JAMB Biology 2004

C: increase in solute concentration in the guard cells

An increase in guard-cell solute concentration lowers water potential. Water enters by osmosis, turgor rises and the guard cells bow apart, opening the pore.

A: contains selectively permeable cell membranes

Living yam tissue contains selectively permeable cell membranes. These permit osmotic water movement while restricting solute movement, which is the property used in this demonstration.

C: dicot stem and monocot roots

A typical dicot stem has vascular bundles around a central pith, and a typical monocot root also has a broad central pith. Monocot stems generally have scattered bundles without the same distinct pith region.

D: prolactin

Prolactin stimulates milk synthesis in mammary glands. Milk supply also depends on effective milk removal and other factors, so low production alone does not diagnose a hormone deficiency.

C: lipases

Lipases hydrolyse fats into smaller products, including fatty acids and monoglycerides during digestion. They are a specific type of hydrolase, the broader class of enzymes that break bonds using water.

D: Na⁺ and K⁺

In a typical neurone action potential, sodium entry depolarises the membrane and potassium exit helps repolarise it. The relevant cations are Na+ and K+.

A: anther

II points to the pollen-bearing tip of a slender stalk: the anther. The filament supports the anther, while the style and stigma belong to the central female structure.

C: II to III

Pollination transfers pollen from an anther to a stigma. In this figure, II indicates an anther and III the stigma, so the transfer is from II to III.

D: a net 2 ATP molecules and alcohol

Alcoholic fermentation in yeast allows glycolysis to continue without oxygen. Glycolysis provides a net two ATP per glucose; fermentation produces ethanol and carbon dioxide while regenerating NAD+.

B: budding

Hydra and yeast can both reproduce by budding. A new outgrowth develops on the parent and can eventually separate, producing a new individual without fusion of gametes.

B: more rapid elongation of the hypocotyl than the epicotyl

During epigeal emergence, elongation of the hypocotyl raises the cotyledons above the soil. In hypogeal emergence, the cotyledons remain below ground while growth above them becomes prominent.

D: provides an aqueous medium for metabolic reactions

Water provides an aqueous medium in which many metabolic reactants dissolve and interact. It also participates in reactions and helps regulate temperature; it is not the cell’s main energy source.

A: capillaries

Pulmonary capillaries form a fine network around alveoli. Their thin walls and close contact with the alveolar surface allow oxygen and carbon dioxide to diffuse between air and blood.

C: the same egg and sperm

Identical, or monozygotic, twins develop when a single fertilised egg gives rise to two embryos. They therefore originate from the same egg and sperm, although later mutations can create small genetic differences.

A: DNA analysis

DNA analysis compares inherited genetic markers and can assess whether a proposed parent is genetically compatible with a child. Ordinary fingerprints, tongue rolling and blood groups provide far less discriminatory information.

B: pink

With incomplete dominance, crossing true-breeding red and white four-o’clock plants produces pink heterozygous offspring. The intermediate phenotype does not mean the inherited alleles blend permanently.

B: cells

Rods are specialised photoreceptor cells in the retina. They are particularly sensitive in dim light and are individual cells within retinal tissue, not whole organs or organ systems.

C: wriggler

A mosquito larva is commonly called a wriggler because of its movement in water. The pupal stage is often called a tumbler, and the adult is the flying stage.

D: cell walls that are rigid and contain chitin

Fungal hyphae usually have rigid cell walls containing chitin. Some hyphae are divided by septa, while others are coenocytic and contain many nuclei without complete cross walls.

C: chisel-like front teeth

Rodents gnaw with their chisel-shaped incisors at the front of the mouth. These teeth grow continuously and are maintained by wear; the cheek teeth mainly grind food.

A: palaeontology

Palaeontology studies fossils, providing direct evidence of extinct organisms. Comparing fossil features with living organisms helps reconstruct evolutionary relationships and changes through time.

D: storing water in large parenchyma cells

Some plants store water in enlarged parenchyma cells, allowing them to endure dry periods. This is one drought-survival strategy, alongside other features that reduce water loss.

D: clayey

Wet clay-rich soil tends to be sticky and plastic because of its fine particles and water retention. These properties can make cultivation difficult; working it when too wet can also damage soil structure.

C: keratinous scales

The keratinised outer covering of reptiles forms a barrier that helps reduce water loss. This supports life on land, although reptiles still lose water and need suitable sources or conservation strategies.

B: raising the mortality rate

Severe food shortage can raise mortality, directly removing individuals and reducing population size. A lower reproductive rate reduces additions, whereas immigration adds individuals.

A: mutualism

In termites that harbour these protozoans, the microorganisms help break down cellulose and obtain food and a protected habitat in the gut. Both partners benefit, making the association mutualistic.