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WAEC (WASSCE) 2024

2024 WAEC (WASSCE) Biology Past Questions and Answers

The 2024 WAEC (WASSCE) Biology past questions with answers: 50 objective questions from the 2024 paper in the DeeepSolve question bank, each with its answer behind "Show answer". Try each question before you check, then practise the paper as a timed WAEC-style CBT.

Past questions © the examination body (JAMB/WAEC/NECO). DeeepSolve is not affiliated with them. Rights holders: see /copyright.

Questions

  1. 1.

    The two sources of energy that would mostly lead to pollution in the community are

    1. A.solar and kerosene
    2. B.coal and wind
    3. C.kerosene and coal
    4. D.solar and wind
    Show answer

    Answer: C. kerosene and coal

    AI explanation

    Analyze the question: We are asked to pick the two energy sources that cause the most pollution in a community. So we need to separate clean (renewable) sources from polluting (fossil fuel) sources.

    Explain the concept:

    • Renewable, clean sources: solar and wind. They give off no smoke or harmful gases when producing energy.
    • Fossil fuels: coal, kerosene, petrol, diesel, and natural gas. Burning them releases carbon dioxide (CO₂), carbon monoxide (CO), sulphur dioxide (SO₂), nitrogen oxides and soot. These cause air pollution, acid rain, respiratory problems, and global warming.

    Step-by-step solution:

    • A. Solar and kerosene: solar is clean, so this pair is only half polluting. ✗
    • B. Coal and wind: wind is clean, so this pair is only half polluting. ✗
    • C. Kerosene and coal: both are fossil fuels that release smoke and toxic gases when burned. ✓
    • D. Solar and wind: both are clean. ✗

    Answer: Option C. Both kerosene and coal are fossil fuels, so together they contribute the most pollution.

    Exam tip: In energy-and-pollution questions, ask whether the source burns something. If it burns (coal, kerosene, firewood, petrol), it pollutes. If it uses sunlight, wind, or water, it is clean. Choose the option where both items are in the "burning" group.

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  2. 2.

    If a germinating seed is attached horizontally to a revolving klinostat, what would be the effect on the seedling after three days? The

    1. A.plumule will curve vertically upward while the radicle will not show any curvature
    2. B.radicle will curve towards the ground while the plumule will not show any curvature.
    3. C.plumule and radicle will not show any curvature.
    4. D.plumule will curve vertically upwards while the radicle will curve towards the ground
    Show answer

    Answer: C. plumule and radicle will not show any curvature.

    AI explanation

    Analyze the question A klinostat is a device that rotates a seedling slowly and continuously about a horizontal axis. We need to know what happens to the plumule (shoot) and radicle (root) when it is attached to one.

    Concept: Geotropism

    • Normally, gravity acts on a seedling from one direction. The radicle shows positive geotropism (grows downward), and the plumule shows negative geotropism (grows upward).
    • This happens because gravity causes auxin to accumulate unevenly on the lower side of the organ. The uneven distribution leads to uneven growth, and that causes curvature.
    • A klinostat rotates the seedling continuously, so every side of the seedling is exposed to gravity equally over time. Auxin is therefore distributed evenly, and the effect of gravity is cancelled out.

    Solution

    1. The seed is fixed horizontally on the revolving klinostat.
    2. Rotation means gravity no longer acts on one side only. Its effect is spread evenly around the organ.
    3. Auxin is distributed evenly in both the plumule and the radicle.
    4. Growth is equal on all sides, so both organs grow straight, with no curvature.

    Compare the options:

    • A, B and D all suggest that gravity still produces a one-sided effect on at least one organ. That would only happen on a stationary seedling.
    • C correctly says that neither organ curves.

    Answer: C. The plumule and radicle will not show any curvature.

    Exam tip: Remember that a klinostat eliminates the one-sided effect of gravity (or light, in phototropism experiments). If the question says the klinostat is revolving, expect straight growth. If it says the klinostat is stationary, expect normal curvature: the plumule grows up and the radicle grows down.

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  3. 3.This question needs a diagram, table or passage that we don't have yet, so it isn't shown.

  4. 4.

    Which of the following traits is not inheritable? Ability to

    1. A.taste P.T.C
    2. B.roll the tongue
    3. C.move the ear
    4. D.roll the eyeball
    Show answer

    Answer: D. roll the eyeball

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  5. 5.

    The illustrated organism is capable of reproducing by

    1. A.sexual means only
    2. B.asexual means only
    3. C.vegetative propagation only
    4. D.sexual and asexual means
    Show answer

    Answer: C. vegetative propagation only

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  6. 6.This question needs a diagram, table or passage that we don't have yet, so it isn't shown.

  7. 7.

    Grasses → Grasshoppers → Lizards  → Hawks If the individual species of organisms in the food chain are counted and arranged as a pyramid, the result would be a pyramid of

    1. A.numbers
    2. B.energy
    3. C.biomass
    4. D.biomes
    Show answer

    Answer: A. numbers

    AI explanation

    Step 1: Analyze the question The food chain is: Grasses → Grasshoppers → Lizards → Hawks. The question says the individual organisms are counted and arranged as a pyramid. The key word is counted.

    Step 2: Explain the concept There are three types of ecological pyramids:

    • Pyramid of numbers: based on the count of individual organisms at each trophic level.
    • Pyramid of biomass: based on the total dry mass of living material at each level.
    • Pyramid of energy: based on the energy (e.g., kJ) at each level.

    A biome (option D) is a large ecological region such as the tropical rainforest or savanna. It is not a type of pyramid.

    Step 3: Apply to the chain

    • Grasses: very many individuals
    • Grasshoppers: many, but fewer than the grasses
    • Lizards: fewer still
    • Hawks: very few

    Counting the individuals gives a broad base of grasses narrowing to a small number of hawks at the top. This is a pyramid of numbers.

    (Note: if a single large tree were the producer, a pyramid of numbers could look inverted. Here the producers are grasses, which are small and numerous, so the pyramid is upright.)

    Step 4: Answer The correct option is A. numbers.

    Exam tip: Match the key word in the question to the pyramid type:

    • "counted" → numbers
    • "mass/weight of living material" → biomass
    • "energy transferred/kJ" → energy

    Also remember that "biome" is never a pyramid. It is a major habitat type.

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  8. 8.

