0610/11 May/June 2025 Worked Answers (IGCSE Biology 0610 Core)
40 questions · 40 marks · 45 minutes
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Worked answers for 30 questions
- Step 1: In the binomial system the first part of the name is the genus and the second part is the species. Step 2: In Homo sapiens, Homo is the first part and sapiens is the second part. Step 3: So Homo is the genus and sapiens is the species.Method:Recall that a binomial name is written as genus then species and apply it to Homo sapiens.Examiner tips
- Remember the order: genus first (with a capital letter), then species.
- Step 1: Fish are cold-blooded, so they do not maintain a constant body temperature, and their bodies are covered in scales. Step 2: Fish lay their eggs in water with a jelly-like covering and have no external ears. Step 3: So fish have no constant body temperature, eggs covered in jelly, no external ears, and scales present.Method:Recall the standard features of fish and match each of the four characteristics in turn.Examiner tips
- Fish are cold-blooded, scaly, gill-breathing vertebrates that lay eggs in water.
- Step 1: Red blood cells contain the red pigment haemoglobin, which binds to oxygen. Step 2: They are adapted with a biconcave shape and no nucleus to carry as much oxygen as possible. Step 3: So the red blood cell transports oxygen.Method:Recall the function of each specialised cell and pick the one adapted to carry oxygen.Examiner tips
- Match each specialised cell to the one job it is adapted for.
- Step 1: Drawing length = actual length multiplied by magnification. Step 2: Student 2 gives 0.125 multiplied by 300 = 37.5 mm; student 1 gives 18 mm; student 3 gives 33.75 mm; student 4 gives 35 mm. Step 3: The largest value is 37.5 mm, so student 2 produced the longest drawing.Method:Calculate actual length times magnification for each student and choose the largest result.Examiner tips
- Drawing size = actual size x magnification; the largest product wins.
- Step 1: Respiration produces carbon dioxide, so the substance is carbon dioxide. Step 2: A substance diffuses from where it is more concentrated to where it is less concentrated. Step 3: To move from the blood vessel into the alveolus the carbon dioxide must be at a high concentration in the blood and a low concentration in the alveolus.Method:Name the waste gas of respiration, then set the concentrations so it diffuses out of the blood.Examiner tips
- Identify the gas first, then use the high-to-low rule for diffusion.
- Step 1: Water enters cells by osmosis when the surroundings are more dilute (have more water) than the cell contents. Step 2: Distilled water is the most dilute surrounding, so water moves into the potato fastest and its mass increases the most. Step 3: The sugar solutions are more concentrated, so less water enters or water is lost, and the piece in air dries out.Method:Rank the surroundings by water concentration; the most dilute gives the greatest mass gain.Examiner tips
- The most dilute surrounding (pure water) makes a cell gain the most water by osmosis.
- Step 1: Starch is a large carbohydrate that contains only carbon, hydrogen and oxygen. Step 2: Starch is built from many glucose molecules joined together. Step 3: Fats contain glycerol and fatty acids, and only proteins contain nitrogen, so the correct match is starch made from glucose.Method:Match each large molecule to its elements and sub-units, using nitrogen to rule out fat.Examiner tips
- Starch = glucose units; fats = glycerol + fatty acids; only proteins have nitrogen.
- Step 1: DCPIP is a blue dye that is decolourised (turned colourless) by vitamin C. Step 2: So a sample that turns blue DCPIP colourless contains vitamin C. Step 3: Starch is tested with iodine, protein with biuret solution, and fat with the ethanol emulsion test.Method:Recall the reagent used in each food test and match DCPIP to vitamin C.Examiner tips
- Learn which reagent tests for each nutrient: iodine, biuret, Benedict, ethanol and DCPIP.
- Step 1: Photosynthesis uses carbon dioxide and water as its raw materials. Step 2: It produces glucose and oxygen. Step 3: So the substances taken in (1 and 2) are water and carbon dioxide, and those given out (3 and 4) are glucose and oxygen.Method:Use the photosynthesis equation to split the four substances into reactants and products.Examiner tips
- Carbon dioxide + water are used; glucose + oxygen are produced.
- Step 1: Iron is used to make haemoglobin in red blood cells. Step 2: Haemoglobin carries oxygen, so without enough iron the body cannot make enough red blood cells, causing anaemia. Step 3: Rickets is caused by lack of vitamin D, scurvy by lack of vitamin C, and teeth are strengthened by calcium and fluoride.Method:Recall the role of each nutrient and match iron to haemoglobin formation.Examiner tips
- Link iron to haemoglobin and the carrying of oxygen.
