2023 WAEC (WASSCE) Biology Past Questions and Answers

Questions

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

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

3. 3.

   Organisms that feed on dead, decaying tissues of other organisms are known as

   1. A.saprophytes
   2. B.autotrophs
   3. C.parasites
   4. D.heterotrophs

   Show answer

   Answer: A. saprophytes

   AI explanation

   Step 1: Analyze the question The question asks for the term for organisms that feed on dead, decaying tissues of other organisms.

   Step 2: Explain the concepts

   • Saprophytes (saprotrophs): These organisms get nutrients from dead and decaying organic matter. They secrete enzymes onto the material and absorb the digested food. Examples are mushrooms, bread mould (Rhizopus) and many bacteria.
   • Autotrophs: These make their own food, usually by photosynthesis (green plants, algae).
   • Parasites: These feed on living host organisms and harm them (tapeworm, Plasmodium, mistletoe).
   • Heterotrophs: This is a broad group of organisms that cannot make their own food and depend on other organisms. It includes saprophytes, parasites and animals that eat food. The term is correct in a general sense, but it does not specifically describe feeding on dead, decaying matter.

   Step 3: Work through the options

   • A. Saprophytes: they feed on dead, decaying matter, so this fits.
   • B. Autotrophs: they make their own food, so this is wrong.
   • C. Parasites: they feed on living hosts, so this is wrong.
   • D. Heterotrophs: this is too general. Parasites and herbivores are also heterotrophs, so it is not the specific answer.

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

   Exam tip: Remember that "sapro" means rotten or decayed. Saprophyte = Spoiled/rotten food eater. When a question gives both a broad term (heterotroph) and a specific term (saprophyte), choose the one that matches the details in the question.

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4. 4.

   The mouthparts of a grasshopper are adapted for

   1. A.sucking
   2. B.chewing
   3. C.grinding
   4. D.absorption

   Show answer

   Answer: B. chewing

   AI explanation

   Step 1: Analyze the question The question asks about the feeding function of the grasshopper's mouthparts. This depends on the type of food it eats and how it feeds.

   Step 2: Explain the concept Insects have different mouthpart types depending on their diet:

   • Sucking (siphoning): butterflies and moths, which feed on nectar
   • Piercing and sucking: mosquitoes and aphids, which feed on blood or plant sap
   • Sponging: houseflies, which feed on liquids
   • Biting and chewing: grasshoppers, cockroaches, and termites, which feed on solid food

   Step 3: Apply to the grasshopper A grasshopper feeds on leaves and grasses, which are solid plant material. Its mouthparts include:

   • Labrum: the upper lip, which holds food
   • Mandibles: strong, toothed jaws that bite and chew the food
   • Maxillae: which hold and manipulate the food
   • Labium: the lower lip
   • Palps: sensory structures that help detect food

   The mandibles move sideways, like scissors, to cut and chew the leaves. This is a biting and chewing mouthpart type.

   Step 4: Evaluate the options

   • A. Sucking: this belongs to butterflies and mosquitoes, so it is wrong.
   • B. Chewing: correct, because grasshoppers eat solid leaves.
   • C. Grinding: the mandibles do crush food somewhat, but the standard classification is "biting and chewing," so this is not the best answer.
   • D. Absorption: this belongs to organisms such as fungi and tapeworms, so it is wrong.

   Answer: B. Chewing

   Exam tip: Match the mouthpart to the food. Solid food means chewing (grasshopper, cockroach). Liquid food means sucking (butterfly, mosquito, housefly). Remember: "Grasshopper grabs grass, so it chews."

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5. 5.

   Study the list of organisms below and use them to answer the questions. I-Hydra II-Owl III-Snake IV-Snail The Phylum of the organism labeled IV is

   1. A.Platyhelminthes
   2. B.mollusca
   3. C.Arthropoda
   4. D.Coelenterata

   Show answer

   Answer: B. mollusca

   AI explanation

   Analyze the question: You're asked for the phylum of organism IV, which is the snail.

   Concept: Animals are placed in phyla based on their body structure.

   • Coelenterata (Cnidaria): Hydra, jellyfish and sea anemones. They have a hollow body with stinging cells.
   • Platyhelminthes: Flatworms such as tapeworm and planaria. They have flat, unsegmented bodies.
   • Arthropoda: Insects, crabs, spiders and millipedes. They have jointed legs and an exoskeleton made of chitin.
   • Mollusca: Snails, slugs, mussels, oysters and octopus. They have a soft, unsegmented body, usually a muscular foot, and often a hard calcareous shell.

   Solution:

   1. The snail has a soft, unsegmented body.
   2. It moves on a muscular foot.
   3. It is protected by a coiled calcareous shell.
   4. These are the defining features of Mollusca.
   5. Option A is wrong because a snail is not flat-bodied. Option C is wrong because a snail has no jointed legs. Option D is wrong because Coelenterata is the phylum of Hydra (organism I), not the snail.

   Answer: B. Mollusca

   Tip: Remember "Mollusca = Soft body + Shell + Foot". Snail, slug, oyster and octopus all belong here. For the other organisms in this list, Hydra is Coelenterata, while the owl and snake are both Chordata (the owl is a bird, the snake a reptile).

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6. 6.

   A Rhesus negative woman may experience stillbirth of the second child that is Rhesus positive because

   1. A.the foetus is deprived of nourishment
   2. B.they have poor circulatory system
   3. C.the blood of the foetus might clump
   4. D.the woman is susceptible to diseases during pregnancy

   Show answer

   Answer: C. the blood of the foetus might clump

   AI explanation

   Step 1: Analyze the question The question is about Rhesus incompatibility (Rh factor) between a Rh-negative mother and a Rh-positive baby, and why this can cause stillbirth in a second pregnancy.

