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WAEC (WASSCE) 2022

2022 WAEC (WASSCE) Biology Past Questions and Answers

The 2022 WAEC (WASSCE) Biology past questions with answers: 46 objective questions from the 2022 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.

    Study the food chain illustrated below and use it to answer this question. J-K-L-M-N Organism J is normally sustained by energy from?

    1. A.Green plants
    2. B.carbohydrates
    3. C.organism
    4. D.sunlight
    Show answer

    Answer: D. sunlight

    AI explanation

    Analyze the question The food chain is J → K → L → M → N. Organism J is at the start of the chain, so it is the producer (a green plant). The question asks where J gets its energy from.

    Explain the concept Every food chain starts with a producer. Producers (green plants, algae) carry out photosynthesis, which converts light energy into chemical energy stored in food:

    6CO₂ + 6H₂O → (sunlight, chlorophyll) → C₆H₁₂O₆ + 6O₂

    The original source of energy for almost all food chains on Earth is the sun. Energy then flows from producers to primary consumers, then to secondary consumers, and so on.

    Step-by-step solution

    1. J is first in the chain, so it is the producer.
    2. A producer does not eat other organisms. It makes its own food.
    3. To make food, it must absorb light energy, which is sunlight.
    4. Checking the options: • A. Green plants: J is itself the green plant, so it is not sustained by other green plants. • B. Carbohydrates: these are the product J makes, not its source of energy. • C. Organism: this is too vague and does not apply to a producer. • D. Sunlight: this is the source of energy for photosynthesis.

    Answer: D. Sunlight

    Tip: In any food chain question, ask yourself: "Who is first?" The first organism is the producer, and its energy always comes from the sun. Remember: Sun → Producer → Consumers.

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  2. 2.

    The major source of vitamin A are ?

    1. A.egg yolk, carrot and palm oil
    2. B.mango, pawpaw,and eggs
    3. C.sorghum,soya bean and liver
    4. D.rice,bran,green vegetables and milk
    Show answer

    Answer: A. egg yolk, carrot and palm oil

    AI explanation

    Analyze the question: It asks which group of foods are the major sources of vitamin A (retinol and its precursor, beta-carotene).

    Concept: Vitamin A comes from two types of sources:

    • Preformed vitamin A (retinol): animal sources such as egg yolk, liver, milk, butter, fish liver oil.
    • Provitamin A (beta-carotene): yellow, orange, and red plant foods such as carrot, red palm oil, ripe pawpaw, ripe mango, and dark green leafy vegetables. The body converts beta-carotene into vitamin A.

    Evaluating the options:

    • A. Egg yolk, carrot and palm oil: Egg yolk has retinol, while carrot and red palm oil are very rich in beta-carotene. All three are well-known major sources. ✔
    • B. Mango, pawpaw and eggs: These do contain vitamin A, but this is a weaker choice because the option is less commonly listed as the "major" sources than A. Still partly correct.
    • C. Sorghum, soya bean and liver: Sorghum and soya bean are not significant sources (they provide mainly carbohydrate and protein). Liver is a good source, but the group as a whole is wrong.
    • D. Rice bran, green vegetables and milk: Rice bran is mainly a source of vitamin B (thiamine), so this is not a good group.

    Tip: Think "colour": yellow, orange, and red foods (carrot, palm oil, ripe pawpaw) plus animal products (egg yolk, liver, milk) mean vitamin A. Also remember that a deficiency of vitamin A causes night blindness and xerophthalmia, which is a frequent follow-up question.

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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.

    Use the following processes to answer this question. I-Ribs move upward and outward II- Diaphragm relaxes IIl-Volume of thorax increases IV-Air is forced out of the lungs which of the following processes is a direct result of contraction of the intercostal muscles?

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

    Answer: A. I

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

  6. 6.

    The diagrams above are illustrations of two different cells involved in biological processing in mammals. Study them and answer this question. If the number of chromosomes in the skin cells of mammals is 46, how many chromosomes would be found in P and Q respectively?

    1. A.23 and 23
    2. B.23 and 46
    3. C.46 and 23
    4. D.46 and 46.
    Show answer

    Answer: A. 23 and 23

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  7. 7.

    Which of the following blood components has the greatest affinity for oxygen and carbon (IV) oxide?

    1. A.Lymphocyte
    2. B.Erythrocyte
    3. C.Blood plasma
    4. D.Thrombocyte
    Show answer

    Answer: B. Erythrocyte

    AI explanation

    Analyze the question: It asks which blood component binds oxygen and carbon (IV) oxide most strongly. The answer is the cell that carries these gases.

