Biology 2025 Jamb Examination

In ecology, the carrying capacity is the maximum population size of a biological species that can be sustained by that specific environment, given the food, habitat, water, and other available resources. When a population exceeds this limit, resources become depleted, leading to a decrease in population size until it stabilizes back at the carrying capacity.

Plants that are adapted to survive in environments with very little liquid water, such as deserts or ice-covered regions, are called xerophytes. They possess specialized features like thick waxy cuticles, fleshy stems for water storage (succulence), and reduced leaf surface area (spines) to minimize transpiration. Hydrophytes live in water, and mesophytes live in moderate water conditions.

While the question mentions 'flower,' it refers to the dispersal of the fruit/seed resulting from the flower. A cypsela is a dry, single-seeded fruit (typical of the family Asteraceae, like dandelions) that often possesses a 'pappus'—a tuft of hairs that acts like a parachute, allowing it to be easily dispersed by wind.

Rhizopus (commonly known as bread mold) is a saprophyte, meaning it obtains its nutrients by absorbing dissolved organic matter from dead and decaying plant or animal tissues. Bladderwort and sundew are carnivorous plants, while mistletoe is a partial parasite.

Ferns are vascular plants (tracheophytes), which means they possess true roots, stems, and leaves. They use their roots to absorb water and dissolved mineral nutrients from the soil. Rhizomes are underground stems, and rhizoids are root-like structures found in simpler, non-vascular plants like mosses.

The mosquito possesses specialized mouthparts designed for piercing the skin of animals and sucking blood. This structure, called a proboscis, consists of several needle-like stylets. In contrast, cockroaches have biting and chewing mouthparts, while butterflies and moths have siphoning mouthparts used for drinking nectar.

According to Mendel's First Law (Law of Segregation), the two alleles for a trait separate or segregate from each other during gamete formation (meiosis). This ensures that each gamete carries only one allele for each gene. Fertilization, on the other hand, restores the diploid number by bringing two alleles together.

Hibernation is a behavioural adaptation where animals enter a state of deep sleep or inactivity during winter to survive extreme cold and food shortages. This is often accompanied by physiological changes like a lowered body temperature and slowed heart rate. Hiding is more of a defensive tactic, and swelling up is often a physical response or a threat display.

In plants, cell sap (the fluid found inside the large central vacuole) serves as a medium for the movement of water and dissolved substances within individual cells and across tissues via osmosis and diffusion. While xylem and phloem are the tissues responsible for bulk transport, cell sap is the liquid medium involved in the internal cellular environment. However, note that in many contexts, cytoplasm is also a transport medium within the cell.

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The coronary arteries are the specific blood vessels that carry oxygenated blood to the heart muscle (myocardium) itself to ensure it has the energy to pump. While the pulmonary artery carries blood away from the heart to the lungs, and the aorta carries blood away from the heart to the rest of the body, the coronary arteries supply the heart tissue.