Biology Paper 2 June 2024

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Answer this when you sit the paper.

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Answer this when you sit the paper.

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Answer this when you sit the paper.

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1. AIt joins the hydrogen atoms to the oxygen atom within a single water molecule, holding that molecule's own shape together.
2. BIt attracts sodium and chloride ions apart from each other, which is the reason table salt dissolves so readily in water.
3. CIt holds neighbouring water molecules to one another, giving water a high boiling point and letting it be pulled up a plant in an unbroken column.
4. DIt splits large food molecules such as starch into smaller soluble units during digestion in the gut.

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1. AThe high density of the molecule pulls any dissolved substance straight to the bottom of its container, away from the surrounding water.
2. BThe partial charges on the molecule attract and separate the particles of ionic and polar substances, so those substances dissolve and can be carried around the body in solution.
3. CThe small size of the molecule lets it slip between the particles of a solid without dissolving them, keeping the solid intact while suspended in the water.
4. DThe covalent bonds inside the molecule release heat as they break, and this heat melts any solid substance placed into the water.

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1. AGlycogen is a single small soluble sugar molecule, while glucose is a large insoluble molecule built from many glycogen units joined together.
2. BGlucose and glycogen are both large insoluble polysaccharides, differing only in the particular sugar unit each is built from.
3. CGlucose is made only inside plant cells, while glycogen is made only inside animal cells, though the two share an identical molecular structure.
4. DGlucose is a single small soluble sugar molecule, while glycogen is a large insoluble molecule built from many glucose units joined together.

1. AIt is a horizontal stem with long internodes that grows sideways from the parent plant, bearing buds at its nodes.
2. BIt is a swollen underground stem packed with stored food, from which a single new shoot grows upward the following season.
3. CIt is a modified root that swells with stored food and produces a new bud at its narrower end.
4. DIt is a single seed released from a fruit that germinates some distance away from the parent plant.

1. AThe node absorbs water directly from the air and swells into a storage organ before any root or shoot appears.
2. BThe whole runner curls downward and buries itself, and a new plant then grows from its buried tip only.
3. CA bud at the node grows roots down into the soil and a shoot up into the light, forming a new plantlet.
4. DA flower forms at the node and, once pollinated, produces a seed that falls and germinates nearby.

1. AIt continues to receive water and food from the parent plant along the runner until it is self-supporting, and then the runner connecting them withers.
2. BIt stops receiving anything from the parent plant from the moment its first root appears, and grows entirely on its own from that point.
3. CThe parent plant flowers and produces a seed at the plantlet's position, which then replaces the plantlet as the new independent plant.
4. DThe runner thickens permanently, so the plantlet remains physically joined to the parent plant for the rest of both their lives.

1. AIt slows the root's growth so that the shoot can grow first and reach the light before the root uses up food reserves.
2. BIt bends the root toward the nearest source of running water, sensed directly rather than through the pull of gravity.
3. CIt directs the root down into the soil, anchoring the plant and bringing it into contact with the water and mineral salts held there.
4. DIt directs the root up towards the surface, so it can photosynthesise alongside the leaves in bright light.

1. AIt lifts the leaves toward the light needed for photosynthesis and lifts the flowers into a position where pollinators or wind can reach them.
2. BIt keeps the shoot pressed flat against the soil, so less water is lost from its surface by transpiration.
3. CIt draws the shoot down into cracks in the soil, protecting the young leaves from being eaten by grazing animals.
4. DIt shortens the shoot so that all of the plant's food reserves can instead be spent on downward root growth.

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1. AIt releases lysozyme onto its surface, an enzyme that digests the cell walls of any bacteria landing on it.
2. BIt continually sheds tears across its whole surface, physically flushing pathogens away before they can settle.
3. CIt secretes hydrochloric acid over its surface, which is strong enough to kill most bacteria and fungi on contact.
4. DIt forms a tough, largely unbroken physical barrier of dead, keratinised cells that is difficult for a pathogen to penetrate.

1. AIt amplifies sound waves as they travel down the ear canal, which has no connection to preventing infection.
2. BIt dissolves any microorganism that lands on it within seconds, using digestive enzymes it secretes continuously.
3. CIt is sticky and traps dust, debris and microorganisms carried into the ear canal, stopping them from reaching the eardrum.
4. DIt vibrates in time with sound waves, a vibration strong enough to shake loose bacteria out of the ear canal.