    Explain the concept:

    • Erythrocytes (red blood cells) contain haemoglobin, a protein with iron (Fe²⁺) that combines readily with oxygen to form oxyhaemoglobin. Haemoglobin also carries some CO₂ as carbaminohaemoglobin.
    • Erythrocytes also contain the enzyme carbonic anhydrase, which helps convert CO₂ into bicarbonate for transport.

    Check each option:

    • A. Lymphocyte: a white blood cell that produces antibodies for immunity. It does not carry gases.
    • B. Erythrocyte: contains haemoglobin, which has a high affinity for O₂ and also carries CO₂. This is correct.
    • C. Blood plasma: transports most CO₂ as dissolved bicarbonate, and only a very small amount of O₂ is dissolved in it. Its affinity is much lower than that of haemoglobin.
    • D. Thrombocyte (platelet): helps blood clot. It has no role in gas transport.

    Answer: The erythrocyte (red blood cell) is correct, which is option B.

    Exam tip: Remember "Erythrocyte = Exchange of gases" (and Red = Respiratory gases). Likewise, the white cells (leucocytes/lymphocytes) are for defence, and thrombocytes are for clotting.

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  8. 8.

    Study the food chain illustrated below and use it to answer this question. J-K-L-M-N The position occupied by each of organisms  J K L M N in the food chain is known as the

    1. A.energy level
    2. B.trophic level
    3. C.food web
    4. D.pyramid of numbers
    Show answer

    Answer: B. trophic level

    AI explanation

    Analyze the question: The food chain is J → K → L → M → N. The question asks what we call the position each organism occupies in the chain.

    Explain the concept:

    • A food chain shows the linear transfer of food and energy from one organism to another, starting with a producer.
    • Each feeding step or position in the chain is called a trophic level. • 1st trophic level: producers (e.g., J, a green plant) • 2nd trophic level: primary consumers (K) • 3rd trophic level: secondary consumers (L) • 4th trophic level: tertiary consumers (M) • 5th trophic level: quaternary consumers (N)

    Check each option:

    • A. Energy level: This term is used in Physics and Chemistry (for example, electron energy levels). It is not the standard Biology term for a position in a food chain.
    • B. Trophic level: This is the correct term for the feeding position an organism occupies in a food chain.
    • C. Food web: This is a network of many interconnected food chains, not a single position.
    • D. Pyramid of numbers: This is a diagram showing the number of organisms at each trophic level, not the position itself.

    Answer: The position occupied by each organism in the food chain is its trophic level, which is option B.

    Exam tip: Remember that "trophic" comes from the Greek word for nourishment/feeding. So trophic level = feeding level. If a question asks about a position in a food chain, think "trophic." If it asks about many interlinked chains, think "food web."

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  9. 9.

    Diagrams X and Y above are illustrations of transverse sections of a part of plants, Study them and answer this question.   The part responsible for conducting water and dissolved mineral salts from the soil to the leaves is labelled

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

    Answer: D. IV

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  10. 10.

    Study the food chain illustrated below and use it to answer this question. J-K-L-M-N which of the following statements about organism L is correct?

    1. A.feeds on organism
    2. B.is a primary consumer
    3. C.is the producer
    4. D.is a secondary consumer
    Show answer

    Answer: D. is a secondary consumer

    AI explanation

    Analyze the question: The food chain is J → K → L → M → N. The question asks which statement about organism L is correct. Arrows in a food chain point from the organism being eaten to the organism that eats it, so energy flows from left to right.

    Concept: Trophic levels in a food chain:

    • 1st organism: Producer (a green plant)
    • 2nd organism: Primary consumer (herbivore)
    • 3rd organism: Secondary consumer (carnivore or omnivore that eats the herbivore)
    • 4th organism: Tertiary consumer
    • 5th organism: Quaternary consumer

    Step-by-step solution:

    1. J is first, so J is the producer.
    2. K feeds on J, so K is the primary consumer.
    3. L feeds on K, so L is the secondary consumer.
    4. M is the tertiary consumer and N is the quaternary consumer.

    Checking the options:

    • A. "feeds on organism" is incomplete and doesn't name an organism, so it can't be the answer.
    • B. Primary consumer is K, not L, so this is wrong.
    • C. Producer is J, not L, so this is wrong.
    • D. Secondary consumer is L, so this is correct.

    Tip: Count the position along the chain. Position 1 is the producer, position 2 is the primary consumer, position 3 is the secondary consumer, and so on. The consumer number is always the position minus one. L is in position 3, so it is a secondary consumer.

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  11. 11.

