May/June 2025 Paper 13 Worked Answers (IGCSE Biology 0610 Core)
40 questions · 40 marks · 45 minutes
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Worked answers for 27 questions
- Step 1: The leaf detects the insect landing and responds, which is sensitivity, and the rapid folding of the leaf is movement. Step 2: Digesting the insect to obtain nutrients is nutrition, so movement, sensitivity and nutrition are all involved. Step 3: Excretion (removing waste) and growth (a permanent increase in size) are not shown by trapping and digesting the insect, so options including them are wrong.Method:Break the description into actions and match each to a characteristic of living organisms.Examiner tips
- Match each described action to a characteristic: detecting = sensitivity, folding = movement, digesting = nutrition.
- Step 1: In the binomial system a scientific name has two parts: the first is the genus and the second is the species. Step 2: So in Rattus rattus the two parts refer to the genus and the species. Step 3: Kingdom is a much larger classification group and "group" is not a level of the binomial name, so the other options are wrong.Method:Recall the two levels of a binomial name and match them in order.Examiner tips
- Binomial name = genus then species.
- Step 1: Animal cells contain cytoplasm and a nucleus, which they share with plant cells. Step 2: Animal cells do not contain chloroplasts, because they do not photosynthesise. Step 3: So an animal cell has cytoplasm and a nucleus but no chloroplasts; the other combinations either add chloroplasts or remove the cytoplasm or nucleus, which is wrong.Method:Recall which structures animal cells have, then pick the matching combination.Examiner tips
- Animal cell = cytoplasm + nucleus (+ cell membrane), but no chloroplasts and no cell wall.
- Step 1: Magnification = image (drawing) length divided by actual length. Step 2: This gives 30 mm ÷ 200 mm = 0.15. Step 3: The drawing is smaller than the real animal, so the magnification is less than 1; 6.67 divides the wrong way round, 15 misplaces the decimal, and 6000 multiplies instead of divides.Method:Put the drawing length over the actual length and divide.Examiner tips
- Magnification = image size ÷ actual size; a drawing smaller than the real object gives a value below 1.
- Step 1: In the concentrated sugar solution the water outside the cells is less concentrated in water than inside, so water leaves the potato cells by osmosis and the mass decreases. Step 2: In distilled water there is more water outside than inside the cells, so water enters by osmosis and the mass increases. Step 3: So the mass goes down in the sugar solution and up in the distilled water.Method:Compare water concentration inside and outside the cells for each liquid and predict the mass change.Examiner tips
- Concentrated solution: water leaves, mass falls. Distilled water: water enters, mass rises.
- Step 1: Active transport moves particles against their concentration gradient, that is from a lower to a higher concentration, using energy from respiration. Step 2: It takes place across the cell membrane, and animal cells do not have a cell wall. Step 3: So the correct description is from a lower to a higher concentration across a cell membrane; moving from high to low is diffusion, and animal cells have no cell wall.Method:Recall the direction of active transport and the structure it crosses in an animal cell.Examiner tips
- Active transport = low to high concentration, across the cell membrane, using energy.
- Step 1: Reducing sugars are tested with Benedict’s solution, which turns from blue to brick red when heated with a reducing sugar. Step 2: Vitamin C is tested with DCPIP solution, which is decolourised by vitamin C. Step 3: So the correct pair is Benedict’s for reducing sugars and DCPIP for vitamin C; the biuret test is for protein and the ethanol emulsion test is for fats, so they are wrong.Method:Recall the specific reagent for each substance and choose the matching pair.Examiner tips
- Benedict’s = reducing sugars; DCPIP = vitamin C; biuret = protein; ethanol emulsion = fats.
- Step 1: Plant cell walls are made of cellulose, a carbohydrate built from many glucose units. Step 2: So cellulose is the carbohydrate used to build plant cell walls. Step 3: Glycogen is an animal energy store, starch is a plant energy store, and sucrose is a transport sugar, so none of these builds the cell wall.Method:Recall the roles of each carbohydrate and pick the structural one.Examiner tips
- Cellulose = plant cell walls; starch = plant store; glycogen = animal store; sucrose = transport sugar.
