JAMB Biology 1994

27 reviewed questions with answers and explanations.

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Question 1

The membrane surrounding the vacuole in a plant cell is called the

  1. plasmalemma
  2. tonoplast
  3. nuclear membrane
  4. endoplasmic reticulum
Answer and explanation

B: tonoplast

The tonoplast is the membrane enclosing a plant cell vacuole. It helps control exchanges between the vacuole and cytoplasm, supporting storage, ion balance and the development of turgor pressure.

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Question 4

The soil swallowed by the earthworm to form the worm cast is ground up in the

  1. clitellum
  2. prostomium
  3. mouth
  4. gizzard
Answer and explanation

D: gizzard

The earthworm gizzard has muscular walls that grind swallowed material, often using ingested grit. The resulting material passes into the intestine, where digestion and absorption continue.

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Question 6

In Amoeba, osmoregulation is carried out by the

  1. pseudopodium
  2. food vacuole
  3. contractile vacuole
  4. nucleus
Answer and explanation

C: contractile vacuole

The contractile vacuole collects and expels excess water from a freshwater amoeba. Water enters by osmosis, and periodic expulsion helps prevent excessive swelling while maintaining internal water balance.

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Question 8

The mouthparts of a cockroach are adapted for

  1. biting and chewing
  2. suckling and chewing
  3. biting and sucking
  4. piercing and sucking
Answer and explanation

A: biting and chewing

A cockroach has mandibulate mouthparts suited to biting and chewing solid food. This differs from the piercing and sucking apparatus of a mosquito or the specialised sucking mouthparts of some other insects.

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Question 11

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Which numbered part allows efficient absorption of water and minerals?

  1. I
  2. II
  3. III
  4. IV

Question 12

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Starch is usually stored in which numbered part?

  1. I
  2. II
  3. III
  4. IV

Question 14

Which animal has the adult dental formula I 3/3, C 1/1, PM 4/4, M 2/3, where each fraction gives upper/lower counts on one side?

  1. goat
  2. rabbit
  3. man
  4. dog
Answer and explanation

D: dog

The formula gives three incisors, one canine and four premolars on each side of both jaws, with two upper and three lower molars. This is the typical adult dog formula and totals 42 teeth.

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Question 15

The nitrifying bacteria, Nitrosomonas, convert ammonia to

  1. nitrites
  2. nitric acid
  3. nitrates
  4. nitrous oxide
Answer and explanation

A: nitrites

Nitrosomonas oxidises ammonia or ammonium to nitrite in the first stage of nitrification. Other nitrifying organisms can then oxidise nitrite to nitrate, which plants can use as a nitrogen source.

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Question 16

The activity of ptyalin is likely to decrease as the concentration of which substance increases?

  1. oxygen
  2. starch
  3. protein
  4. acid
Answer and explanation

D: acid

Ptyalin is salivary amylase, which works well near neutral pH. Increasing acidity sufficiently lowers its activity because the altered chemical environment disrupts conditions needed for effective starch breakdown.

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Question 17

The phloem parenchyma is sometimes used for

  1. food storage
  2. supporting the stem
  3. production of the sieve tube
  4. transporting water
Answer and explanation

A: food storage

Phloem parenchyma consists of living cells that can store organic substances such as starch. Long-distance sugar transport mainly occurs through sieve elements, while water transport is chiefly associated with xylem.

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Question 18

A red blood cell placed in distilled water takes up water and bursts. What is the bursting and release of its contents called?

  1. osmosis
  2. plasmolysis
  3. turgidity
  4. haemolysis
Answer and explanation

D: haemolysis

Haemolysis is rupture of a red blood cell with release of its contents. Distilled water can cause this by entering the cell osmotically, but osmosis names the water movement rather than the final rupture.

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Question 22

Which respiratory waste product can leave plant tissues through stomata and lenticels?

  1. Carbon dioxide
  2. Alkaloids
  3. Tannins
  4. Anthocyanins
Answer and explanation

A: Carbon dioxide

Carbon dioxide produced during respiration can diffuse out of plant tissues through stomata and lenticels. These openings exchange gases; non-volatile compounds such as tannins and alkaloids do not leave through them as respiratory gases.

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Question 25

In animals, meiosis comes

  1. after fertilization
  2. after every mitotic division
  3. before fertilization
  4. before every mitotic division
Answer and explanation

C: before fertilization

In the usual animal sexual life cycle, meiosis produces haploid gametes before fertilisation. Fertilisation then combines two gametes and restores the diploid chromosome number in the zygote.

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Question 26

The fleshy base of a flower to which the different floral parts are attached is known as

  1. calyx
  2. sepals
  3. thalamus
  4. hypothalamus
Answer and explanation

C: thalamus

The thalamus, also called the floral receptacle, is the enlarged end of the flower stalk on which floral organs are borne. The calyx consists of sepals, while the hypothalamus is a part of the vertebrate brain.

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Question 27

When a short-sighted person views a distant object without spectacles, the image is formed

  1. on the retina
  2. in front of the retina
  3. behind the retina
  4. on the blind spot
Answer and explanation

B: in front of the retina

In myopia, parallel rays from a distant object are brought to a focus in front of the retina when the eye is uncorrected. The light is therefore out of focus when it reaches the retinal surface.