    A farmer planted many seeds on a small piece of land. The plants that germinated are as shown above. Which of the following effects would not be observed among the population of the plants?

    1. A.Rise in disease condition
    2. B.Death
    3. C.Mutualistic relationship
    4. D.Competition
    Show answer

    Answer: B. Death

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  9. 9.

    Habitats of the organisms respectively are

    1. A.river and stream
    2. B.rainforest and stream
    3. C.pond and leaf litter
    4. D.garden and desert
    Show answer

    Answer: B. rainforest and stream

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  10. 10.

    The physical appearance of an organism is described as its

    1. A.phenotype
    2. B.genotype
    3. C.allele
    4. D.chromosome
    Show answer

    Answer: A. phenotype

    AI explanation

    1. Analyze the question The question asks for the term used for the physical appearance of an organism, meaning the traits you can see or measure, such as height, skin colour, or flower colour.

    2. Explain the concept

    • Phenotype: the observable characteristics of an organism. It results from the genotype interacting with the environment.
    • Genotype: the genetic makeup of an organism, meaning the combination of alleles it carries (e.g., TT, Tt, tt). You cannot see it just by looking.
    • Allele: one of the alternative forms of a gene (e.g., T for tall, t for dwarf).
    • Chromosome: a thread-like structure in the nucleus that carries genes.

    3. Work through the options

    • A. Phenotype: describes physical appearance. ✔
    • B. Genotype: describes genetic composition, not appearance. ✘
    • C. Allele: a form of a gene, not an appearance. ✘
    • D. Chromosome: a structure carrying genes. ✘

    4. Answer The physical appearance of an organism is its phenotype.

    5. Tip Link the words: Phenotype = Physical appearance. Genotype = Genes. Also remember the formula: Genotype + Environment → Phenotype.

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  11. 11.This question needs a diagram, table or passage that we don't have yet, so it isn't shown.

  12. 12.

    Which of the following organisms consists of unicellular cells joined to form a filament?

    1. A.Amoeba
    2. B.Spirogyra
    3. C.Euglena
    4. D.Chlamydomonas
    Show answer

    Answer: B. Spirogyra

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  13. 13.

    Which of the following organisms contains Chlorophyll in its cells?

    1. A.Caterpillar
    2. B.Paramecium
    3. C.Euglena
    4. D.Grasshopper
    Show answer

    Answer: C. Euglena

    AI explanation

    Step 1: Analyze the question The question asks which organism has chlorophyll, the green pigment used in photosynthesis, in its cells.

    Step 2: Concept Chlorophyll is found in chloroplasts. These are present in plants, algae and some protists. Animals and most animal-like protists do not have chlorophyll because they feed heterotrophically (they take in ready-made food).

    Step 3: Examine each option

    • A. Caterpillar: an insect larva that feeds on leaves. It is an animal with no chlorophyll.
    • B. Paramecium: a ciliated, animal-like protozoan that feeds heterotrophically on bacteria. It has no chlorophyll.
    • C. Euglena: a unicellular protist that has chloroplasts containing chlorophyll. It photosynthesizes in the light, so it is autotrophic. It can also feed heterotrophically when light is absent, so it is described as having both plant and animal features.
    • D. Grasshopper: an insect and an animal, so it has no chlorophyll.

    Step 4: Answer The correct option is C. Euglena.

    Tip: Remember "Euglena = green protist." It is the classic example of an organism that sits between plants and animals. It has chlorophyll like a plant but can move with a flagellum like an animal. Whenever WAEC asks about chlorophyll in a list of mostly animals, look for Euglena, Spirogyra, or Chlamydomonas.

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  14. 14.

    An environmental problem caused by Sulphur (IV) oxide is

    1. A.acid rain
    2. B.deforestation
    3. C.global warming
    4. D.Erosion
    Show answer

    Answer: A. acid rain

    AI explanation

    Step 1: Analyze the question The question asks which environmental problem is caused by sulphur (IV) oxide (SO₂).

    Step 2: Explain the concept Sulphur (IV) oxide is released when fuels containing sulphur (coal, diesel, petroleum) are burned. It also comes from gas flaring, industrial smelting, and volcanic activity. This is a major concern in places like the Niger Delta, where gas flaring is common.

    In the atmosphere, SO₂ reacts with oxygen and water vapour to form sulphuric acid:

    • 2SO₂ + O₂ → 2SO₃
    • SO₃ + H₂O → H₂SO₄ (sulphuric acid)

    This acid falls to the ground with rainfall, causing acid rain.

    Step 3: Evaluate the options

    • A. Acid rain: Correct. SO₂ (and nitrogen oxides) are the main causes.
    • B. Deforestation: This is the clearing of forests by humans through logging and farming. It is not caused by SO₂, although acid rain can damage trees.
    • C. Global warming: This is mainly caused by greenhouse gases such as carbon dioxide and methane, not SO₂.
    • D. Erosion: This is caused by water, wind, and poor land management, not SO₂.

    Step 4: Answer The correct answer is A. acid rain.

    Effects of acid rain to remember: it damages crops and forests, corrodes buildings and zinc roofing sheets, makes soil acidic, and harms aquatic life in rivers and lakes.

    Exam tip: Remember "Sulphur → Sour rain." Link SO₂ and NO₂ with acid rain, and CO₂ and CH₄ with global warming. Also, CO is linked to poisoning, and CFCs to ozone depletion.

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  15. 15.

    Which type of breeding is represented by industrial melanism in peppered moths?

    1. A.Artificial selection
    2. B.Natural selection
    3. C.Inbreeding
    4. D.Outbreeding
    Show answer

    Answer: B. Natural selection

    AI explanation

    Step 1: Analyze the question The question asks what process industrial melanism in peppered moths (Biston betularia) represents. Although it says "type of breeding," the best fit among the options is the evolutionary mechanism involved.

    Step 2: Explain the concept

    • Natural selection: Organisms with traits that suit their environment survive and reproduce more, passing those traits on. The environment does the "selecting."
    • Artificial selection: Humans deliberately choose which organisms breed (e.g., breeding high-yield crops or cattle).
    • Inbreeding: Mating between closely related individuals.
    • Outbreeding: Mating between unrelated individuals.