   Step 2: The concept

   • The Rh factor is an antigen on the surface of red blood cells. Rh-positive people have it; Rh-negative people don't.
   • First pregnancy: During childbirth, some of the Rh-positive baby's blood can enter the Rh-negative mother's bloodstream. Her immune system sees the Rh antigen as foreign and makes anti-Rh antibodies.
   • Second pregnancy: If the next baby is also Rh-positive, the mother's anti-Rh antibodies cross the placenta into the foetus's blood. They attack the foetal red blood cells, causing agglutination (clumping) and destruction of the cells (haemolysis). This is called haemolytic disease of the newborn (erythroblastosis fetalis). The foetus becomes severely anaemic and can die, which results in stillbirth.

   Step 3: Check the options

   • A. Nourishment is not the issue. The placenta still functions. ✗
   • B. Poor circulation is not the cause. ✗
   • C. The foetal blood clumps because of the mother's antibodies. ✓
   • D. The problem isn't general susceptibility to disease. It is a specific antigen-antibody reaction. ✗

   Step 4: Answer The correct option is C: the blood of the foetus might clump.

   Tip: Remember "Rh- mother, Rh+ baby, second child is at risk." The first baby sensitises the mother (antibodies form), and the second baby faces the attack. Link the keyword antibodies → agglutination (clumping). Today, doctors give Rh-negative mothers an anti-D injection after the first birth to prevent this.

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

8. 8.

   Which of the following hormones is wrongly paired with its secretory organ?

   1. A.oestrogen and ovary
   2. B.Oxytocin and hypothalamus
   3. C.adrenalin and kidney
   4. D.insulin and pancreas

   Show answer

   Answer: C. adrenalin and kidney

   AI explanation

   Analyze the question: We need the pair in which the hormone does not match the organ that secretes it.

   Concept: Each hormone is made by a specific endocrine gland or organ.

   Checking each option:

   • A. Oestrogen and ovary: Correct. The ovary (Graafian follicle) secretes oestrogen.
   • B. Oxytocin and hypothalamus: Correct. Oxytocin is made in the hypothalamus and stored and released by the posterior pituitary. Many textbooks therefore accept the hypothalamus as its source.
   • C. Adrenalin and kidney: Wrong. Adrenalin (adrenaline or epinephrine) is secreted by the adrenal medulla, part of the adrenal glands. These sit on top of the kidneys but are not the kidneys themselves. The kidney secretes other hormones, such as erythropoietin and renin.
   • D. Insulin and pancreas: Correct. The beta cells of the islets of Langerhans in the pancreas secrete insulin.

   Answer: The wrongly paired option is C, adrenalin and kidney.

   Tip: The adrenal glands are "ad-renal", meaning "next to the kidney". Being next to the kidney does not make them part of it. Remember adrenalin as the "fight or flight" hormone from the adrenal gland, not the kidney.

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9. 9.

   A vestigial structure in humans is

   1. A.earlobe
   2. B.gallbladder
   3. C.tailbone
   4. D.villus

   Show answer

   Answer: C. tailbone

   AI explanation

   Analyze the question: A vestigial structure is a body part that has lost most or all of its original function over the course of evolution. It was useful to ancestors but is now reduced or unnecessary.

   Explain the concept: Vestigial structures are evidence of evolution. Examples in humans include:

   • The appendix
   • The tailbone (coccyx)
   • Wisdom teeth
   • Body hair (goosebumps)
   • The muscles that move the ears

   Check each option:

   • A. Earlobe: This is just the fleshy lower part of the outer ear. It is not a vestigial structure in the usual sense, and it has no ancestral function that was lost.
   • B. Gallbladder: This stores bile and is still functional. It is not vestigial.
   • C. Tailbone (coccyx): This is the remnant of the tail our primate ancestors had. Humans no longer have an external tail, so the coccyx is a classic vestigial structure. (It still gives some muscle attachment support, but it has lost its original tail function.)
   • D. Villus: Villi are finger-like projections in the small intestine that absorb digested food. They are very functional.

   Answer: The tailbone is the vestigial structure, so the correct option is C.

   Exam tip: Remember that "vestigial" means "a leftover trace." If a question asks for a vestigial organ in humans, think of the appendix, coccyx (tailbone), and wisdom teeth. If the options include an organ that clearly does an active job (like the gallbladder or villi), eliminate it.

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10. 10.

    The diagrams above are illustrations of forms in which a particular group of organisms exist. Study them and answer the question. in which of the illustrated forms does the organism that causes cholera exist?

    1. A.III
    2. B.II
    3. C.IV
    4. D.V

    Show answer

    Answer: C. IV

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11. 11.

    Fishes survive in water mainly because they possess

    1. A.streamlined body
    2. B.scales
    3. C.paired fins
    4. D.gills

    Show answer

    Answer: D. gills

    AI explanation

    Analyze the question: It asks what mainly allows fishes to survive in water. Survival in water depends on being able to obtain oxygen there, so we are looking for the feature that makes this possible.

    Explain the concept: Fishes are aquatic vertebrates. Their key adaptations are:

    • Streamlined body: reduces resistance so they swim easily (aids movement).
    • Scales: protect the body and reduce friction (protection).
    • Paired fins (pectoral and pelvic): help with balance, steering and stopping (stability and movement).
    • Gills: the respiratory organs. They extract dissolved oxygen from water and release carbon dioxide (gaseous exchange).

