Biology 2022 Jamb Examination

Annelids, such as earthworms, have a cylindrical body shape which significantly increases their surface area relative to their volume. This high surface area to volume ratio allows more efficient diffusion of gases across their moist skin into the blood capillaries, unlike flatworms where diffusion is limited due to their flattened shape. Option C is correct because it directly explains why gaseous exchange is more efficient in annelids.

The centromere is the specialized region of a chromosome that holds the two sister chromatids together. During cell division, spindle fibers attach to the centromere to pull the chromatids apart. Spindle is the structure that separates chromatids, cellulose is a plant cell wall component, and chromatid refers to each of the two identical strands, making C correct.

In mammals, blood flows from the heart into large arteries, which branch into smaller arterioles, and finally reach the capillaries that supply tissues. Veins and venules carry blood back to the heart. Hence, the correct sequence is heart -> artery -> arteriole -> tissues, making B correct.

Colour blindness is an X-linked recessive trait. If a woman is colour blind (XᴄXᴄ) and the man is normal (XᴺY), all sons will inherit the Xᴄ from the mother and Y from the father. Therefore, all sons (100%) will be colour blind. The daughters will be carriers (XᴺXᴄ). Hence, B is correct.

Tropical rainforests are characterized by dense vegetation, tall trees with buttress roots to support their height in shallow soils, and evergreen leaves due to constant photosynthesis throughout the year. Savannas have scattered trees and grassland, and temperate grasslands lack tall evergreen trees. Therefore, C is correct.

Crossing over is the exchange of genetic material between homologous chromosomes during prophase I of meiosis. This process increases genetic variation in gametes. It does not occur in mitosis or fertilization, making D correct.

A man with genotype HbAHbS is a carrier for sickle cell trait. Marrying a woman with HbA HbA ensures that the offspring will have at most one HbS allele, preventing sickle cell disease. Marrying a woman with HbS HbS would risk offspring having the disease, making A correct.

A wind vane is an instrument that shows the direction from which the wind is blowing. An anemometer measures wind speed, a Secchi disc measures water transparency, and a slope gauge measures terrain slope. Therefore, B is correct.

Mucor is a saprophytic fungus that obtains nutrients by decomposing dead organic matter such as bread. It releases enzymes to digest the substrate externally and absorbs the nutrients. It does not engage in commensalism or autotrophism. Hence, D is correct.

Photosynthesis is the process by which plants convert carbon dioxide from the atmosphere into glucose and other organic molecules using light energy. This stores chemical bond energy in organic compounds. Transpiration is water loss, digestion is breakdown of food, and respiration releases stored energy. Therefore, B is correct.