    Step 3: Apply it to the peppered moth

    1. Before the Industrial Revolution, trees in England were covered with light-colored lichens. The light (peppered) moths were camouflaged, while the dark (melanic) ones were easily seen and eaten by birds.
    2. Industrial pollution (soot) killed the lichens and darkened the tree trunks.
    3. Now the dark moths were camouflaged, and the light ones were easily spotted by birds.
    4. Dark moths survived and reproduced more, so the dark-colored allele became more common in the population.

    No human chose which moths would mate. The environment (soot-darkened trees plus bird predation) acted as the selecting pressure. That is natural selection.

    Step 4: Eliminate the wrong options

    • A: Humans did not deliberately select the moths. Pollution was an accidental side effect.
    • C and D: These describe mating patterns, not the survival-based change in the population's traits.

    Answer: B. Natural selection

    Exam tip: Whenever you see "camouflage," "predation," "survival of the fittest," or "environment favors a trait," think natural selection. If a farmer or breeder is choosing, think artificial selection.

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  16. 16.This question needs a diagram, table or passage that we don't have yet, so it isn't shown.

  17. 17.This question needs a diagram, table or passage that we don't have yet, so it isn't shown.

  18. 18.

    The part labelled III is the

    1. A.iris.
    2. B.pupil
    3. C.sclera
    4. D.cornea
    Show answer

    Answer: B. pupil

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  19. 19.

    The phenomenon by which a farmland that is left to fallow for several years develops into a forest is called

    1. A.Succession
    2. B.afforestation
    3. C.population
    4. D.colonization
    Show answer

    Answer: A. Succession

    AI explanation

    Step 1: Analyze the question The question describes a farmland that is abandoned (left fallow) and, over several years, gradually changes into a forest. We need the term for this gradual, orderly change in a community.

    Step 2: Explain the concept Ecological succession is the gradual, orderly, and predictable replacement of one plant community by another over time until a stable community, called the climax community, is reached.

    For farmland left fallow, the typical sequence is:

    • Bare or cleared land → grasses and herbs (pioneer species)
    • → shrubs and small plants
    • → fast-growing trees
    • → mature forest (climax community)

    Because the soil is already present, this is called secondary succession.

    Step 3: Check each option

    • A. Succession: Correct. It describes the gradual change from farmland to forest.
    • B. Afforestation: This is the deliberate planting of trees by people on land that had no forest. The question describes a natural process, so it does not fit.
    • C. Population: This is a group of organisms of the same species living in an area. It is not a process.
    • D. Colonization: This is the arrival and establishment of organisms in a new area. It is only one stage within succession, not the whole process of change.

    Step 4: Answer The correct option is A. Succession.

    Exam tip: Remember the keywords "gradual change", "over time", and "one community replaced by another". They point to succession. If the question says "deliberate planting of trees", think afforestation instead.

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  20. 20.

    Which of the following statements is correct about the ABO blood group system?

    1. A.Antigens are located on the surface of white blood cells
    2. B.Antibodies are located in the blood plasma
    3. C.Antibodies are located on the surface of the red blood cells
    4. D.Antigens are located in the blood plasma
    Show answer

    Answer: B. Antibodies are located in the blood plasma

    AI explanation

    Step 1: Analyze the question The question asks which statement correctly describes where antigens and antibodies are found in the ABO blood group system.

    Step 2: Key concept

    • Antigens (A and B) are protein/carbohydrate markers found on the surface of red blood cells (RBCs).
    • Antibodies (anti-A and anti-B) are found in the blood plasma.

    | Blood group | Antigen on RBC | Antibody in plasma | |---|---|---| | A | A | anti-B | | B | B | anti-A | | AB | A and B | none | | O | none | anti-A and anti-B |

    Step 3: Check each option

    • A. Antigens on white blood cells. Wrong. In the ABO system, the antigens are on red blood cells.
    • B. Antibodies in the blood plasma. Correct. Anti-A and anti-B antibodies are dissolved in the plasma.
    • C. Antibodies on the surface of red blood cells. Wrong. That is where the antigens are, not the antibodies.
    • D. Antigens in the blood plasma. Wrong. Antigens are on the RBC surface.

    Step 4: Answer

    Tip: Remember "Antigens are on the Animal cells (RBCs); Antibodies are in the plasma (fluid)." Another way: antiGens = Gate (surface), antiBodies = Body fluid (plasma).

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  21. 21.

    The structures that contain grey matter and white matter are found in the

    1. A.reproductive system.
    2. B.nervous system.
    3. C.respiratory system.
    4. D.digestive system.
    Show answer

    Answer: B. nervous system.

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  22. 22.

    Which of the following gases is released during the decomposition of organic matter?

    1. A.Carbon(II) oxide
    2. B.Sulphur (IV) oxide
    3. C.Hydrogen Sulphide
    4. D.Nitrous oxide
    Show answer

    Answer: C. Hydrogen Sulphide

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  23. 23.

    Sunlight is the major source of

    1. A.Vitamin D
    2. B.vitamin C
    3. C.vitamin B
    4. D.vitamin A
    Show answer

    Answer: A. Vitamin D

    AI explanation

    Step 1: Analyze the question The question asks which vitamin has sunlight as its major source.

    Step 2: Explain the concept Vitamin D is often called the "sunshine vitamin." When ultraviolet B (UVB) rays from the sun strike the skin, a cholesterol-related compound in the skin (7-dehydrocholesterol) is converted into vitamin D3 (cholecalciferol). The liver and kidneys then convert this into the active form of the vitamin.

    Why vitamin D matters:

    • It helps the body absorb calcium and phosphorus from food.
    • It supports strong bones and teeth.
    • A deficiency causes rickets in children and osteomalacia in adults.

    Step 3: Check the other options

    • B. Vitamin C (ascorbic acid): Comes from fruits and vegetables such as oranges, guava, and pawpaw. A deficiency causes scurvy.
    • C. Vitamin B: Comes from whole grains, beans, meat, and eggs. A deficiency causes beriberi (B1) and other disorders.
    • D. Vitamin A: Comes from carrots, palm oil, liver, and green leafy vegetables. A deficiency causes night blindness.

    None of these is made mainly through exposure to sunlight.

    Step 4: Answer Sunlight is the major source of Vitamin D, which is option A.

    Exam tip: Remember "D for Daylight" or "D for Sunshine." Also pair each vitamin with its deficiency disease, since WASSCE and JAMB often ask about these:

    • A: night blindness
    • B1: beriberi
    • C: scurvy
    • D: rickets

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  24. 24.