    Diagram J is a protease while diagrams K,L,M, and N are food substances, study them and answer this question. Protease J would react with the particular illustrated substance because enzymes?

    1. A.are denatured at a high frequency
    2. B.are specific in their action
    3. C.remain unchanged after a reaction
    4. D.speed
    Show answer

    Answer: A. are denatured at a high frequency

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  12. 12.

    Two tall plants were crossed and all the F1 plants were tall. when the F1 plants were selfed, some of the F2 plants were tall while others were short what are the possible genotypes of the original plants ?

    1. A.Tt and tt
    2. B.TT and TT
    3. C.tt and tt
    4. D.TT and Tt
    Show answer

    Answer: D. TT and Tt

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  13. 13.

    The region of a plant stem in which cells divide to increase its diameter is

    1. A.cambium
    2. B.phloem
    3. C.xylem
    4. D.collenchyma
    Show answer

    Answer: A. cambium

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  14. 14.

    An accident victim was successfully transfused with blood from the father whose blood, group is AB. The blood group of the accident victim is

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

    Answer: C. AB

    AI explanation

    Analyze the question: The victim was transfused successfully with blood from a donor whose group is AB. We need the victim's blood group, so we have to work out which recipients can safely receive AB blood.

    Concept: Blood groups are defined by the antigens on red blood cells and the antibodies in the plasma:

    | Group | Antigens on RBC | Antibodies in plasma | |---|---|---| | A | A | anti-B | | B | B | anti-A | | AB | A and B | none | | O | none | anti-A and anti-B |

    A recipient's plasma must not contain antibodies against the donor's red cell antigens. Otherwise the donor cells clump (agglutinate).

    Solution:

    • Donor AB has both A and B antigens.
    • Group A recipient: has anti-B, which attacks the B antigen, so it is not safe.
    • Group B recipient: has anti-A, which attacks the A antigen, so it is not safe.
    • Group O recipient: has both anti-A and anti-B, so it is not safe.
    • Group AB recipient: has no antibodies, so it is safe.

    AB blood can only be given safely to an AB recipient. AB individuals are called universal recipients, but AB donors can give only to AB.

    Answer: The victim's blood group is AB, which is option C.

    Tip: Remember "AB can receive from all, but give only to AB." Match the donor's antigens against the recipient's antibodies. If the recipient has no antibody against those antigens, the transfusion is safe.

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  15. 15.

    Which of the followig traits in humans is an example of physiological variation?

    1. A.skin colour
    2. B.fingerprint
    3. C.tongue rolling
    4. D.height
    Show answer

    Answer: C. tongue rolling

    AI explanation

    Analyze the question: The question asks which trait is an example of physiological variation in humans.

    Concept: Variation among individuals of a species can be:

    • Morphological (structural) variation: differences in physical form or appearance that can be seen or measured, e.g. height, skin colour, fingerprints, body mass.
    • Physiological variation: differences in how the body functions or in its ability to perform a function, e.g. the ability to roll the tongue, blood group, ability to taste PTC, sickle cell trait, and metabolic rate.

    Working through the options:

    • A. Skin colour: a visible physical feature, so it is morphological.
    • B. Fingerprint: the pattern of ridges is a structural feature, so it is morphological.
    • C. Tongue rolling: this is the ability to perform a function (curling the tongue into a U-shape). It is a functional difference, so it is physiological. It is also a discontinuous variation, because you either can roll your tongue or you cannot.
    • D. Height: this is measurable body size, so it is morphological. It is also a continuous variation.

    Answer: Tongue rolling is the only option that describes a difference in ability or function rather than physical structure.

    Exam tip: Ask yourself, "Can I see or measure it as a physical feature, or is it about what the body can do?" If you can see or measure it, it is morphological. If it is an ability, such as tongue rolling, taste ability, or blood group, it is physiological.

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  16. 16.

    The diagrams above are illustrations of two different cells involved in biological processing in mammals. Study them and answer this question. Which parts of P and Q fuse to complete the biological process?

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

    Answer: D. IV and II

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  17. 17.

    An evidence of the occurrence of photosynthesis in an experiment is the?

    1. A.release of carbon (IV) oxide
    2. B.release of oxygen
    3. C.formation of water molecules
    4. D.formation and release of fructose
    Show answer

    Answer: B. release of oxygen

    AI explanation

    Analyze the question: The question asks which observable sign shows that photosynthesis has taken place in an experiment.

