiration faster than it is taken up by the roots. Step 2: Water then moves out of the cells by osmosis, so the cells become flaccid and lose their turgor pressure. Step 3: Plants rely on this turgor pressure pushing on the cell walls for support, so without it the leaves and stem droop and the plant wilts.

Question 17 · Answer A

Step 1: The leaf is rolled into a tube and has hairs and sunken stomata on its inner surface. Step 2: These features trap a layer of moist air next to the stomata and reduce air movement across them. Step 3: The trapped moist air reduces the concentration gradient of water vapour out of the stomata, so less water vapour diffuses out and transpiration is reduced.

Question 18 · Answer A

Step 1: The septum is the muscular wall down the middle of the heart that keeps the oxygenated blood on the left separate from the deoxygenated blood on the right. Step 2: The valves between each atrium and ventricle are the atrioventricular valves, which stop blood flowing back into the atria. Step 3: The aorta, vena cava and coronary artery are blood vessels, not the dividing wall, so only the first option is correct.

Question 19 · Answer A

Step 1: The left ventricle wall contains more muscle than the right ventricle wall. Step 2: More muscle lets it contract with greater force, creating a higher pressure. Step 3: This higher pressure is needed to pump blood all the way around the whole body, whereas the right ventricle only pumps blood the short distance to the lungs.

Question 20 · Answer A

Step 1: Blood from the vena cava enters the right atrium, then the right ventricle. Step 2: The right ventricle pumps it through the pulmonary artery to the lungs, and it returns through the pulmonary vein to the left atrium. Step 3: From the left atrium it passes to the left ventricle, which pumps it out through the aorta, so the first order is correct.

Question 21 · Answer A

Step 1: During exercise the muscles respire faster, so the heart beats faster (helped by the hormone adrenaline) to deliver more oxygen and glucose to the muscles and to remove the extra carbon dioxide. Step 2: When the muscles respire anaerobically they produce lactic acid, creating an oxygen debt. Step 3: The heart rate stays high after exercise to keep supplying oxygen so the lactic acid can be broken down in the liver, which is why the rate only returns to normal slowly.

Question 22 · Answer A

Step 1: A diet high in saturated fat or salt raises the risk of coronary heart disease. Step 2: Smoking tobacco and high levels of stress also increase the risk. Step 3: Eating fruit, exercising and keeping a healthy body mass lower the risk, so only the first option lists risk factors.

Question 23 · Answer A

Step 1: Photosynthesis uses carbon dioxide and water as its reactants. Step 2: It produces glucose and oxygen, giving 6CO2 + 6H2O → C6H12O6 + 6O2, which is balanced. Step 3: The reverse equation is aerobic respiration, the third equation uses oxygen as a reactant wrongly, and the last is anaerobic respiration in yeast.

Question 24 · Answer A

Step 1: Plants need magnesium ions to make chlorophyll. Step 2: Without enough magnesium the leaves cannot make chlorophyll and turn yellow. Step 3: Nitrate ions are needed to make amino acids and proteins, while calcium and chloride are not used to make chlorophyll.

Question 25 · Answer A

Step 1: Plants store carbohydrate as starch. Step 2: Starch is insoluble, so it does not affect osmosis and is a good storage molecule. Step 3: Glucose is the soluble sugar made in photosynthesis, cellulose makes cell walls, and glycogen is the storage carbohydrate of animals, not plants.

Question 26 · Answer A

Step 1: A tropism is a growth response towards or away from a stimulus. Step 2: The shoot grows towards the light, so the stimulus is light and the response is towards it. Step 3: Growth towards light is positive phototropism, not a response to gravity.

Question 27 · Answer A

Step 1: Auxin is made in the shoot tip and diffuses down the shoot. Step 2: It becomes more concentrated on the shaded side of the shoot. Step 3: The auxin stimulates the cells on the shaded side to elongate more than those on the light side, so the shoot bends towards the light.

Question 28 · Answer A

Step 1: By growing towards the light, the shoot and its leaves receive more light. Step 2: More light means the plant can carry out more photosynthesis. Step 3: More photosynthesis produces more glucose for growth and for respiration, so growing towards light is an advantage.

Question 29 · Answer A

Step 1: The scrotum is the sac that holds and protects the testes. Step 2: The prostate gland produces seminal fluid, and the urethra carries both urine and sperm out of the body. Step 3: The sperm duct carries sperm from the testis to the urethra, so the first option names all four structures correctly in order.

Question 30 · Answer A

Step 1: Testosterone is the male sex hormone produced in the testes. Step 2: At puberty testosterone causes the secondary sexual characteristics, including the deepening of the voice. Step 3: Oestrogen is the female sex hormone, insulin controls blood glucose, and adrenaline prepares the body for action, so testosterone is the correct hormone.

Question 31 · Answer A

Step 1: A sperm has a tail (flagellum) that lets it swim towards the egg. Step 2: It contains many mitochondria, which release the energy needed for this swimming. Step 3: It has an acrosome containing enzymes that break down the jelly coat of the egg so the sperm can fertilise it, so the first option gives three correct adaptations.