    In a test, a student paired some scientists with their famous work as shown below. Use it to answer questions 49 and 50.       Scientist                Famous work I.  Charles Darwin →  Preservation of some food with heat II. Gregor Mendel →  Natural selection III. Jean Baptiste Lamarck → Inheritance of acquired characteristics IV. Louis Pasteur → Independent assortment of genes. The Scientists that are not correctly paired with their famous work are

    1. A.I and II only
    2. B.II and III only
    3. C.I, II and IV.
    4. D.II, III and IV.
    Show answer

    Answer: C. I, II and IV.

    AI explanation

    Analyze the question: We need to find which scientists are wrongly paired with their famous work.

    Check each pairing:

    • I. Charles Darwin → Preservation of food with heat. Wrong. Darwin is famous for natural selection and the theory of evolution. Preserving food with heat (pasteurization) is Louis Pasteur's work.
    • II. Gregor Mendel → Natural selection. Wrong. Mendel is famous for the laws of inheritance (segregation and independent assortment), worked out from his pea plant experiments. Natural selection is Darwin's.
    • III. Jean Baptiste Lamarck → Inheritance of acquired characteristics. Correct. This is Lamarck's theory.
    • IV. Louis Pasteur → Independent assortment of genes. Wrong. Independent assortment is Mendel's work. Pasteur is known for pasteurization and disproving spontaneous generation.

    Incorrect pairings: I, II and IV.

    Notice that the work of I, II and IV is mixed up among Darwin, Mendel and Pasteur, while Lamarck's pairing is correct.

    Answer: C

    Tip: Remember each scientist with a keyword:

    • Darwin = Evolution/Natural selection
    • Mendel = Genetics/Inheritance
    • Pasteur = Pasteurization/Germs
    • Lamarck = Acquired characteristics

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  25. 25.

    The process of food digestion in mammals would

    1. A.make energy immediately available to the body
    2. B.promote growth and repair of tissues
    3. C.provide sufficient food materials within the body
    4. D.render food substances soluble and absorbable
    Show answer

    Answer: D. render food substances soluble and absorbable

    AI explanation

    Analyze the question: It asks about the purpose or main result of digestion in mammals.

    Explain the concept: Digestion is the breakdown of large, complex, insoluble food molecules into small, simple, soluble molecules. These can pass through the walls of the small intestine (ileum) into the blood. Examples:

    • Starch → glucose (by amylase)
    • Proteins → amino acids (by proteases)
    • Fats → fatty acids and glycerol (by lipase)

    Evaluate each option:

    • A. Make energy immediately available to the body: Incorrect. Energy is released by respiration, which comes after digestion, absorption and transport.
    • B. Promote growth and repair of tissues: Incorrect. This is the function of proteins after assimilation, not of digestion itself.
    • C. Provide sufficient food materials within the body: Incorrect. Digestion does not add food. It only changes food already eaten.
    • D. Render food substances soluble and absorbable: Correct. This is exactly what digestion does. It converts insoluble, large molecules into soluble, small ones that can be absorbed into the bloodstream.

    Answer: D

    Tip: Remember the sequence Ingestion → Digestion → Absorption → Assimilation. Digestion is about preparing food for absorption. Energy release, growth and repair come later, at the assimilation and respiration stages.

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  26. 26.

    Mutation leads to evolution because it

    1. A.kills all organisms where it has occurred.
    2. B.gives rise to offspring having same characteristics as the parents
    3. C.does not confer adaptability to the offspring
    4. D.gives rise to new individuals that differ from their parents
    Show answer

    Answer: D. gives rise to new individuals that differ from their parents

    AI explanation

    Step 1: Analyze the question We are asked why mutation leads to evolution. We need the option that explains how mutation contributes to evolutionary change.

    Step 2: Explain the concept A mutation is a sudden, permanent change in the genetic material (DNA or chromosomes) of an organism. Evolution is the gradual change in the inherited characteristics of a population over many generations. For evolution to happen, there must be variation among individuals. Mutation is one of the main sources of new variation. When a mutation occurs in the reproductive (gamete) cells, it can be passed to offspring. These offspring then show new traits that were not present in their parents. If a new trait helps the organism survive and reproduce in its environment, natural selection favors it, and it becomes more common over generations. That is evolution.

    Step 3: Evaluate each option

    • A. Kills all organisms where it has occurred. Wrong. Many mutations are harmless or even beneficial, and if all mutated organisms died, no change could accumulate.
    • B. Gives rise to offspring having same characteristics as the parents. Wrong. This describes heredity without variation, which would produce no change.
    • C. Does not confer adaptability to the offspring. Wrong. Some mutations do confer adaptability, and these are the ones natural selection favors.
    • D. Gives rise to new individuals that differ from their parents. Correct. This is the variation that evolution depends on.

    Step 4: Answer

    Tip: Remember the chain Mutation → Variation → Natural selection → Evolution. If an option mentions "new" or "different" traits, it is usually pointing toward the right answer. Options saying "same," "all die," or "no adaptation" usually do not support evolution.

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  27. 27.

    The bursting of a red blood cell placed  in a hypotonic solution is called

    1. A.crenation
    2. B.haemolysis
    3. C.plasmolysis
    4. D.cytolysis
    Show answer

    Answer: B. haemolysis

    AI explanation

    Step 1: Analyze the question A red blood cell is placed in a hypotonic solution, meaning the solution has a lower solute concentration (more water) than the cell's cytoplasm. We need the term for the cell bursting.

    Step 2: The concept Water moves by osmosis from a region of high water potential to one of low water potential, across a partially permeable membrane.

    • In a hypotonic solution, water enters the red blood cell.
    • The cell swells. Animal cells have no cell wall, so the membrane eventually ruptures and the cell bursts.

    Step 3: Examine each option

    • A. Crenation: the shrinking and shriveling of a red blood cell in a hypertonic solution. This is the opposite process.
    • B. Haemolysis: the bursting of red blood cells, releasing haemoglobin. It fits the question exactly.
    • C. Plasmolysis: the shrinking of the protoplast away from the cell wall in a plant cell placed in a hypertonic solution.
    • D. Cytolysis: the bursting of any cell by osmotic swelling. It is a general term, and it is technically also true for a red blood cell. But when the cell is specifically a red blood cell, the standard term is haemolysis.