    Concept: Photosynthesis is the process by which green plants use light energy, carbon (IV) oxide and water to make glucose (food), releasing oxygen:

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

    Evaluate each option:

    • A. Release of carbon (IV) oxide: Wrong. CO₂ is taken in during photosynthesis. Its release is a sign of respiration.
    • B. Release of oxygen: Correct. Oxygen is a by-product that can be observed directly. In an aquatic plant experiment (e.g., Hydrilla or Elodea under a funnel in water), bubbles of gas collect in the test tube. The gas relights a glowing splint, which confirms it is oxygen.
    • C. Formation of water molecules: Wrong. Water is a raw material that is used up. (Water is actually produced in respiration, not as the evidence of photosynthesis.)
    • D. Formation and release of fructose: Wrong. The main product is glucose, which is converted to starch for storage. It is not released from the plant as fructose.

    Answer: The release of oxygen is the easily observable evidence, so the answer is B.

    Exam tip: Remember "Photosynthesis gives off O₂, respiration gives off CO₂." In experiments, the evidence for photosynthesis is usually one of two things:

    1. Oxygen bubbles (aquatic plants), or
    2. Starch present in a leaf (iodine turns blue-black).

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  18. 18.

    Diagram J is a protease while diagrams K,L,M, and N are food substances, study them and answer this question. After a reaction between protease J and the food substance, the end product would be

    1. A.fatty acids
    2. B.glucose
    3. C.amino acids
    4. D.water
    Show answer

    Answer: D. water

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  19. 19.

    The total number of caudal vertebrae in animals X and Y is 4 and 27 respectively. The animals are likely to be.

    1. A.fish and human
    2. B.toad and rat
    3. C.toad and fish
    4. D.humans and rat
    Show answer

    Answer: D. humans and rat

    AI explanation

    Analyze the question: Caudal vertebrae are the tail vertebrae. We need to match 4 caudal vertebrae (X) and 27 (Y) to the right animals.

    Concept:

    • Humans have a vestigial tail, the coccyx, made of about 3-5 fused caudal vertebrae. So 4 fits a human.
    • Rat has a long tail with many caudal vertebrae, roughly 25-30. So 27 fits a rat.
    • Toad (adult frog/toad) has no real tail. Its caudal vertebrae are fused into a single rod-like urostyle, so it has very few.
    • Fish have many caudal vertebrae, often more than 20, depending on the species.

    Step-by-step check of the options:

    • A. fish and human: X = fish (4) is wrong, because fish have many caudal vertebrae. Y = human (27) is wrong. ✗
    • B. toad and rat: Toad has only a urostyle (about 1 fused element, not 4), so it is a poor fit. The rat fits 27. This is partly plausible, but the toad's count doesn't match well. ✗
    • C. toad and fish: The toad could be low, but fish would be an unspecific match. The pairing is weaker than D. ✗
    • D. humans and rat: Human coccyx has about 4 caudal vertebrae, and a rat has about 27. ✓

    Answer: D. humans and rat

    Tip: For vertebral formula questions, remember the human formula: cervical 7, thoracic 12, lumbar 5, sacral 5 (fused), caudal 4 (fused, the coccyx). If a number is small (3-5), think of an animal with a reduced tail, such as a human. If it is large (20+), think of an animal with a long tail, such as a rat.

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  20. 20.

    Organ level of organization in living things is found in?

    1. A.waterleaf plant
    2. B.virus particle
    3. C.kidney
    4. D.spermatozoon
    Show answer

    Answer: C. kidney

    AI explanation

    Step 1: Analyze the question The question asks which option shows the organ level of organization. Living things are organized in this order:

    Cell → Tissue → Organ → Organ system → Organism

    Step 2: Explain the concept

    • Cell level: a single cell that performs its own functions (e.g., spermatozoon, red blood cell).
    • Tissue level: a group of similar cells doing the same job (e.g., muscle tissue).
    • Organ level: different tissues working together to perform a specific function (e.g., kidney, heart, leaf, stomach).
    • Organ system level: several organs working together (e.g., the excretory system).
    • Organism level: a complete living individual.

    Step 3: Go through the options

    • A. Waterleaf plant: This is a whole organism, so it is at the organism level, not the organ level.
    • B. Virus particle: A virus is not cellular. It is just genetic material in a protein coat and does not show the levels of organization.
    • C. Kidney: This is an organ made of different tissues (epithelial, connective, and so on) that work together to filter blood and form urine. This fits the organ level.
    • D. Spermatozoon: This is a single specialized cell, so it is at the cell level.

    Step 4: Answer The kidney is the only option that is an organ.

    Tip: Remember the sequence "C-T-O-S-O" (Cell, Tissue, Organ, System, Organism). When you see a named body part like the heart, kidney, liver, or leaf, think "organ." A single cell is cell level, and a whole plant or animal is organism level.

