JAMB Biology 1985

B: Whistling pine

Whistling pine, a Casuarina tree, produces seeds. Despite its common name, it is a flowering plant rather than a true pine. Mosses, liverworts and ferns reproduce by spores rather than seeds, and the listed algal filament is not a seed plant.

C: Snail

A snail belongs to the molluscs. The other animals are arthropods, which share a segmented body, a cuticular exoskeleton and jointed appendages. A shell alone does not make an animal an arthropod.

E: Lateral line

The lateral-line system contains mechanosensory receptors that respond to nearby water movement and vibration. It helps a fish detect surrounding disturbances. Gills exchange gases, the operculum covers the gills, and nostrils are associated with smell.

D: Can manufacture its own organic food

In suitable light, a photosynthetic Euglena uses light energy to make organic food from carbon dioxide. This is autotrophic nutrition. Some Euglena are mixotrophs and can also obtain organic nutrients from their environment.

A: Contains chlorophyll

Mucor is a fungus and does not contain chlorophyll. It obtains nutrients by external digestion and absorption. Its body consists of hyphae; sporangia produce asexual spores, and compatible hyphae can participate in sexual reproduction.

E: Lack true vascular tissues

Bryophytes lack the true xylem and phloem of vascular plants. Flowering plants possess these tissues. Moist habitats, small size and both modes of reproduction are not unique to bryophytes; some mosses have specialised conducting cells without true vascular tissue.

D: Rhizoids

Rhizoids help anchor a moss to its substrate. They are not true roots and do not provide the same vascular transport system. Much water absorption in mosses occurs across the plant surface rather than through a root system.

C: Above the phloem, towards the upper leaf surface

The xylem is usually on the upper, or adaxial, side of a typical leaf vascular bundle, with phloem towards the lower side. Xylem delivers water and mineral ions; phloem transports sugars and other organic substances.

B: Central pith

A typical young dicot stem has vascular bundles arranged around central pith. A typical monocot root also has pith at its centre, surrounded by vascular tissues. Cortex width and the arrangement of rays or fibres do not provide the same shared defining comparison.

B: Impaired skeletal growth

Calcium is a major mineral component of bone. Inadequate calcium can impair normal bone mineralisation and skeletal development. This effect differs from the classic deficiency associations of iron with anaemia, iodine with goitre and thiamine with beriberi.

A: Chyme

Chyme is the semifluid mixture formed as food is churned with gastric secretions. It passes through the pylorus into the duodenum in controlled amounts. Glycogen is a storage carbohydrate, and roughage refers to dietary fibre.

B: Filter lymph and help remove bacteria

Lymph passes through nodes containing macrophages and lymphocytes. These structures filter lymph and support immune responses to microbes and foreign material. Red blood-cell formation normally takes place in bone marrow, while oxygen is transported mainly by blood.

C: Superior vena cava

Veins from the head and upper limbs drain into the brachiocephalic veins and then the superior vena cava. This vessel enters the right atrium. The inferior vena cava returns blood chiefly from the lower body, and pulmonary veins return blood from the lungs.

D: AB

Group AB has both A and B antigens and normally lacks anti-A and anti-B antibodies. In the simplified ABO red-cell model, it can receive red cells from O, A, B or AB. Real transfusions also require other compatibility checks; AS is a haemoglobin genotype, not an ABO group.

D: No usable energy is obtained

Glycolysis can provide a small net ATP yield without oxygen. Fermentation regenerates NAD⁺ so glycolysis can continue. Products depend on the organism: lactate is associated with lactic fermentation, while ethanol and carbon dioxide occur in alcoholic fermentation.

A: 1, 2, 3

A gas-exchange surface stays moist so gases can dissolve, and a blood supply maintains concentration gradients. Its thin cellular barrier allows respiratory gases to diffuse without being freely permeable to every substance. A dry barrier would not provide the usual efficient exchange conditions.

D: An oily substance

Sebaceous glands secrete sebum, an oily mixture that helps lubricate skin and hair. Sweat is produced by sweat glands. Vitamin D synthesis involves skin cells and ultraviolet light rather than secretion by sebaceous glands.

B: 2

Label 2 indicates the renal cortex. Bowman’s capsules surround glomeruli to form renal corpuscles, which lie in the cortex. These microscopic capsules collect filtrate; they are different from the outer capsule covering the entire kidney.

