JAMB Biology 2003

C: pileus

The pileus is the expanded cap of a typical mushroom. The stipe supports it, while the mycelium is the network of fungal hyphae and a basidium is a microscopic spore-producing cell.

A: evaporation and osmosis

Water can evaporate from a frog’s moist skin exposed to air. Water can enter the submerged skin by osmosis when the surrounding water has a higher water potential than the body fluids.

D: kingdom

A kingdom is the broadest taxonomic rank listed and contains organisms from many lower groups. Members of a species are generally much more similar than members of the same kingdom.

A: ribosome

Prokaryotic cells contain ribosomes that synthesise proteins. They lack a membrane-bound nucleus and the mitochondria and chloroplasts characteristic of eukaryotic cells.

B: embryo disc

In a fertilised bird egg, early embryonic cells form a disc on the yolk surface. The yolk supplies nutrients, while the chalazae support the yolk and albumen surrounds it.

A: transpiration occurs through the leaves

The leafy shoot produces water vapour that condenses on the jar. Comparison with the leafless shoot supports water loss through leaves, while the oil limits evaporation directly from the beaker.

C: Evaporation

The oil layer covers the free water surface in each beaker, reducing direct evaporation. This helps distinguish water released by the shoot from water evaporating from the container.

C: xylem

Water absorbed by a plant moves upward mainly through xylem. A suitable dissolved dye can follow that water stream and stain the conducting xylem tissues.

B: compatible Rhizobium bacteria

Compatible Rhizobium bacteria can form nitrogen-fixing nodules on legume roots. They convert atmospheric nitrogen into compounds that can support the plant’s nitrogen nutrition.

B: IV

The ratios correspond to 0.5, about 0.33, 0.25 and 0.20 units of surface area per unit volume. IV has the least exchange surface relative to its volume and therefore the greatest transport challenge on this criterion.

C: the part played by the pleural cavity and diaphragm in respiration

Pulling the sheet down increases the enclosed volume and lowers pressure, so air enters and expands the sacs. The model illustrates the mechanical role of diaphragm movement and a sealed chest space in ventilation.

A: diaphragm

The movable rubber sheet represents the diaphragm. Pulling it downward increases the space inside the jar, modelling how diaphragm contraction increases thoracic volume during inhalation.

C: Ethylene

Ethylene promotes ripening in many climacteric fruits. It can trigger changes in texture, colour and aroma, although ripening control differs among fruit types.

D: liver

The liver converts nitrogenous products of amino-acid breakdown into urea. Urea then circulates to the kidneys for excretion; the bladder mainly stores urine.

D: urethra

The male urethra provides a route for urine and also for semen at different times. The ureters carry urine to the bladder, while the vas deferens transports sperm toward the ejaculatory pathway.

A: stem cuttings

Sugarcane is commonly propagated using pieces of stem containing viable buds. The buds produce shoots and roots, preserving the selected variety through vegetative propagation.

A: nastic movement

Nastic movement responds to a stimulus without its direction being determined by the direction from which the stimulus comes. This differs from directional growth responses such as phototropism and gravitropism.

A: peripheral and central nervous systems

Neurones occur in both the central and peripheral nervous systems. The illustrated cell has a body, branched processes and a long insulated process, features not restricted to only one of those divisions.

C: node of Ranvier

I marks a gap between successive insulating segments along the long process. Such gaps are nodes of Ranvier, where the membrane can regenerate an action potential during saltatory conduction.

A: meiosis

Homologous chromosomes separate during the first meiotic division. Sister chromatids separate later in meiosis II; in ordinary mitosis it is sister chromatids rather than homologous pairs that separate.

D: maize grain

A maize grain is a caryopsis, a dry one-seeded fruit with the fruit wall fused to the seed coat. This close fusion is characteristic of cereal grains.

A: roots of higher plants

Mycorrhizae are associations between fungi and plant roots. The fungus can improve uptake of water and minerals, while receiving carbon compounds from the plant.

B: Sahel savanna → Sudan savanna → Guinea savanna → tropical rain forest → estuarine

Across the broad north-to-south climatic gradient, Nigerian vegetation passes from drier savanna zones toward wetter forest and coastal environments. Sahel, Sudan and Guinea savannas precede tropical rain forest and estuarine areas in that order.

D: coal

Coal forms from ancient organic material altered by burial, heat and pressure over geological time. It is therefore a fossil fuel, unlike freshly cut firewood.

D: sexual

Sexual reproduction combines genetic material from parents and involves meiotic processes that reshuffle alleles. This creates new combinations among offspring, although mutations can also generate variation in asexual lineages.

C: AGT

DNA base pairing matches thymine with adenine and cytosine with guanine. Written opposite 5′-TCA-3′, the complementary strand is 3′-AGT-5′.

D: reduce water loss

Sunken stomata and folded leaves can shelter moist air near exchange surfaces. This reduces exposure to moving dry air and can lower transpiration and water loss.

A: physical defence

Spines can make an animal difficult to grasp or swallow, and shells form a protective barrier. Both provide physical defence against injury or predation.

A: aestivation

Aestivation is a dormant state associated with hot or dry conditions. It reduces activity and metabolic demand when heat or water shortage makes normal activity difficult.