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  21. 21.

    In which of the following structures is simple sugar produced?

    1. A.Vacuole
    2. B.Cytoplasm
    3. C.Chloroplast
    4. D.Cell wall
    Show answer

    Answer: C. Chloroplast

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  22. 22.

    The biological association that contributes directly to succession in a community is

    1. A.competition
    2. B.predation
    3. C.parasitism
    4. D.commensialism
    Show answer

    Answer: A. competition

    AI explanation

    Step 1: Analyze the question The question asks which biological association contributes directly to ecological succession. Succession is the gradual, orderly replacement of one community by another until a stable climax community is reached.

    Step 2: Explain the concept Succession happens in stages:

    • Pioneer species (e.g., lichens, mosses) colonize bare ground.
    • They change the environment by forming soil and adding nutrients.
    • New species move in and compete with the earlier ones for light, water, space, and nutrients.
    • The better-adapted species outcompete and replace the earlier ones. This repeats until a climax community (e.g., a rainforest) forms.

    Step 3: Evaluate the options

    • A. Competition: This is the driving force of replacement. Species that are better adapted displace weaker ones, so one community gives way to the next. This is a direct contributor to succession.
    • B. Predation: It regulates population sizes, but it does not directly drive the replacement of one plant community by another.
    • C. Parasitism: It affects the host's health and numbers, but it is not a main driver of community change.
    • D. Commensalism: One organism benefits and the other is unaffected. It may help in small ways (for example, one plant giving shade), but it is not the main direct cause of replacement.

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

    Tip: For succession questions, remember "Pioneers change, competitors replace." Whenever you see the word replacement of species in a community, think competition.

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  23. 23.

    Diagrams X and Y above are illustrations of transverse sections of a part of plants, Study them and answer this question.   The part labelled Il is the?

    1. A.Pith
    2. B.xylem
    3. C.Phloem
    4. D.endodermis
    Show answer

    Answer: A. Pith

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  24. 24.

    which of the following statements about living things is correct?

    1. A.animals respire using carbon(iv)oxide as a raw material
    2. B.growth in plants is limited after some time
    3. C.most plants respond to stimulus slowly
    4. D.higher animals can reproduce asexually
    Show answer

    Answer: C. most plants respond to stimulus slowly

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

  26. 26.

    The burning of farmlands ahould be discouraged because?

    1. A.destroys organic components of the soil
    2. B.increases population of wild animals
    3. C.increases dormancy period of some seeds
    4. D.destroys some plant seeds
    Show answer

    Answer: A. destroys organic components of the soil

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  27. 27.

    which of the follwing pyramids is not used in ecology? pyramid of

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

    Answer: D. orgsnisms

    AI explanation

    Analyze the question: You're asked which of the four is NOT a type of ecological pyramid.

    Concept: Ecological pyramids show how living things are arranged across the trophic levels (feeding levels) of a food chain. The three standard types are:

    1. Pyramid of numbers shows how many individual organisms are at each trophic level.
    2. Pyramid of biomass shows the total dry mass of living material at each trophic level.
    3. Pyramid of energy shows how much energy flows through each trophic level, usually in kJ/m²/year.

    Solution:

    • A. Energy: a recognised ecological pyramid.
    • B. Numbers: a recognised ecological pyramid.
    • C. Biomass: a recognised ecological pyramid.
    • D. "Organisms": not a standard type. Organisms are what the pyramids describe, and "numbers of organisms" is already covered by the pyramid of numbers. "Pyramid of organisms" is not a recognised term in ecology.

    Answer: D

    Tip: Remember the three ecological pyramids as N-B-E: Numbers, Biomass, Energy. If an option isn't one of these, it's probably the odd one out. Also remember that the pyramid of energy is always upright, while numbers and biomass can sometimes be inverted, such as numbers on a single big tree supporting many insects.

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  28. 28.

    The diagrams above are illustrations of two different cells involved in biological processing in mammals. Study them and answer this question. Which of the following statements about P and Q is correct?

    1. A.Both cells are structures for asexual reproduction
    2. B.Both cells normally belong to the same individual
    3. C.Both cells are found in plants
    4. D.The union of both cells gives rise to a new mammal
    Show answer

    Answer: A. Both cells are structures for asexual reproduction

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

  30. 30.

    The process by which the amount of water and solutes in the blood is controlled is known as

    1. A.hemolysis
    2. B.diffusion
    3. C.turgidity
    4. D.osmoregulation
    Show answer

    Answer: D. osmoregulation

    AI explanation

    Step 1: Analyze the question The question asks for the name of the process that controls the amount of water and dissolved substances (solutes) in the blood.

