Biology 2024 Jamb Examination

Blood group is an example of discontinuous variation because it falls into distinct categories (A, B, AB, and O) without intermediate forms. Traits like shape of the head, complexion, and nose type show continuous variation with a range of possibilities, unlike blood group which is clear-cut.

Continuous variation refers to characteristics that show a gradual range with no sharp differences between individuals, such as height, weight, or skin color. Extremes blend smoothly into each other. Discontinuous variation, in contrast, has distinct categories without intermediates.

Cockroaches are pests that contaminate food and utensils with pathogens, leading to the transmission of diseases such as food poisoning and dysentery. Mosquitoes transmit malaria and yellow fever, butterflies are harmless, and bees are beneficial pollinators.

Bryophytes are considered an intermediate group between higher algae and pteridophytes. They are non-vascular plants that show a transition from simple algae to more complex vascular plants, as they have multicellular structures but lack true vascular tissues.

Ecological succession begins when organisms colonize a newly formed habitat, such as bare rock after a volcanic eruption or a newly exposed sand dune. Over time, pioneer species modify the environment, making it suitable for other species, leading to gradual ecosystem development.

The earliest organisms are believed to have originated in aquatic habitats. Water provided a stable environment, protection from harsh solar radiation, and a medium for essential biochemical reactions. Terrestrial and desert environments came much later in evolutionary history, while arboreal habitats are associated with advanced land animals.

For germination to occur, seeds require water to activate enzymes and initiate metabolism, and heat (a suitable temperature) to support enzymatic activity. Soil, manure, and microbes are not necessary in a controlled laboratory experiment, though they may influence natural germination.

An aggregate fruit develops from a single flower that has many free carpels. Each carpel forms a small fruitlet, and together they make up the aggregate fruit, as seen in strawberries and raspberries. Simple fruits come from one carpel, multiple fruits from many flowers, and false fruits involve additional floral parts.

Liverworts are small, non-vascular plants commonly found in the moist ground layer of tropical rainforests. Obeche, mahogany, and oil palm are large trees or taller plants that occupy the canopy and understory layers of the forest rather than the ground layer.

The gland located in the part labelled I of the diagram is the pituitary gland, often called the 'master gland.' It is located at the base of the brain and controls other endocrine glands such as the thyroid, adrenal glands, and reproductive glands through hormone secretion.