    Step 4: Answer The question specifically names a red blood cell, so the precise term is haemolysis (haemo = blood, lysis = breaking).

    Note: Cytolysis (D) is a broader term that could also describe this event, so the question is a little loose. The examiners clearly want the term specific to red blood cells, which is haemolysis.

    Exam tip:

    • Hypotonic + red blood cell → swell and burst → haemolysis
    • Hypertonic + red blood cell → shrink → crenation
    • Hypertonic + plant cell → plasmolysis
    • Hypotonic + plant cell → becomes turgid (the cell wall prevents bursting)

    Remember: "Haemo" = blood. If the question says red blood cells, think haemolysis.

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  28. 28.

    The condition necessary for reproduction to occur between plants P and Q after pollination is that plants P and Q should be

    1. A.of the same species.
    2. B.brightly coloured.
    3. C.well scented
    4. D.of different species.
    Show answer

    Answer: A. of the same species.

    AI explanation

    Step 1: Analyze the question The question asks what must be true of plants P and Q for reproduction to succeed after pollination. Pollination alone (the transfer of pollen to the stigma) does not guarantee reproduction. Fertilisation must also occur.

    Step 2: Explain the concept After a pollen grain lands on a stigma:

    1. It must recognise and be accepted by the stigma. This is a chemical compatibility check.
    2. It then germinates and grows a pollen tube down the style.
    3. The male gamete fuses with the ovule's egg cell (fertilisation).

    This compatibility exists mainly between plants of the same species. Pollen from a different species is usually rejected, because the stigma does not support its germination and the genetic material is incompatible. Fertilisation therefore fails.

    Step 3: Evaluate the options

    • A. Of the same species. Correct. Same-species plants have compatible pollen and stigma, so the pollen tube can grow and fertilisation can occur.
    • B. Brightly coloured. Colour only helps attract pollinators before pollination. It plays no part in fertilisation afterward.
    • C. Well scented. Like colour, scent attracts insects before pollination. It is irrelevant once pollen has landed.
    • D. Of different species. Incorrect. Cross-species pollen is usually incompatible, so reproduction normally fails.

    Step 4: Answer The correct answer is A. of the same species.

    Exam tip: Remember that colour and scent are for attracting pollinators (before pollination), while species compatibility is for fertilisation (after pollination). If a question says "after pollination", think compatibility, pollen tube growth and fertilisation, not attraction.

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  29. 29.

    Which of the following events does not occur in the light reaction stage of photosynthesis?

    1. A.Chlorophyll absorbs sunlight
    2. B.Carbon (IV) oxide combines with hydrogen
    3. C.Photolysis of water occurs
    4. D.Hydroxyl ions are produced
    Show answer

    Answer: B. Carbon (IV) oxide combines with hydrogen

    AI explanation

    Analyze the question: We need the event that does NOT happen in the light stage (light-dependent reaction) of photosynthesis.

    Concept: Photosynthesis has two stages:

    1. Light reaction (in the grana of the chloroplast, needs light): • Chlorophyll absorbs light energy and becomes excited. • Photolysis of water occurs: 2H₂O → 4H⁺ + 4e⁻ + O₂. In the older WASSCE/NECO textbook version, water splits into hydrogen ions (H⁺) and hydroxyl ions (OH⁻), and the OH⁻ gives up its electrons to form water and oxygen. • ATP is formed (photophosphorylation), and NADP is reduced to NADPH using the hydrogen. • Oxygen is released as a by-product.
    1. Dark reaction (in the stroma, does not need light directly): • CO₂ is fixed and reduced by the hydrogen (from NADPH) using ATP to form glucose (carbohydrate).

    Checking each option:

    • A. Chlorophyll absorbs sunlight: Occurs in the light stage. ✔
    • B. Carbon (IV) oxide combines with hydrogen: This is the reduction of CO₂, which is the dark reaction (Calvin cycle). ✘ It does not occur in the light stage.
    • C. Photolysis of water occurs: Occurs in the light stage. ✔
    • D. Hydroxyl ions are produced: In the WASSCE syllabus model, water splits into H⁺ and OH⁻ during photolysis. ✔

    **Answer: B.

    Tip: Remember the split: Light stage = water splitting, ATP, O₂ released. Dark stage = CO₂ is used up to make sugar. Whenever you see CO₂ combining or glucose forming, think dark reaction.

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  30. 30.This question needs a diagram, table or passage that we don't have yet, so it isn't shown.

  31. 31.

    Which of the scientists were involved in the study of evolution? Scientist                Famous work I.  Charles Darwin →  Preservation of some food with heat II. Gregor Mendel →  Natural selection III. Jean Baptiste Lamarck → Inheritance of acquired characteristics IV. Louis Pasteur → Independent assortment of genes.

    1. A.I and III
    2. B.II and III
    3. C.I, II and IV
    4. D.II. III and IV
    Show answer

    Answer: A. I and III

    AI explanation

    The question as printed has the "famous work" entries mismatched with the scientists, so let's sort that out first.

    Step 1: Analyze the question We need the scientists involved in the study of evolution. The question lists each scientist with a "famous work", but several of these pairings are scrambled.

    Step 2: Check each scientist and the work listed

    • I. Charles Darwin → "Preservation of some food with heat." Darwin is the father of evolution by natural selection. Preserving food with heat (pasteurization) belongs to Louis Pasteur. Darwin is an evolution scientist, but the work listed beside his name is wrong.
    • II. Gregor Mendel → "Natural selection." Mendel worked on heredity (pea plant experiments), not natural selection. Natural selection is Darwin's work. Mendel is a genetics scientist, not an evolution scientist.
    • III. Jean Baptiste Lamarck → "Inheritance of acquired characteristics." This pairing is correct. Lamarck proposed an early theory of evolution based on use and disuse and the inheritance of acquired traits.
    • IV. Louis Pasteur → "Independent assortment of genes." Independent assortment is Mendel's work. Pasteur worked on microbiology, pasteurization, and disproving spontaneous generation. He was not an evolution scientist.

    Step 3: Pick the answer The scientists involved in the study of evolution are Darwin (I) and Lamarck (III). This matches option A. Mendel and Pasteur were not evolutionary theorists.

    The listed works for Darwin, Mendel, and Pasteur are swapped around in the question, which is a quirk of the printed question. The question asks who was involved in evolution, so the answer is based on the scientists themselves: Darwin and Lamarck.

