IGCSE Biology 0610/13 October/November 2025 Past Paper with Answers

Question 1

The sundew is a carnivorous plant that can trap small insects with sticky hair-like structures on its leaves. When an insect gets stuck, other nearby sticky hairs bend over to trap the insect. Which characteristics of living organisms are demonstrated when the sundew traps an insect in this way?

1. movement and sensitivity
2. growth and excretion
3. growth and sensitivity
4. movement and excretion

Question 2

An arthropod has three pairs of legs. To which group of arthropods does this organism belong?

1. insects
2. arachnids
3. crustaceans
4. myriapods

Question 3

A dichotomous key for vertebrates asks, in order: does it have fur? (yes leads to a mammal); if no, does it have feathers? (yes leads to a bird); if no, does it have dry skin? (yes leads to a reptile); if no, does it have scales? (yes leads to a fish, and no leads to the endpoint Z). Which type of animal would be found at endpoint Z?

1. amphibian
2. fish
3. mammal
4. reptile

Question 4 · Answer A

Step 1: A plasmid is a small circular piece of DNA found in bacterial cells, separate from the main loop of DNA. Step 2: It carries extra genes that the bacterium can use. Step 3: The liquid part of blood is plasma, aerobic respiration happens in mitochondria, and protein synthesis happens at the ribosomes, so none of those describe a plasmid.

Question 5 · Answer A

Step 1: A typical plant cell has a cellulose cell wall, a large permanent vacuole and chloroplasts as well as the usual nucleus, cytoplasm and membrane. Step 2: A cell with a cell wall, large vacuole and chloroplasts is therefore a plant cell. Step 3: A rounded cell with no wall is an animal cell, a biconcave cell with no nucleus is a red blood cell, and a small cell with a loop of DNA but no nucleus is a bacterium.

Question 6 · Answer A

Step 1: Actual size = image size divided by magnification. Step 2: The image size is 90 mm and the magnification is 225, so actual size = 90 ÷ 225 = 0.40 mm. Step 3: So the alveolus is 0.40 mm across.

Question 7 · Answer A

Step 1: A longer diffusion distance means particles have further to travel, so diffusion is slower. Step 2: Increasing temperature, surface area or concentration gradient all speed diffusion up. Step 3: So the factor that decreases the rate of diffusion is an increased diffusion distance.

Question 8 · Answer A

Step 1: A cell membrane is partially permeable, letting water through but holding back larger molecules. Step 2: Dialysis (Visking) tubing is partially permeable, so it behaves like a cell membrane. Step 3: Filter paper lets everything through, while a measuring cylinder and a test-tube are containers, not membranes.

Question 9 · Answer A

Step 1: Oxygen moves from a higher concentration in the soil to a lower concentration inside the cell. Step 2: Movement of a gas down its concentration gradient is diffusion. Step 3: Osmosis is the movement of water, respiration is a chemical reaction inside the cell, and ventilation is the movement of air in breathing, so the process is diffusion.

Question 10 · Answer A

Step 1: The biuret test turns from blue to purple when protein is present, so a protein-containing food gives a purple result. Step 2: Blue DCPIP is decolourised (turns colourless) by vitamin C, so a food with vitamin C turns DCPIP colourless. Step 3: With both protein and vitamin C present, the biuret test is purple and the DCPIP test is colourless.

Question 11 · Answer A

Step 1: Amylase is an enzyme, and enzymes are biological catalysts. Step 2: A catalyst speeds up a reaction without being used up. Step 3: The product is what is made, the substrate is what is broken down, and a solvent is a liquid that dissolves things, so amylase acts as a catalyst.

Question 12 · Answer A

Step 1: The sugar can be stored as starch, used in respiration to release energy, and used to make cellulose for cell walls, so all three of these are yes. Step 2: Photosynthesis is the process that makes the sugar, so the plant does not use sugar for photosynthesis. Step 3: So the correct row is starch yes, photosynthesis no, respiration yes, cellulose yes.

Question 13 · Answer A

Step 1: The stomach produces hydrochloric acid, so its contents are acidic. Step 2: The muscular wall of the stomach churns and squeezes the food, which is physical digestion. Step 3: The mouth is not acidic, and the small and large intestines are not acidic, so food is physically digested in acidic conditions in the stomach.