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1. AThe pathogen immediately divides inside the phagocyte, multiplying before it can be destroyed.
2. BThe pathogen is enclosed within a vacuole inside the phagocyte's cytoplasm.
3. CThe pathogen is pushed back out through the phagocyte's cell membrane, unharmed.
4. DThe phagocyte itself bursts open, releasing the pathogen back into the bloodstream.

1. AThe vacuole freezes the pathogen in place, starving it of oxygen until it dies days later.
2. BThe pathogen is passed unchanged from the vacuole directly into the phagocyte's nucleus, where it is stored.
3. CAntibodies produced by the same phagocyte flood the vacuole and neutralise the pathogen's toxins only.
4. DDigestive enzymes, released from lysosomes into the vacuole, break down and digest the pathogen.

1. ADNA that occurs naturally when two different species interbreed and produce offspring.
2. BDNA copied exactly from a single organism using a chemical process in a laboratory.
3. CDNA that has had one of its bases changed by a mutation during cell division.
4. DDNA formed by artificially joining together DNA from two different sources.

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1. ACell Y undergoes meiosis, halving its chromosome number and producing four genetically different daughter cells.
2. BCell Y is exposed to ultraviolet light, which causes it to mutate repeatedly into many different new cell types.
3. CCell Y is grown in a fermenter under controlled conditions, where it divides repeatedly by binary fission, producing genetically identical copies of itself.
4. DCell Y is fused with a second, unrelated bacterial cell, and the fused cell then divides to produce a mixture of different cell types.

1. AMicroorganisms require an animal host to survive, so slaughtering animals is still necessary either way.
2. BMicroorganisms reproduce extremely quickly, so a large quantity of insulin can be produced in a short time from a small starting culture.
3. CMicroorganisms need years to reach a usable size before any insulin can be extracted from them at all.
4. DMicroorganisms can only be grown one at a time, so each fermenter yields exactly one dose of insulin.

1. AIt contains fragments of animal tissue that stimulate the body's immune system to work harder against other diseases.
2. BIt is chemically identical to adrenaline, so the body responds to it in exactly the same way it responds to its own insulin.
3. CIt is identical to human insulin, so it does not trigger the allergic or immune reactions that animal insulin can sometimes cause.
4. DIt is a completely different hormone from human insulin, so the body treats it as harmless because it does not recognise it at all.

1. AIt is the condition in which a single gene has three or more different alleles present across a population.
2. BIt is the condition in which one allele of a gene completely masks the effect of the other allele in a heterozygote.
3. CIt is the condition in which two alleles of the same gene are both fully expressed together in a heterozygote.
4. DIt is the condition in which two different genes on the same chromosome are always inherited together as a unit.

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1. AGamma radiation, which is ionising and damages the structure of the cell's DNA.
2. BA rise in the humidity of the surrounding air, which slows water loss from the cell.
3. COrdinary visible light of low intensity, most of which is reflected by the skin's surface.
4. DA diet that is short of protein, leaving the cell without enough amino acids to build new proteins.

1. A0, since the mother has no i allele that she could pass on to a child.
2. B1 in 4, since one of the four boxes of the Punnett square holds two i alleles.
3. C1 in 2, since half of the father's gametes carry the i allele he is heterozygous for.
4. D3 in 4, since three of the four boxes hold at least one i allele between them.

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1. Ai gametes only, since the recessive allele is always the one carried in a gamete.
2. BI^A gametes and I^B gametes only, since she carries no i allele to pass on.
3. CI^A, I^B and i gametes, since every parent in a genetics cross can pass on all three alleles.
4. DI^B gametes only, since I^B is co-dominant with I^A and so is passed on preferentially.

1. Aa community of organisms interacting with each other and their non-living environment.
2. Ba group of organisms of the same species living together in the same area.
3. Cthe non-living, physical surroundings of an organism, such as soil, water and climate.
4. Dall the different species of organisms living in one habitat, excluding their surroundings.

