Biology 2025 Jamb Examination

In the human dentition, the canines are specifically adapted for tearing food. Based on the standard arrangement in such diagrams, the canine is usually pointed and sits between the incisors and premolars. If label II points to the sharp, pointed tooth, it represents the canine.

The bush rat is a fossorial animal, meaning it is adapted to digging and living underground in burrows. This provides protection from predators and extreme environmental conditions. Doves are arboreal (trees), chameleons are also mostly arboreal, and snails often seek shade or leaf litter rather than digging complex burrows.

This is a classic example of camouflage (concealing coloration). By matching the color of its environment (the dry grass), the grasshopper becomes difficult for predators to spot, increasing its chances of survival.

Cross-fertilization (allogamy) promotes genetic variation by combining DNA from two different parents. This genetic diversity often results in healthier, more vigorous offspring (hybrid vigor) that are better equipped to survive changing environmental conditions compared to self-fertilized offspring.

Comparing the physical structures of different organisms to find similarities in their 'basic plan' (homologous structures) is the study of comparative anatomy. It suggests that these organisms shared a common ancestor from which they inherited these skeletal frameworks.

Mating colouration is a form of sexual selection where one sex (usually the male) develops bright or distinct colours to attract a mate. The male agama lizard is a classic example; during the breeding season, its head turns a brilliant orange or red, and its body becomes bright blue. This serves as a visual signal of health and dominance to females and a warning to rival males, whereas the chameleon's colour change is primarily for camouflage or mood expression rather than specific seasonal mating patterns.

Birds, like mammals and reptiles, use kidneys as their primary excretory organs to filter waste from the blood. However, birds are uricotelic, meaning they convert nitrogenous waste into uric acid to conserve water, which is excreted as a white paste. In contrast, Nephridia are found in earthworms, Malpighian tubules are found in insects, and Green glands (antennal glands) are the excretory organs of crustaceans like crayfish.

Jean-Baptiste Lamarck proposed the theory of 'Inheritance of Acquired Characteristics.' He argued that if an organism used a body part more frequently (like a giraffe stretching its neck to reach high leaves), that part would develop further, and this new trait would be passed down to the next generation. While Darwin focused on Natural Selection and Mendel on genetics, Lamarck's theory was later disproven because phenotypic changes acquired during a lifetime do not typically alter the genetic information (DNA) passed to offspring.

Loamy soil is considered the best for general crop cultivation because it is a balanced mixture of sand, silt, and clay. It possesses excellent 'tilt' or structure, meaning it has enough pore space to hold adequate air and water while also being rich in organic matter (humus). Sandy soil drains too quickly and lacks nutrients, while clayey soil becomes waterlogged and is difficult for roots to penetrate. Loam provides the ideal physical and chemical environment for most Nigerian staples like maize, yams, and cassava.

The calyx is the outermost whorl of a flower, made up of individual units called sepals. When these sepals are fused or joined together to form a tube-like structure, the condition is termed gamosepalous. If the sepals are free and separate from each other, it is called polysepalous. Similarly, 'gamopetalous' refers to fused petals, and 'polypetalous' refers to free petals. Understanding these botanical terms is essential for plant identification and classification.