JAMB Biology 1986

D: Flowering plants and conifers

Flowering plants and conifers use pollen and pollen tubes to deliver the male gametes without an external film of water. Ferns and mosses rely on swimming sperm for fertilisation. This reproductive adaptation helps seed plants reproduce in terrestrial environments.

B: Hydra

Hydra has a body organised around a central oral-to-basal axis, with tentacles around the mouth. This is the radial body plan of a cnidarian polyp. Squid and cockroaches have bilateral body plans, while adult snails show asymmetry associated with torsion.

C: Barbules

Barbules are the small branches on the feather barbs. Hooklets on some barbules engage neighbouring barbules, linking the barbs into a continuous vane. The rachis is the central shaft, while the vane is the broader feather surface.

C: Its normal filaments are branched

Spirogyra normally forms unbranched chains of cells with spiral chloroplasts. A filament can break into fragments that continue growing. Sexual reproduction involves conjugation between compatible cells rather than branching of the filament.

B: Grasshopper

A grasshopper develops from egg to nymph to adult, without a pupal stage. Nymphs resemble small adults but are not yet sexually mature and usually have undeveloped wings. Butterflies, mosquitoes and houseflies pass through larval and pupal stages.

C: Dependent on the temperature of their surroundings

In most fishes, heat exchange with the surrounding water strongly influences body temperature. Ectothermic does not mean always cold: a fish in warm water can have a higher temperature than one in cold water. Some fish have specialised heat-retention adaptations.

B: A pair of anal styles

The adult male American cockroach has short anal styles that are absent from the adult female. Both sexes have mandibles, respiratory spiracles and cerci. Styles should therefore not be confused with the longer paired cerci.

C: Pelvic and pectoral

Pectoral and pelvic fins occur as left–right pairs and correspond to the two paired appendage sets. Dorsal and caudal fins are median fins. Ventral is commonly used for the pelvic fin, so it does not name a separate second pair.

A: On the same radius within each bundle

In a collateral stem bundle, xylem lies towards the inside and phloem towards the outside along the same radius. In a typical root, xylem and phloem occupy alternating positions. This comparison concerns their relative arrangement, not simply the presence of either tissue.

C: Water

Water is split during the light-dependent reactions, supplying electrons and releasing oxygen. Carbon dioxide supplies carbon for carbohydrate formation. Chlorophyll captures light energy but is not the substance consumed to supply the released oxygen atoms.

C: Fats, carbohydrates and proteins

Fats, carbohydrates and proteins are carbon-based organic nutrient classes. Mineral salts are inorganic components. The body also contains other important organic substances, including nucleic acids, so this is not an exhaustive list of all organic molecules.

D: Iron

Each haem group contains an iron ion that binds oxygen reversibly. Haemoglobin combines these haem groups with globin protein chains to transport oxygen in red blood cells. Sodium, potassium and calcium have other physiological roles.

D: Scurvy

Vitamin C supports normal collagen formation. Severe deficiency causes scurvy, which can involve fragile connective tissues, bleeding gums and poor wound healing. Beriberi is associated with thiamine deficiency and pellagra with niacin deficiency.

C: Protein

In the biuret test, copper ions in alkaline solution form a coloured complex with peptide bonds. Proteins contain many peptide bonds and can give the violet result. Fat and carbohydrate molecules do not have this protein backbone.

B: Pulp cavity

The pulp cavity contains living connective tissue, blood vessels and nerves. Enamel is a hard, non-living covering of the crown. The gum surrounds the tooth, while cementum covers the root rather than containing the tooth’s central neurovascular tissue.

A: Passes through the heart twice in a complete circuit

Blood travels from the heart to the lungs and back, then from the heart to the body tissues and back. These pulmonary and systemic circuits make two passages through the heart in one complete journey through both circuits.

C: 2 → 1 → 3 → 4

Water arrives in the leaf veins, moves into mesophyll tissues and evaporates into internal air spaces. Water vapour then diffuses through substomatal spaces and out through stomata. Thus the sequence is 2 → 1 → 3 → 4.