- Step 1: Protease enzymes digest proteins into amino acids. Step 2: The protease in the stomach is made by the stomach lining, so protease is produced in the stomach and forms amino acids. Step 3: Amylase is made in the salivary glands and digests starch into simple reducing sugars, so the other rows mix up the enzymes and products.Method:Pair each enzyme with the correct substrate, site of production and product.Examiner tips
- Protease + stomach gives amino acids; amylase + salivary glands gives sugars.
- Step 1: Xylem vessels carry water and dissolved minerals up from the roots through the stem. Step 2: The red dye is carried up inside the xylem, so the xylem becomes stained red. Step 3: Phloem carries sugars, the cuticle is a waxy outer layer, and a style is part of a flower, so none of these carry the water.Method:Identify the water-carrying tissue (xylem) that the dye would travel through.Examiner tips
- Xylem carries water; a dye in water marks the xylem.
- Step 1: The body uses oxygen and releases carbon dioxide, so expired air contains more carbon dioxide and less oxygen than inspired air. Step 2: Therefore carbon dioxide is lower in inspired air, making statement 2 correct, and oxygen is higher in inspired air, making statement 3 correct. Step 3: So statements 2 and 3 are the correct pair.Method:Compare oxygen and carbon dioxide levels in inhaled versus exhaled air and pick the true statements.Examiner tips
- Inspired air: more oxygen, less carbon dioxide; expired air: the opposite.
- Step 1: Germinating seeds need water to activate their enzymes and oxygen for aerobic respiration to release energy. Step 2: The chemical in the tube absorbs the carbon dioxide the seeds give out, so carbon dioxide is not a substance the seeds need. Step 3: Chlorophyll is only needed later for photosynthesis once leaves form, so the seeds need oxygen and water.Method:Recall the conditions needed for germination and rule out the gas the seeds produce.Examiner tips
- Germination needs water, oxygen and a suitable temperature, not light or chlorophyll.
- Step 1: Anaerobic respiration in yeast is called fermentation. Step 2: Yeast break down glucose without oxygen to produce alcohol (ethanol) and carbon dioxide. Step 3: Lactic acid is the product in human muscle, while oxygen and water are not products of anaerobic respiration.Method:Recall the products of fermentation in yeast and distinguish them from muscle respiration.Examiner tips
- Yeast (anaerobic) makes alcohol and carbon dioxide; muscle makes lactic acid.
- Step 1: Urea is a waste product made in the liver and carried in the blood. Step 2: The kidneys filter urea out of the blood to form urine. Step 3: The bladder only stores urine, the lungs excrete carbon dioxide, and the stomach is part of digestion.Method:Identify the organ that filters urea from the blood to make urine.Examiner tips
- Urea is made in the liver but excreted by the kidneys in urine.
- Step 1: Direct contact means the pathogen passes straight from one person to another, for example through their blood. Step 2: Contaminated blood spreads pathogens by direct contact between people. Step 3: Contaminated air, food and surfaces are indirect routes, because the pathogen passes through the environment before reaching a new person.Method:Separate direct (person-to-person) from indirect (through the environment) transmission.Examiner tips
- Direct contact = body fluids passing straight between people; indirect = through air, food or objects.
- Step 1: The pancreas releases insulin into the blood. Step 2: Insulin lowers blood glucose concentration when it rises too high. Step 3: Adrenaline comes from the adrenal glands, oestrogen from the ovaries, and testosterone from the testes.Method:Recall which gland makes each hormone and match the pancreas to insulin.Examiner tips
- Link the pancreas to insulin and the control of blood glucose.
- Step 1: Roots grow towards gravity (positive gravitropism), so statement 2 is correct and statement 1 is wrong. Step 2: Shoots grow towards light (positive phototropism), so statement 4 is correct and statement 3 is wrong. Step 3: So the correct examples are statements 2 and 4.Method:Recall the direction of root and shoot growth and select the two correct statements.Examiner tips
- Positive tropism = growth towards the stimulus; roots to gravity, shoots to light.
- Step 1: Antibiotics are medicines that kill bacteria or stop them growing. Step 2: They have no effect on viruses, which is why they cannot treat viral infections such as colds. Step 3: Antibiotics are manufactured as drugs; they are not produced by platelets or white blood cells.Method:Recall what antibiotics act on and rule out viruses and body-made substances.Examiner tips
- Antibiotics kill bacteria only; viruses are unaffected.
