0610/12 May/June 2025 Worked Answers (IGCSE Biology 0610 Core)
40 questions · 40 marks · 45 minutes
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Worked answers for 24 questions
- Step 1: Detecting a change in the surroundings and responding to it is sensitivity. Step 2: The herbivore senses the carnivore and reacts, so it is showing sensitivity. Step 3: Excretion removes waste, growth is an increase in size, and reproduction makes new organisms, so none of these match the reaction described.Method:Match the action of detecting and responding to a stimulus to the characteristic of sensitivity.Examiner tips
- Sensitivity means sensing a stimulus and responding to it.
- Step 1: A binomial name has two Latin parts, the genus then the species, such as Vulpes vulpes. Step 2: Brown seaweed, polar bear and red fox are ordinary common names, not Latin scientific names. Step 3: So only Vulpes vulpes is named using the binomial system.Method:Identify the two-part Latin name as the one written using the binomial system.Examiner tips
- Binomial names are Latin and have two parts: genus then species.
- Step 1: The arthropod groups are insects, arachnids, crustaceans and myriapods. Step 2: Arachnids, crustaceans and myriapods are all arthropod groups, so this list contains only arthropods. Step 3: Amphibians, fish and reptiles are vertebrates, not arthropods, so the other lists each include a non-arthropod.Method:Recall the arthropod groups and reject any list that includes a vertebrate group.Examiner tips
- Remember the four arthropod groups: insects, arachnids, crustaceans, myriapods.
- Step 1: Actual length = image length divided by magnification. Step 2: X gives 0.20 ÷ 50 = 0.0040 mm; Y gives 0.50 ÷ 150 = 0.0033 mm; Z gives 0.40 ÷ 250 = 0.0016 mm. Step 3: Putting these from smallest to largest gives Z (0.0016), then Y (0.0033), then X (0.0040), so the order is Z, Y, X.Method:Calculate the actual length of each specimen and arrange them from smallest to largest.Examiner tips
- Actual size = image size ÷ magnification; the smallest value is first.
- Step 1: Fats and oils are built from glycerol and fatty acids, so glycerol is a basic unit of oils. Step 2: Carbohydrates such as glycogen are built from simple sugars, and proteins are built from amino acids. Step 3: So the other statements pair the wrong basic units with their molecules; only glycerol as a unit of oils is correct.Method:Recall the building blocks of fats, carbohydrates and proteins and find the correct pairing.Examiner tips
- Oils/fats = glycerol + fatty acids; carbohydrates = simple sugars; proteins = amino acids.
- Step 1: The biuret test for protein gives a positive result by turning from blue to purple. Step 2: A purple colour therefore shows protein is present. Step 3: Blue-black is the iodine test for starch, brick red is the Benedict test for reducing sugar, and blue is the negative biuret colour.Method:Recall the colour change for the biuret protein test and pick purple.Examiner tips
- Biuret + protein gives purple; iodine + starch gives blue-black; Benedict + sugar gives brick red.
- Step 1: Photosynthesis uses carbon dioxide and water as its raw materials. Step 2: Using light energy, these are converted into glucose and oxygen. Step 3: Glucose and oxygen are products of photosynthesis, not raw materials, so any option containing glucose as a raw material is wrong.Method:Use the photosynthesis equation to identify the two reactants.Examiner tips
- Carbon dioxide + water are used; glucose + oxygen are produced.
- Step 1: Magnesium ions are needed to make chlorophyll, so without them chlorophyll production decreases. Step 2: Chlorophyll is the green pigment, so with less chlorophyll the leaves cannot be fully green and turn yellow. Step 3: So a lack of magnesium causes chlorophyll production to decrease and the leaves to be yellow.Method:Link magnesium to chlorophyll, then deduce that less chlorophyll gives yellow leaves.Examiner tips
- No magnesium means less chlorophyll, so leaves go yellow (chlorosis).
- Step 1: Plant material such as vegetables, fruit and cereals is rich in dietary fibre. Step 2: So a diet with a lot of plant material will supply plenty of fibre, which is therefore unlikely to be deficient. Step 3: Meat is a major source of protein, fat and vitamin D, so cutting out meat makes these more likely to be lacking.Method:Identify the component plentiful in plant foods and so unlikely to be deficient.Examiner tips
- Plant foods are high in fibre, so fibre is rarely short in a plant-rich diet.
- Step 1: The roots of the teeth sit in sockets in the jaw bone and are surrounded by the gums. Step 2: So the teeth are embedded in the gums and the bone. Step 3: Enamel, dentine, cement and pulp are parts of the tooth itself, not the structures the tooth is embedded in.Method:Separate the supporting structures (gums and bone) from the parts of the tooth itself.Examiner tips
- Teeth sit in sockets in the jaw bone and are surrounded by the gums.
- Step 1: The small intestine absorbs the digested food (and a lot of water) into the blood. Step 2: The colon (large intestine) mainly absorbs the remaining water. Step 3: So the colon absorbs water, while the small intestine absorbs both digested food and water.Method:Match each region of the gut to what it absorbs, remembering the colon reabsorbs water.Examiner tips
- Small intestine: digested food and water; colon: water.
- Step 1: A vessel carrying blood towards the heart is a vein. Step 2: The vein that brings blood from the lungs to the heart is the pulmonary vein. Step 3: The aorta and pulmonary artery carry blood away from the heart, and the vena cava brings blood from the body, not the lungs.Method:Recall that veins return blood to the heart and pick the one coming from the lungs.Examiner tips
- Pulmonary vein = lungs to heart; pulmonary artery = heart to lungs.
