Biology 2023 Jamb Examination

Cell growth generally occurs by cell division, specifically mitosis or meiosis, depending on whether the cell is for growth or reproduction. While external factors can influence growth, it is not solely dependent on them. Cells do not just increase organelles indefinitely but undergo controlled growth and division to maintain balance. Thus, the accurate statement is that cell growth occurs by cell division.

The urinary tubule, part of the nephron in the kidney, plays a crucial role in urine formation. After blood is filtered in the glomerulus, the filtrate passes into the tubule where selective reabsorption and secretion occur. This process regulates water, electrolytes, and waste products, leading to the production of urine. The ureter, not the tubule, connects the kidneys to the bladder, while filtration happens in the glomerulus. Thus, the correct function of the urinary tubule is urine production through modification of the filtrate.

The liver is a vital organ responsible for detoxifying harmful substances, metabolizing nutrients from digestion, storing glycogen, producing bile for fat digestion, and processing drugs. While it has secondary roles in hormone regulation, its primary and most essential function lies in detoxification and metabolism. Temperature regulation and blood pressure control are functions of other systems, not the liver. Therefore, the main function is detoxification and metabolism of nutrients and drugs.

Ecological succession is the natural process through which ecosystems change and develop over time. It involves the gradual replacement of one group of species by another in an environment, leading to a stable climax community. This can be primary succession (on bare surfaces) or secondary succession (in disturbed ecosystems). It is not about migration, competition, or natural selection directly, though these may influence it. The best description is a gradual, predictable change in a community over time.

In biology, adaptation refers to inherited traits that provide an advantage in survival and reproduction within a specific environment. These traits are passed down genetically, not acquired during an individual’s lifetime. For example, camouflaging coloration in animals or drought-resistant features in plants are adaptations. It does not mean actively changing the environment or developing traits within one lifetime. Hence, the correct definition is an inherited trait that enhances survival and reproduction.

Digestive enzymes such as amylase, protease, and lipase catalyze the breakdown of complex food molecules like starch, proteins, and fats into simpler molecules such as glucose, amino acids, and fatty acids. These simpler molecules can then be absorbed into the bloodstream. Absorption, pH regulation, and movement of food involve other processes, but the specific role of digestive enzymes is the chemical breakdown of food. Therefore, their main function is breaking food down into smaller molecules.

One of the most important distinctions between plant and animal cells is that plant cells contain chloroplasts, which enable them to perform photosynthesis and produce their own food. Both plant and animal cells have a nucleus, both possess cell membranes, but only plants also have a rigid cell wall. While differences in vacuoles exist, the defining unique feature is the presence of chloroplasts in plant cells but not in animal cells.

The cochlea is the spiral-shaped structure in the inner ear that contains hair cells responsible for converting mechanical sound vibrations into electrical signals. These signals are then transmitted to the brain via the auditory nerve. The eardrum and ossicles help in the conduction and amplification of sound, while the auditory canal channels sound waves to the eardrum. However, it is the cochlea that directly transmits vibrations to the auditory nerve, making it the correct answer.

Carbon is the primary building block of life because it forms the backbone of organic molecules such as carbohydrates, proteins, lipids, and nucleic acids. Its ability to form four covalent bonds makes it highly versatile in building complex molecules essential for life. While nitrogen, water, and sulphur are also vital, they play secondary roles compared to carbon.

Transpiration is the process through which plants lose water vapor to the atmosphere primarily through stomata in their leaves. This process is crucial for cooling the plant, maintaining nutrient flow, and water uptake. Guttation is the loss of liquid water droplets, translocation refers to transport of food, and evaporation is a general physical process.