IGCSE Biology 0610/22 May/June 2025 Past Paper with Answers

Question 1

An animal carries out four processes: excretion, growth, digestion and respiration. How many of these four processes are characteristics of all living organisms?

1. 3
2. 1
3. 2
4. 4

Question 2

Part of the DNA base sequence of four species was determined. Species 1 is T C A G G A T T, species 2 is T G A G C A A T, species 3 is T G A G C A A G, and species 4 is T G A G G A T T. The more bases that differ between two species, the less closely related they are. Which two species are the least closely related?

1. species 1 and species 3
2. species 1 and species 2
3. species 2 and species 4
4. species 3 and species 4

Question 3

A single-celled organism has chloroplasts, a cell wall and a nucleus. In which kingdom is this organism placed?

1. protoctist
2. fungus
3. plant
4. prokaryote

Question 4 · Answer A

Step 1: A cell is a single unit and a tissue is a group of similar cells, but a leaf contains several different tissues. Step 2: A structure made of several tissues working together for one job is an organ. Step 3: An organ system is several organs together, which is larger than a single leaf, so a leaf is an organ.

Question 5 · Answer A

Step 1: Actual length = magnified length divided by magnification, so actual length = 5.00 mm divided by 250 = 0.02 mm. Step 2: Converting 0.02 mm to micrometres gives 0.02 × 1000 = 20 µm. Step 3: Written in standard form this is 2.00 × 10¹ µm. Multiplying instead of dividing, or using the wrong power of ten, gives the other answers.

Question 6 · Answer A

Step 1: Diffusion is faster when there is a larger surface area to diffuse across. Step 2: It is also faster when the concentration gradient is steeper (a high gradient). Step 3: And it is faster when the distance to travel is shorter. So the fastest diffusion needs a high surface area, a high gradient and a short path.

Question 7 · Answer A

Step 1: A cylinder lengthens when water enters its cells by osmosis. Step 2: Water moves in when the surrounding liquid is more dilute than the cell contents, which is true for pure water (1) and the solution less concentrated than the cells (2). Step 3: Liquid 3 is more concentrated, so water leaves and the cylinder shrinks; liquid 4 is the same concentration, so there is no net change.

Question 8 · Answer A

Step 1: Enzymes are made of protein, so they are proteins, not carbohydrates. Step 2: They speed up reactions without being used up, which makes them biological catalysts. Step 3: A substrate is the substance an enzyme acts on, not the enzyme itself, so enzymes are proteins that act as biological catalysts.

Question 9 · Answer A

Step 1: At point 1 the rate is still rising as carbon dioxide increases, so carbon dioxide concentration is a limiting factor at point 1. Step 2: At point 3 the temperature curve is falling, which happens because enzymes are being denatured, so it is wrong to say none are denatured. Step 3: At point 4 the rate has levelled off, so light is no longer limiting, and at point 2 the rate is at its highest, so temperature is at its best and is not limiting.

Question 10 · Answer A

Step 1: The tall column-shaped cells just below the upper surface, packed with chloroplasts, are palisade mesophyll cells. Step 2: Their shape and position let them absorb the most light for photosynthesis. Step 3: Epidermis cells form a thin protective surface layer, guard cells surround stomata, and spongy mesophyll cells are the rounded, loosely packed cells lower down.

Question 11 · Answer A

Step 1: Physical digestion is the breaking of food into smaller pieces without changing it chemically. Step 2: This happens in the mouth, where teeth chew the food (part 1), and in the stomach, where muscular churning breaks it up (part 2). Step 3: The small intestine (parts 3 and 4) carries out chemical digestion and absorption, not physical digestion.

Question 12 · Answer A

Step 1: Lipase is the enzyme that digests fats and oils. Step 2: It breaks oil down into fatty acids and glycerol. Step 3: Protein to amino acids is done by protease, starch to maltose by amylase, and maltose is not turned into starch by a digestive enzyme.

Question 13 · Answer A

Step 1: Microvilli are tiny folds on the surface of the cells lining the small intestine. Step 2: These folds greatly increase the surface area of the lining. Step 3: A larger surface area means more digested food can be absorbed at once, so microvilli increase the surface area for absorption.

Question 14 · Answer A

Step 1: Xylem vessels have thick walls strengthened with lignin, which support the plant and stop the vessels collapsing. Step 2: Mature xylem vessels are dead, empty tubes with no living contents. Step 3: Because they are dead, they contain no mitochondria, so xylem vessels have thick walls and no mitochondria.

