0610/31 Oct/Nov 2025 Worked Answers (IGCSE Biology 0610 Core)
32 questions · 80 marks · 75 minutes
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Worked answers for 25 questions
- Step 1: Organisms are placed in groups according to the features (shared characteristics) they have in common. Step 2: The internationally agreed system for naming species is the binomial system. Step 3: A binomial scientific name is made of two parts, the genus name and the species name, so the missing words are features; binomial; genus; species.Method:Recall how organisms are grouped and the structure of a binomial scientific name.Examiner tips
- Group by features; name with the binomial system as genus then species.
- Step 1: Arachnids (such as spiders) have four pairs of legs, and insects have three pairs of legs and usually wings. Step 2: Myriapods (such as centipedes and millipedes) have long bodies of many segments, each bearing legs. Step 3: Crustaceans have more than four pairs of legs and two pairs of antennae, so the first option matches every group correctly.Method:Match each arthropod group to the leg and body features that define it.Examiner tips
- Insects: 3 pairs of legs; arachnids: 4 pairs; myriapods: many segments with legs; crustaceans: many legs + 2 pairs of antennae.
- 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.Method:Recall the three elements that make up all carbohydrates and exclude carbon.Examiner tips
- Carbohydrates contain only carbon, hydrogen and oxygen.
- 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.Method:Match each small molecule to the large molecule that is built from it.Examiner tips
- amino acids -> proteins; glycerol -> fats; glucose -> starch/glycogen/cellulose.
- 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.Method:Define a balanced diet by completeness, correct proportions and sufficient energy.Examiner tips
- Balanced diet = all nutrients, in the correct proportions, with enough energy.
- 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.Method:Match each named vitamin and mineral to the deficiency disease it prevents or the role it plays.Examiner tips
- Vitamin C -> scurvy; vitamin D + calcium -> bones; iron -> haemoglobin.
- 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.Method:Pick the structure found only in plant cells, not in animal cells.Examiner tips
- Plant-only structures: cell wall, chloroplasts, large permanent vacuole.
- 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.Method:Recall the reactants and products of aerobic respiration and order them correctly.Examiner tips
- Aerobic respiration: glucose + oxygen -> carbon dioxide + water (+ energy).
- 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.Method:Compare the wall thickness, lumen width and presence of valves of a vein against an artery.Examiner tips
- Veins: thinner wall, wider lumen, valves. Arteries: thick wall, narrow lumen, no valves.
- 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.Method:State that capillaries allow exchange of substances between the blood and the cells.Examiner tips
- Capillaries exchange oxygen, glucose and wastes between blood and cells.
- 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.Method:Name the large vein that brings blood from the body into the right atrium.Examiner tips
- Vena cava -> right atrium; pulmonary vein -> left atrium.
- 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.Method:Pick the three lifestyle features that increase the chance of coronary heart disease.Examiner tips
- Risk factors include high saturated fat, smoking, obesity, stress and lack of exercise.
- 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.Method:State that the nervous system coordinates and regulates the body.Examiner tips
- The nervous system coordinates and controls the body using electrical impulses.
- 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.Method:Name the junction where two neurones meet.Examiner tips
- The junction (gap) between two neurones is a synapse.
- 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.Method:Link nitrate ions to the nitrogen-containing molecules that plants build.Examiner tips
- Nitrate -> nitrogen -> amino acids -> proteins.
- 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.Method:Describe the sequence from rapid plant growth to oxygen loss and death of aquatic life.Examiner tips
- Eutrophication: extra nutrients -> algal growth -> decay -> oxygen used up -> organisms die.
- 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.Method:Compare the counts species by species and summarise the differences.Examiner tips
- Read each row of data and state which river has more of each species.
- 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.Method:Identify the species whose numbers collapse in the polluted river.Examiner tips
- A pollution-sensitive (indicator) species is scarce in polluted water.
- 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.Method:Work out the increase, then express it as a percentage of the 1995 value.Examiner tips
- Find the increase, divide by the starting value, then multiply by 100.
- 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.Method:Recall the features of bacteria that make them suited to industrial use.Examiner tips
- Bacteria: rapid reproduction + ability to make complex molecules.
- 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.Method:Pick the modifications that protect the crop or raise its yield and quality.Examiner tips
- GM crops: herbicide resistance, pest resistance, higher yield, better nutrition.
- 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.Method:Choose the enzyme whose optimum pH matches the pH of the washing powder.Examiner tips
- Match the enzyme optimum to the pH where it will be used.
- 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.Method:Match each carbon transfer to the named process in the carbon cycle.Examiner tips
- Carbon cycle: respiration out, photosynthesis in, feeding along chains, dead remains form fossil fuels.
- 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.Method:Name the breakdown of dead organisms by microorganisms.Examiner tips
- Decomposition by microorganisms returns carbon from dead matter to the air.
- 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.Method:Follow the chain from burning fuels to more carbon dioxide, an enhanced greenhouse effect and climate change.Examiner tips
- Combustion -> more CO2 -> enhanced greenhouse effect -> climate change; methane is another greenhouse gas.
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