Biology Paper 2 November 2023

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1. ALeave the equipment permanently switched on so its wiring never cools and cracks.
2. BHandle the equipment only with bare, slightly damp hands for a better grip.
3. CSwitch off and unplug the equipment before cleaning or repairing it.
4. DCover the equipment with a wet cloth before starting any repair work.

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1. ABecause the board is painted a bright colour that the sign is meant to match.
2. BBecause the board carries mains voltage that can electrocute anyone who opens it carelessly.
3. CBecause the board is the coolest place in the building and needs no other warning.
4. DBecause the board is the heaviest fixture and could fall and crush someone standing near it.

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1. ABecause the equipment inside is extremely cold and could cause frostbite on contact.
2. BBecause the substation door is kept open to the public for regular guided tours.
3. CBecause the equipment inside steps up or carries a voltage well above what the human body can safely withstand.
4. DBecause the substation is usually the tallest structure in the area and needs marking for aircraft.

1. AA structural protein that forms the rigid cell wall surrounding a plant cell.
2. BA biological catalyst, a protein that speeds up a specific chemical reaction without being used up.
3. CA carbohydrate store built up inside plant cells for later use as an energy source.
4. DA hormone released into the bloodstream that carries a chemical message to a target organ.

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1. AThe substrate molecules are broken down directly by the heat, leaving the enzyme with less work to do.
2. BThe water surrounding the reaction evaporates, concentrating the enzyme and substrate closer together.
3. CThe enzyme and substrate molecules gain kinetic energy, so they collide more often and more collisions succeed.
4. DThe enzyme molecules multiply as they are heated, giving many more active sites for the substrate to fill.

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1. AHeat breaks the bonds holding the enzyme's folded shape, so its active site changes and the substrate no longer fits it.
2. BHeat dissolves the enzyme completely into the surrounding water, so it can no longer meet the substrate at all.
3. CHeat converts the enzyme into a different enzyme that acts on a substrate not present in the mixture.
4. DHeat freezes the substrate molecules in place, so they can no longer diffuse towards the enzyme.

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1. AIt transports dissolved food such as sucrose and amino acids from the leaves to other parts of the plant.
2. BIt transports water and dissolved mineral salts from the root up to the stem and leaves.
3. CIt absorbs water directly from the soil through a large surface area of fine hairs.
4. DIt stores starch reserves that the root draws on during the dry season.

1. AIt produces the hormones that control the opening and closing of the stomata.
2. BIt transports water and dissolved mineral salts from the root up to the stem and leaves, and its lignified walls support the plant.
3. CIt transports dissolved sugars made in the leaves down to the root for storage.
4. DIt absorbs mineral salts directly from the soil solution surrounding the root hairs.

1. AIt stores excess sugar made during photosynthesis for later use.
2. BIt produces the auxin that controls the bending of a shoot towards light.
3. CIt builds the cellulose that thickens and strengthens the cell wall.
4. DIt creates the pull that draws water and dissolved mineral salts up through the xylem.

1. Apoisons the plant, since the water vapour released carries waste products out through the stomata.
2. Bcools the plant, since the evaporation of water from the leaf surface removes heat.
3. Cwarms the plant, since the water vapour released traps heat close to the leaf surface.
4. Dfeeds the plant, since the water vapour released is absorbed again as a source of food.

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1. Aglucose -> ethanol + carbon dioxide (+ energy)
2. Bglucose + oxygen -> carbon dioxide + water (+ energy)
3. Cglucose -> lactic acid (+ energy)
4. Dcarbon dioxide + water -> glucose + oxygen

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1. AIt requires oxygen and breaks glucose down incompletely to lactic acid.
2. BIt requires no oxygen and breaks glucose down incompletely to ethanol and carbon dioxide.
3. CIt requires oxygen and breaks glucose down completely to carbon dioxide and water.
4. DIt requires no oxygen and breaks glucose down completely to carbon dioxide and water.

1. AAnaerobic respiration releases much more energy per glucose molecule than aerobic respiration does.
2. BAerobic and anaerobic respiration release exactly the same amount of energy per glucose molecule.
3. CNeither aerobic nor anaerobic respiration releases any usable energy from glucose.
4. DAerobic respiration releases much more energy per glucose molecule than anaerobic respiration does.