    Step-by-step solution:

    1. Every living organism needs oxygen for respiration, and without it the organism dies.
    2. In water, oxygen is available only in dissolved form. Fishes cannot use lungs like land animals.
    3. Gills have thin, highly vascularised filaments with a large surface area. Water flows over them, and dissolved oxygen diffuses into the blood while carbon dioxide diffuses out.
    4. Streamlining, scales and fins help with movement and protection, but a fish could not stay alive without gills. Gills are therefore the main feature enabling survival in water.

    Answer: The correct option is D. gills.

    Exam tip: When a question says "survive" or "breathe" in water, think gills. When it says "move" or "swim," think streamlined body and fins. Match the function to the organ: gills = respiration, fins = balance and movement, scales = protection.

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

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

14. 14.

    The androecium in a flowering plant is a collection of

    1. A.stamens
    2. B.sperms
    3. C.ovules
    4. D.filament

    Show answer

    Answer: A. stamens

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15. 15.

    Placentation in fruits is referred to as the

    1. A.arrangement of ovules in the ovary of a flower
    2. B.part of the ovary where the ovules originate and remain till maturity
    3. C.ovules borne on a central column of tissues in an ovary
    4. D.formation of a single carpel joined at the two edges of an ovule

    Show answer

    Answer: A. arrangement of ovules in the ovary of a flower

    AI explanation

    Analyze the question: It asks for the definition of placentation, a term from flowering plant (angiosperm) reproductive structure.

    Explain the concept: The placenta is the tissue in the ovary wall to which ovules are attached. Placentation is the arrangement of ovules (and their placentae) within the ovary. Common types include:

    • Marginal: ovules along one edge of a single carpel (e.g. beans, peas)
    • Axile: ovules on a central column in a multi-chambered ovary (e.g. hibiscus, tomato, orange)
    • Parietal: ovules on the ovary wall
    • Free-central: ovules on a central column without partitions (e.g. primrose)
    • Basal: ovules at the base of the ovary
    • Apical: ovules at the top of the ovary

    Solution, option by option:

    • A. Arrangement of ovules in the ovary: this is exactly what placentation means. ✔
    • B. This describes the placenta itself (the site of attachment), not the arrangement, and "remain till maturity" is not part of the definition.
    • C. This describes only one type of placentation (axile or free-central), not placentation in general.
    • D. This describes a simple carpel and is not a definition of placentation. Also, carpels join at their edges, not "at the two edges of an ovule."

    Answer: Option A. Placentation is the arrangement of ovules in the ovary of a flower.

    Exam tip: Remember that the placenta is the place where ovules attach, while placentation is the pattern of that attachment. When a question asks for a general definition, avoid options that describe just one specific type, like option C.

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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.

    Stunted growth and small yellow leaves in plants are symptoms of the deficiencies of

    1. A.nitrogen
    2. B.iron
    3. C.sulphur
    4. D.magnesium

    Show answer

    Answer: A. nitrogen

    AI explanation

    1. Analyze the question The question gives two symptoms: stunted growth and small yellow leaves (chlorosis). We need to find the mineral whose deficiency causes both.

    2. Explain the concept Plants need mineral elements for healthy growth. Each deficiency shows a different pattern:

    • Nitrogen: It is a key part of proteins, chlorophyll, and nucleic acids. Without enough of it, the plant grows slowly (stunted growth), and the leaves turn pale green or yellow and stay small. Because nitrogen is mobile in the plant, the older leaves yellow first.
    • Iron: It is needed to make chlorophyll. Deficiency causes yellowing of the young leaves, but the veins often stay green. It is not typically linked to stunting.
    • Sulphur: The symptoms look similar to nitrogen deficiency, but the yellowing begins on the young leaves. It is less commonly the standard textbook answer.
    • Magnesium: It is the central atom of the chlorophyll molecule. Deficiency causes yellowing between the veins of older leaves (interveinal chlorosis).

    3. Solution

    • Stunted growth means protein synthesis and cell growth are poor, which points to a lack of nitrogen.
    • Small yellow leaves mean there is too little chlorophyll and the leaves have not developed fully, which also points to nitrogen.
    • Iron and magnesium cause chlorosis with particular patterns, such as interveinal yellowing, but they do not classically cause general stunting with small leaves.
    • Sulphur deficiency is possible but is not the standard answer.

    The best match is nitrogen.

    4. Answer A. nitrogen

    5. Exam tip Remember: "Nitrogen = Growth." Stunted growth plus yellowing (chlorosis) points to nitrogen. For magnesium, think "Mg = interveinal chlorosis." For iron, think "young leaves yellow."

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18. 18.

    The capturing and digestion of insects by a pitcher plant is a special form of nutrition that is

    1. A.heterotrophic
    2. B.saprophytic
    3. C.chemosynthetic
    4. D.autotrophic

    Show answer

    Answer: A. heterotrophic

    AI explanation

    Analyze the question The question asks what type of nutrition a pitcher plant uses when it captures and digests insects.

    Explain the concept

    • Autotrophic: the organism makes its own food from simple inorganic substances, usually by photosynthesis.
    • Heterotrophic: the organism depends on ready-made organic food from other organisms.
    • Saprophytic: the organism feeds on dead or decaying organic matter.
    • Chemosynthetic: the organism makes food using energy from chemical reactions, as some bacteria do.

    Solution

    1. A pitcher plant has green leaves and photosynthesizes, so it is partly autotrophic.
    2. It also traps insects in its pitcher-shaped leaves and digests them with enzymes, mainly to get nitrogen, because it grows in nitrogen-poor soil.
    3. Taking in and digesting living animals is feeding on organic food made by other organisms. That is heterotrophic nutrition, specifically the insectivorous (carnivorous) type.
    4. It is not saprophytic because the insects are captured alive, not taken from decaying matter.
    5. It is not chemosynthetic because it does not use chemical-reaction energy to make food.
    6. Autotrophic describes its photosynthesis, but not the capture and digestion of insects, which is what the question asks about.

