IGCSE Biology 0610/31 October/November 2025 Past Paper with Answers

Question 1

A set of statements describes how living organisms are classified and named: organisms are classified into groups by the ____ that they share; the internationally agreed system for naming species is the ____ system; and the scientific name of an organism is made up of the ____ name and the ____ name. Which set of words correctly completes the statements?

1. features; binomial; genus; species
2. habitats; binomial; species; genus
3. features; dichotomous; kingdom; genus
4. habitats; dichotomous; genus; kingdom

Question 2

A key identifies six crustaceans from their features: if pincers are visible go to step 2, if not go to step 4; (2) pincers the same size go to step 3, pincers different sizes is Minuca pugnax; (3) body nearly round is Maja brachydactyla, body long is Astacus leptodactylus; (4) body has visible segments go to step 5, no visible segments is Daphnia pulex; (5) fewer than eight spots is Porcellio expansus, more than eight spots is Porcellio haasi. Species A has same-size pincers and a round body; B has no pincers, segments and fewer than eight spots; C has no pincers and no segments; D has same-size pincers and a long body; E has pincers of different sizes; F has no pincers, segments and more than eight spots. Which set identifies A to F correctly?

1. A Maja brachydactyla, B Porcellio expansus, C Daphnia pulex, D Astacus leptodactylus, E Minuca pugnax, F Porcellio haasi
2. A Minuca pugnax, B Porcellio haasi, C Daphnia pulex, D Astacus leptodactylus, E Maja brachydactyla, F Porcellio expansus
3. A Astacus leptodactylus, B Porcellio expansus, C Porcellio haasi, D Maja brachydactyla, E Minuca pugnax, F Daphnia pulex
4. A Maja brachydactyla, B Daphnia pulex, C Porcellio expansus, D Minuca pugnax, E Astacus leptodactylus, F Porcellio haasi

Question 3

Arthropods are sorted into groups by features such as the number of legs and body sections. Which option correctly matches the arthropod groups to their key features?

1. arachnids have four pairs of legs, insects have three pairs of legs, myriapods have many body segments each bearing legs, and crustaceans have more than four pairs of legs
2. arachnids have three pairs of legs, insects have four pairs of legs, myriapods have a single pair of legs, and crustaceans have no legs
3. arachnids have six pairs of legs, insects have many segments each with legs, myriapods have three pairs of legs, and crustaceans have four pairs of legs
4. arachnids have wings and three pairs of legs, insects have four pairs of legs, myriapods have two pairs of legs, and crustaceans have one pair of legs

Question 4 · Answer A

Step 1: Carbohydrates are made only of the elements carbon, hydrogen and oxygen. Step 2: Carbon is already given, so the other two elements are hydrogen and oxygen. Step 3: Nitrogen is found in proteins and phosphorus in other molecules, so neither is part of a carbohydrate.

Question 5 · Answer A

Step 1: Amino acids are the sub-units that join together to build proteins. Step 2: Glycerol (with fatty acids) is used to build fats and oils. Step 3: Glucose units join to build starch (or glycogen or cellulose), so amino acid builds protein, glycerol builds fat, and glucose builds starch.

Question 6 · Answer A

Step 1: A balanced diet contains all of the food groups (nutrients) the body needs. Step 2: These must be present in the correct proportions or quantities. Step 3: It must also supply enough energy for the body, so a balanced diet has all the food groups in the right amounts to provide sufficient energy.

Question 7 · Answer A

Step 1: Vitamins and minerals prevent deficiency diseases; vitamin C keeps gums healthy and prevents scurvy. Step 2: Vitamin D helps form strong bones and teeth and prevents rickets, and calcium also strengthens bones and teeth. Step 3: Iron is needed to make haemoglobin in red blood cells, so the first option matches every nutrient to its correct role.

Question 8 · Answer A

Step 1: The clear jelly-like region filling the cell is the cytoplasm, which is L. Step 2: The tiny dots in the cytoplasm are ribosomes, so a ribosome is J. Step 3: The structure that controls the activities of the cell is the nucleus, the large round structure M, so cytoplasm L, ribosome J and control M.