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1. AIt controls voluntary, conscious movement of the body.
2. BIt coordinates balance and the fine control of muscular movement.
3. CIt controls automatic processes such as heart rate and breathing rate.
4. DIt releases hormones that regulate growth and metabolism.

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1. AIt maintains posture by continuously adjusting the tension of skeletal muscles.
2. BIt is the centre of memory, reasoning, learning and personality.
3. CIt relays sensory impulses from the spinal cord up towards the rest of the brain unchanged.
4. DIt secretes hormones directly into the bloodstream to control other organs.

1. AAs a sound wave travelling along fluid filled ducts within the body.
2. BAs a stream of blood cells carrying a coded message to a distant organ.
3. CAs an electrical impulse travelling rapidly along a nerve fibre to a specific effector.
4. DAs a chemical hormone travelling slowly through the bloodstream to several organs at once.

1. AAs a chemical hormone released into the bloodstream, acting more slowly but often for longer than a nerve impulse.
2. BAs an electrical impulse travelling instantly along a nerve fibre to one exact effector.
3. CAs a sound vibration passed from cell to cell across the body.
4. DAs a burst of light signal passed between neighbouring organs.

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1. AA digestive enzyme dissolves the whole donor cell so that its DNA floats free in solution.
2. BA microscope needle physically tears a fragment of chromosome out of the donor nucleus.
3. CUltraviolet light burns a hole through the donor DNA at the exact position of the gene.
4. DA restriction enzyme cuts the gene out of the donor DNA and also cuts open the vector, leaving matching sticky ends.

1. AThe recombinant plasmid is injected directly into the recipient's bloodstream, where it becomes a permanent part of every cell at once.
2. BThe recombinant plasmid is absorbed through the recipient's skin during normal contact between the two species.
3. CThe recombinant plasmid replaces the recipient's entire set of chromosomes the moment the two cells touch.
4. DThe recombinant plasmid is taken up by a recipient cell (commonly a bacterium) through transformation, and copies as the cell divides.

1. AIt is coated in wax on both surfaces, blocking almost all light from reaching the mesophyll.
2. BIt is broad, flat and thin, giving a large surface area for light absorption and a short path for gas diffusion.
3. CIt is thick and rolled, giving a small surface area that reduces water loss in shade.
4. DIt is covered in dense hairs on both surfaces, trapping a layer of still air against the leaf.

1. AThat position is farthest from the stomata, keeping the chloroplasts away from incoming carbon dioxide.
2. BThat position receives the strongest light, so packing chloroplasts there captures the most light energy.
3. CThat position is coolest, protecting the chloroplasts from heat damage during the day.
4. DThat position is closest to the xylem, letting chloroplasts absorb sugar instead of making it.

1. AThey open and close under the control of guard cells, allowing carbon dioxide in and oxygen out.
2. BThey open and close under the control of guard cells, pumping water directly into the palisade cells.
3. CThey stay permanently open, providing a fixed channel for sugar to leave the leaf.
4. DThey stay permanently closed during the day, protecting the leaf from excess light.

1. ANitrogen is needed to build the waxy cuticle that reduces water loss from the leaf.
2. BNitrogen is needed to build amino acids and so proteins, which form enzymes and structural tissue for growth.
3. CNitrogen is needed to build cellulose, the main carbohydrate of the cell wall.
4. DNitrogen is needed to build starch, the main storage carbohydrate of the plant.

1. AThe leaves yellow (chlorosis), because nitrogen is needed to build chlorophyll and its shortage reduces photosynthesis.
2. BThe leaves thicken and darken, because nitrogen shortage causes extra wax to build up on the surface.
3. CThe leaves curl tightly inward, because nitrogen shortage stiffens the veins running through them.
4. DThe leaves drop their stomata, because nitrogen shortage dissolves the guard cells around each pore.

1. AAntibodies are injected into the fetus by the doctor during a routine prenatal scan.
2. BAntibodies pass from the father's sperm into the fetus at the moment of fertilisation.
3. CMaternal antibodies cross the placenta from mother to fetus during pregnancy.
4. DThe fetus manufactures its own antibodies from the moment its heart starts beating.