- Step 1: The top of the leaf is covered by a waxy cuticle, which lies on top of the upper epidermis. Step 2: Below the epidermis is the palisade mesophyll, then the spongy mesophyll towards the lower surface. Step 3: So the order is cuticle, epidermis, palisade mesophyll, spongy mesophyll; putting epidermis above the cuticle or spongy above palisade is wrong.Method:Start at the waxy surface and list the layers in order down the leaf.Examiner tips
- From the top: cuticle, upper epidermis, palisade mesophyll, spongy mesophyll.
- Step 1: Iron is needed to make haemoglobin in red blood cells. Step 2: Without enough iron, fewer red blood cells (with less haemoglobin) are made, causing anaemia. Step 3: Bleeding gums and poor wound healing are caused by lack of vitamin C, and weak bones and teeth by lack of calcium or vitamin D, so these are not the result of lacking iron.Method:Link iron to haemoglobin and red blood cells, then choose that effect.Examiner tips
- Iron makes haemoglobin, so a lack of iron means fewer red blood cells (anaemia).
- Step 1: The stomach makes protease, which digests protein, so the stomach, protease and protein go together. Step 2: Amylase, made in the mouth and pancreas, digests starch, not protein. Step 3: So protease acting on protein in the stomach is the correct row; the others pair an enzyme with the wrong substrate or the wrong site.Method:Check each row that the enzyme, its substrate and its site of action all agree.Examiner tips
- Stomach + protease + protein is the matching set; amylase acts on starch.
- Step 1: Water is absorbed first by the root hair cells, then passes across the root cortex cells. Step 2: It then enters the xylem, which carries it up to the leaves. Step 3: In the leaf it passes into the mesophyll cells, so the order is root hair cells, root cortex cells, xylem, mesophyll cells.Method:Follow water from the soil into the root and up to the leaf, in order.Examiner tips
- Root hairs absorb water, then cortex, then xylem up the stem, then mesophyll in the leaf.
- Step 1: A vessel carrying blood away from an organ towards the heart is a vein. Step 2: The vein that carries blood away from the kidney is the renal vein. Step 3: The renal artery carries blood into the kidney, while the pulmonary vessels connect the heart and lungs, not the kidney.Method:Use "renal" for kidney and "vein" for blood leaving towards the heart.Examiner tips
- Renal vein = blood away from the kidney; renal artery = blood into the kidney.
- Step 1: Aerobic respiration releases energy from glucose using oxygen, and this takes place in the mitochondria. Step 2: So the mitochondrion is the site of aerobic respiration in plant cells. Step 3: The chloroplast carries out photosynthesis, the nucleus controls the cell, and ribosomes make proteins, so none of these is the site of aerobic respiration.Method:Recall the function of each structure and pick the one that releases energy.Examiner tips
- Mitochondria are the site of aerobic respiration in both plant and animal cells.
- Step 1: In human muscles, anaerobic respiration breaks down glucose without oxygen to form lactic acid. Step 2: So lactic acid is the product of anaerobic respiration in muscles. Step 3: Alcohol (and carbon dioxide) are products of anaerobic respiration in yeast, not human muscle, and glucose is the reactant, not a product.Method:Recall the product of anaerobic respiration in animals and pick it.Examiner tips
- Anaerobic respiration: muscles make lactic acid; yeast makes alcohol and carbon dioxide.
- Step 1: Insulin is released by the pancreas when blood glucose is high and causes glucose to be taken up and stored, lowering the blood glucose concentration. Step 2: So insulin decreases blood glucose. Step 3: Adrenaline and glucagon raise blood glucose, and oestrogen is a sex hormone that does not control blood glucose, so they do not match.Method:Recall the hormone released when glucose is high and pick the one that lowers it.Examiner tips
- Insulin lowers blood glucose; glucagon and adrenaline raise it.
- Step 1: Asexual reproduction involves only one parent and no gametes, so the offspring are produced from that single parent. Step 2: Because there is no mixing of genetic material, the offspring are genetically identical to the parent and to each other (clones). Step 3: So asexual reproduction gives genetically identical offspring from one parent; involving two parents or producing genetically different offspring describes sexual reproduction.Method:Recall the number of parents and the genetic outcome of asexual reproduction.Examiner tips
- Asexual = one parent + identical offspring (clones); sexual = two parents + variation.