Question 9 · Answer A

Step 1: Aerobic respiration takes place in the mitochondria of a cell. Step 2: The oval sausage-shaped structure where this happens is a mitochondrion. Step 3: The nucleus controls the cell, ribosomes make proteins, and a vacuole stores cell sap, so structure K is a mitochondrion.

Question 10 · Answer A

Step 1: Plant cells have extra structures that animal cells lack, including a cell wall, chloroplasts and a large permanent vacuole. Step 2: A cell wall is present in plant cells but absent in animal cells. Step 3: The cell membrane, cytoplasm and nucleus are found in both plant and animal cells, so they are not unique to plants.

Question 11 · Answer A

Step 1: Aerobic respiration uses glucose and oxygen as its reactants. Step 2: It releases energy and produces carbon dioxide and water as the products. Step 3: So the word equation is glucose + oxygen produces carbon dioxide + water; the reverse is photosynthesis and the alcohol equation is anaerobic respiration in yeast.

Question 12 · Answer A

Step 1: Veins carry blood at low pressure, so they have a thinner wall than arteries. Step 2: Veins have a wider lumen to help blood flow back to the heart. Step 3: Veins also contain valves to stop blood flowing backwards, so a vein has a thinner wall, a wider lumen and valves.

Question 13 · Answer A

Step 1: Capillaries have very thin walls, one cell thick, and run close to the body cells. Step 2: This lets useful substances such as oxygen and glucose pass to the cells and waste substances pass back into the blood. Step 3: Pumping blood is the heart’s job and making red blood cells happens in the bone marrow, so the function of capillaries is the exchange of substances.

Question 14 · Answer A

Step 1: Deoxygenated blood returning from the body enters the heart at the right atrium. Step 2: The large vein that brings this blood from the body to the right atrium is the vena cava. Step 3: The aorta carries blood out to the body, the pulmonary artery goes to the lungs, and the pulmonary vein returns blood from the lungs to the left atrium.

Question 15 · Answer A

Step 1: Coronary heart disease is made more likely by an unhealthy lifestyle. Step 2: A diet high in saturated fat, smoking and a lack of exercise all increase the risk. Step 3: A high-fibre diet, regular exercise and not smoking reduce the risk, so only the first option lists genuine risk factors.

Question 16 · Answer A

Step 1: The nervous system detects stimuli and sends electrical impulses around the body. Step 2: This allows it to coordinate and regulate the activities of the body so that parts work together. Step 3: Transporting oxygen is done by the blood, digestion by the gut, and antibodies by white blood cells, so the role of the nervous system is coordination.

Question 17 · Answer A

Step 1: The peripheral nervous system is made of the nerves outside the brain and spinal cord. Step 2: The sensory neurone T and the motor neurone X run outside the spinal cord, so both are part of the peripheral nervous system. Step 3: The spinal cord V and the relay neurone W inside it belong to the central nervous system, so any pair with V or W is not fully peripheral.

Question 18 · Answer A

Step 1: The painful stimulus is detected by the receptor S in the skin, and the impulse passes along the sensory neurone T to the spinal cord. Step 2: In the spinal cord the impulse is passed to the relay neurone W, then out along the motor neurone X. Step 3: The motor neurone carries the impulse to the effector muscle R, which produces the response, so the order is S, T, W, X, R.

Question 19 · Answer A

Step 1: Where two neurones meet there is a tiny gap rather than a direct connection. Step 2: This junction between two neurones is called a synapse. Step 3: A receptor detects stimuli, an effector produces a response, and a reflex is the automatic action, so the junction itself is the synapse.

Question 20 · Answer A

Step 1: Plants absorb nitrate ions from the soil to provide nitrogen. Step 2: This nitrogen is used to make amino acids, which are joined to build proteins. Step 3: Glucose, starch and cellulose are carbohydrates made from photosynthesis and contain no nitrogen, so the substance made using nitrate ions is amino acids.