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Question 28

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The graph compares body temperature with external temperature for a dog and a lizard. Which deduction is supported over the plotted range?

  1. Lizards are more likely to survive hazards than dogs
  2. Both animals maintain a constant body temperature
  3. The dog’s body temperature is approximately independent of the external temperature
  4. The lizard’s body temperature varies with that of the dog

Question 29

The part of the brain that controls heart beat and breathing is the

  1. olfactory lobe
  2. cerebellum
  3. cerebral hemisphere
  4. medulla oblongata
Answer and explanation

D: medulla oblongata

The medulla oblongata contains centres involved in regulating breathing and cardiovascular activity. These support vital involuntary functions, working with other brain regions and sensory feedback.

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Question 30

In one habitat the listed constituents are: 1. Mango; 2. Speargrass; 3. Goat; 4. Sheep; 5. Temperature; 6. Beans; 7. Rock; 8. Water. Items 1–4 together can be regarded as

  1. a population
  2. a community
  3. an ecosystem
  4. a niche
Answer and explanation

B: a community

A community consists of populations of different species living in the same area. Mango, speargrass, goats and sheep represent different living species, whereas an ecosystem also includes their physical surroundings.

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Question 32

Which set contains typical decomposers that break down dead organic matter by extracellular digestion?

  1. Rhizopus, earthworm and protozoa
  2. Mushrooms, Rhizopus and bacteria
  3. Bacteria, earthworm and nematodes
  4. Earthworm, sedges and platyhelminthes
Answer and explanation

B: Mushrooms, Rhizopus and bacteria

Many fungi, including mushrooms and Rhizopus, and many bacteria release enzymes onto dead organic material and absorb the breakdown products. This external digestion makes them major decomposers in ecosystems.

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Question 33

Which order represents the food chain for (1) grasses, (2) hawks, (3) snakes, (4) grasshoppers and (5) lizards, with arrows from food to consumer?

  1. 1 → 2 → 3 → 4 → 5
  2. 5 → 4 → 3 → 2 → 1
  3. 1 → 4 → 5 → 3 → 2
  4. 3 → 2 → 4 → 5 → 1
Answer and explanation

C: 1 → 4 → 5 → 3 → 2

The represented chain starts with grasses, followed by grasshoppers that eat them, lizards that eat grasshoppers, snakes that eat lizards and hawks that eat snakes. Food-to-consumer arrows preserve this feeding order.

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Question 37

In the classical model, ecological succession leads toward a relatively stable

  1. niche
  2. population
  3. pioneer community
  4. climax community
Answer and explanation

D: climax community

In the classical model of succession, a climax community is a relatively stable community reached after successive changes in species composition. Continued stability depends on environmental conditions and disturbance.

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Question 38

In a drought situation, plants suffer from water stress which could result in

  1. reduced biochemical activities
  2. enhanced chemical activities
  3. enhanced microbial activities
  4. reduced phototropic activities
Answer and explanation

A: reduced biochemical activities

Water stress can reduce photosynthesis and other biochemical activities, slowing plant growth. Stomatal closure limits water loss but can also reduce carbon dioxide entry, while dehydration affects cellular processes.

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Question 41

The differences and similarities among living things account for

  1. diversity
  2. stability
  3. competition
  4. evolution
Answer and explanation

A: diversity

Diversity describes the variety among living organisms, including differences in structures, functions and inherited characteristics. Shared features also help organise organisms into related groups.

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Question 43

In a simplified autosomal model, brown allele B is dominant to blue allele b. A BB girl has a bb brother. What are their parents’ eye-colour phenotypes in this model?

  1. Both parents have blue eyes
  2. Their father has blue eyes and their mother has brown eyes
  3. Both parents have brown eyes
  4. Their mother has blue eyes and their father has brown eyes
Answer and explanation

C: Both parents have brown eyes

In the stated single-gene model, a BB child must receive B from each parent, while a bb child must receive b from each. Both parents must therefore be Bb and show the dominant brown-eye phenotype in this model.

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Question 45

Which inherited condition commonly follows an X-linked pattern and impairs blood clotting?

  1. anaemia
  2. anorexia
  3. haemophilia
  4. haemolysis
Answer and explanation

C: haemophilia

Haemophilia is an inherited bleeding disorder caused by deficiency of particular clotting factors. Common forms are X-linked and can cause prolonged bleeding, though the severity varies among affected people.

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Question 47

Breathing root is an adaptation for survival in the

  1. mangrove swamp
  2. desert
  3. arboreal habitat
  4. savanna
Answer and explanation

A: mangrove swamp

Breathing roots, or pneumatophores, project above waterlogged soil and allow gas exchange with the air. They help certain mangroves obtain oxygen when the surrounding mud has little available oxygen.

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Question 50

Which homologous anatomical pattern supports common ancestry among whales, humans, birds and dogs?

  1. thick skin
  2. the underlying pentadactyl limb pattern, modified in different groups
  3. tail
  4. epidermal structures
Answer and explanation

B: the underlying pentadactyl limb pattern, modified in different groups

The shared underlying limb pattern in these vertebrates is evidence of common ancestry. The structures have been modified for swimming, grasping, flying or running, but comparable bones remain recognisable.

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