- Step 1: Sperm are made in the testes, which contain the tubes where sperm are produced. Step 2: So sperm are produced in the testes. Step 3: The penis delivers sperm, the prostate gland adds fluid to make semen, and the scrotum is the sac that holds the testes, so none of these produces sperm.Method:Recall the function of each male structure and pick the sperm-producing one.Examiner tips
- Sperm are made in the testes, held in the scrotum.
- Step 1: In a 28-day cycle, ovulation (the release of an egg from the ovary) happens around the middle, on about day 14. Step 2: So the ovary releases an egg on day 14. Step 3: The uterus lining breaks down at the start of the cycle (around days 1 to 5), then builds up after that, so the other statements give the wrong day or the wrong event.Method:Place each event on the cycle timeline and find the correct one.Examiner tips
- Day 1 = bleeding (lining breaks down); about day 14 = ovulation.
- Step 1: A gene can exist as different versions called alleles, and B and b are two different alleles of the same gene. Step 2: Having two different alleles of a gene is described as heterozygous, so Bb is heterozygous. Step 3: Homozygous means two identical alleles (such as BB or bb), and "two different genes of the same allele" is the wrong way round, so the other options are incorrect.Method:Decide if the two alleles are the same or different, then use the correct term.Examiner tips
- Different alleles = heterozygous; identical alleles = homozygous.
- Step 1: Inheritance is the passing on of genetic information from parents to their offspring. Step 2: So inheritance is the transmission of genetic information from one generation to the next. Step 3: The other statements describe particular individuals (not pure-breeding), a comparison of genotypes, or just dominant alleles, none of which is the meaning of inheritance.Method:Recall the definition of inheritance and match the statement.Examiner tips
- Inheritance = passing genetic information from parents to offspring.
- Step 1: Natural selection acts on the genetic variation that exists within a population, so that better-adapted individuals survive and reproduce. Step 2: So genetic variation within populations is a feature of natural selection. Step 3: Resources are usually limited (causing competition), offspring vary rather than being identical, and selection by humans is artificial selection, so the other options do not describe natural selection.Method:Recall the conditions for natural selection and pick the one that applies.Examiner tips
- Natural selection acts on genetic variation; selection by humans is artificial selection.
- Step 1: Energy enters most food chains when plants capture light energy from the Sun during photosynthesis. Step 2: So the Sun is the principal source of energy input to biological systems. Step 3: Carbon dioxide and minerals are raw materials, and glucose is made by plants using the Sun’s energy, so none of these is the original energy source.Method:Trace energy back to its origin at the start of food chains.Examiner tips
- The Sun is the original energy source for nearly all ecosystems.
- Step 1: Restricting the animals’ movement means they use less energy moving about, so more energy from their food goes into growth. Step 2: This increases the yield of animal product (such as meat), which is an advantage of method 1. Step 3: Increased pollution, more food eaten per animal, and a faster spread of disease are all disadvantages of intensive farming, not advantages.Method:Decide which listed effect would actually benefit production.Examiner tips
- Restricting movement reduces energy loss, raising the yield of product.
- Step 1: Biodiversity is maintained when the variety of species and their habitats is conserved. Step 2: Protecting habitats keeps the conditions that many species need, so it helps to maintain biodiversity. Step 3: Herbicides and insecticides kill plants and insects, and large-scale monocultures replace varied habitats with a single crop, so all of these reduce biodiversity.Method:Choose the practice that conserves species and habitats.Examiner tips
- Protecting habitats conserves species; chemicals and monocultures reduce biodiversity.
- Step 1: Bacteria can be given a gene so that they make a useful complex molecule, such as a protein like insulin. Step 2: Being able to make complex molecules is what makes bacteria useful in genetic modification. Step 3: Having a cell membrane or a cell wall is a general feature of many cells, and bacteria actually reproduce quickly, not slowly, so these are not the reason they are useful.Method:Pick the feature that lets bacteria produce a useful product.Examiner tips
- Modified bacteria are used because they can make complex molecules such as proteins.
- Step 1: The modification increases lycopene, a substance that may give health benefits when eaten. Step 2: Adding a beneficial nutrient improves the nutritional quality of the fruit, so that is the purpose. Step 3: The change does not involve pest resistance, herbicide resistance, or growing more fruit, so the other purposes do not match the information given.Method:Match the effect of the added substance to the correct purpose.Examiner tips
- Adding a health-giving nutrient improves nutritional quality, not yield or resistance.
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