Question 21 · Answer A

Step 1: Excess fertiliser provides extra nutrients, so algae and water plants grow rapidly. Step 2: When this excess plant material dies, microorganisms (decomposers) break it down and use up the oxygen in the water. Step 3: With little oxygen left, aquatic animals and other organisms die and biodiversity falls, which is the process of eutrophication.

Question 22 · Answer A

Step 1: Freshwater shrimps number 97 in river A but only 1 in river B, so there are far more shrimps in river A. Step 2: Bloodworms number 27 in river B against 15 in river A, and sludge worms number 74 in river B against 2 in river A, so both are higher in river B. Step 3: So river A is dominated by shrimps while river B has many more bloodworms and sludge worms.

Question 23 · Answer A

Step 1: A species that is sensitive to pollution will be rare in the polluted river. Step 2: The freshwater shrimp drops from 97 in the clean river to just 1 in the polluted river, so it is harmed most by pollution. Step 3: Bloodworms and sludge worms are more common in the polluted river, so they tolerate pollution better, making the shrimp the least tolerant.

Question 24 · Answer A

Step 1: Reading the graph at 1998 gives a population of about 24 thousand, which is 24000. Step 2: The highest point on the line is at the year 2000, so that is the largest population. Step 3: The 1995 value of about 12 thousand is matched again in 2004, so the 1995 population equals the 2004 population.

Question 25 · Answer A

Step 1: The increase is 52000 minus 12000, which is 40000. Step 2: Percentage increase is the increase divided by the starting value times 100, so it is 40000 divided by 12000, times 100. Step 3: This gives 333.3 recurring, which rounds to 333% to the nearest whole number.

Question 26 · Answer A

Step 1: Bacteria divide very quickly, so large numbers are produced in a short time. Step 2: Bacteria can be made to produce useful complex molecules, such as proteins. Step 3: Slow reproduction, being easy to see, and photosynthesis are not reasons bacteria are useful, so the two reasons are rapid reproduction and making complex molecules.

Question 27 · Answer A

Step 1: Crops can be modified to resist herbicides, so weeds can be sprayed without harming the crop. Step 2: They can be made resistant to insect pests, reducing damage. Step 3: They can also be given a higher yield or improved nutritional quality, so the first option lists genuine improvements.

Question 28 · Answer A

Step 1: At pH 10 enzyme B still shows activity while enzyme A has dropped away, so enzyme B is more active than enzyme A at pH 10. Step 2: Enzyme A peaks at about 33 arbitrary units, so that is its maximum activity. Step 3: The two curves are furthest apart at about pH 5, where A is high and B is low, so the largest difference is at pH 5.

Question 29 · Answer A

Step 1: A washing powder at pH 9 needs an enzyme that works well in alkaline conditions. Step 2: Enzyme A is most active near pH 5 and barely works at pH 9, so it is unsuitable. Step 3: Enzyme B is still active and close to its optimum at pH 9, so enzyme B is the better choice.

Question 30 · Answer A

Step 1: Living things release carbon dioxide to the atmosphere by respiration, and plants take carbon dioxide from the atmosphere by photosynthesis. Step 2: Carbon passes from plants to animals when the animals eat the plants, which is feeding. Step 3: Fossil fuels form over a long time from the remains of dead organisms, so the first option matches every transfer correctly.

Question 31 · Answer A

Step 1: Microorganisms such as bacteria and fungi feed on dead organisms and break them down. Step 2: As they respire, they release the carbon in the dead material back to the atmosphere as carbon dioxide. Step 3: This breakdown by microorganisms is called decomposition; photosynthesis takes carbon in, transpiration is water loss, and combustion is burning fuels.

Question 32 · Answer A

Step 1: Burning fossil fuels releases carbon dioxide, so combustion increases the concentration of carbon dioxide in the atmosphere. Step 2: Extra carbon dioxide causes an enhanced greenhouse effect, which leads to climate change (global warming). Step 3: Methane is another gas that traps heat in the same way, so the words are increases; enhanced; climate change; methane.