JAMB Biology 1987

28 reviewed questions with answers and explanations.

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Question 3

A growth on a bare rock consists of a fungus associated with a photosynthetic alga. It is a

  1. Plant epiphyte
  2. Lichen
  3. Bryophyte
  4. Fern
Answer and explanation

B: Lichen

A lichen is an association involving a fungus and a photosynthetic partner, commonly an alga or cyanobacterium. It is not a single plant combining plant and fungal organs. Bryophytes and ferns are distinct land-plant groups.

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Question 4

In a plant life cycle with alternation of generations, the diploid multicellular generation is the

  1. Gametophyte
  2. Spermatophyte
  3. Holophyte
  4. Sporophyte
Answer and explanation

D: Sporophyte

The sporophyte is the diploid multicellular generation and produces haploid spores by meiosis. Spores develop into the haploid gametophyte generation, which produces gametes. Fertilisation restores the diploid stage.

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Question 7

A reproductive function of the earthworm clitellum is to

  1. Aid digestion
  2. Prevent drying of the whole body
  3. Assist locomotion
  4. Secrete a cocoon
Answer and explanation

D: Secrete a cocoon

The clitellum is a glandular band that secretes material forming a cocoon. Eggs and sperm enter this structure, which supports reproduction and early development. Movement instead depends mainly on body-wall muscles and anchoring bristles.

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Question 8

Which crayfish feature is characteristic of the arthropod body covering?

  1. A cephalothorax and an abdomen
  2. Antennae and antennules
  3. A pair of appendages on every segment
  4. A chitin-containing exoskeleton
Answer and explanation

D: A chitin-containing exoskeleton

Arthropods have a chitin-containing exoskeleton that supports and protects the body and provides attachment for muscles. A crayfish also has specialised crustacean features, but the body covering is the feature requested here.

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Question 10

In many true ferns, sporangia are grouped into clusters called

  1. Indusia
  2. Fronds
  3. Prothalli
  4. Sori
Answer and explanation

D: Sori

A sorus is a cluster of sporangia, and sori is the plural. An indusium may cover a sorus in some ferns. A frond is a fern leaf, while a prothallus is the small gametophyte generation.

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Question 11

Why is a film of water needed for fertilisation in mosses?

  1. Because their habitat is moist
  2. Because water is needed, without any further mechanism
  3. Because the male gametes swim to the egg
  4. Because spores are produced
Answer and explanation

C: Because the male gametes swim to the egg

Moss sperm have flagella and move through a film of water to reach the egg in an archegonium. This explains the water requirement for fertilisation. Producing or dispersing spores is a different stage of the life cycle.

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Question 12

Which two systems have longitudinal structures extending along a tapeworm’s body?

  1. Nerve cords and excretory canals
  2. Sperm ducts and nerve cords
  3. Genital pores and excretory canals
  4. Sperm ducts and genital pores
Answer and explanation

A: Nerve cords and excretory canals

Longitudinal nerve cords and excretory canals extend through the tapeworm’s chain of segments. Reproductive ducts and genital openings belong to the repeated reproductive units rather than forming the same pair of continuous longitudinal systems.

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Question 14

In a butterfly species whose larvae feed on crop leaves, which stage causes the feeding damage?

  1. Maggot
  2. Nymph
  3. Caterpillar
  4. Pupa
Answer and explanation

C: Caterpillar

A butterfly larva is a caterpillar and commonly feeds actively on plant tissue. A pupa is the transforming stage and generally does not feed. Maggot describes many fly larvae, while nymph is used for immature stages in insects with incomplete metamorphosis.

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Question 16

Secondary thickening of a typical dicot stem is driven by the activity of the

  1. Xylem parenchyma alone
  2. Secondary phloem alone
  3. Endodermis
  4. Cambium
Answer and explanation

D: Cambium

The vascular cambium divides to produce secondary xylem towards the inside and secondary phloem towards the outside. This increases stem girth. Cork cambium also contributes to the protective outer tissues during secondary growth.