    Answer The correct option is A. heterotrophic.

    Tip Insectivorous plants such as the pitcher plant, sundew and Venus flytrap are autotrophic and heterotrophic at once. When a question focuses on catching and digesting insects, choose heterotrophic.

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19. 19.

    The eye defect caused by an uneven curvature of the cornea or lens or both is

    1. A.myopia
    2. B.presbyopia
    3. C.astigmatism
    4. D.hypermetropia

    Show answer

    Answer: C. astigmatism

    AI explanation

    Step 1: Analyze the question The question asks which eye defect is caused by an uneven curvature of the cornea, the lens, or both.

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

    • Myopia (short-sightedness): The eyeball is too long, or the lens is too strong (too convex). Light focuses in front of the retina, so distant objects look blurred. It is corrected with a concave (diverging) lens.
    • Presbyopia: An age-related defect. The lens loses elasticity, so the eye cannot focus on near objects. It is corrected with reading glasses (convex lenses or bifocals).
    • Astigmatism: The cornea or lens is not perfectly spherical. One direction curves more than another, like the back of a spoon or a rugby ball. Light does not focus at a single point on the retina, so images look blurred or distorted. It is corrected with a cylindrical lens.
    • Hypermetropia (long-sightedness): The eyeball is too short, or the lens is too weak. Light focuses behind the retina, so near objects look blurred. It is corrected with a convex lens.

    Step 3: Match the definition "Uneven curvature of the cornea or lens or both" is exactly the description of astigmatism. The other three defects involve eyeball length or lens flexibility and strength, not an irregular curvature.

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

    Exam tip: Think of the "A" in Astigmatism as meaning "Asymmetrical" curvature. Quick guide for the other defects:

    • Myopia = Myopia, Myopic, "near is clear" (distant objects blurred)
    • Hypermetropia = "far is clear" (near objects blurred)
    • Presbyopia = Past-age (old age)

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20. 20.

    The rate of decomposition of dead organisms is faster in the tropical rainforest than in other biomes because

    1. A.of consistent cool temperature
    2. B.of availability of moisture
    3. C.of the relatively constant day light.
    4. D.there are more plants

    Show answer

    Answer: B. of availability of moisture

    AI explanation

    Step 1: Analyze the question We are asked why dead organisms decompose faster in the tropical rainforest than in other biomes.

    Step 2: The concept Decomposition is carried out mainly by bacteria and fungi (decomposers). These organisms work fastest when conditions are:

    • Warm (high temperature, which boosts enzyme activity)
    • Moist (water is needed for microbial growth and for enzyme action)
    • Well supplied with oxygen

    The tropical rainforest has high temperatures and heavy, year-round rainfall and humidity. This is why leaf litter there breaks down quickly, and nutrients are recycled fast.

    Step 3: Evaluate each option

    • A. Consistent cool temperature: Wrong. The rainforest is warm or hot, not cool. Cool temperatures slow down enzyme activity and decomposition.
    • B. Availability of moisture: Correct. Abundant rainfall and humidity keep the litter moist, so bacteria and fungi thrive and decompose dead matter rapidly.
    • C. Relatively constant daylight: Light does not directly affect decomposers, since most of them do not photosynthesize. It is not the reason.
    • D. There are more plants: More plants means more dead material, but not a faster rate of decomposition. Rate depends on the conditions for decomposers.

    Step 4: Answer The correct option is B, availability of moisture.

    Tip: Remember "Warm + Wet = Quick Rot." Whenever a question asks about the rate of decomposition, look for temperature (warm, not cool) and moisture. In this question, only B fits among the options.

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

22. 22.

    What is the probability that a pregnancy would result in a male child?

    1. A.$\frac{3}{4}$
    2. B.$\frac{1}{2}$
    3. C.1
    4. D.$\frac{1}{4}$

    Show answer

    Answer: B. $\frac{1}{2}$

    AI explanation

    Analyze the question: It asks for the chance that a pregnancy produces a boy. This is a basic sex-determination genetics question.

    Concept:

    • Humans have 23 pairs of chromosomes, including one pair of sex chromosomes.
    • Females are XX, and males are XY.
    • The mother can only give an X chromosome in her egg.
    • The father can give either an X or a Y in his sperm, with equal chance.

    Step-by-step solution (Punnett square):

    | | X (mother) | X (mother) | |---|---|---| | X (father) | XX (girl) | XX (girl) | | Y (father) | XY (boy) | XY (boy) |

    The four possible outcomes are XX, XX, XY, XY.

    • Number of male outcomes (XY) = 2
    • Total outcomes = 4

    Probability of a male child = 2/4 = 1/2

    Why the others are wrong:

    • A (3/4): there is no genetic basis for this ratio in sex determination.
    • C (1): this would mean every child is male, which is not the case.
    • D (1/4): this is the chance of a specific single genotype box, not of being male. Both XY boxes count.

    Tip: The sex of the child is decided by the father's sperm, either X or Y, each with a 50% chance. So the chance of a boy is always 1/2, and the chance of a girl is also 1/2. This holds for every pregnancy, regardless of the sex of previous children.

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

24. 24.

    The diagrams above are illustrations of forms in which a particular group of organisms exist. Study them and answer the question. Which group of organisms is illustrated?

    1. A.protozoa
    2. B.viruses
    3. C.fungi
    4. D.bacteria

    Show answer

    Answer: C. fungi

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25. 25.