Question 14 · Answer A

Step 1: Each stoma is a small pore in a leaf, controlled by a pair of cells on either side. Step 2: These cells are guard cells, which change shape to open and close the stoma. Step 3: Ciliated cells move mucus, egg cells are female sex cells, and mesophyll cells carry out photosynthesis, so the cells around a stoma are guard cells.

Question 15 · Answer A

Step 1: The atria are the upper chambers, so the left atrium is an upper chamber. Step 2: Viewed from the front, the left side of the heart appears on the right-hand side as you look at it. Step 3: So the left atrium is the upper chamber on the right-hand side; the upper-left chamber is the right atrium and the lower chambers are the ventricles.

Question 16 · Answer A

Step 1: Direct contact means the pathogen passes straight from one person to another. Step 2: Exchanging body fluids passes the pathogen directly between people, so it is direct contact. Step 3: Air, food and contaminated surfaces all pass the pathogen through the environment first, so they are indirect transmission.

Question 17 · Answer A

Step 1: The body uses oxygen in respiration, so expired air has less oxygen than inspired air. Step 2: Respiration produces carbon dioxide, so expired air has more carbon dioxide than inspired air. Step 3: So expired air has a lower oxygen concentration and a higher carbon dioxide concentration.

Question 18 · Answer A

Step 1: Aerobic respiration uses glucose and oxygen as its raw materials, so both are used. Step 2: It produces carbon dioxide and water, so both of these are produced. Step 3: So carbon dioxide is produced, glucose used, oxygen used and water produced.

Question 19 · Answer A

Step 1: Alveoli are tiny air sacs found at the ends of the air passages in the chest. Step 2: These air sacs make up the lungs, where oxygen and carbon dioxide are exchanged with the blood. Step 3: The heart pumps blood, the liver makes bile and the kidneys make urine, so alveoli are found in the lungs.

Question 20 · Answer A

Step 1: The central nervous system is the brain and spinal cord. Step 2: The relay neurone lies entirely within the spinal cord, so it is found only in the central nervous system. Step 3: The receptor is in the skin, while the sensory and motor neurones run between the body and the spinal cord, so they are not found only in the central nervous system.

Question 21 · Answer A

Step 1: Light first passes through the cornea, the clear curved layer at the front of the eye. Step 2: The curved cornea bends (refracts) the light, changing its direction as it enters. Step 3: The iris controls how much light enters, the pupil is the gap that light passes through, and the retina detects light, so the cornea changes the light direction.

Question 22 · Answer A

Step 1: Endocrine glands secrete hormones directly into the blood. Step 2: Insulin is a hormone made by the pancreas, so it is secreted by an endocrine gland. Step 3: Glucose is a sugar, lactic acid is made in muscles during anaerobic respiration, and starch is a storage carbohydrate, so none of these is a hormone.

Question 23 · Answer A

Step 1: A gravitropic response is a response to gravity, so the stimulus must be gravity, not light. Step 2: Growing away from the stimulus means the shoot grows in the opposite direction to gravity, which is upwards. Step 3: So the correct seedling is the one where gravity acts downwards and the shoot grows upwards; the light seedlings show responses to light, not gravity.

Question 24 · Answer A

Step 1: Antibiotics work by attacking structures found in bacteria. Step 2: Viruses do not have these structures, so antibiotics do not kill viruses. Step 3: Antibiotics therefore kill bacteria only, not viruses or all microorganisms.

Question 25 · Answer A

Step 1: The new plants come from one parent and are genetically identical to it. Step 2: Producing genetically identical offspring from a single parent is asexual reproduction. Step 3: Fertilisation and pollination are steps in sexual reproduction, which involves two parents and produces variation, so this is asexual reproduction.

Question 26 · Answer A

Step 1: The sticky tip at the top of the central stalk is the part that catches pollen grains. Step 2: This sticky pollen-receiving tip is the stigma. Step 3: The style is the stalk below it, the anther is the pollen-producing part on a separate filament, and the ovary is at the base, so P is the stigma.

