Biology 2025 Jamb Examination

A vestigial structure is an anatomical feature that has lost all or most of its original function through the course of evolution. The human appendix is a classic example; in our herbivorous ancestors, it was a large organ (caecum) used for digesting cellulose, but in modern humans, it is greatly reduced and no longer essential for digestion. In contrast, the elephant's trunk, bird wings, and fish gills are highly functional, specialized organs.

In the double-helix structure of DNA, nitrogenous bases follow specific pairing rules known as Chargaff's rules. Adenine (A) always pairs with Thymine (T) via two hydrogen bonds, and Guanine (G) always pairs with Cytosine (C) via three hydrogen bonds. Therefore, adenine - thymine is the only correct base pair listed.

When different species compete for the same limited resources (food, space, or light) in a habitat, the species better adapted to those conditions will thrive and reproduce more successfully, while the less adapted species may decline or disappear. This concept is summarized as survival of the fittest, which is the driving mechanism behind the broader process of natural selection.

By comparing the anatomical structures of different animals, scientists can find 'homologous' structures that suggest a common ancestry. The human appendix and the herbivore caecum are structurally similar but have different sizes and functions today. Studying these similarities and differences falls under comparative anatomy, providing evidence that humans and herbivores evolved from a common ancestor with a functional caecum.

Countershading is a type of camouflage where an animal's pigmentation is darker on the upper side and lighter on the underside. This helps the animal blend into its environment by neutralizing the effect of shadows, making it appear flat and unnoticed to predators or prey. Hibernation, aestivation, and migration are behavioral adaptations related to survival in harsh seasons, not colouration.

GMO technology allows scientists to insert specific genes into plants to give them desirable traits. A major benefit to farmers is the creation of resistant crop varieties—crops that can withstand pests, diseases, or harsh herbicides. This leads to higher yields and reduced spending on chemical pesticides, making farming more efficient and profitable.

In forensic science and crime detection, investigators look for variations that are unique to every individual and remain constant throughout life. Fingerprints are the most reliable tool because no two people (including identical twins) have the same ridge patterns. Tongue rolling, height, and skin colour are not unique enough for specific identification in criminal cases.

The Sahel is a semi-arid region characterized by low rainfall and high temperatures. Borno State falls within this zone in Northern Nigeria, where the climate is suitable for the growth of drought-resistant trees like the date palm. Plateau and Taraba are more temperate or guinea savanna regions with higher rainfall.

The receptacle (or torus) is the thickened part of a stem (pedicel) from which the flower organs grow. It serves as the base that supports the calyx, corolla, stamens, and pistil. The pedicel is the stalk itself, while the calyx and corolla are the sepals and petals, respectively.

In the carbon cycle, carbon is exchanged between the atmosphere and organisms. Combustion is a key process where the burning of fossil fuels or organic matter releases stored carbon back into the atmosphere as carbon dioxide (\(CO_2\)). Nitrification is part of the nitrogen cycle, while evaporation and transpiration are parts of the water cycle.