    The diagrams below are illustrations of organisms in a habitat. Study them and answer the question, The feeding relationship between the organisms labelled III and IV in the diagrams is

    1. A.predation
    2. B.mutualism
    3. C.parasitism
    4. D.saprophytism

    Show answer

    Answer: B. mutualism

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

27. 27.

    Which of the following processes does not occur during photosynthesis?

    1. A.Energy from sunlight is absorbed
    2. B.Carbon (IV) oxide is evolved
    3. C.oxygen is evolved
    4. D.water is split

    Show answer

    Answer: B. Carbon (IV) oxide is evolved

    AI explanation

    Analyze the question: We need the one process that does NOT happen during photosynthesis.

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

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

    It has two stages:

    • Light stage (in the grana): Chlorophyll absorbs sunlight energy. Water is split (photolysis), releasing oxygen and hydrogen.
    • Dark stage (in the stroma): Carbon (IV) oxide is taken in (fixed) and reduced using the hydrogen to form glucose.

    Checking each option:

    • A. Energy from sunlight is absorbed: This happens. Chlorophyll traps light energy. ✔
    • B. Carbon (IV) oxide is evolved: This does not happen. CO₂ is absorbed (used up) in photosynthesis, not given off. It is evolved in respiration. ✘
    • C. Oxygen is evolved: This happens. Oxygen is released as a by-product from the splitting of water. ✔
    • D. Water is split: This happens (photolysis of water). ✔

    Answer: B. Carbon (IV) oxide is evolved is the process that does not occur during photosynthesis, because CO₂ is used up, not released.

    Tip: Remember the opposites:

    • Photosynthesis: takes in CO₂, gives out O₂
    • Respiration: takes in O₂, gives out CO₂

    When you see "evolved" in a question, ask yourself, "is this gas being given out?" For photosynthesis, only O₂ is given out.

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28. 28.

    The type of nutrition in which organisms take solid organic materials into their body is

    1. A.parasitic
    2. B.holozoic
    3. C.saprophytic
    4. D.symbiotic

    Show answer

    Answer: B. holozoic

    AI explanation

    Step 1: Analyze the question The question asks which type of nutrition involves taking solid organic food into the body (ingestion of solid food).

    Step 2: Explain the concepts

    • Parasitic: The organism lives on or in a host and gets nutrients from it, harming the host (e.g., tapeworm, mistletoe).
    • Holozoic: The organism ingests solid organic food, digests it internally, absorbs the nutrients, and egests the waste (e.g., humans, dogs, amoeba).
    • Saprophytic: The organism feeds on dead or decaying matter by secreting enzymes onto it and absorbing the dissolved nutrients (e.g., mushrooms, bread mould). It does not take in solid food.
    • Symbiotic: Two different organisms live together in a close relationship that is beneficial to both (e.g., Rhizobium in the root nodules of legumes).

    Step 3: Apply to the question Only holozoic nutrition involves taking in solid food through the mouth or cell membrane. This is followed by these stages:

    1. Ingestion
    2. Digestion
    3. Absorption
    4. Assimilation
    5. Egestion

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

    Exam tip: Think "holo = whole." Holozoic organisms take in whole pieces of food. Saprophytes only absorb dissolved food, so remember "sapro = soaks up."

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29. 29.

    Which of the following factors is the main problem facing xerophytes?

    1. A.Conservation of excess water
    2. B.competition for sunlight
    3. C.lack of adequate water
    4. D.formation of poor roots

    Show answer

    Answer: C. lack of adequate water

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30. 30.

    Which of the following characteristics shows discontinuous variation in plants?

    1. A.Colour of flower
    2. B.Leaf size
    3. C.Height of plant
    4. D.fruit size

    Show answer

    Answer: A. Colour of flower

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31. 31.

    Which of the following organisms would be the producer in a food chain?

    1. A.Goat
    2. B.maize
    3. C.man
    4. D.bacterium

    Show answer

    Answer: B. maize

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32. 32.

    Which of the following soil types have a high capillarity?

    1. A.Sand and clay
    2. B.loam and sand
    3. C.silt and sand
    4. D.silt and clay

    Show answer

    Answer: D. silt and clay

    AI explanation

    Analyze the question: Capillarity is the ability of soil to draw water upward through its tiny spaces (pores) between particles. It depends on the size of those pores.

    Explain the concept:

    • Capillarity is high when soil particles are very small, because the pores are narrow. Narrow pores pull water up strongly through adhesion and cohesion.
    • Capillarity is low when soil particles are large, because the pores are wide and water drains straight down instead of rising.

    Compare the soil types:

    • Sand: Large particles and big pores. It has high drainage and low capillarity.
    • Clay: Very fine particles and very narrow pores. It has high capillarity, though water moves slowly.
    • Silt: Fine particles, smaller than sand and larger than clay. It has high capillarity.
    • Loam: A mixture of sand, silt and clay. It has moderate capillarity.

    Check the options:

    • A. Sand and clay: sand has low capillarity, so this is wrong.
    • B. Loam and sand: sand has low capillarity, so this is wrong.
    • C. Silt and sand: sand has low capillarity, so this is wrong.
    • D. Silt and clay: both have fine particles and narrow pores, so both have high capillarity. This is correct.

    Tip: Remember "small particles, small pores, high capillarity." Sand is the odd one out because it has coarse particles. Any option containing sand is wrong when the question asks about high capillarity. You can use this to eliminate A, B and C quickly.

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33. 33.

