JAMB Biology 1999

B: muscles of pig

In the usual life cycle of Taenia solium, pigs act as intermediate hosts and cysticerci develop in their tissues, especially muscle. The adult tapeworm, by contrast, lives in the human intestine.

A: birds and reptiles

Birds and reptiles both include animals with scales, shelled eggs and a bony skull. Bird scales can be seen on the legs and feet. These features are not the same as saying every species in each group lays eggs.

C: Arachnida

Arachnids lack antennae. Their anterior appendages include chelicerae and pedipalps rather than the antennae found in insects, centipedes, millipedes and crustaceans.

B: liver

The liver is an organ composed of several tissue types working together. A guard cell is a single cell, blood is connective tissue and a xylem bundle is part of a conducting tissue system.

A: bilateral symmetry

Bilateral symmetry means that one longitudinal plane divides the body into matching left and right halves. A section is a cut through a body, whereas symmetry describes how its parts are arranged.

D: Spirogyra

Spirogyra has a filament of relatively similar photosynthetic cells. Ordinary vegetative cells can grow and participate in reproduction, including conjugation, rather than being separated into the organs of a fern or moss.

C: lenticels

Lenticels are regions in the bark through which gases can pass between internal tissues and the surrounding air. They provide exchange routes through the otherwise relatively impermeable outer tissues of a woody stem.

C: sieve tubes

Sieve tubes are the main conducting pathways in angiosperm phloem for sugars and other organic solutes. Companion cells support their activity but are not the longitudinal sieve-tube conduits.

C: hepatic portal vein

During absorption of glucose from digested yam, blood from the small intestine enters the hepatic portal vein before reaching the liver. This route carries the newly absorbed glucose and can have a higher glucose concentration than the other listed vessels.

C: the stimulation of marrow to produce more erythrocytes

At high altitude, reduced oxygen partial pressure can stimulate erythropoietin signalling and increase red blood cell production in the bone marrow. More erythrocytes increase the blood’s oxygen-carrying capacity during acclimatization.

B: red palm oil and carrots

Red palm oil and carrots supply substantial provitamin A carotenoids, which the body can convert to vitamin A. Ordinary unfortified groundnut oil and rice are much poorer sources; oranges are less concentrated sources than red palm oil.

A: cohesion of water molecules to one another by hydrogen bonds

Hydrogen bonds between water molecules produce cohesion. This helps maintain a continuous column of water in xylem as transpiration creates tension. Attraction to the vessel walls is adhesion, a different interaction.

B: subclavian vein

Lymph returns to the venous circulation near the junctions of the subclavian and internal jugular veins. The main lymphatic ducts discharge there, returning fluid collected from the tissues to the bloodstream.

D: upper part of the oviduct

Human fertilization usually occurs in the ampulla, the widened part of the uterine tube toward the ovary. The early embryo then travels toward the uterus, where implantation normally occurs later.

A: feed on the nectar

Many insects visit flowers to obtain food such as nectar. Pollen can be transferred during feeding, but pollination is a consequence of the visit rather than the insect’s food-seeking purpose.

A: carried above the ground by the elongating hypocotyls

In epigeal germination, elongation of the hypocotyl lifts the cotyledons above the soil. The hypocotyl is the embryonic axis below the cotyledons; the epicotyl lies above them.

C: binary fission

Most bacteria reproduce by binary fission: DNA is copied and one cell divides into two daughter cells. Repeated divisions can rapidly increase a population when conditions support growth.

D: dissolved chemicals → sensory cells → olfactory nerve → brain

Odorant molecules dissolve in nasal mucus and interact with receptors on olfactory sensory cells. Signals then travel through their nerve fibres to brain pathways where the smell is processed.

B: hinge joint

The elbow joint between the upper limb bone and the adjacent forearm bone allows mainly bending and straightening. This is a hinge arrangement, unlike the broad rotation of a ball-and-socket joint.

D: IV

IV points to the radius, one of the two forearm bones. II marks the other forearm bone near its upper projection, III the upper limb bone and I the broad shoulder blade.

D: malaria, bilharziasis and onchocerciasis

Water projects can change mosquito, snail and blackfly habitats. Under suitable local conditions, these changes can increase malaria, schistosomiasis and onchocerciasis risks; the effect is not inevitable at every dam.

B: commensalism

Commensalism describes an interaction in which one participant benefits while the other has no significant effect under the conditions considered. It is represented by the signs + and 0.

C: 2,3 and 7

Primary consumers obtain food directly from the producer. The arrows from plant 1 lead to moth 2, grasshopper 3 and herbivorous bug 7, so those three occupy primary-consumer positions.

D: 5 → 4 → 3 → 1

In the usual upright biomass pattern for a terrestrial food chain, biomass tends to be greater toward the producer level. The feeding chain plant 1 → grasshopper 3 → praying mantis 4 → lizard 5 is therefore read in reverse for increasing biomass.

B: 3

The first cross bb × BB produces Bb offspring. Crossing two of those offspring gives BB, Bb, bB and bb. Bb and bB are the same genotype, so there are three distinct genotypes: BB, Bb and bb.

B: invertebrates as opposed to vertebrates

Invertebrate animal lineages appear in the fossil record before vertebrates. Very old fossil-bearing deposits are therefore more likely to preserve invertebrates than vertebrates, although the actual fossils depend on the environment and preservation.

D: counter shading of coat colour

Countershading affects how an animal is seen by others. It does not directly provide grip or mechanical balance for climbing, unlike limbs, claws and, in many tree-living species, a balancing tail.

D: new species originate through the inheritance of acquired traits

Lamarck proposed that characteristics acquired during an organism’s lifetime could be inherited. This historical idea differs from natural selection acting on inherited variation across generations.

D: warn its chicks and other chickens of impending danger

A hen’s alarm call can alert chicks and other chickens to a nearby predator. The response helps others take cover or remain vigilant and differs from a territorial advertisement.