October/November 2025 Paper 32 Worked Answers (IGCSE Biology 0610 Core)
38 questions · 80 marks · 75 minutes
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Worked answers for 32 questions
- Step 1: Organisms with a bony internal skeleton that move about and feed on other organisms are animals. Step 2: They cannot make their own food by photosynthesis, so they are not plants. Step 3: Fungi feed by decomposition and bacteria are single-celled prokaryotes, so the organisms belong to the animal kingdom.Method:Use the features (skeleton, movement, feeding) to place the organisms in the correct kingdom.Examiner tips
- Animals move, feed on other organisms and many have a skeleton of bones.
- Step 1: Animals that have a backbone made of vertebrae are called vertebrates. Step 2: Invertebrates have no backbone, and arthropods (such as insects) are invertebrates. Step 3: Mammals are only one group of vertebrates, so the group that shares the backbone is the vertebrates.Method:Name the group defined by the presence of a backbone.Examiner tips
- A backbone (vertebral column) is the key feature of all vertebrates.
- Step 1: Fish have fins, supported by thin fin bones, that they use to swim. Step 2: They also have gills rather than legs or wings. Step 3: Walking legs and feathered wings belong to land vertebrates and birds, and an external shell is not a fish feature, so the fin bones identify a fish.Method:Pick the visible feature that is unique to fish.Examiner tips
- Fish have fins (and gills) for life in water.
- Step 1: Mammals have hair or fur covering the body and mammary glands that produce milk to feed their young. Step 2: They also have external ears (pinnae), sweat glands and different types of teeth. Step 3: Feathers belong to birds, gills and scales to fish, and dry scales to reptiles, so the mammal features are hair or fur and mammary glands.Method:Choose the two features that are characteristic of mammals.Examiner tips
- Mammals: hair/fur, mammary glands, external ears, sweat glands, varied teeth, a diaphragm.
- Step 1: The curved bones that form a cage around the chest to protect the heart and lungs are the ribs. Step 2: The skull protects the brain and the backbone runs along the body. Step 3: Limb bones support the legs or arms, so the curved chest bone labelled P is a rib.Method:Identify the curved chest-cage bone as a rib.Examiner tips
- Ribs are the curved bones forming the cage around the heart and lungs.
- Step 1: A binomial scientific name has two parts: the genus name first, then the species name. Step 2: In Phasianus colchicus, Phasianus is the genus name and colchicus is the species name. Step 3: The full name together is the binomial and animal is a kingdom, so the species name is colchicus.Method:Take the second word of the two-part scientific name as the species name.Examiner tips
- Binomial name = genus (first) + species (second).
- Step 1: A species is a group of organisms of the same type with very similar features. Step 2: Members of a species can reproduce together to produce offspring. Step 3: Importantly, those offspring are fertile (can themselves reproduce), so a species is a group that breeds to give fertile offspring, not just organisms sharing a habitat or genus.Method:Define a species by similar organisms that breed to give fertile offspring.Examiner tips
- Species = same type of organism that reproduces to give fertile offspring.
- Step 1: Blood plasma is mostly water and carries many dissolved substances around the body. Step 2: These include nutrients such as glucose and amino acids, the waste product urea, hormones and ions. Step 3: Bone is not transported in plasma, haemoglobin is inside red cells, and starch and large fat droplets are not dissolved in plasma, so the plasma carries glucose and urea.Method:Choose the dissolved nutrient and waste that plasma transports.Examiner tips
- Plasma transports glucose, amino acids, urea, hormones, ions and water.
- Step 1: Distilled water is more dilute than the cell contents, so water enters the plant cell by osmosis. Step 2: The vacuole fills and the cell becomes swollen and firm (turgid). Step 3: The strong cell wall stops the cell bursting, so the membrane is pushed tightly against the wall rather than the cell shrinking or bursting.Method:Predict turgidity from water entering the cell by osmosis.Examiner tips
- Plant cell in water -> water enters by osmosis -> turgid (swollen and firm).
- Step 1: Both diffusion and osmosis happen in all living cells and both involve the random movement of particles, so the first two statements are true for both. Step 2: Osmosis is the movement of water across a partially permeable membrane, so that statement is true for osmosis only. Step 3: Ions (not water) move down a concentration gradient by diffusion, so that statement is true for diffusion only.Method:Classify each statement using the definitions of diffusion and osmosis.Examiner tips
- Osmosis = water across a partially permeable membrane; diffusion = particles/ions down a gradient.
- Step 1: Some particles are moved across the membrane using energy released by respiration. Step 2: This energy-requiring movement, often against the concentration gradient, is active transport. Step 3: Diffusion and osmosis are passive and need no energy, and evaporation is a change of state, so the process is active transport.Method:Name the energy-requiring movement of particles as active transport.Examiner tips
- Active transport uses energy from respiration and can move particles up a gradient.