1. AAntibodies are manufactured by the mother's stomach and passed to the infant through her saliva.
2. BAntibodies form in the infant's own bloodstream the moment it starts breathing air.
3. CAntibodies are absorbed from the infant's own urine as it is recycled through the digestive system.
4. DAntibodies present in breast milk, especially the first milk (colostrum), are absorbed through the infant's gut wall.

1. AThe antibodies work only while the infant remains inside the uterus and stop working completely once it is born.
2. BThe antibodies convert into the infant's own red blood cells once absorbed, so they no longer function as antibodies.
3. CReady-made antibodies are supplied rather than produced by the infant's own immune system, and no memory cells are formed, so the antibodies are gradually broken down and not replaced.
4. DThe antibodies are destroyed the instant the infant's own immune system begins to develop, usually within a few hours of birth.

1. AThe individual's own immune system manufactures antibodies after meeting an antigen, giving protection that is slow to start but long-lasting.
2. BReady-made antibodies are received from an outside source, giving protection that takes weeks to start but then lasts a lifetime.
3. CThe individual's own immune system manufactures antibodies before ever meeting an antigen, giving permanent protection from birth.
4. DReady-made antibodies are received from an outside source, giving protection that is immediate but short-lived since no memory cells are formed.

1. AReady-made antibodies are transferred from another individual, giving protection that lasts only a few weeks.
2. BThe individual's own immune system produces antibodies before any antigen has ever been encountered.
3. CReady-made antibodies are absorbed from food, giving protection that strengthens every time a meal is eaten.
4. DThe individual's own immune system produces antibodies in response to an antigen, through infection or vaccination, and memory cells give lasting protection.

1. AA restriction enzyme isolates the insulin gene from human DNA and cuts open a bacterial plasmid, leaving matching sticky ends.
2. BThe insulin gene is copied by hand from a printed sequence and glued onto the outside of a bacterial cell wall.
3. CThe whole human pancreas is transplanted into a bacterium so that its cells begin making insulin directly.
4. DA virus infects a human cell and carries the entire human genome, unmodified, into a bacterium.

1. AThe recombinant plasmid is heated until it evaporates, releasing insulin gas that is collected and bottled.
2. BThe recombinant plasmid replaces every chromosome in a human cell, turning it permanently into a bacterium.
3. CThe recombinant plasmid is introduced into a bacterium such as Escherichia coli by transformation.
4. DThe recombinant plasmid is swallowed directly by a patient with diabetes so it reaches their pancreas.

1. AThe transformed bacteria are injected whole into a patient's bloodstream, where they live permanently and release insulin.
2. BThe transformed bacteria are burned, and the insulin is collected from the smoke they release.
3. CThe transformed bacteria are frozen solid and implanted under the skin as a slow-release insulin capsule.
4. DThe transformed bacteria are cultured in large fermenters, and the insulin they produce is extracted and purified.

1. ARecombinant plasmids are radioactive and contaminate any laboratory that stores them for more than a day.
2. BA marker gene for antibiotic resistance could spread from engineered bacteria to disease-causing bacteria, making infections harder to treat.
3. CEvery recombinant bacterium eventually turns into a virus, since bacteria and viruses share the same genetic code.
4. DInsulin made by recombinant bacteria always contains bacterial DNA that a patient's body permanently incorporates.

1. AA genetically modified organism instantly becomes larger than its natural relatives, making it easy to recapture.
2. BA genetically modified organism cannot survive outside a laboratory, so containment is never actually necessary.
3. CA genetically modified organism could escape and interbreed with wild relatives, disrupting natural gene pools and reducing biodiversity.
4. DA genetically modified organism can never reproduce, so a single escape would have no lasting effect at all.

1. AIn a heterozygote, neither allele is expressed, so the phenotype shows a characteristic belonging to neither parent.
2. BIn a heterozygote, the two alleles blend completely, producing a phenotype exactly halfway between the two parental characteristics.
3. CIn a heterozygote, one allele (dominant) completely masks the expression of the other (recessive), so only the dominant characteristic shows in the phenotype.
4. DIn a heterozygote, both alleles are expressed equally and simultaneously, so both characteristics show together in the phenotype.

1. AIn a heterozygote, neither allele masks the other, so both are fully and simultaneously expressed in the phenotype, as with blood group AB.
2. BIn a heterozygote, one allele completely masks the other, so only one characteristic ever shows in the phenotype.
3. CIn a heterozygote, the two alleles cancel each other out, so neither characteristic appears in the phenotype.
4. DIn a heterozygote, one allele destroys the other physically, so only one allele is passed on to the next generation.