- Step 1: Pathogens are spread on dirty hands and contaminated food, so good hygiene reduces their spread. Step 2: Washing hands before and after handling raw food removes pathogens and stops them being passed on. Step 3: Leaving food uncovered, washing hands only after meals, and using the same equipment for raw and cooked food all let pathogens spread.Method:Choose the hygienic action that removes pathogens rather than spreading them.Examiner tips
- Hand-washing and keeping food covered reduce the spread of pathogens.
- Step 1: Carbon dioxide is tested using limewater, which turns from clear to milky (cloudy) when carbon dioxide is bubbled through it. Step 2: So limewater turning milky shows carbon dioxide is present. Step 3: DCPIP tests for vitamin C, ethanol is used in the test for fats, and iodine solution tests for starch.Method:Recall the chemical test for carbon dioxide and pick limewater.Examiner tips
- Limewater turns milky with carbon dioxide; remember the test for each substance.
- Step 1: In yeast, anaerobic respiration (fermentation) breaks down glucose to alcohol and carbon dioxide, while aerobic respiration does not make alcohol. Step 2: So only anaerobic respiration produces alcohol. Step 3: Both types produce carbon dioxide, only aerobic respiration produces water, and only aerobic respiration uses oxygen, so the other statements are wrong.Method:Compare the reactants and products of each type and find the true statement.Examiner tips
- Yeast fermentation gives alcohol and carbon dioxide; aerobic respiration uses oxygen and gives water.
- Step 1: A structure in the skin that detects a stimulus such as heat is a receptor, so P is a receptor. Step 2: A neurone that carries the impulse from the receptor to the central nervous system is a sensory neurone, so Q is a sensory neurone. Step 3: Effectors (muscles or glands) carry out responses, and motor neurones carry impulses away from the central nervous system, so they do not match P or Q here.Method:Name the stimulus detector as a receptor and the neurone to the CNS as sensory.Examiner tips
- Receptor detects the stimulus; sensory neurone carries the impulse to the CNS.
- Step 1: Testosterone is the male sex hormone and brings about male secondary sexual characteristics. Step 2: Growth of facial hair is a male characteristic caused by testosterone. Step 3: Breast development, the start of the menstrual cycle and widening of the hips are female characteristics caused by oestrogen, not testosterone.Method:Recall that testosterone causes male features and pick facial hair growth.Examiner tips
- Testosterone = male features (facial hair, deeper voice); oestrogen = female features.
- Step 1: A gene can exist in different versions, and each version is called an allele. Step 2: So an alternative form of a gene is an allele. Step 3: A chromosome is a thread of DNA carrying many genes, a genotype is the set of alleles an organism has, and a protein is a molecule made using a gene, so none of these is an alternative form of a gene.Method:Recall the genetics vocabulary and match an alternative form of a gene to an allele.Examiner tips
- An allele is a version of a gene; a genotype is the set of alleles present.
- Step 1: Each heterozygous parent (for example Ff) can pass on either a normal allele or the recessive allele. Step 2: Crossing Ff with Ff gives offspring in the ratio 1 FF : 2 Ff : 1 ff, and only the ff child has cystic fibrosis. Step 3: One out of the four possible combinations is ff, so the probability is 1 in 4, which is 25%.Method:Carry out the monohybrid cross of two heterozygotes and read off the affected proportion.Examiner tips
- Two heterozygous parents give a 1 in 4 (25%) chance of an affected child.
- Step 1: Continuous variation shows a range of values with no distinct groups, such as a measurement like mass. Step 2: Body mass in cats varies smoothly across a range, so it shows continuous variation. Step 3: ABO blood groups, seed colour and seed shape each fall into a few distinct categories, so they show discontinuous variation.Method:Separate measured ranges (continuous) from distinct categories (discontinuous).Examiner tips
- Measured features that vary smoothly (like mass or height) are continuous variation.
- Step 1: An adaptation to prevent predation should help the butterfly avoid being caught and eaten. Step 2: Spots that look like large eyes can startle or confuse a predator into thinking the butterfly is a bigger animal, helping it escape. Step 3: Flying slowly and being easier to see would make it more likely to be caught, and detecting nectar is about feeding, not avoiding predators.Method:Choose the feature that helps the butterfly avoid being caught by predators.Examiner tips
- Eyespots can startle predators and are a defence against predation.
- Step 1: Energy enters most ecosystems as light from the Sun. Step 2: Plants capture this light energy in photosynthesis, so the original source of energy is the Sun. Step 3: Photosynthesis and respiration are processes that transfer energy, not the source of it, and kinetic energy is energy of movement, not the input to ecosystems.Method:Trace energy back to its origin: light from the Sun.Examiner tips
- The Sun is the original source of energy for nearly all ecosystems.
- Step 1: Bacteria are useful because they can make complex molecules such as proteins (statement 1) and because they reproduce very quickly to give large numbers fast (statement 2). Step 2: Having a cell wall (statement 3) is a general feature of bacteria and does not make them useful for biotechnology. Step 3: So only statements 1 and 2 explain their usefulness.Method:Judge each statement for whether it is an advantage in biotechnology.Examiner tips
- Fast reproduction and making useful molecules are the advantages; cell walls are not.
- Step 1: Plant biomass is broken down to release the sugar glucose, so K is glucose. Step 2: Yeast is added to ferment the glucose by anaerobic respiration, so organism L is yeast. Step 3: Anaerobic respiration of glucose by yeast produces ethanol (alcohol), which is extracted as the biofuel, so M is ethanol.Method:Follow the fermentation: glucose from biomass, yeast added, ethanol produced.Examiner tips
- Biomass gives glucose; yeast ferments it to ethanol, the biofuel.
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