- Step 1: A healthy leaf carries out photosynthesis to make food, using chlorophyll to absorb light. Step 2: A leaf badly damaged by a pathogen loses chlorophyll and cannot photosynthesise properly. Step 3: Combustion, digestion in a stomach, fertilisation and filtration of blood are not leaf processes, so the lost processes are photosynthesis and chlorophyll production.Method:Pick the leaf processes that a damaged, discoloured leaf can no longer perform.Examiner tips
- Healthy leaf processes: photosynthesis, chlorophyll production, gas exchange, transpiration.
- Step 1: Pathogens are disease-causing organisms or agents. Step 2: The main types are bacteria, viruses and fungi. Step 3: Red blood cells, enzymes, hormones and blood vessels are normal parts of the body, not pathogens, so two types of pathogen are bacteria and viruses.Method:Name two disease-causing types, such as bacteria and viruses.Examiner tips
- Types of pathogen: bacteria, viruses, fungi (and protoctists).
- Step 1: Pathogens can spread directly when one tree touches another, for example when branches or roots are in contact. Step 2: They can also be carried indirectly by animals such as insects, or by wind, water or soil. Step 3: Photosynthesis, transpiration, active transport, osmosis and antibody production are normal processes, not ways of spreading pathogens, so transmission is by contact and by insects.Method:Choose genuine routes of transmission, by contact and by carriers.Examiner tips
- Transmission: direct contact, animals/insects, air/wind, water/soil.
- Step 1: Forests are often cleared so the land can be used for farming and growing crops. Step 2: Trees are also cut down to harvest timber and to clear land for building houses, factories and roads. Step 3: Planting forests and protecting habitats reduce deforestation, and natural cycles are not causes, so the three causes are farming, timber and building.Method:Pick the three human land uses that cause forests to be cleared.Examiner tips
- Deforestation causes: farming, timber, building/roads, mining.
- Step 1: The values show the area removed fell from about 27 thousand km2 in 2004 to about 5 thousand km2 in 2013. Step 2: After 2013 the area removed rose again towards 2022 but stayed well below the 2004 figure. Step 3: So overall the area removed decreased from 2004, with a fall to a minimum in 2013 followed by a partial rise.Method:Read the key values and describe the fall to a minimum and the overall decrease.Examiner tips
- Describe trends using the start, the minimum and the overall direction, with data quotes.
- Step 1: Biodiversity is a measure of the variety of living things. Step 2: It is described as the number of different species found in an area. Step 3: It is not the count of one species, the mass of one organism, or the number of factories, so biodiversity is the number of different species in an area.Method:Define biodiversity as the variety (number) of species in an area.Examiner tips
- Biodiversity = the number of different species in an area.
- Step 1: Removing trees destroys the habitats that animals and plants depend on. Step 2: Tree roots no longer hold the soil, so soil is eroded and washed away, and flooding can increase. Step 3: Fewer trees means less carbon dioxide is removed by photosynthesis, so atmospheric carbon dioxide rises and adds to global warming.Method:Choose three genuine harmful consequences of removing forests.Examiner tips
- Deforestation effects: habitat loss, soil erosion, flooding, more carbon dioxide, warming.
- Step 1: Sperm swim up through the uterus and into the oviducts. Step 2: An egg released from an ovary travels along the oviduct, where it meets a sperm. Step 3: Fertilisation (the joining of a sperm and egg nucleus) normally happens in the oviduct, not in the vagina or ovary.Method:Recall that fertilisation occurs in the oviduct.Examiner tips
- Fertilisation normally occurs in the oviduct.
- Step 1: The female reproductive hormone is oestrogen, which is produced by the ovary. Step 2: Oestrogen controls the development of female secondary sexual characteristics at puberty. Step 3: Insulin controls blood glucose, testosterone is a male hormone, and the vagina and uterus do not make these hormones, so the ovary produces oestrogen.Method:Name the ovary and oestrogen, and give its role in secondary sexual characteristics.Examiner tips
- Ovary -> oestrogen -> female secondary sexual characteristics.
- Step 1: The endocrine system is made of glands that release hormones into the blood. Step 2: Some hormones keep the internal environment constant, which is called homeostasis. Step 3: The pancreas produces insulin, which lowers and helps control the blood glucose concentration, so the words are glands; internal; homeostasis; insulin; glucose.Method:Fill each blank with the correct endocrine term, ending with insulin and glucose.Examiner tips
- Endocrine glands -> hormones -> homeostasis; pancreas -> insulin -> blood glucose.