    Answer: A. I and III

    Exam tip: Remember the key links:

    • Darwin → natural selection (evolution)
    • Lamarck → acquired characteristics (evolution)
    • Mendel → genetics and heredity
    • Pasteur → microbiology and pasteurization

    If a question asks about "evolution," think "Darwin and Lamarck."

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  32. 32.

    Discouraging the use of poison to kill fish in a large water body is a way of

    1. A.impoverishing the people.
    2. B.conserving the fish species.
    3. C.allowing the fittest organism to survive
    4. D.making the fish adapt to their environment
    Show answer

    Answer: B. conserving the fish species.

    AI explanation

    Step 1: Analyze the question The question asks what purpose is served by discouraging people from using poison to catch fish in rivers, lakes, or other large water bodies.

    Step 2: Explain the concept Conservation is the careful management and protection of natural resources so they are not depleted or destroyed. Poisoning fish is a destructive method of harvesting because it:

    • Kills fish indiscriminately, including young fish, eggs, and non-target species
    • Pollutes the water and harms other aquatic organisms (plants, amphibians, invertebrates)
    • Can wipe out whole populations, so they cannot reproduce and recover

    Stopping this practice protects the fish population so it can continue to breed and be available in the future. This is an example of conservation.

    Step 3: Evaluate the options

    • A. Impoverishing the people: Wrong. Protecting fish stocks supports livelihoods in the long run.
    • B. Conserving the fish species: Correct. Banning poison protects fish populations from being wiped out.
    • C. Allowing the fittest organism to survive: Wrong. This describes natural selection, and poison kills fit and unfit fish alike. It is not selective.
    • D. Making the fish adapt to their environment: Wrong. Adaptation happens over generations through natural processes, not through human discouragement of poison.

    Step 4: Answer The correct option is **B. conserving the fish species.

    Exam tip: In WASSCE ecology and conservation questions, whenever you see actions that protect, preserve, or prevent depletion (such as banning poison fishing, bush burning control, or closed hunting seasons), think "conservation." Eliminate options with terms like "fittest" (natural selection) or "adapt" (evolution) unless the question is specifically about those ideas.

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  33. 33.

    An individual found a strange bird that is tagged as an endangered specie. What should the individual do?

    1. A.Kill it
    2. B.Take it to an aquatic environment
    3. C.Return it to its natural habitat
    4. D.Sell it at a very high price
    Show answer

    Answer: C. Return it to its natural habitat

    AI explanation

    Step 1: Analyze the question The question asks what a person should do after finding a bird that is tagged as an endangered species. This is a conservation question: endangered species are at risk of becoming extinct, so the right action must help protect them.

    Step 2: The concept Conservation aims to protect species and their habitats. The best way to protect an endangered animal is to keep it safe and let it live and breed in its natural habitat (in-situ conservation). Killing, selling, or moving it to the wrong environment harms its chances of survival.

    Step 3: Evaluate each option

    • A. Kill it: This reduces the population further and pushes the species closer to extinction. It is also illegal. Wrong.
    • B. Take it to an aquatic environment: A bird (unless it is a water bird) would be moved to an unsuitable environment, and it may not survive. Wrong.
    • C. Return it to its natural habitat: This lets the bird survive and reproduce in the conditions it is adapted to, which supports conservation. Correct.
    • D. Sell it at a very high price: This is illegal wildlife trafficking and encourages poaching. Wrong.

    Step 4: Answer The correct option is C. Return it to its natural habitat.

    Exam tip: In conservation questions, choose the answer that protects the organism and its habitat. Any option involving killing, selling, or exploiting is almost always wrong. In Nigeria, the law against hunting and trading protected species supports this.

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  34. 34.

    A plant with short, vertical underground stem is a

    1. A.bulb
    2. B.corm
    3. C.rhizome
    4. D.tuber
    Show answer

    Answer: B. corm

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  35. 35.

    Which of the following food substances would give a negative reaction with Benedict's reagent?

    1. A.Fructose
    2. B.Glucose
    3. C.Galactose
    4. D.Sucrose
    Show answer

    Answer: D. Sucrose

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  36. 36.

    Filtrates in the Bowman's capsule contain vitamins because

    1. A.they have low molecular weight.
    2. B.most of them are fat soluble.
    3. C.they cannot be reabsorbed into the blood.
    4. D.little amount is required by the blood.
    Show answer

    Answer: A. they have low molecular weight.

    AI explanation

    Step 1: Analyze the question The question asks why vitamins are found in the glomerular filtrate in the Bowman's capsule.

    Step 2: The concept: ultrafiltration Blood enters the glomerulus under high hydrostatic pressure. This forces water and small dissolved substances out of the capillaries into the Bowman's capsule. The basement membrane acts as a filter, so only substances with a low molecular weight pass through.

    • Pass through (small molecules): water, glucose, amino acids, urea, mineral salts, vitamins (especially water-soluble ones)
    • Stay in the blood (large molecules): red blood cells, white blood cells, platelets, plasma proteins

    Step 3: Evaluate the options

    • A. They have low molecular weight. Correct. Vitamins are small molecules, so they pass through the basement membrane during ultrafiltration.
    • B. Most of them are fat soluble. Incorrect. Fat-soluble vitamins (A, D, E, K) are mostly carried bound to proteins, so they filter poorly. Many filtered vitamins are water-soluble (B and C).
    • C. They cannot be reabsorbed into the blood. Incorrect. Many useful substances in the filtrate, such as glucose and amino acids, are reabsorbed in the proximal convoluted tubule. Reabsorption happens after filtration and does not explain why substances are in the filtrate.
    • D. Little amount is required by the blood. Incorrect. How much the body needs has no effect on what passes through the filter. Filtration depends on size and pressure.

    Step 4: Answer Vitamins are present in the filtrate because they are small enough to pass through the filtration barrier.

    Exam tip: Filtration in the kidney depends on size, not on need. Remember: "Small passes, big stays." Later, the tubules reabsorb what the body needs.

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  37. 37.

    The function of the root hair in plants is to

    1. A.absorb soil water by the process of osmosis.
    2. B.excrete water and mineral salts by simple diffusion.
    3. C.purify the soil for the plant.
    4. D.translocate manufactured food.
    Show answer

    Answer: A. absorb soil water by the process of osmosis.