1. A1 in 2, since one parent is already carrying an i allele that is certain to be passed on.
2. B3 in 4, since three of the four possible gamete combinations include at least one i allele.
3. C0, since neither parent's own blood group is O, so an O child is genetically impossible.
4. D1 in 4, since each parent has a 1 in 2 chance of passing on their i allele, and both must do so together.

1. AI^A I^B, I^A i, I^B i, i i, giving blood groups AB, A, B and O.
2. BI^A I^A, I^B I^B, i i, i i, giving blood groups A, B, O and O only.
3. CI^A I^B, I^A I^B, I^A I^B, I^A I^B, giving blood group AB in every child.
4. DI^A i, I^A i, I^B i, I^B i, giving blood groups A and B only, with no AB or O possible.

1. AThe total mass of all living organisms found in a single named ecosystem.
2. BThe number of individual organisms, of any one species, counted in a fixed sample area.
3. CThe list of species officially protected by conservation law in a particular country.
4. DThe variety of living organisms found in an area, including the variety of species, genetic variation within species, and variety of ecosystems.

1. ASuccession, which instantly restores the original community within the same season.
2. BHabitat destruction, which removes the food, shelter and breeding sites many species depend on.
3. CGenetic drift, which only ever affects species that already live in a protected reserve.
4. DMigration, which always increases the number of species found in the cleared area.

1. AA native species becomes immune to disease once a new species is introduced alongside it.
2. BAn invasive alien species may outcompete or prey on native species, reducing their numbers.
3. CA native species always increases in number once a new species arrives to compete with it.
4. DAn invasive alien species instantly interbreeds with every native species, preventing any threat.

1. AMonoculture.
2. BCrop rotation.
3. CIntercropping.
4. DAgroforestry.

1. ACommunity-based programmes such as CAMPFIRE, which share tourism and safari revenue with local communities.
2. BBuilding large dams across every major river to create new artificial habitat for wildlife.
3. CRemoving all fencing around national parks so wildlife can roam freely across farmland.
4. DBanning all forms of tourism in and around national parks and game reserves.

1. ASetting aside national parks and game reserves, such as Hwange and Gonarezhou.
2. BEncouraging unrestricted settlement inside every existing game reserve.
3. CRemoving anti-poaching patrols so rangers can focus only on tourism duties.
4. DAllowing unlimited, unlicensed hunting throughout the whole country.

1. AAny solid food that provides energy and nutrients needed for normal growth.
2. BAny liquid that is safe to drink and causes no change to how the body functions.
3. CA substance produced only by the human body itself, such as a natural hormone.
4. DA chemical substance that, when taken into the body, alters how the body works physically or psychologically.

1. AIt replaces a hormone the body itself is failing to produce.
2. BIt relieves or reduces pain without affecting a person's consciousness.
3. CIt kills or stops the growth of bacteria that are causing an infection.
4. DIt is taken beforehand to prevent a disease or infection from occurring.

1. AIt is taken beforehand to prevent a disease or infection from ever occurring.
2. BIt numbs a part of the body completely during a surgical operation.
3. CIt kills or stops the growth of bacteria, treating a bacterial infection.
4. DIt relieves pain without affecting a person's level of consciousness.

1. AIt is taken to prevent a disease or infection from occurring in the first place, such as an anti-malarial taken before travel.
2. BIt kills or stops the growth of bacteria already causing an infection.
3. CIt relieves pain that is already being felt, without affecting consciousness.
4. DIt replaces blood lost during a major injury or operation.

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1. AComplete immunity to addiction develops after the very first use.
2. BFamily relationships strengthen automatically the longer the habit continues.
3. CImpaired judgement, memory and concentration lead to poor performance at school or work.
4. DImproved memory and concentration lead to consistently better performance at school or work.

1. ABecause Cannabis is legal everywhere in the world, a user never risks any conflict with the law.
2. BEmployers consistently promote known Cannabis users ahead of other staff.
3. CPeer groups universally discourage a user from continuing the habit once it starts.
4. DBecause Cannabis is illegal in many places, a user risks conflict with the law, including arrest and imprisonment.