E: 2 and 4

Region 2 is the cortex and region 4 is the medulla. Renal tubules in these regions reabsorb substances from tubular fluid into the body. Much nutrient and ion reabsorption occurs in the proximal tubules of the cortex, while other tubular segments contribute in the medulla.

E: Girdles and limbs

The appendicular skeleton includes the limb bones and the pectoral and pelvic girdles that connect them to the body. The skull belongs to the axial skeleton. Phalanges, ulna and radius are only subsets of the appendicular bones.

B: Develops from an ovary

A maize grain is a caryopsis: a dry, one-seeded fruit whose fruit wall is closely fused with the seed coat. Its development from the ovary identifies it as a fruit. The embryo inside still contains structures that form the root and shoot.

E: Reduce self-pollination within that flower

In protandry, pollen is released before the stigma of the same flower becomes receptive. The timing reduces the opportunity for self-pollination within that flower. It does not guarantee that pollen cannot move between different flowers on the same plant.

E: Stem tuber

An Irish potato tuber is an enlarged underground stem. Its eyes are buds associated with nodes, and they can produce new shoots. These stem features distinguish it from a storage root.

A: Phenotype

Phenotype includes observable characteristics such as form, physiology and behaviour. It arises through the interaction of inherited information and environmental influences. Genotype refers to genetic constitution rather than the full set of expressed traits.

E: DNA

DNA stores the genetic information inherited by cellular organisms. RNA has important roles in expressing that information, but cellular genomes are DNA-based. Some viruses have RNA genomes; viruses are not cellular organisms.

C: Epigeal

In epigeal germination, elongation lifts the cotyledonary region above the soil surface. In hypogeal germination the cotyledons remain below ground. Hypocotyl, epicotyl and plumule name parts of the developing shoot, not this germination category.

D: Chemical coordination through hormones

Endocrine glands release hormones that coordinate activity in target tissues. These signals influence many processes, including metabolism, growth and aspects of water balance. Nervous impulses are the main signalling mode of the nervous system.

D: Sensory neurons

Sensory, or afferent, neurons carry information from receptors towards the central nervous system. Motor neurons carry commands towards effectors such as muscles. Dendrites and synapses participate in signalling but do not name the complete functional neuron type requested.

D: Human and freshwater snail

Adult Schistosoma worms mature and reproduce sexually in the human definitive host. Larval development and multiplication occur in a suitable freshwater snail, the intermediate host. Infective cercariae leave the snail and can penetrate human skin.

D: Onchocerciasis

Onchocerciasis is caused by the filarial worm Onchocerca volvulus and is transmitted by infected blackflies. The other listed diseases have bacterial causes. A worm is a multicellular animal, distinct from a bacterium.

C: Sleeping sickness

Infected tsetse flies transmit Trypanosoma parasites that cause African sleeping sickness. River blindness is associated with blackflies and malaria with Anopheles mosquitoes. The insect vector is therefore important for distinguishing these infections.

E: Burning off vegetation

Cover crops and mulch protect the soil surface. Contouring and terracing help reduce the speed or concentration of runoff. Burning off vegetation removes protective cover and can expose the surface to greater erosion, rather than serving as a direct erosion-control measure.

C: Rich in clay and humus but poor in sand

Clay has small pores and a large surface area, while humus also helps hold water. A soil rich in both therefore tends to retain considerable water. Total retained water is not the same as water readily available to plants, because some water may be held too tightly.

D: Weathered rock

Physical and chemical weathering break down rocks and alter minerals, producing the mineral fraction of soil. Humus comes from decomposed organic material. Water and organisms contribute to weathering but are not themselves the main mineral parent material.

A: Denitrification by bacteria

Denitrifying microorganisms reduce oxidised nitrogen compounds through a pathway that can release nitrogen gas. Nitrogen fixation moves atmospheric nitrogen into biologically usable compounds, while nitrification converts ammonium to more oxidised forms such as nitrate.

D: 30.0%

Retained water = 50 − 35 = 15 mL. As a percentage of the 50 mL added, this is (15 ÷ 50) × 100 = 30%. This calculation uses the water added as the denominator; soil mass or soil volume would be needed for a soil-water-content percentage.