    AI explanation

    Step 1: Analyze the question The question asks about the main function of root hairs. These are tiny, thin extensions of the epidermal cells of the root, found just behind the root tip.

    Step 2: Explain the concept Root hairs greatly increase the surface area of the root in contact with the soil. They are thin-walled and have a large vacuole containing cell sap, which is a more concentrated solution than the soil water around it. They are specialized for:

    • Absorbing water from the soil by osmosis, because water moves from the soil, where it is dilute, into the root hair cell, where the sap is more concentrated, through a partially permeable membrane.
    • Absorbing mineral salts by diffusion and active transport.

    Step 3: Evaluate each option

    • A. Absorb soil water by the process of osmosis. Correct. This is the main function of root hairs.
    • B. Excrete water and mineral salts by simple diffusion. Wrong. Root hairs take in water and salts. They do not excrete them.
    • C. Purify the soil for the plant. Wrong. Plants do not purify soil through root hairs.
    • D. Translocate manufactured food. Wrong. Translocation of manufactured food (sugars) is done by the phloem, not the root hairs.

    Step 4: Answer The correct option is A.

    Tip: Remember "Root hair = Water in." Root hairs bring in water and salts, xylem carries water up, and phloem carries food around. If an option says root hairs "excrete" or "translocate food", eliminate it immediately.

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  38. 38.

    The element required for chlorophyll formation in plants is

    1. A.Iron
    2. B.Calcium
    3. C.Phosphorus
    4. D.Sulphur
    Show answer

    Answer: A. Iron

    AI explanation

    Step 1: Analyze the question We need the mineral element that plants require to form chlorophyll, the green pigment used in photosynthesis.

    Step 2: Concept Chlorophyll's structure has a porphyrin ring with magnesium at the centre. Magnesium is the element that is part of the chlorophyll molecule itself. Iron is not part of the molecule, but it is essential for its synthesis, because it is needed for enzymes involved in making chlorophyll. Without iron, leaves develop chlorosis (yellowing), especially in young leaves.

    Step 3: Check each option

    • A. Iron: Required for chlorophyll formation (synthesis). Deficiency causes chlorosis. ✔
    • B. Calcium: Builds cell walls (calcium pectate) and supports root growth. Not involved in chlorophyll.
    • C. Phosphorus: Needed for ATP, DNA, and root development. Not involved in chlorophyll.
    • D. Sulphur: Needed for amino acids like cysteine and methionine (proteins). Not involved in chlorophyll.

    Magnesium, the element in the chlorophyll molecule, is not among the options. Of those given, iron is the one needed for chlorophyll formation, so the question is asking about iron.

    Answer: A. Iron

    Exam tip: Remember two key elements for chlorophyll:

    • Magnesium is in the chlorophyll molecule (the "Mg in the middle").
    • Iron is needed to make it (the "formation" wording in the question).

    If you see "formation/synthesis" and magnesium isn't offered, choose iron. If the question says "constituent of chlorophyll" and magnesium is offered, choose magnesium.

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  39. 39.

    The Parachute-like tuft of hairs developed from the

    1. A.pedicel
    2. B.petals
    3. C.receptacle
    4. D.sepals
    Show answer

    Answer: D. sepals

    AI explanation

    Analyze the question The question is about fruit and seed dispersal by wind. Some fruits, such as those of the Asteraceae (Compositae) family, have a parachute-like tuft of hairs called the pappus. Examples are the dandelion, Tridax, and Emilia sonchifolia (common weeds in Nigeria). We need to know which flower part the pappus develops from.

    Explain the concept In the flower, the four whorls from outside to inside are:

    • Sepals (together called the calyx)
    • Petals (corolla)
    • Stamens
    • Carpels

    In the Asteraceae, the flower (floret) is very small and sits on a head (capitulum). The calyx is modified into the pappus, a ring of fine hairs or bristles. After fertilization, the ovary becomes the fruit (a cypsela/achene). The pappus stays attached to the top of the fruit and acts as a parachute, so the wind can carry the fruit over long distances.

    Step-by-step solution

    1. The parachute-like tuft of hairs is the pappus.
    2. The pappus is a modified calyx.
    3. The calyx is made up of the sepals.
    4. The pedicel is the flower stalk, the receptacle is the base that holds the floral parts, and the petals form the corolla. None of these becomes the pappus.

    Answer: The tuft of hairs develops from the sepals, which is option D.

    Exam tip Remember "Pappus = Parachute = calyx (sepals)". When you see wind dispersal with a hairy tuft on a fruit in the sunflower or Tridax family, think of sepals modified into hairs.

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  40. 40.

    Which of the following blood vessels carries oxygenated blood into the heart?

    1. A.Pulmonary artery
    2. B.Anterior vena cava
    3. C.Pulmonary vein
    4. D.Posterior vena cava
    Show answer

    Answer: C. Pulmonary vein

    AI explanation

    Step 1: Analyze the question The question asks which vessel brings oxygenated blood into the heart.

    Step 2: Key concept In the mammalian double circulation:

    • Pulmonary circulation: the heart sends deoxygenated blood to the lungs, and oxygenated blood returns to the heart.
    • Systemic circulation: the heart sends oxygenated blood to the body, and deoxygenated blood returns to the heart.

    Arteries usually carry blood away from the heart, and veins carry blood towards it. The pulmonary vessels are the exception to the "arteries carry oxygenated blood" rule.

    Step 3: Check each option

    • A. Pulmonary artery: carries deoxygenated blood from the right ventricle to the lungs. It leaves the heart, so this is wrong.
    • B. Anterior vena cava: carries deoxygenated blood from the head and upper body into the right atrium. This is wrong.
    • C. Pulmonary vein: carries oxygenated blood from the lungs into the left atrium. This is correct.
    • D. Posterior vena cava: carries deoxygenated blood from the lower body into the right atrium. This is wrong.

    Step 4: Answer The pulmonary vein is the only vessel that brings oxygenated blood into the heart (the left atrium).

    Exam tip: Remember "Pulmonary is the opposite." The pulmonary artery carries deoxygenated blood and the pulmonary vein carries oxygenated blood. Also, every vena cava carries deoxygenated blood to the right side of the heart.

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  41. 41.This question needs a diagram, table or passage that we don't have yet, so it isn't shown.

  42. 42.