- Step 1: A gene is a length of DNA that codes for a feature. Step 2: Many genes exist in more than one form, and each different version is called an allele. Step 3: For pod colour the gene has a green allele (G) and a yellow allele (g), so an allele is an alternative form of a gene.Method:Define an allele as a different version of a gene.Examiner tips
- An allele is one of the alternative forms of a gene.
- Step 1: Each Gg parent produces gametes carrying G or g. Step 2: Combining the gametes gives offspring GG, Gg, Gg and gg in a Punnett square. Step 3: GG and the two Gg are green (have a G), and only gg is yellow, so the ratio is 3 green : 1 yellow.Method:Build the Punnett square for Gg x Gg and read off the 3 : 1 ratio.Examiner tips
- Gg x Gg always gives a 3 : 1 ratio of dominant : recessive.
- Step 1: The spongy mesophyll is a layer of cells in the middle of a leaf. Step 2: It lies below the palisade layer and contains air spaces for gas exchange. Step 3: Roots anchor the plant, flowers are for reproduction and stems support the plant, so spongy mesophyll cells are found in the leaf.Method:Identify the leaf as the organ containing spongy mesophyll.Examiner tips
- Spongy mesophyll is a layer inside the leaf.
- Step 1: The nucleus contains the genetic material (DNA), arranged as chromosomes carrying genes. Step 2: Using these instructions, the nucleus controls the activities of the cell. Step 3: Absorbing light is the chloroplast, respiration is the mitochondrion, and controlling entry and exit is the membrane, so the nucleus stores the genetic material and controls the cell.Method:State that the nucleus holds the DNA and controls the cell.Examiner tips
- Nucleus: contains DNA/chromosomes and controls the cell.
- Step 1: Mitochondria are small organelles where aerobic respiration takes place. Step 2: They are spread throughout the jelly-like cytoplasm of the cell. Step 3: They are not inside the nucleus, the vacuole or the cell wall, so mitochondria are found in the cytoplasm.Method:Place the mitochondria in the cytoplasm.Examiner tips
- Mitochondria are found in the cytoplasm.
- Step 1: Mitochondria carry out aerobic respiration inside the cell. Step 2: This process releases energy from glucose for the cell to use. Step 3: Absorbing light is the chloroplast, storing genetic material is the nucleus, and controlling entry is the membrane, so mitochondria release energy by respiration.Method:State that mitochondria release energy by aerobic respiration.Examiner tips
- Mitochondria: site of aerobic respiration and release of energy.
- Step 1: Spongy mesophyll cells contain chloroplasts, which absorb light energy for photosynthesis. Step 2: The cells are loosely packed, leaving air spaces between them. Step 3: These air spaces and the large surface area let carbon dioxide diffuse easily to the cells for photosynthesis, so the tissue is well adapted.Method:Link chloroplasts, air spaces and surface area to efficient photosynthesis.Examiner tips
- Spongy mesophyll: chloroplasts + air spaces + large surface area for carbon dioxide.
- Step 1: Physical (mechanical) digestion breaks food into smaller pieces, for example by the teeth, without changing the molecules. Step 2: Chemical digestion breaks down large food molecules into smaller ones. Step 3: Chemical digestion involves chemical changes and uses enzymes, so physical = smaller pieces, while chemical = food molecules, chemical changes and enzymes.Method:Separate the size-changing (physical) description from the enzyme/molecule (chemical) descriptions.Examiner tips
- Physical = smaller pieces; chemical = enzymes break down molecules.
- Step 1: Egestion is the removal of undigested food from the body. Step 2: Undigested material forms faeces, which pass out through the anus at the end of the alimentary canal. Step 3: The stomach and small intestine digest and absorb food, and the mouth is where ingestion happens, so egestion occurs at the anus.Method:Recall that undigested waste is egested at the anus.Examiner tips
- Egestion of undigested waste occurs at the anus.
- Step 1: The pulp cavity is the soft living centre of the tooth. Step 2: It contains nerves, which detect pain and temperature, and blood vessels, which supply the living tooth. Step 3: Enamel and dentine are the hard layers around the pulp, and muscles, tendons, cartilage and bone are not inside the pulp, so the pulp contains nerves and blood vessels.Method:Name the nerves and blood vessels found in the pulp.Examiner tips
- Pulp cavity contains nerves and blood vessels.
- Step 1: Molars are the large teeth at the back of the mouth used for grinding and chewing. Step 2: They have a broad flat top (grinding surface) and are anchored by more than one root. Step 3: Incisors are chisel-shaped for biting and canines are pointed for tearing, so a tooth with a flat grinding surface and multiple roots is a molar.Method:Use the grinding surface and number of roots to identify the molar.Examiner tips
- Molars: broad flat grinding surface and multiple roots.
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