- Step 1: Sexual reproduction involves the fusion of the nuclei of two gametes at fertilisation, so statement 4 is correct. Step 2: This mixing of genetic material from two parents produces offspring that are genetically different, so statement 1 is correct. Step 3: Sexual reproduction occurs in plants as well as animals and does not make identical offspring, so statements 2 and 3 are wrong.Method:Test each statement against the definition of sexual reproduction.Examiner tips
- Sexual reproduction = gametes fusing + genetically different offspring.
- Step 1: The menstrual cycle is counted from the first day of menstruation, a period. Step 2: At the start of the cycle the thickened uterus lining breaks down and is lost as blood through the vagina. Step 3: The lining only repairs, thickens and grows new blood vessels later in the cycle, and implantation happens only if an egg is fertilised.Method:Recall that the cycle begins with a period and identify the change to the lining.Examiner tips
- The cycle starts with menstruation, when the lining breaks down.
- Step 1: HIV is spread mainly through body fluids, including during unprotected sex. Step 2: Using condoms acts as a barrier that stops the exchange of these fluids, reducing transmission. Step 3: Clean water, hygienic food and sewage treatment prevent diseases spread by water or food, not HIV.Method:Recall how HIV is spread and choose the measure that blocks body-fluid exchange.Examiner tips
- HIV is spread by body fluids; barrier methods such as condoms reduce its spread.
- Step 1: A gene can exist in different versions, for example a version for brown eyes and a version for blue eyes. Step 2: These alternative forms of the same gene are called alleles. Step 3: A chromosome is a thread of DNA carrying many genes, a genotype is the alleles an organism has, and a phenotype is its observable features.Method:Match the definition "alternative form of a gene" to the correct genetics term.Examiner tips
- Allele = one version of a gene; genotype = the alleles present; phenotype = the visible feature.
- Step 1: There are only two distinct types of ear wax with no values in between, which is discontinuous variation. Step 2: This feature is determined by genes alone, with no environmental effect. Step 3: So it is discontinuous variation controlled by genes only.Method:Classify the variation as continuous or discontinuous, then decide what controls it.Examiner tips
- Discontinuous variation gives separate categories controlled by genes only.
- Step 1: Natural selection acts when individuals vary and some are better suited to their surroundings. Step 2: Giraffes with longer necks could reach more food, so they were better adapted and more likely to survive and reproduce. Step 3: Breeding chosen animals is artificial selection, and with no competition or no trees there would be no advantage to a long neck.Method:Pick the statement that describes the better-adapted individuals surviving by natural selection.Examiner tips
- Natural selection: variation, competition, survival of the better adapted, then breeding.
- Step 1: Alpine plants have only a short snow-free season in which to reproduce. Step 2: To complete reproduction in this short time they must both flower and produce seeds quickly. Step 3: Flowering or seeding slowly would not leave enough time before the snow returns.Method:Link the short snow-free season to the need for rapid flowering and seed production.Examiner tips
- A short season favours quick flowering and quick seed production.
- Step 1: Agricultural machinery lets farmers work larger areas of land efficiently, so statement 1 is correct. Step 2: Selective breeding produces livestock that give more meat or milk, so statement 3 is correct. Step 3: Herbicides kill weeds and so reduce competition with crops rather than increase it, so statement 2 is wrong.Method:Judge each method against how it affects food production and reject the herbicide claim.Examiner tips
- Machinery and selective breeding raise yields; herbicides reduce weed competition.
- Step 1: Conservation aims to protect species and stop their numbers falling further. Step 2: Seed banks store seeds so that plant species can be grown again in the future, which helps to conserve them. Step 3: Monocultures, overharvesting and reducing biodiversity all harm species rather than conserve them.Method:Pick the method that protects or stores species rather than harming them.Examiner tips
- Seed banks and protected areas help conserve endangered species.
- Step 1: Useful bacteria for biotechnology should reproduce quickly so that large numbers build up fast. Step 2: They should also have a high ability to make complex molecules, which are the useful products. Step 3: Type 4 has both the fastest reproduction rate, 3.0 divisions per hour, and a high ability to make complex molecules, so it is the most useful.Method:Compare both features and pick the type that scores highly on reproduction rate and molecule production.Examiner tips
- Look for the type that is best on both features at once.
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