    Use the information below to answer the question I - making shoes from crocodile skin II - making tables with plastic III - using elephant tusk for decoration IV - using firewood for cooking In order to avoid some of the acts that would have negative effects on conservation. Government should

    1. A.encourage over-utilization of forest resources
    2. B.enact and enforce laws towards conservation of resources
    3. C.encourage indiscriminate killing of wildlife
    4. D.promote felling of trees without planting new ones

    Show answer

    Answer: B. enact and enforce laws towards conservation of resources

    AI explanation

    Analyze the question: The listed activities are:

    • I. Making shoes from crocodile skin (kills wildlife)
    • II. Making tables with plastic (plastic is non-biodegradable, though it reduces timber use)
    • III. Using elephant tusk for decoration (poaching of elephants)
    • IV. Using firewood for cooking (deforestation)

    Some of these acts harm conservation, which means protecting and wisely managing natural resources. The question asks what the Government should do to avoid those harmful acts.

    Concept: Conservation is the planned management of natural resources to prevent their wasteful use, loss, or extinction. Governments achieve this mainly through legislation and enforcement, such as:

    • banning hunting of endangered species
    • creating game reserves and national parks (e.g., Yankari, Cross River National Park)
    • regulating logging and requiring replanting
    • penalizing illegal trade in animal products like ivory and skins

    Evaluate the options:

    • A. Encourage over-utilization of forest resources: This causes depletion, so it is wrong.
    • B. Enact and enforce laws towards conservation of resources: This directly discourages killing animals for skins and tusks and restricts excessive tree felling, so it is correct.
    • C. Encourage indiscriminate killing of wildlife: This leads to extinction, so it is wrong.
    • D. Promote felling of trees without planting new ones: This causes deforestation, so it is wrong.

    Options A, C, and D all work against conservation, so only B fits.

    Answer: B

    Exam tip: In conservation questions, the answer that involves laws, protection, regulation, or replanting is almost always correct. Options with words like "encourage over-use," "indiscriminate," or "without replanting" are usually distractors.

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

35. 35.

    Which of the following instruments is not used in measuring abiotic factors in a habitat?

    1. A.microscope
    2. B.Wind vane
    3. C.thermometer
    4. D.hygrometer

    Show answer

    Answer: A. microscope

    AI explanation

    Step 1: Analyze the question We need the instrument that is NOT used to measure abiotic (non-living) factors in a habitat.

    Step 2: Concept Abiotic factors are the non-living components of an environment, such as temperature, humidity, wind direction and speed, light, rainfall, and soil pH.

    Step 3: Check each option

    • A. Microscope: It magnifies tiny objects such as cells and microorganisms. It does not measure any abiotic factor. It is used to study living things (biotic).
    • B. Wind vane: It shows wind direction, which is an abiotic factor.
    • C. Thermometer: It measures temperature, which is an abiotic factor.
    • D. Hygrometer: It measures humidity (moisture in the air), which is an abiotic factor.

    Step 4: Answer The microscope is the only instrument that does not measure an abiotic factor.

    Tip: Link each instrument to what it measures:

    • Thermometer → temperature
    • Hygrometer → humidity
    • Wind vane → wind direction
    • Anemometer → wind speed
    • Rain gauge → rainfall
    • Barometer → air pressure

    The odd one out is the instrument that studies living organisms, not environmental conditions.

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36. 36.

    Use the information below to answer the question I - making shoes from crocodile skin II - making tables with plastic III - using elephant tusk for decoration IV - using firewood for cooking The act that should be encouraged for the conservation of wildlife and forests is

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

    Show answer

    Answer: C. II

    AI explanation

    Analyze the question: The question asks which act helps conserve wildlife and forests. We need the practice that does NOT harm animals or trees.

    Concept: Conservation means protecting and wisely using natural resources. Practices that kill endangered animals or cut down trees for ordinary use damage wildlife and forests. Using substitutes, such as plastic in place of wood, reduces pressure on those resources.

    Evaluating each act:

    • I. Making shoes from crocodile skin: This requires killing crocodiles, which reduces wildlife populations. It should not be encouraged.
    • II. Making tables with plastic: Plastic replaces timber, so fewer trees are felled. This protects forests, and it harms no animals. It should be encouraged.
    • III. Using elephant tusk for decoration: This encourages poaching of elephants, which are endangered. It should not be encouraged.
    • IV. Using firewood for cooking: This leads to deforestation and loss of habitat. It should not be encouraged.

    Answer: Only act II supports conservation of both wildlife and forests, so the answer is C.

    Tip: In conservation questions, look for the option that uses a substitute (like plastic, gas, or kerosene) in place of wildlife products or timber. Options that involve killing animals or cutting trees are usually the wrong ones.

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37. 37.

    Growth in animals differs from that in plants because growth in

    1. A.plants is indefinite
    2. B.plants is intercalary
    3. C.animals is apical
    4. D.plants is from within

    Show answer

    Answer: A. plants is indefinite

    AI explanation

    Step 1: Analyze the question The question asks how growth in animals differs from growth in plants. We need the statement that correctly describes a real difference.

    Step 2: Key concepts

    • Plants grow throughout their lives (indefinite or unlimited growth) because they have meristems, which are regions of actively dividing cells at the root and shoot tips (apical) and in the cambium (lateral).
    • Animals generally grow until they reach a certain adult size, after which growth stops (definite or limited growth). Growth occurs all over the body, not just at specific points.

    Step 3: Check each option

    • A. Plants is indefinite: Correct. Plants keep growing as long as they live, while animals stop growing at maturity.
    • B. Plants is intercalary: Intercalary growth does occur in some plants (for example grasses, at the nodes), but it is not the general feature of plant growth. It is not the standard distinguishing point.
    • C. Animals is apical: Wrong. Apical growth (at the tips) is characteristic of plants, not animals.
    • D. Plants is from within: Wrong. Growth in both plants and animals comes from within, through cell division and enlargement, so this does not separate them.