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1. AThe population's food supply increases automatically to match the new, larger number of individuals.
2. BEvery individual in the population immediately becomes immune to disease, since crowding strengthens the immune system.
3. CThe carrying capacity of the ecosystem rises permanently to match whatever size the population happens to reach.
4. DFood and other resources become insufficient for the population, so the death rate rises and the population size falls.

1. AThe soil becomes permanently more fertile as more organisms live and feed on it.
2. BPredators voluntarily leave the area so that the overcrowded population can recover undisturbed.
3. COvergrazing strips away the vegetation cover, leaving the soil exposed and vulnerable to erosion.
4. DThe extra individuals build new water sources for the whole population to share equally.

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1. ABoth soils have the same air content, since particle size has no effect on how tightly soil particles pack together.
2. BNeither soil contains any air at all, since the spaces between soil particles are always completely filled with water.
3. CSandy soil has a high air content, since its large particles pack loosely leaving big air spaces; clay soil has a low air content, since its fine particles pack tightly leaving little space.
4. DSandy soil has a low air content, since its large particles pack tightly leaving no space; clay soil has a high air content, since its fine particles pack loosely leaving large gaps.

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1. ASandy soil has poor drainage and easily becomes waterlogged; clay soil has good, free drainage since water passes quickly through it.
2. BBoth soils drain water at exactly the same rate, since drainage depends only on rainfall and not on particle size.
3. CNeither soil allows any water to drain through it at all, so both remain permanently waterlogged after rain.
4. DSandy soil has good, free drainage since water passes quickly through its large air spaces; clay soil has poor drainage and easily becomes waterlogged.

1. AA thermometer, used only for checking body temperature.
2. BAntiseptic (antiseptic lotion or wipes).
3. CA pair of scissors, used only for cutting clothing away from a wound.
4. DA set of safety pins, used only for securing a folded bandage.

1. AAn adhesive plaster (dressing strip).
2. BA crepe bandage, used only to hold a splint against a broken limb.
3. CCotton wool, used only for padding underneath a splint.
4. DA pair of disposable gloves, worn only by the person giving first aid.

1. AAdhesive tape, used only to label the first aid kit's contents.
2. BPain relief tablets, used only after the wound has already been dressed.
3. CA thermometer, used only to check for fever after an injury.
4. DA bandage (crepe or triangular).

1. AFirst aid is only useful for treating illnesses, and has no role to play in an injury such as a cut or a fracture.
2. BFirst aid is required by law to be given only by a qualified doctor, never by a teacher or trained first aider.
3. CPrompt, correctly applied first aid can stop a minor injury from becoming a serious one before proper medical help arrives.
4. DFirst aid replaces the need for a learner to ever see a doctor or go to a hospital, whatever the injury.

1. AIt replaces the need for the school to keep any emergency contact details for its learners.
2. BIt reduces the risk of further injury or infection, for example by immobilising a fracture before it is moved or cleaning a wound before it becomes infected.
3. CIt permanently cures any chronic illness a learner already has, without any further medical treatment.
4. DIt guarantees that no learner at the school will ever be injured again after receiving first aid once.

1. AWhy each enzyme is specific, catalysing only the reaction of the one substrate whose shape fits its active site.
2. BWhy every enzyme in the body can catalyse any reaction, regardless of the shape of the substrate involved.
3. CWhy an enzyme is permanently changed and destroyed the first time it catalyses a reaction.
4. DWhy enzymes work only outside living cells, never inside the cytoplasm of the cell that makes them.

1. AThe active site is left unchanged and free to bind another substrate molecule, so the same enzyme can be reused repeatedly.
2. BThe active site permanently changes shape to fit the product instead, so the enzyme can never bind that substrate again.
3. CThe active site is destroyed along with the substrate, so a new enzyme molecule must be made for every reaction.
4. DThe active site seals shut permanently once one reaction has taken place, ending that enzyme molecule's activity for good.

1. AThe active site no longer fits the substrate, so the enzyme can no longer catalyse that reaction, just as a bent key no longer opens its lock.
2. BThe active site becomes able to fit every substrate in the cell at once, so the enzyme catalyses many more reactions than before.
3. CThe enzyme's specificity is unaffected by denaturation, so it continues to catalyse the same reaction at the same rate.
4. DThe substrate itself changes shape to match the enzyme's new active site, so the reaction proceeds even faster than before.

