JAMB Biology 1993

C: Chromosomes

Genes are units of hereditary information carried in DNA organised into chromosomes. Ribosomes translate genetic messages, while the Golgi apparatus and endoplasmic reticulum handle production or processing of cellular materials.

B: conifers

Conifers are gymnosperms and produce seeds not enclosed within an ovary-derived fruit. Grasses, legumes and palms are flowering plants, whose seeds develop within fruits. Naked does not mean lacking a seed coat.

D: Presence of a vascular system

Pteridophytes possess vascular tissues for water and food transport, while bryophytes lack a true xylem-and-phloem system. Both groups lack flowers and have alternating generations, and their motile sperm need water for fertilisation.

C: Chloroplasts

In a typical green fern life cycle, both the leafy sporophyte and the small gametophyte photosynthesise and contain chloroplasts. The gametophyte has rhizoids, while the sporophyte has true roots and leaves.

B: Euglena

A typical photosynthetic Euglena is a single cell with chloroplasts and a flagellum. It can carry out photosynthesis, movement and the other life processes within that cell. Spirogyra forms filaments rather than this flagellated unicellular body.

C: Rattus

Rattus is the rat genus, and rats store carbohydrate as glycogen, particularly in liver and muscle. The listed green algae and mango plant instead use starch as their principal storage polysaccharide.

B: Arthropoda

Arthropoda includes insects, arachnids, crustaceans and other joint-legged animals. It contains more described animal species than any other phylum, largely because of the enormous diversity of insects.

D: it pollinates flowers of crops and other plants

Butterflies can transfer pollen between flowers as they visit them. This supports fertilisation and seed or fruit production in plants they pollinate, giving them an important ecological and agricultural role.

B: phloem

Phloem transports organic products of photosynthesis, especially sugars, from source regions to sinks where they are used or stored. Xylem chiefly carries water and mineral nutrients from roots.

D: fatty acids and glycerol

Complete hydrolysis of a triglyceride releases its glycerol backbone and three fatty acids. During intestinal digestion, partial products such as monoglycerides also occur before absorption and further processing.

A: excretory materials from tissues

Blood carries metabolic waste products away from tissues toward organs that remove them. It also supplies oxygen and nutrients, but the directions given for those substances in the other alternatives are incorrect.

D: to remove excess water

A contractile vacuole collects excess water and expels it from the cell. This is especially important for freshwater protists, which continually gain water by osmosis because their surroundings are more dilute.

D: geotropism

Geotropism, also called gravitropism, is directional growth in response to gravity. Roots usually grow toward gravity, while shoots grow away from it. Light, water and touch are different directional stimuli.

C: Atlas → axis → remaining cervical → thoracic → lumbar → sacral

The atlas and axis are the first two cervical vertebrae. Moving toward the tail, they are followed by the remaining cervical vertebrae, then the thoracic, lumbar and sacral regions.

C: courtship

The conspicuous feathers and displays of a peacock act as courtship signals. Such traits can influence mate choice and are examples of sexual selection, rather than simply features for human appreciation.

A: attract pollination agents

Petals often provide colour, scent or visual patterns that attract animal pollinators. Some also provide a landing surface. Sepals usually protect the developing flower while it is still enclosed in the bud.

A: sympathetic and parasympathetic systems

The sympathetic and parasympathetic divisions are the two principal divisions traditionally described in the autonomic nervous system. They regulate involuntary functions such as heart activity and digestion.

B: the hypocotyl grows faster than the epicotyl

In epigeal germination, elongation of the hypocotyl lifts the cotyledons above the soil. In hypogeal germination the cotyledons remain below ground while the epicotyl extends upward.

B: constrict to reduce the amount of blood flowing to the skin

When the body is cold, constriction of small blood vessels supplying the skin reduces skin blood flow. Less warm blood reaches the surface, helping reduce heat loss to the surroundings.

C: Eardrum → ossicles → oval window

Sound causes the eardrum to vibrate. These vibrations pass through the middle-ear ossicles to the oval window, where they generate pressure waves in the fluid of the inner ear.

A: The level of blood sugar would increase

The pancreas supplies insulin, which helps regulate blood glucose by promoting its uptake and storage. Removing the pancreas without replacement insulin removes this control and can cause blood glucose to rise.

B: Tertiary consumers

A persistent pollutant that biomagnifies can become more concentrated at successive feeding levels. Tertiary consumers feed above primary and secondary consumers, so they may have the greatest concentration among these levels.

A: Microscope

A microscope magnifies small structures rather than directly measuring an abiotic habitat condition. A thermometer measures temperature, a hygrometer humidity and a wind vane wind direction.

C: halophytes

Halophytes are plants adapted to saline conditions, including salt marshes. Their adaptations can include excluding salt, secreting it or storing it in tissues while maintaining water uptake.

B: crop rotation and cover crops

Rotating crops and using cover crops can maintain soil structure, protect the surface and return organic material. Including suitable legumes may also add biologically fixed nitrogen to the cropping system.

C: combining with haemoglobin

Carbon monoxide binds to haemoglobin, forming carboxyhaemoglobin. This reduces effective oxygen transport and delivery to tissues. The resulting oxygen deprivation is a major mechanism of carbon monoxide toxicity.

B: Tongue rolling

When tongue rolling is recorded simply as can roll or cannot roll, the observations fall into separate categories. Height and body weight vary across a range, and skin pigmentation is also a quantitative trait.

B: 1 homozygous smooth : 2 heterozygous smooth : 1 wrinkled

The four cells contain SS, Ss, sS and ss. Ss and sS are the same heterozygous genotype, giving one homozygous smooth, two heterozygous smooth and one homozygous wrinkled entry.

A: poikilothermic

Poikilothermic describes an animal whose body temperature varies substantially. This differs from homeothermy, in which body temperature is relatively stable. Heat source and temperature variability are related but distinct classifications.