    Step 4: Answer The main difference is that plant growth is indefinite (continuous throughout life), whereas animal growth is definite (stops at maturity).

    Correct answer: A

    Exam tip: Remember "Plants = Perpetual, Animals = Aged-out." Plants have meristems for continuous growth, while animals stop growing at adulthood. When you see "apical" or "meristem" in an option, it is almost always linked to plants.

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38. 38.

    The tricuspid valve is located between the

    1. A.right auricle and right ventricle.
    2. B.aorta and the left ventricle
    3. C.left auricle and left ventricle
    4. D.right auricle and the superior vena cava

    Show answer

    Answer: A. right auricle and right ventricle.

    AI explanation

    Analyze the question: You're asked where the tricuspid valve sits in the mammalian heart.

    Concept: Heart valves keep blood flowing in one direction. Each valve sits between two specific chambers or vessels:

    | Valve | Location | |---|---| | Tricuspid (right atrioventricular) | Between the right atrium (auricle) and right ventricle | | Bicuspid / Mitral (left atrioventricular) | Between the left atrium (auricle) and left ventricle | | Aortic semilunar | Between the left ventricle and the aorta | | Pulmonary semilunar | Between the right ventricle and the pulmonary artery |

    Step-by-step solution:

    1. "Tricuspid" means "three flaps" (tri = three, cusp = flap). This valve is on the right side of the heart.
    2. It is an atrioventricular valve, so it lies between an auricle (atrium) and a ventricle on the same side.
    3. On the right side, that means between the right auricle and right ventricle.
    4. Checking the options: • A. Right auricle and right ventricle: correct. • B. Aorta and left ventricle: this is the aortic semilunar valve. • C. Left auricle and left ventricle: this is the bicuspid (mitral) valve. • D. Right auricle and superior vena cava: no major valve is located here.

    Answer: A

    Function: When the right auricle contracts, blood passes through the tricuspid valve into the right ventricle. When the ventricle contracts, the valve closes to prevent backflow, and blood goes to the lungs through the pulmonary artery.

    Exam tip: Remember "Tri on the Right": both have an "R" sound, and the tricuspid valve is on the right. The bicuspid (two flaps) is on the left, and "LAB" helps too: Left Atrium Bicuspid.

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39. 39.

    An example of a process that involves osmosis is the

    1. A.movement of water from root hairs into cortical cell
    2. B.reabsorption of food nutrients from the kidney into blood capillaries
    3. C.translocation of starch from leaves to all parts of a plant
    4. D.movement of digested food from ileum into blood capillaries

    Show answer

    Answer: A. movement of water from root hairs into cortical cell

    AI explanation

    Step 1: Analyze the question We need the process that involves osmosis. Osmosis is the movement of water molecules from a region of high water potential (dilute solution) to a region of low water potential (concentrated solution) through a partially permeable (selectively permeable) membrane.

    Step 2: Explain the concept Osmosis applies only to the movement of water. Movement of dissolved solutes such as glucose and amino acids usually happens by diffusion or active transport, not osmosis.

    Step 3: Check each option

    • A. Movement of water from root hairs into cortical cells: Soil water is dilute, so it has a high water potential. The cell sap of the root hair is more concentrated, and water moves from the root hair cell into the cortical cells along a water potential gradient. This is osmosis. ✔
    • B. Reabsorption of food nutrients from the kidney into blood capillaries: This involves nutrients (solutes) such as glucose, which are reabsorbed mainly by active transport. ✘
    • C. Translocation of starch from leaves: Starch is insoluble and is not translocated. Sugars (sucrose) are carried in the phloem by active, pressure-flow processes. ✘
    • D. Movement of digested food from ileum into blood capillaries: Digested food is absorbed by diffusion and active transport. ✘

    Step 4: Answer The correct option is A.

    Tip: When you see "osmosis" in an exam, look for the option that involves only water moving across a membrane. Water uptake by root hairs is the classic example. If the option mentions food, nutrients, or sugars, it is probably not osmosis.

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40. 40.

    Paternity disputes could be resolved accurately through

    1. A.finger printing
    2. B.tongue rolling
    3. C.DNA test
    4. D.blood group

    Show answer

    Answer: C. DNA test

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41. 41.

    The following activities are associated with termites except

    1. A.nuptial flight
    2. B.searching for food
    3. C.communication
    4. D.pollination

    Show answer

    Answer: D. pollination

    AI explanation

    Analyze the question: We need the activity that is NOT associated with termites. Termites are social insects that live in colonies with a caste system (king, queen, workers, soldiers, reproductives).

    Explain the concept: Termites show social organization. Each caste has its own duties, and the colony depends on cooperation.

    Go through the options:

    • A. Nuptial flight: This is true of termites. At the start of the rainy season, winged reproductives (alates) leave the colony, pair up, shed their wings, and start new colonies. This is a well-known feature in Nigeria, where the winged termites swarm around lights after the first rains.
    • B. Searching for food: This is true of termites. Worker termites forage for wood, cellulose, and plant material to feed the colony.
    • C. Communication: This is true of termites. They communicate using chemicals (pheromones), touch, and vibrations, for example to signal danger or mark food trails.
    • D. Pollination: This is not associated with termites. Pollination is typically done by bees, butterflies, moths, and other flower-visiting insects. Termites feed on dead wood and plant matter and do not carry pollen between flowers as part of their life activities.

    Answer: The activity not associated with termites is pollination, which is option D.

