Biology 2023 Jamb Examination

A mosquito transmitting malaria is a clear example of a microorganism acting as a disease vector. The mosquito carries the Plasmodium parasite in its salivary glands and transfers it into the bloodstream of humans when feeding. This relationship shows how insects can serve as carriers of pathogens, facilitating their spread between hosts without directly causing the disease themselves.

Irritability in cells refers to the ability to detect and respond to environmental changes or stimuli. This characteristic is essential for survival as it allows organisms to adapt to external conditions such as light, temperature, or chemical signals. Without this responsiveness, organisms would be unable to interact with their environment effectively.

Evolutionary evidence comes from many sources. Fossils provide records of extinct species, embryonic development shows common ancestry, and homologous structures indicate shared evolutionary pathways. Since all these lines of evidence contribute to understanding evolution, the correct choice is that all of them provide supportive proof.

The tonoplast is the specialized membrane that encloses the vacuole in plant cells. It regulates the movement of ions and molecules into and out of the vacuole, helping to maintain turgor pressure and store essential substances such as water, nutrients, and waste products. This function is crucial for plant survival and growth.

Social insects like ants, bees, and termites develop caste systems where individuals specialize in roles such as workers, soldiers, and queens. This division of labor increases efficiency and survival of the colony, ensuring that tasks like food gathering, defense, and reproduction are effectively managed. It is a key adaptation for social living.

The alimentary canal is the continuous tube that food passes through, including the mouth, oesophagus, stomach, intestines, and anus. The liver, while important in digestion, is not part of this canal but instead an accessory organ that produces bile to help break down fats.

A major trend in evolution is the increase of genetic diversity within populations. This variation provides raw material for natural selection to act upon, allowing species to adapt to changing environments. Populations with higher diversity are generally more resilient to diseases and environmental stresses.

Members of Kingdom Plantae have chloroplasts containing chlorophyll, which allow them to carry out photosynthesis. Unlike animals, they possess cell walls made of cellulose and are primarily autotrophic. The presence of chloroplasts distinguishes them clearly from many other kingdoms of life.

Steppe grasslands are vast treeless regions with hot summers and warm winters. They are dominated by grasses and have limited rainfall, making them unsuitable for the growth of large trees. These conditions distinguish steppes from savannahs, which typically support scattered trees.

Physiological variations are differences in body functions among individuals of the same species. Blood pressure variation is a classic example, as it reflects differences in circulatory efficiency and metabolism rather than structural traits such as beak shape or fur color.