    Step 2: Explain the concept Organisms must keep the water and salt content of their body fluids within a narrow range. This is called osmoregulation (osmo = osmotic pressure, regulation = control). In humans, the kidneys are the main organs of osmoregulation. They are helped by the hormone ADH (antidiuretic hormone), which adjusts how much water is reabsorbed.

    Step 3: Check each option

    • A. Hemolysis: This is the bursting of red blood cells, for example when they take in too much water. It is not a control process.
    • B. Diffusion: This is the movement of particles from a region of high concentration to a region of low concentration. It is a passive transport process, not the regulation of blood water and solutes.
    • C. Turgidity: This is the swollen, firm state of plant cells when they are full of water. It has nothing to do with blood.
    • D. Osmoregulation: This is the control of water and solute levels in body fluids, including blood. It matches the question exactly.

    Step 4: Answer The correct option is D. osmoregulation.

    Tip: Break the word into parts. "Osmo" refers to water and solute balance, and "regulation" means control. Whenever a question says "controlling water and salt levels," think osmoregulation. Also remember that homeostasis is the broad term for keeping the internal environment stable, and osmoregulation is the water and salt part of it.

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  31. 31.

    The organelles in cells which are also referred to as suicidal bags are the

    1. A.mithchondria
    2. B.lysosomes
    3. C.ribosomes
    4. D.nuclei
    Show answer

    Answer: B. lysosomes

    AI explanation

    Step 1: Analyze the question The question asks which organelle is nicknamed "suicidal bags." The nickname hints at an organelle that can cause a cell to destroy itself.

    Step 2: Explain the concept Lysosomes are small, membrane-bound sacs filled with powerful digestive (hydrolytic) enzymes. Their functions include:

    • Digesting worn-out organelles (autolysis)
    • Breaking down food particles and foreign materials, such as bacteria
    • Releasing their enzymes when the cell is damaged or dying, so the cell digests itself

    Because they can burst and digest their own cell, they are called "suicide bags" or "suicidal bags."

    Step 3: Check each option

    • A. Mitochondria: the "powerhouse" of the cell, the site of aerobic respiration and ATP production.
    • B. Lysosomes: contain digestive enzymes and cause autolysis, so they are the "suicidal bags."
    • C. Ribosomes: the site of protein synthesis.
    • D. Nuclei: control the activities of the cell and contain the genetic material (DNA).

    Step 4: Answer The correct option is B. lysosomes.

    Exam tip: Match each organelle to its nickname:

    • Mitochondria → powerhouse
    • Lysosomes → suicide bags
    • Ribosomes → protein factories
    • Nucleus → control center

    Think "Lysosome = Lethal enzymes" to remember it.

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  32. 32.

    Use the following processes to answer this question. I-Ribs move upward and outward II- Diaphragm relaxes IIl-Volume of thorax increases IV-Air is forced out of the lungs  Which of the processes take place during inspiration?

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

    Answer: A. I and III only

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

  34. 34.

    Which of the following statements best describes a test cross?

    1. A.to determine the genotype of an individual whose phenotype is to be known
    2. B.to determine the phenotype of an individual whose genotype is known
    3. C.between the progeny of parents to ascertain external expressions
    4. D.between two homozygous recessive individuals to confirm the genotypes
    Show answer

    Answer: A. to determine the genotype of an individual whose phenotype is to be known

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  35. 35.

    The use of a lighter instead of matchsticks is a way of conserving

    1. A.petroleum
    2. B.forest
    3. C.water
    4. D.wildlife
    Show answer

    Answer: B. forest

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  36. 36.

    which of the following features is not an adaptation?

    1. A.Breathing roots for entry air
    2. B.flowers are raised above water to attract pollinators
    3. C.spongy tissues containing gases for boyancy
    4. D.hairy structures on the leaves to reduce water loss
    Show answer

    Answer: D. hairy structures on the leaves to reduce water loss

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  37. 37.

    The process that brings about the shrinking of a spirogyra cell when placed in a strong solution is ?

    1. A.osmosis
    2. B.autolysis
    3. C.plasmolysis
    4. D.diffusion
    Show answer

    Answer: C. plasmolysis

    AI explanation

    Step 1: Analyze the question The question asks for the process that makes a Spirogyra cell shrink when it is placed in a strong (concentrated) solution. Spirogyra is a green alga with cells that have a cell wall, a cell membrane, and a large central vacuole.

