Biology 2023 Jamb Examination

Competition drives natural selection by creating pressure on individuals to survive and reproduce. Those with favorable traits are more likely to succeed, passing those traits on to future generations. Over time, this leads to adaptations that improve survival in the given environment.

Sex-linked traits are controlled by genes located on the sex chromosomes (X and Y). For example, hemophilia and color blindness are X-linked traits. They can be inherited from either parent, but they often appear more frequently in males since they have only one X chromosome.

Gibberellins are plant hormones that promote cell elongation, stem growth, seed germination, and flowering. Abscisic acid primarily inhibits growth, ethylene regulates fruit ripening, and cytokinins stimulate cell division rather than elongation.

Industrial discharge releases chemicals, heavy metals, and untreated waste into rivers, lakes, and oceans, directly polluting aquatic ecosystems. While soil erosion, air pollution, and deforestation impact the environment, industrial discharge is the primary direct source of aquatic pollution.

Plants lack bones and muscles, so their structural support comes from rigid cell walls made of cellulose and the internal water pressure within cells (turgor pressure). This combination keeps plants upright and stable.

Metamorphosis is the transformation in form and structure that occurs during the life cycle of certain organisms, such as insects and amphibians. For example, a caterpillar develops into a butterfly, or a tadpole transforms into a frog.

The kidneys filter waste products, such as urea and excess salts, from the blood and excrete them through urine. The liver processes toxins, lungs expel carbon dioxide, and the pancreas regulates digestion and blood sugar, but the kidneys are the main excretory organs.

Carbohydrates are classified as macronutrients because they are required in large amounts by the body to provide energy. Micronutrients, such as vitamins and minerals, are needed in smaller amounts. Lipids are fats, and phytonutrients are plant-based compounds with health benefits but are not essential macronutrients.

Myopia, commonly known as short-sightedness, is caused when light entering the eye focuses in front of the retina rather than directly on it. This makes nearby objects appear clear while distant objects appear blurry. It occurs due to the elongation of the eyeball or excessive curvature of the cornea. Glaucoma, on the other hand, is related to optic nerve damage due to increased eye pressure. Cataracts involve clouding of the lens, and astigmatism is caused by irregular curvature of the cornea. Therefore, the inability of the eye to focus light properly on the retina best describes myopia.

Germination refers to the biological process where a seed resumes growth after dormancy, usually under favorable conditions such as moisture, oxygen, and suitable temperature. It begins with the absorption of water by the seed, which activates enzymes and leads to the growth of the embryo. The radicle (root) emerges first, followed by the shoot. Photosynthesis starts later when the seedling develops leaves. Thus, germination is best defined as the breaking of dormancy and initiation of growth.