D: Bicuspid valve

The bicuspid, or mitral, valve lies between the left atrium and left ventricle. It closes during ventricular contraction to prevent blood flowing back into the atrium. The tricuspid valve occupies the corresponding opening on the right side.

B: The diaphragm rises into a more domed position

During inhalation, the diaphragm contracts and flattens downwards, while the external intercostal muscles help raise the ribs. The expanding chest allows lung volume to increase and pressure to fall, drawing air in. A rising, more domed diaphragm is associated with relaxation during expiration.

D: C6H12O6 → 2C2H5OH + 2CO2 + energy

Alcoholic fermentation converts glucose into ethanol and carbon dioxide without consuming oxygen in the net equation. Coupled glycolysis captures a small amount of usable energy. The balanced products contain the same total numbers of carbon, hydrogen and oxygen atoms as the glucose.

D: Malpighian layer

The living epidermal layers traditionally called the Malpighian layer include keratin-producing cells and cells associated with melanin production or storage. Melanin contributes pigmentation, while keratin helps give the epidermis mechanical strength.

A: A short spinous process and transverse foramina

Typical mid-cervical vertebrae have transverse foramina and relatively small bodies, with short spinous processes. The atlas, axis and seventh cervical vertebra have special features, so the typical pattern should not be applied unchanged to every neck vertebra.

B: Independent of the direction from which the stimulus comes

Nastic movements have a direction determined by the plant’s structure rather than the direction of the triggering stimulus. A leaf may fold after touch regardless of which side was touched. A directional growth response towards or away from a stimulus is a tropism.

B: 3

Part 3 marks the embryo region, which contains the developing shoot and root. During germination these grow into the seedling. Stored food supports this growth, but the food store and the grain’s attachment do not themselves become the new plant.

D: Seed coat, fused with the fruit wall

Label 1 points to the protective outer covering. A maize grain is a caryopsis, in which the seed coat is closely fused with the fruit wall. The plumule and radicle are developing shoot and root structures located within the embryo.

B: Nourish the embryo and its growing parts

Part 2 is the endosperm, which stores nutrients, particularly starch, that support the embryo during germination. These reserves are mobilised while the young seedling is becoming able to obtain resources through its roots and leaves.

C: Of development from fertilisation to birth

Gestation encompasses prenatal development from fertilisation until birth, including the early embryonic stages and later fetal development. It does not begin only when the embryo is called a fetus and does not include postnatal growth.

B: Preferred handedness, such as left-handed or right-handed

Hand preference can be recorded as categories, including left, right or mixed preference. Height, body weight and pigmentation intensity can vary across a numerical range. Categorical recording does not imply that handedness is controlled by a single gene.

C: Clinostat

A clinostat turns the plant so that a stimulus does not act persistently from one direction relative to it. Comparing suitable rotating and stationary setups helps investigate tropic responses. Rotation does not remove gravity; it changes the plant’s orientation relative to it.

B: Primary consumers

Plants are producers because they make organic material using an external energy source. An animal eating those plants obtains food directly from the producer level and acts as a primary consumer. Eating a primary consumer would place an animal at a higher trophic level.

A: Crops, pests and beneficial insects

Biotic components are living organisms, such as crop plants and insects. Temperature, humidity and water are abiotic conditions or materials. Soil contains living organisms but soil as a whole is not simply a living organism.

D: Onchocerciasis

There is no available vaccine for preventing onchocerciasis. Vaccines exist for polio, cholera and tuberculosis, although their protection and recommended uses differ. BCG is particularly important against severe childhood forms of tuberculosis.

B: Decomposers

Decomposers digest dead organic matter and make its chemical constituents available for further cycling. Many bacteria and fungi carry out this role. Not every bacterium or fungus has the same mode of nutrition, so the role depends on the organism’s activity.

A: Virus

Cacao swollen shoot disease is associated with a group of related viruses. Infection can produce swollen shoots and declining tree health. Mealybugs can transmit the viruses, but the insect vector is different from the disease-causing agent.