JAMB Biology 1991

C: secretion

Label 5 indicates the curved membrane stack of the Golgi apparatus. It modifies and sorts cellular products and packages them into vesicles, including vesicles that take secreted products to the cell surface.

D: spermatophyta

Angiosperms and gymnosperms are seed plants, traditionally grouped as Spermatophyta. Flowering plants enclose seeds within fruits, while gymnosperms have seeds not enclosed in an ovary-derived fruit.

D: lenticels

Breathing roots project into air above oxygen-poor soil or mud. Lenticels allow gases to pass between the atmosphere and internal tissues, supporting respiration in the submerged root system.

C: feeding

Maxillipeds are appendages near a crayfish’s mouth that handle food and help move it toward the mouthparts. Their position and specialisation distinguish them from walking legs and swimming appendages.

B: mantle

In a typical air-breathing land snail, the vascularised mantle cavity acts as a lung. Gas exchange occurs across its moist lining; the radula scrapes food, and the muscular foot is used for movement.

A: feeding

Label 4 points to the coiled digestive tract within the tadpole. This structure processes food and supports nutrient absorption, so it belongs to the feeding system rather than the respiratory or attachment system.

B: becomes shorter

Label 5 indicates the tadpole’s tail. During metamorphosis into the adult frog or toad, this tissue is resorbed and the tail becomes shorter. The hind limbs develop separately rather than being made by conversion of the tail.

A: feeding

Gill rakers help retain food and prevent it from escaping through the gill openings. In filter-feeding fish they can trap small particles. The thin gill filaments and lamellae, rather than the rakers, provide the main gas-exchange surface.

C: liver

The liver is an accessory digestive organ because it produces bile that helps emulsify fats in the small intestine. Food does not pass through the liver itself; bile enters the digestive tract through ducts.

A: hydrogen

Proteins, carbohydrates and lipids all contain hydrogen, along with carbon and oxygen. Nitrogen is characteristic of proteins but not ordinary carbohydrates, while sulphur and phosphorus are not present in every member of all three classes.

D: enamel

Enamel forms the hard outer covering of the crown of a typical mammalian tooth. Dentine lies beneath it, and cementum covers the root. Dental caries is tooth decay rather than a normal covering tissue.

B: lactic acid (lactate)

When oxygen supply is insufficient for aerobic demand, human muscle cells can convert pyruvate to lactate. This regenerates NAD+ so glycolysis can continue producing a limited amount of ATP from glucose.

D: Reduced humidity

Lower atmospheric humidity generally steepens the water-vapour gradient between a moist leaf and the air, increasing transpiration when stomatal opening and other conditions remain unchanged. Humid air reduces that gradient.

B: rise in Y only

Water moves through the membrane from the weaker sugar solution in X toward the stronger solution in Y. Sugar remains separated, so the liquid level in Y rises while that in X falls until pressure effects balance the net movement.

B: osmosis

Osmosis is net movement of water across a selectively permeable membrane down its water-potential gradient. With equal starting levels, the stronger sugar solution has lower water potential and receives water from the weaker solution.

B: clotting of blood

Prothrombin is converted into thrombin during coagulation. Thrombin converts soluble fibrinogen into fibrin, which forms a mesh helping stabilise the blood clot. These proteins therefore participate in clotting.

C: pulmonary artery

The pulmonary artery leaves the right ventricle and divides into branches carrying relatively deoxygenated blood to the lungs. Pulmonary veins return oxygenated blood to the left atrium after gas exchange.

B: a taxis

Taxis is a directional movement of an entire motile organism or cell in response to a stimulus. It may be toward a favourable stimulus or away from an unfavourable one, unlike growth bending of a rooted plant part.

A: Atlas

The atlas is the first cervical vertebra. It is ring-shaped and lacks the typical vertebral body or centrum. The axis has a body and dens, while thoracic and lumbar vertebrae also have distinct vertebral bodies.

C: crossing over

Crossing over exchanges corresponding DNA segments between non-sister chromatids of homologous chromosomes during meiosis. It produces new allele combinations without being the same process as a test cross or a new mutation.

A: the physical and biotic environment

An organism’s environment includes both abiotic conditions and living organisms. Food, water, temperature, predators and competitors influence life in a habitat, but each is only part of the complete environmental setting.

C: producers and consumers

Producers make organic material from inorganic resources, while consumers obtain organic material from other organisms or their products. These broad feeding roles organise energy flow through an ecosystem. Decomposers are heterotrophs too.

B: II was wiped out from the environment at the end of the experiment

Curve II rises at first and then reaches the horizontal axis, indicating zero organisms at the end of the observation. Curve I begins at the same level, rises and remains above zero, so only II disappears from the observed community.

A: root nodules

Legumes form root nodules containing symbiotic nitrogen-fixing bacteria. The plant supplies carbon compounds, while the bacteria convert atmospheric nitrogen into forms that can enter the plant’s nitrogen metabolism.