    Step 2: Explain the concept

    • Osmosis is the movement of water from a region of high water potential to one of low water potential through a semi-permeable membrane. It is the underlying mechanism, but it is not the name for the shrinking itself.
    • Plasmolysis is the shrinking of the protoplasm (cytoplasm and vacuole) away from the cell wall. It happens when a plant cell loses water by osmosis in a hypertonic (strong) solution.
    • Autolysis is the self-digestion of cells by their own enzymes, usually after cell death.
    • Diffusion is the movement of particles from high to low concentration. It does not specifically describe cell shrinkage.

    Step 3: Solve

    1. The Spirogyra cell is placed in a strong solution, which is hypertonic to the cell sap.
    2. Water leaves the vacuole and cytoplasm by osmosis.
    3. The protoplasm shrinks and pulls away from the cell wall.
    4. This shrinking of the protoplasm is called plasmolysis.

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

    Tip: Remember "Plasmo-lysis = protoplasm pulls away." Osmosis is the cause (water movement), while plasmolysis is the visible effect in plant cells. If you see the words "shrinking of the cell" with a plant cell in a strong solution, think plasmolysis. The opposite, in which a cell swells and becomes firm in a dilute solution, is called turgidity.

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  38. 38.

    Which of the following statements about sex linked traits is not correct?

    1. A.male inherit sex linked traits from thier fathers
    2. B.sex linked traits are more common in males
    3. C.females can be carriers beacuse they can be heterozygous for the trait
    4. D.males are never carriers since they only recieve one sex chromosome
    Show answer

    Answer: A. male inherit sex linked traits from thier fathers

    AI explanation

    Analyze the question: We need the statement that is NOT correct about sex-linked traits (mostly X-linked traits, e.g., colour blindness and haemophilia).

    Concept:

    • Females are XX; males are XY.
    • A son receives his Y chromosome from his father and his X chromosome from his mother.
    • X-linked genes are carried on the X chromosome. Males have only one X (hemizygous), so a single recessive allele shows up in them.
    • Females can be heterozygous (X^H X^h), so they can be carriers without showing the trait.

    Check each option:

    • A. Males inherit sex-linked traits from their fathers. This is false. A father passes his Y to his sons, and the Y carries no allele for X-linked traits like colour blindness. Sons get the X-linked trait from their mothers. (Fathers pass their X to their daughters, not their sons.)
    • B. Sex-linked traits are more common in males. This is true. One recessive allele is enough for a male to show the trait.
    • C. Females can be carriers because they can be heterozygous. This is true.
    • D. Males are never carriers since they only receive one sex chromosome. This is the textbook idea. Males have only one X, so if they have the allele they show the trait and are not "carriers" in the heterozygous sense. Strictly, they receive two sex chromosomes (X and Y), so the reason is worded loosely. But the main idea, that males cannot be carriers of X-linked recessive traits, is accepted.

    Answer: Option A is the incorrect statement.

    Worked example: Colour-blind father (X^c Y) × normal non-carrier mother (X^C X^C):

    • Sons: X^C Y, all normal. They got X from the mother and Y from the father.
    • Daughters: X^C X^c, all carriers.

    The father's colour blindness was not passed to his sons.

    Exam tip: Remember "Sons get their X from Mum." Whenever an option says a son inherits an X-linked trait from his father, mark it wrong.

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

  40. 40.

    The conservation of natural resources is enhanced by the following practices except

    1. A.controlling farm activities
    2. B.protecting endangered species
    3. C.poaching in game reserves
    4. D.establishing parks and gardens
    Show answer

    Answer: C. poaching in game reserves

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  41. 41.

    The property of clayey soil that prevents it from supporting thick vegetation is its?

    1. A.composition of chemically weathered granite rocks
    2. B.inability to retain much water
    3. C.tendency of becoming waterlogged
    4. D.porosity and low water retention ability
    Show answer

    Answer: C. tendency of becoming waterlogged

    AI explanation

    Step 1: Analyze the question We're asked which property of clayey soil stops it from supporting thick vegetation.

    Step 2: Recall the concept Clay soil has very fine particles, so:

    • It has small pore spaces, meaning it is poorly drained and poorly aerated (not porous in the sense of large air spaces).
    • It retains a lot of water, which makes it sticky and heavy.
    • Because of poor drainage, it easily becomes waterlogged. Waterlogging drives out air, so roots cannot get enough oxygen for respiration, and many plants cannot grow well.