    Exam tip: For "except" questions, test each option against what you know about the organism. Remember termite keywords: caste system, nuptial flight, cellulose feeding, pheromones, colony. Pollination goes with bees, butterflies, and flowers.

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

43. 43.

    The ability of organisms to maintain a constant internal environment is known as

    1. A.diuresis
    2. B.plasmolysis
    3. C.endosmosis
    4. D.homeostasis

    Show answer

    Answer: D. homeostasis

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44. 44.

    Study the list of organisms below and use them to answer the questions. I-Hydra II-Owl III-Snake IV-Snail The arrangement of the organisms in order of increasing complexity is

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

    Show answer

    Answer: B. I-IV-III - II

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45. 45.

    Which of the following activities is against the conservation of natural resources?

    1. A.Contour ploughing
    2. B.establishment of game reserves
    3. C.deforestation
    4. D.afforestation

    Show answer

    Answer: C. deforestation

    AI explanation

    Step 1: Analyze the question The question asks which activity works against conservation. Conservation means protecting, managing, and using natural resources wisely so they last for future generations. So we are looking for the activity that destroys or depletes resources.

    Step 2: Explain the concept Conservation practices include:

    • Protecting soil from erosion
    • Protecting wildlife and their habitats
    • Replanting and maintaining forests
    • Using resources sustainably

    Step 3: Evaluate each option

    • A. Contour ploughing: Ploughing across the slope, not down it, reduces water runoff and soil erosion. This supports conservation.
    • B. Establishment of game reserves: These protect wildlife and their habitats from hunting and destruction. This supports conservation.
    • C. Deforestation: This is the clearing or cutting down of forests, often for farming, timber, or building. It leads to soil erosion, loss of biodiversity, habitat destruction, reduced rainfall, and increased carbon dioxide in the atmosphere. This works against conservation.
    • D. Afforestation: This is planting trees in areas that were not previously forested. It restores vegetation and protects soil and climate. This supports conservation.

    Step 4: Answer The activity against conservation is deforestation, which is option C.

    Tip: Look at the prefixes. "De-" means removal or reversal (deforestation = removing forest), while "af-" means adding to (afforestation = adding forest). In "against conservation" questions, pick the option that destroys or removes resources. Also remember that in Nigeria, deforestation contributes to erosion in the southeast and desert encroachment in the north.

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46. 46.

    The food substance that would produce the highest amount of energy is

    1. A.protein
    2. B.amino acid
    3. C.fat
    4. D.glucose

    Show answer

    Answer: C. fat

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47. 47.

    The structure that its action could result in choking when talking and eating at the same time is

    1. A.oesophagus
    2. B.epiglottis
    3. C.pharynx
    4. D.liver

    Show answer

    Answer: B. epiglottis

    AI explanation

    Analyze the question: We need the structure whose action (or failure to act) causes choking when you talk and eat at the same time.

    Concept: The pharynx (throat) is a shared passage for food and air. Below it, two tubes branch off:

    • The oesophagus (food pipe) leads to the stomach.
    • The trachea (windpipe) leads to the lungs.

    The epiglottis is a flap of elastic cartilage at the top of the trachea. When you swallow, it closes over the glottis (the opening of the trachea) so food goes into the oesophagus and not the windpipe. When you breathe or talk, it stays open to let air pass.

    Solution:

    1. Eating requires the epiglottis to close the trachea during swallowing.
    2. Talking requires air to flow through the trachea, so the epiglottis must stay open.
    3. If you talk and eat at the same time, the epiglottis may be open when food passes the pharynx. Food can then enter the trachea, and you choke and cough.

    Checking the other options:

    • A. Oesophagus: It only carries food to the stomach by peristalsis. It is not involved in choking in this way.
    • C. Pharynx: It is just the common passage. It does not control the direction of food.
    • D. Liver: It produces bile and has no role in swallowing.

    Answer: The epiglottis, which is option B.

    Tip: Remember "Epiglottis = the traffic warden of the throat". It directs food to the oesophagus and air to the trachea. If it is not in position, there is a "traffic jam" and you choke. So, no talking while eating!

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

49. 49.

    A group of organisms belonging to different species that coexist in the same habitat and interact is referred to as

    1. A.community
    2. B.biosphere
    3. C.niche
    4. D.population

    Show answer

    Answer: A. community

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50. 50.

    A sudden change in the genetic composition of an organism is termed

    1. A.mutation
    2. B.linkage
    3. C.variation
    4. D.epistasis

    Show answer

    Answer: A. mutation

    AI explanation

    Step 1: Analyze the question The question asks for the term for a sudden change in the genetic composition (genes or chromosomes) of an organism.

    Step 2: Explain the concepts

    • Mutation: A sudden, random change in the DNA sequence of a gene or in the structure or number of chromosomes. It can be spontaneous or caused by mutagens such as X-rays, UV light, or certain chemicals. Mutations are heritable if they occur in gametes.
    • Linkage: The tendency of genes located on the same chromosome to be inherited together.
    • Variation: Differences among individuals of the same species. These may come from genetic causes (including mutation) or from the environment, and they are not necessarily sudden.
    • Epistasis: An interaction in which one gene masks or suppresses the expression of another gene at a different locus.

    Step 3: Match the definition

    • "Sudden" together with "genetic composition" points directly to mutation.
    • Linkage describes inheritance patterns, not a change.
    • Variation is a broad result, not a sudden genetic event.
    • Epistasis is about gene interaction, not change in the genes themselves.

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

    Tip: Link the keyword "sudden" with "mutation." Also remember that mutation is the ultimate source of new genetic variation. Linkage means "linked together," and epistasis means "one gene masking another."

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