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Question 17

Why is a plant nutrient-culture bottle covered with an opaque material during a mineral-nutrition experiment?

  1. To prevent algal growth in the nutrient solution
  2. To make root growth possible only in complete darkness
  3. To stop mineral elements breaking down in light
  4. To prevent ordinary roots from carrying out photosynthesis
Answer and explanation

A: To prevent algal growth in the nutrient solution

Blocking light from the nutrient solution suppresses photosynthetic algae. Algae could otherwise use dissolved nutrients and change the culture conditions, interfering with the plant experiment. The covering need not exclude light from the plant’s leaves.

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Question 18

The vitamin which is important in the formation of the retina pigments is

  1. vitamin A
  2. vitamin B
  3. vitamin C
  4. vitamin D
Answer and explanation

A: vitamin A

Vitamin A supplies retinal, the light-sensitive component of visual pigments such as rhodopsin. Light changes retinal shape and starts a photoreceptor response.

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Question 19

Which list contains only structures directly involved in digestion or absorption?

  1. Oesophagus, bronchus, stomach, pancreas and anus
  2. Spleen, pharynx, duodenum, jejunum and rectum,
  3. Teeth, oesophagus, ileum lungs and large intestine,
  4. Salivary gland, liver, stomach, villi and colon
Answer and explanation

D: Salivary gland, liver, stomach, villi and colon

Salivary glands and liver supply digestive secretions; the stomach processes food, villi support absorption and the colon absorbs water. Other lists contain non-digestive structures.

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Question 20

In an aquatic-plant experiment demonstrating oxygen release during photosynthesis, sodium bicarbonate is added mainly to

  1. neutralize the acid in water
  2. supply mineral salts to water plant,
  3. supply carbon dioxide for photosynthesis
  4. Kill micro-organism in water
Answer and explanation

C: supply carbon dioxide for photosynthesis

Bicarbonate supplies dissolved inorganic carbon that can replenish carbon dioxide consumed during photosynthesis. This helps prevent carbon shortage limiting the oxygen-release demonstration.

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Question 22

In a typical eukaryotic cell, oxidative phosphorylation in cellular respiration takes place in the

  1. mitochondria
  2. ribosomes
  3. endoplasmic reticulum
  4. Golgi bodies
Answer and explanation

A: mitochondria

The respiratory electron-transport chain and ATP synthase are in the inner mitochondrial membrane. Glycolysis is a separate stage in the cytosol; ribosomes make proteins.

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Question 24

The function of the loop of Henle is to

  1. increase the flow of urine
  2. concentrate amino acids in the kidney tissue
  3. build up sodium chloride in the medullary interstitial fluid
  4. increase the volume of urine
Answer and explanation

C: build up sodium chloride in the medullary interstitial fluid

The loop of Henle helps establish a medullary osmotic gradient. Salt leaves the ascending limb while that segment resists water movement; the gradient supports water recovery.

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Question 27

The principal mechanical effect of lignifying sclerenchyma cell walls is to

  1. strengthen and support the plant
  2. transport synthesized food
  3. conduct water and salt
  4. protect the plant from injury
Answer and explanation

A: strengthen and support the plant

Lignin makes thick secondary walls rigid and strong. Sclerenchyma fibres and sclereids consequently provide mechanical support. Water conduction and food transport are distinct functions.

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Question 32

Cultivated plantain is commonly propagated using developed basal shoots called

  1. suckers
  2. buds
  3. fragments
  4. spores
Answer and explanation

A: suckers

Plantain suckers develop from the underground stem and can be separated as planting material. A sucker originates from a bud, but the developed propagating shoot is called a sucker.

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Question 33

Which measurement best estimates increasing biomass in a Spirogyra population while excluding changes in water content?

  1. total lengths of the filaments
  2. total widths of the filaments
  3. rate of photosynthesis in the population
  4. dry mass of the population
Answer and explanation

D: dry mass of the population

Dry mass excludes variable water content and estimates accumulated biomass. Filament dimensions measure size, while photosynthesis rate measures activity rather than material already present.

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Question 34

Which cell type is generally unable to re-enter ordinary mitotic division?