Question 27 · Answer A

Step 1: Germinating seeds need water to activate their enzymes and start growth. Step 2: They also need oxygen for aerobic respiration to release energy. Step 3: So seeds will only germinate when both oxygen and water are present.

Question 28 · Answer A

Step 1: Seminal fluid is the liquid that carries and nourishes the sperm. Step 2: It is produced by the prostate gland and other glands. Step 3: The penis passes semen out of the body, the scrotum holds the testes, and the testes make sperm, so seminal fluid is produced by the prostate gland.

Question 29 · Answer A

Step 1: Secondary sexual characteristics develop at puberty under the control of sex hormones. Step 2: The growth of the sexual organs happens in both males and females. Step 3: Fat on the hips and thighs and widening hips develop mainly in females, while facial hair develops mainly in males, so the change shared by both is the growth of the sexual organs.

Question 30 · Answer A

Step 1: HIV is spread through infected blood and body fluids. Step 2: Screening blood used for transfusions removes infected blood, so more screening reduces the number of new infections. Step 3: More illegal drug use, reusing needles and unprotected sexual contact would all increase transmission, so only increased blood screening explains a fall.

Question 31 · Answer A

Step 1: A gene can exist in different versions that give different forms of a feature. Step 2: Each of these versions is called an allele, so an allele is an alternative form of a gene. Step 3: A sequence of amino acids is a protein, an observable feature is a phenotype, and the genotype is the full set of alleles, so none of those describes a single allele.

Question 32 · Answer A

Step 1: The offspring show about three red to one white (93 to 28), which is the 3 : 1 ratio. Step 2: A 3 : 1 ratio comes from crossing two heterozygous parents, Rr and Rr. Step 3: White offspring (rr) need an r allele from each parent, and both parents are red, so both must be Rr.

Question 33 · Answer A

Step 1: Almost all food chains start with the energy captured by plants in photosynthesis. Step 2: The hazel trees capture light energy from the Sun, and this energy then passes to the truffle and the deer. Step 3: So the original source of energy for the food chain is the Sun.

Question 34 · Answer A

Step 1: Every organism in the chain respires to release energy from its food. Step 2: Much of this energy is eventually released to the surroundings as heat, so it is lost from the food chain. Step 3: Ingestion is taking in food, photosynthesis captures energy rather than releasing it, and transpiration is water loss, so the energy is lost through respiration.

Question 35 · Answer A

Step 1: The slow, almost flat start of the curve is the lag phase, when the population grows very slowly. Step 2: The part that rises more and more steeply is the exponential phase, when the population grows faster and faster. Step 3: The curve does not level off or fall, so there is no stationary phase or death phase; the phases shown are the lag phase and the exponential phase.

Question 36 · Answer A

Step 1: Weeds are unwanted plants growing among the crop. Step 2: A herbicide is a chemical designed to kill plants such as weeds. Step 3: A fertiliser and magnesium ions help plants grow, and an insecticide kills insects, so the weeds are killed with a herbicide.

Question 37 · Answer A

Step 1: Pathogens are microorganisms that cause disease. Step 2: Untreated sewage contains human waste with many pathogens, so it pollutes water with disease-causing microbes. Step 3: An antibiotic treats infections, chlorophyll is a plant pigment, and methane is a gas, so none of those is a source of pathogens in water.

Question 38 · Answer A

Step 1: Level 4 is the producer (a plant) and level 3, which eats the producer, is the herbivore (primary consumer). Step 2: Carnivores are animals that eat other animals, so they are found above the herbivore. Step 3: Levels 2 and 1 eat the animals below them, so both are carnivores; only levels 1 and 2 contain carnivores.

Question 39 · Answer A

Step 1: In 90 minutes there are 90 ÷ 15 = 6 divisions, and the number doubles at each division. Step 2: Starting from 1 bacterium, after 6 doublings there are 2 to the power 6 = 64 bacteria. Step 3: The increase in number is 64 − 1 = 63 bacteria.

Question 40 · Answer A

Step 1: Intensive farming uses large areas for a single crop or for housing many animals together. Step 2: This removes hedges and wild areas, so there are fewer habitats for wildlife, which is a disadvantage. Step 3: Lower cost, fewer workers needed and less land needed are advantages of intensive farming, not disadvantages.