Question 15 · Answer A

Step 1: The water lost from each tube was taken up by the plant and transpired. Tube X lost 5.7 g but tube Y lost only 1.6 g, so tube Y transpired less. Step 2: The plastic bag traps water vapour around the leaves, which raises the humidity. Step 3: Higher humidity reduces the difference in water vapour between the leaf and the air, so transpiration is slower in tube Y.

Question 16 · Answer A

Step 1: In a double circulation, blood passes through the heart twice for each complete circuit of the body. Step 2: The heart pumps the blood again before sending it to the body, so it reaches the body cells at high pressure. Step 3: This delivers oxygen quickly. Mixing of blood is actually prevented, the pressure in the lungs is kept low to protect the capillaries, and carbon dioxide removal is not reduced.

Question 17 · Answer A

Step 1: The septum is the wall of muscle running down the middle of the heart. Step 2: It keeps the left side, carrying oxygenated blood, completely separate from the right side, carrying deoxygenated blood. Step 3: The valves control the direction of blood flow between chambers, and the atrium wall is just part of one chamber, so they do not separate the two types of blood.

Question 18 · Answer A

Step 1: Veins carry blood back to the heart at low pressure, so they do not need thick walls; their walls are thin compared with the vessel diameter. Step 2: They have a large lumen to let blood flow back easily. Step 3: They contain valves to stop the low-pressure blood flowing backwards, so a vein has a thin wall, a large lumen and valves present.

Question 19 · Answer A

Step 1: Antibodies passed from mother to baby in breast milk give passive immunity, so statement 1 is correct. Step 2: Passive immunity is short-term and makes no memory cells, so statement 2 is wrong. Step 3: Vaccination introduces antigens that make the body produce its own antibodies and memory cells, which is active immunity, so statement 3 is correct. Only 1 and 3 are correct.

Question 20 · Answer A

Step 1: The depth of each breath is the total volume of air divided by the breathing rate. Step 2: Between 0 and 10 minutes the rate stays at 12 breaths per minute, but the total volume rises from 5000 to 15000 cm3, so each breath must be deeper. Step 3: Therefore the depth of breathing increases in that period; the rate clearly does change from 10 to 20 minutes, and the depth does not fall from 15 to 20 minutes.

Question 21 · Answer A

Step 1: Glucose is a simple sugar made of carbon, hydrogen and oxygen. Step 2: Each glucose molecule contains 6 carbon atoms, 12 hydrogen atoms and 6 oxygen atoms. Step 3: So its chemical formula is C6H12O6; the other formulae have the wrong number of hydrogen or carbon atoms.

Question 22 · Answer A

Step 1: During the race the muscles respired anaerobically and produced lactic acid, which causes the oxygen debt. Step 2: To repay the debt, the extra oxygen taken in is used to break down the lactic acid. Step 3: Breaking it down using oxygen is aerobic respiration of lactic acid, so that is what happens at X.

Question 23 · Answer A

Step 1: Excess amino acids cannot be stored, so they are broken down in the liver in a process called deamination. Step 2: Deamination produces urea, so urea is made in the liver. Step 3: The kidney removes urea from the blood and the bladder stores urine, but neither produces urea, and the pancreas makes enzymes and hormones.

Question 24 · Answer A

Step 1: To focus on a near object the ciliary muscle (Q) contracts. Step 2: When Q contracts, it pulls inwards, so the suspensory ligaments (S) become slack. Step 3: With the ligaments slack, the lens (R) is no longer pulled thin and springs into a fatter, more rounded shape, bending the light more to focus the near object.

Question 25 · Answer A

Step 1: Glucagon is a hormone that raises blood glucose when it gets too low. Step 2: It is made and released by the pancreas. Step 3: The adrenal gland makes adrenaline, the ovary makes oestrogen, and the liver responds to glucagon by changing glycogen to glucose but does not make the hormone.

Question 26 · Answer A

Step 1: The seedling is underground in the dark, so there is no light to cause phototropism. Step 2: The responses must therefore be to gravity, which is gravitropism. Step 3: The shoot grows up, away from gravity, and the root grows down, towards gravity, so both the root and the shoot show gravitropism and neither shows phototropism.

Question 27 · Answer A

Step 1: The increase in the number of people is 6200 minus 1300, which is 4900. Step 2: Percentage increase = increase divided by the original number, times 100, so it is 4900 divided by 1300, times 100. Step 3: This gives 376.9, which is 377% to the nearest whole number.