  1. activated lymphocytes
  2. mature neurons
  3. dividing Malpighian-layer cells
  4. germ-line precursor cells
Answer and explanation

B: mature neurons

Most mature neurons are post-mitotic and do not divide to replace themselves. Neural stem cells can form new neurons in some contexts, but those precursors differ from mature neurons.

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Question 36

The growth of a coleoptile towards unilateral light source is due to

  1. rapid rate of photosynthesis
  2. unequal distribution of auxin
  3. the effect of geotropism
  4. the effect of photolysis
Answer and explanation

B: unequal distribution of auxin

Unilateral light can produce unequal auxin distribution across a shoot. Greater elongation on the shaded side bends the coleoptile towards light; this requires differential growth.

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Question 37

Starting at the oval window and moving towards the eardrum, the ossicles are

  1. malleus, incus and stapes
  2. malleus, stapes and incus
  3. stapes, incus and malleus
  4. stapes, malleus and incus
Answer and explanation

C: stapes, incus and malleus

The stapes footplate meets the oval window; the stapes connects to the incus, and the incus to the malleus at the eardrum. Sound normally travels in the opposite direction.

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Question 38

The centre for controlling body temperature in the brain is the

  1. cerebrum
  2. cerebellum
  3. medulla
  4. hypothalamus
Answer and explanation

D: hypothalamus

The hypothalamus integrates temperature information and coordinates sweating, shivering and skin blood-flow changes. These adjust heat loss and production to maintain body temperature.

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Question 42

RRYY (round, yellow) is crossed with rryy (wrinkled, green). With complete dominance of R and Y, all offspring seeds are

  1. blue and wrinkled
  2. round and yellow
  3. wrinkled and yellow
  4. round and greenish-yellow
Answer and explanation

B: round and yellow

The RRYY parent forms RY gametes and the rryy parent forms ry gametes. Every offspring is RrYy. Complete dominance of R and Y produces round shape and yellow colour.

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Question 44

For X-linked recessive red–green colour-vision deficiency, which cross produces affected daughters only?

  1. affected mother × affected father
  2. affected mother × unaffected father
  3. carrier mother × affected father
  4. carrier mother × unaffected father
Answer and explanation

A: affected mother × affected father

An affected mother gives an affected X allele to every child; an affected father gives his affected X to every daughter. Thus all daughters receive two affected alleles.

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Question 45

Which of the following relates to edaphic factors?

  1. The structure of the earth’s surface
  2. The influence of living organisms on each other
  3. Temperature, rainfall and humidity
  4. The influence of soils on plants and animals
Answer and explanation

D: The influence of soils on plants and animals

Edaphic factors concern soil properties such as texture, pH, moisture and nutrient availability. They affect organisms living in or supported by soil, and differ from climatic or topographic factors.

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Question 46

An epiphyte uses a tree branch for support without taking nutrients from or significantly harming the tree. This relationship is

  1. parasitism
  2. commensalism
  3. saprotrophy
  4. holophytism
Answer and explanation

B: commensalism

An epiphyte gains a place to grow while its supporting tree is largely unaffected. This is commensalism. It obtains its own resources rather than taking nutrients from the living host tissue.

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Question 47

Poliomyelitis is an infectious disease caused by

  1. virus
  2. protozoan
  3. bacterium
  4. fungus
Answer and explanation

A: virus

Poliovirus causes poliomyelitis. It can invade the nervous system and cause paralysis in some infections. It is a virus rather than a bacterium, protozoan or fungus.

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Question 49

Nitrifying bacteria are important because they

  1. release nitrogen to the atmosphere
  2. convert Atmosphere nitrogen to ammonia
  3. combine ammonia with nitrogen
  4. oxidise ammonium through nitrite to nitrate
Answer and explanation

D: oxidise ammonium through nitrite to nitrate

Nitrification oxidises ammonium first to nitrite and then nitrate. Different microbial groups can perform the steps. Fixation introduces atmospheric nitrogen; denitrification can return nitrogen gas to air.

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