1. AThey break down large, insoluble stain molecules, such as protein or fat, into smaller soluble molecules that dissolve and rinse away.
2. BThey bleach the colour out of the stain directly, the same way a chlorine-based bleach does.
3. CThey coat the stain in a waterproof layer that prevents it from spreading further into the fabric.
4. DThey raise the temperature of the wash water directly, which is what actually removes the stain.

1. AIt prevents the enzymes in the powder from ever being denatured, however hot the water later becomes.
2. BIt uses less energy to heat the water and is gentler on delicate fabrics than washing at a high temperature.
3. CIt causes the enzymes in the powder to work faster than they would at any higher temperature.
4. DIt kills every microorganism on the fabric instantly, which hot water alone cannot do.

1. AIn bright light the leaf stops making water vapour altogether, since all of its water is used up in photosynthesis instead.
2. BIn bright light the stomata open wider, letting more carbon dioxide in for photosynthesis and more water vapour escape, so transpiration increases.
3. CIn bright light the stomata close completely to protect the leaf from the heat of the light, so transpiration falls to zero.
4. DLight intensity has no effect on the stomata at all, so transpiration stays exactly the same in light or darkness.

1. AIt gives water molecules more kinetic energy, so they evaporate and diffuse out through the stomata faster, increasing transpiration.
2. BIt causes every stoma on the leaf to seal shut permanently, so transpiration falls to zero above a certain temperature.
3. CIt has no effect on transpiration, since only light intensity and humidity influence the rate of water loss.
4. DIt slows the movement of water molecules, so less water evaporates from the leaf's internal surfaces.

1. AIt has no effect on transpiration, since only the light and temperature reaching a leaf influence how fast it loses water.
2. BIt causes the stomata to open only at night, so transpiration during the day falls to its lowest point.
3. CIt creates a large difference in water vapour concentration between the inside of the leaf and the air, so water diffuses out quickly, increasing transpiration.
4. DIt creates a large difference in water vapour concentration that pulls water vapour into the leaf from the air, decreasing transpiration.

1. AThe cells absorb air through the stomata and swell, so leaves and soft stems are held out even more firmly.
2. BThe cells take in extra mineral salts from the soil, which makes their sap stronger and the leaves stand more upright.
3. CThe cell walls dissolve completely, causing the cell's contents to leak out and the leaf to collapse instantly.
4. DThe cells lose water from their vacuole and cytoplasm and become flaccid, so leaves and soft stems droop.

1. AWater vapour is forced back into the leaf from the surrounding air, restoring the cells' turgor within seconds.
2. BLess carbon dioxide can diffuse into the leaf, so the rate of photosynthesis falls and less food is made.
3. CMore carbon dioxide floods into the leaf through the closed stomata, so photosynthesis speeds up.
4. DMineral salts can no longer be absorbed by the roots at all, so the whole plant turns yellow within minutes.

1. AIt increases the heart rate and the force of each heartbeat, increasing the volume of oxygenated blood pumped to the muscles and brain.
2. BIt slows the heart rate and weakens each heartbeat, conserving energy for a period of rest and digestion.
3. CIt stops the heart from beating for a brief period, redirecting all of the body's blood supply to the digestive system.
4. DIt has no measurable effect on the heart at all, acting only on the muscles and skin of the body.

1. AIt causes the liver to release adrenaline of its own, doubling the total amount circulating in the blood.
2. BIt stimulates the breakdown of stored glycogen to glucose and its release into the blood, raising blood glucose concentration.
3. CIt stimulates the liver to store extra glucose as glycogen, lowering blood glucose concentration.
4. DIt stops the liver from carrying out any of its normal functions until the adrenaline has been broken down.

1. AIt contracts the muscle in their walls, narrowing the airways so that less air can pass through them.
2. BIt has no effect on the bronchioles, acting only on organs below the level of the neck.
3. CIt seals the bronchioles shut completely for the duration of the fight-or-flight response.
4. DIt relaxes the muscle in their walls, widening (dilating) the airways so more air, and so more oxygen, can be breathed in and out.