Question 28 · Answer A

Step 1: Asexual reproduction involves only one parent and no gametes, so there is no fusion of gamete nuclei. Step 2: The offspring are produced by mitosis, so they are genetically identical to the parent and to each other. Step 3: Being genetically identical means there is no genetic variety, so asexual reproduction has no fusion of gamete nuclei and no genetic variety.

Question 29 · Answer A

Step 1: Pollen is made in the anther and lands on the stigma, so transfer is always from anther to stigma. Step 2: Cross-pollination means the pollen lands on a different plant of the same species. Step 3: So it is the transfer of pollen from the anther of one plant to the stigma of a different plant; transfer on the same plant is self-pollination.

Question 30 · Answer A

Step 1: Menstruation is the breakdown and loss of the lining of the uterus through the vagina. Step 2: Ovulation is the release of an egg from an ovary, not menstruation. Step 3: The fusion of nuclei is fertilisation, and the start of puberty is not a single process in the cycle, so only menstruation linked to shedding the uterus lining is correct.

Question 31 · Answer A

Step 1: Two affected parents have an unaffected child, so the affected parents must each carry a hidden allele for being unaffected. Step 2: This is only possible if the condition is caused by a dominant allele, so affected people can be heterozygous and pass on the recessive unaffected allele. Step 3: If it were recessive, two affected parents could only have affected children; there is no separate third phenotype (so not codominant) and no clear link to sex (so not necessarily sex-linked).

Question 32 · Answer A

Step 1: An allele is a version of a gene, and a new allele needs a change in the DNA. Step 2: A mutation is a random change in a gene, so it is the way new alleles are formed. Step 3: Artificial and natural selection only choose between alleles that already exist, and sexual reproduction shuffles existing alleles without creating new ones.

Question 33 · Answer A

Step 1: In artificial selection, humans choose which organisms breed, so survival does not depend on competing for resources. Step 2: In natural selection, organisms must compete to survive and reproduce. Step 3: Both types change characteristics, both rely on existing genetic variation, and both act over many generations, so the real difference is the lack of competition in artificial selection.

Question 34 · Answer A

Step 1: A xerophyte must conserve water, so its thick waxy layer reduces (stops) water evaporation from the surface. Step 2: It also needs to gather as much water as possible, so it has extensive root systems to maximise water uptake. Step 3: Labels that increase evaporation or restrict and minimise uptake would lose water or fail to collect it, which would not suit a dry habitat.

Question 35 · Answer A

Step 1: Energy enters a food chain as light, which plants capture during photosynthesis. Step 2: Plants store this energy as chemical energy in food. Step 3: When organisms are eaten, the energy passes along the chain as chemical energy in food; heat is lost to the surroundings rather than transferred between organisms.

Question 36 · Answer A

Step 1: A pyramid of energy is always a regular pyramid that narrows at every level going up, because energy is lost between levels, so it must be pyramid 3. Step 2: For the pyramid of numbers there are many grass plants, fewer zebras, then very many small insects on each zebra, then fewer birds. Step 3: So the numbers narrow sharply for the few zebras and then bulge out for the many insects, which matches pyramid 1.

Question 37 · Answer A

Step 1: Nitrifying bacteria in the soil change ammonium ions into nitrate ions. Step 2: This conversion of ammonium to nitrate is called nitrification. Step 3: Decomposition releases ammonium from dead matter, denitrification turns nitrate back into nitrogen gas, and nitrogen fixation turns nitrogen gas into nitrogen compounds, so none of these match.

Question 38 · Answer A

Step 1: At point Y the number of water fleas falls sharply, so something must be killing or removing large numbers of them. Step 2: Adding predators that eat water fleas would cause this sudden fall. Step 3: More oxygenating plants, a higher birth rate or more food would all let the population grow or stay high, not drop, so they cannot explain the fall.

Question 39 · Answer A

Step 1: A sustainable resource is one that is not used up, so enough fish must be left to breed and replace those caught. Step 2: Smaller fish are usually younger and have not yet bred. Step 3: Leaving the smaller fish lets them grow and reproduce, keeping the population going, so this is the reason linked to sustainability; ease of catching and price are only economic reasons.

Question 40 · Answer A

Step 1: Bacteria are useful because they reproduce rapidly, giving huge numbers quickly (feature 4). Step 2: They can also be used to make complex and useful molecules such as proteins (feature 3). Step 3: Being unaffected by antibiotics is not a useful feature, and bacteria do contain plasmids, which are actually used in genetic engineering, so feature 2 is false.