    The pathway through which nutrient are replenished and circulated in an ecosystem is called a

    1. A.cycle
    2. B.pyramid of energy
    3. C.pyramid of numbers
    4. D.Food chain
    Show answer

    Answer: A. cycle

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  43. 43.

    The structure in the cell that controls the movement of substances in and out of the cell is the

    1. A.cytoplasmic membrane
    2. B.nuclear membrane
    3. C.protoplasm
    4. D.endoplasm
    Show answer

    Answer: A. cytoplasmic membrane

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  44. 44.

    The male and female gametes which bear genes for inheritance in plants are located in the

    1. A.anthers and petals
    2. B.sepals and petals
    3. C.stamens and pistils
    4. D.stamens and petals
    Show answer

    Answer: C. stamens and pistils

    AI explanation

    Analyze the question: It asks which parts of a flowering plant contain the male and female gametes (sex cells) that carry genes from parent to offspring.

    Explain the concept:

    • The male reproductive organ of a flower is the stamen. It is made up of the anther (which produces pollen grains containing the male gametes) and the filament.
    • The female reproductive organ is the pistil (also called the carpel). It is made up of the stigma, style and ovary. The ovary contains ovules, which hold the female gamete (egg cell).
    • Sepals and petals are not reproductive organs. Sepals protect the flower bud, and petals attract insects for pollination.

    Step-by-step solution:

    1. Male gametes come from pollen, which is produced in the anthers of the stamens.
    2. Female gametes (egg cells) are in the ovules inside the ovary of the pistil.
    3. Check the options: • A. Anthers and petals: petals do not carry gametes. ❌ • B. Sepals and petals: neither is reproductive. ❌ • C. Stamens and pistils: male and female reproductive organs. ✅ • D. Stamens and petals: petals are not female organs. ❌

    Answer: C. Stamens and pistils

    Exam tip: Remember "Stamen = Male, Pistil = Female". Think "Stamen = Sir (male)" and "Pistil = Princess (female)". Petals and sepals are only the "supporting cast" and never carry gametes.

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  45. 45.

    Species are groups of organisms that

    1. A.are of different origins and are always found together
    2. B.are of common origin but cannot interbreed freely
    3. C.have similar features and can interbreed freely
    4. D.resemble each other and occupy different niches
    Show answer

    Answer: C. have similar features and can interbreed freely

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  46. 46.

    Which of the following statements is correct about the cross?

    1. A.Both parents are heterozygous
    2. B.The male is not heterozygous
    3. C.The female is homozygous
    4. D.Both parents are homozygous
    Show answer

    Answer: D. Both parents are homozygous

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  47. 47.

    A woman with blood group A gives birth to a child with blood group O. Which of the following blood groups cannot belong to the father?

    1. A.B
    2. B.A
    3. C.AB
    4. D.O
    Show answer

    Answer: C. AB

    AI explanation

    Analyze the question: The mother is blood group A and the child is group O. We need to find which blood group the father cannot have.

    Concept: ABO blood groups are controlled by three alleles: I^A, I^B and i (O). I^A and I^B are dominant over i. A child gets one allele from each parent.

    • Group A: I^A I^A or I^A i
    • Group B: I^B I^B or I^B i
    • Group AB: I^A I^B
    • Group O: ii

    Solution:

    1. The child is group O, so the genotype is ii. One i allele came from the mother and one from the father.
    2. The mother is group A and has passed on an i, so her genotype must be I^A i.
    3. The father must also have an i allele to give. Check each option: • B (I^B i): can give i, so he is possible. • A (I^A i): can give i, so he is possible. • AB (I^A I^B): has no i allele, so he can only pass on I^A or I^B. He cannot have a group O child. • O (ii): can give i, so he is possible.

    Cross example: I^A i × I^A I^B gives I^A I^A, I^A I^B, I^A i and I^B i. These are groups A, AB, A and B, and there is never an O child.

    Answer: C (AB)

    Tip: A group AB parent can never have a group O child, and a group O parent can never have an AB child. For "cannot be the parent" questions, look for the group that lacks the needed allele. The child's O means both parents must carry at least one i.

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  48. 48.

    The rate of photosynthesis decreases in a wilted herbaceous plant because the

    1. A.enzymes in the leaf were denatured
    2. B.chlorophyll in the leaves was not broken down
    3. C.amount of light reaching the plant was reduced
    4. D.amount of carbon dioxide entering the leaf decrease.
    Show answer

    Answer: D. amount of carbon dioxide entering the leaf decrease.

    AI explanation

    Step 1: Analyze the question The question asks why photosynthesis slows down in a wilted herbaceous plant. Wilting happens when the plant loses more water than it absorbs, so the cells lose turgor and the leaves droop.

    Step 2: Explain the concept Carbon dioxide enters the leaf through the stomata. When a plant is short of water, the guard cells lose turgor and the stomata close. This reduces water loss, but it also stops CO₂ from entering the leaf. Since CO₂ is a raw material for photosynthesis, the rate drops.

    The equation is: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (in the presence of light and chlorophyll)

    Step 3: Check each option

    • A. Enzymes denatured: Denaturation needs extreme temperature or pH. Wilting alone does not cause it, so this is not the main reason.
    • B. Chlorophyll not broken down: If chlorophyll stayed intact, photosynthesis would continue normally. This is also illogical.
    • C. Light reduced: Wilting does not reduce the light available to the plant. Drooping leaves may change their angle, but this is not the main cause.
    • D. Less CO₂ entering the leaf: Stomata close during wilting, so less CO₂ gets in. This is correct.

    Step 4: Answer The correct option is D.

    Exam tip: Whenever you see "wilting" or "water stress" in a photosynthesis question, think "stomata close → less CO₂ enters." Remember: Wilt → stomata shut → CO₂ cut.

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  49. 49.

    The lumbar vertebra differs from the thoracic vertebra because it possesses a

    1. A.longer neural spine.
    2. B.wider neural canal.
    3. C.thicker centrum.
    4. D.shorter transverse process.
    Show answer

    Answer: C. thicker centrum.

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  50. 50.

    The diagrams above are the illustrations of organisms from different habitat. Study them and answer questions 32 and 33. The structures labelled I are for

    1. A.Camouflage
    2. B.Chemical offence
    3. C.Physical defence
    4. D.Mimicry
    Show answer

    Answer: C. Physical defence

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