1. AIt raises blood glucose concentration directly, giving the body extra energy to fight the disease.
2. BIt replaces the need to eat any carbohydrate at all, since the injected insulin itself supplies the body's energy.
3. CIt replaces the insulin the pancreas fails to produce enough of, allowing body cells to take up glucose from the blood and lowering blood glucose after meals.
4. DIt permanently repairs the damaged cells of the pancreas, so no further treatment is ever needed again.

1. AA controlled diet and exercise remove the need for a person with diabetes to ever monitor their blood glucose again.
2. BEating large amounts of sugar in a single meal helps stabilise blood glucose by giving the pancreas one clear signal to respond to.
3. CExercise raises blood glucose concentration directly, which is exactly what a person with diabetes needs more of.
4. DA controlled diet avoids large spikes in blood glucose, and exercise increases glucose uptake and use by the muscles, both helping to keep blood glucose within a safe range.

1. AIndustrial effluent discharged into the river from a nearby factory.
2. BRainwater running directly off a forest with no settlement or farming nearby.
3. CGroundwater seeping naturally into the river from an unpolluted aquifer.
4. DLeaves and other plant litter falling from trees growing along the riverbank.

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1. AComplex multicellular eukaryotes without cell walls.
2. BSometimes joined together, simple, single celled eukaryotes.
3. CMulticellular eukaryotes with cell walls that contain chitin.
4. DSimple, single celled prokaryotes.

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1. ASimple, single celled prokaryotes.
2. BComplex multicellular eukaryotes without cell walls.
3. CSometimes joined together, simple, single celled eukaryotes.
4. DMulticellular eukaryotes with cell walls that contain chitin.

1. AThey speed up the reproduction of every species equally, so total biodiversity always rises as the climate changes.
2. BThey affect only species living in the ocean, leaving every species living on land completely unaffected.
3. CThey alter or destroy the habitats species depend on, so species unable to tolerate the new conditions, or unable to migrate to a suitable habitat in time, decline or become locally extinct.
4. DThey make every habitat on Earth equally suitable for every species, so no species is ever at a disadvantage.

1. AThey cause every species to evolve new adaptations within a single generation, so no species is actually lost.
2. BThey directly kill organisms and damage habitats such as forests, wetlands and coral reefs, while favouring a smaller number of hardy species that can spread and dominate.
3. CThey evenly distribute every species across the whole planet, increasing the variety of organisms found in any one place.
4. DThey have no direct effect on organisms at all, only on the buildings and infrastructure people have constructed.

1. AStoring drinking water in open, uncovered containers so it can be seen and checked easily.
2. BDumping household refuse in the open near a water source, so it is easy to find and remove later.
3. CDiscouraging handwashing with soap, since frequent washing is thought to weaken natural skin defences.
4. DBuilding and using proper toilets or latrines instead of open defecation, and keeping them clean.

1. AMixing drinking water with river water before use, to save time collecting water separately for each purpose.
2. BProviding and using a safe, clean water supply, such as a protected well, borehole or treated piped water, and storing it in covered containers.
3. CDrawing drinking water directly from a river shared with livestock, since flowing water is always safe to drink.
4. DLeaving drinking water uncovered in the home, so dust and insects can be seen if they land in it.

1. AAllowing stagnant water to collect near homes, since it slowly evaporates and disappears on its own.
2. BLeaving food uncovered so that flies visiting it can be seen and swatted before they spread further.
3. CRemoving bed nets from sleeping areas, since they are thought to trap warm, stagnant air indoors.
4. DDraining stagnant water and covering stored food, reducing the breeding sites and food sources available to flies and mosquitoes.

1. AIt removes the need to treat the original diagnosed patient at all, since only their contacts require treatment.
2. BIt guarantees that Tuberculosis can never spread within that community again, however the contacts are managed afterwards.
3. CIt identifies only the contacts who are certain never to become infected, so they can be excluded from any further testing.
4. DIt allows infected contacts to be diagnosed and treated early, before they develop severe disease or spread it further.

1. AContact tracing replaces the need for any patient, including the original one, to take Tuberculosis medication.
2. BContacts found to be infected, even without symptoms, can be offered preventive treatment, stopping them from developing active disease and passing it on.
3. CContact tracing physically removes the Tuberculosis bacteria from the air of a community, preventing any further spread.
4. DContact tracing works only after every person in a community has already been infected, so it cannot prevent new infections.