    Step 3: Evaluate each option

    • A. Chemically weathered granite rocks: Clay does form from weathered rocks, but this describes its origin, not a property that limits vegetation. Clay is also rich in nutrients. ❌
    • B. Inability to retain much water: This is wrong. Clay retains a lot of water. This describes sandy soil. ❌
    • C. Tendency of becoming waterlogged: This is correct. Poor drainage and poor aeration deprive roots of oxygen. ✅
    • D. Porosity and low water retention: This is also wrong. It describes sandy soil, since clay has low porosity (in terms of drainage) and high water retention. ❌

    Step 4: Answer

    Tip 💡: Remember the contrast:

    • Sandy soil: well drained, well aerated, low water retention, so plants suffer from drought.
    • Clayey soil: poorly drained, poorly aerated, high water retention, so it becomes waterlogged.
    • Loamy soil: the ideal balance.

    If an option says clay "cannot retain water", it is almost certainly a trap.

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  42. 42.

    Diagrams X  and  Y above are illustrations of transverse sections of a part of plants. study them and answer this question   which of the following statements is not correct?  Diagrams X and Y are sections of

    1. A.roots
    2. B.a dicotyledonous root
    3. C.vascular bundies
    4. D.stems
    Show answer

    Answer: B. a dicotyledonous root

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  43. 43.

    Individuals belonging to the blood group O are universal donors because ?

    1. A.antigens are absent in thier blood cells
    2. B.members of the group consitutute the highest number of humans
    3. C.there are no of antibodies in thier blood plasma
    4. D.the antigens in thier blood cells are easily destroyed
    Show answer

    Answer: A. antigens are absent in thier blood cells

    AI explanation

    Analyze the question: It asks why people with blood group O are called universal donors. Their blood can be given to people of any ABO group.

    Concept: ABO blood groups are determined by two things:

    • Antigens on the surface of red blood cells
    • Antibodies in the plasma

    | Group | Antigens on red cells | Antibodies in plasma | |-------|----------------------|----------------------| | A | A | anti-B | | B | B | anti-A | | AB | A and B | none | | O | none | anti-A and anti-B |

    Solution:

    • In a transfusion, the main danger is that the recipient's antibodies attack the donor's red cell antigens, causing agglutination (clumping).
    • Group O red cells have no A or B antigens, so the recipient's anti-A or anti-B antibodies have nothing to attack. This is why O blood can be given to A, B, AB and O recipients.

    Checking the options:

    • A. Antigens are absent in their blood cells: Correct. This is the real reason.
    • B. Highest number of humans: Being common has nothing to do with compatibility.
    • C. No antibodies in their plasma: False. Group O plasma contains both anti-A and anti-B. (Group AB is the one with no antibodies.)
    • D. Antigens easily destroyed: False. O cells simply never had A or B antigens.

    Answer: A

    Tip: Remember "O = zero antigens, so O gives to all." For the reverse, "AB has no antibodies, so AB receives from all" (universal recipient). Option C is a common trap because it mixes up the two ideas.

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  44. 44.

    which of the following practices will not maintain soil fertility?

    1. A.preventing soil erosion
    2. B.bush fallowing
    3. C.tendency of becoming waterlogged
    4. D.porosity and low water retention ability
    Show answer

    Answer: D. porosity and low water retention ability

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

  46. 46.

    A group of organisms of the same species living in a particular place is known as

    1. A.colony
    2. B.ecosystem
    3. C.Niche
    4. D.population
    Show answer

    Answer: D. population

    AI explanation

    Step 1: Analyze the question The question asks for the term describing a group of organisms of the same species living in a particular place. The key phrases are "same species" and "particular place."

    Step 2: Explain the concepts Let's look at each option:

    • A. Colony: A group of organisms of the same species living closely together, often with cooperation or physical connection (e.g., ants, bees, corals, bacteria). It is a specific kind of grouping, usually social or structural, not the general ecological term.
    • B. Ecosystem: A community of living organisms (many species) interacting with the non-living environment (soil, water, air). It involves multiple species, so it does not fit.
    • C. Niche: The role or function of an organism in its habitat, including what it eats, where it lives, and how it interacts with others. It describes a role, not a group.
    • D. Population: All the individuals of the same species living in a particular area at a given time (e.g., all the tilapia fish in a pond, or all the baobab trees in a savannah reserve).

    Step 3: Solve

    • Same species → rules out ecosystem (many species) and niche (a role).
    • Group in a particular place → matches the ecological definition of a population.
    • Colony is more specific, implying a tightly knit or social group, whereas the question uses the general ecological definition.

    Step 4: Answer The correct option is D. population.

    Tip: Remember the ecological hierarchy: Individual → Population → Community → Ecosystem → Biosphere. A population is always one species in one place. If you see "same species + particular place," think population.

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