2022 JAMB BIOLOGY PAST QUESTIONS AND ANSWERS

Most plants respond to stimuli slowly due to their simpler nervous system compared to animals. Higher animals cannot reproduce asexually, and respiration in animals typically requires oxygen.

Kidney represents an organ level in higher organisms with specialized functions. Waterleaf and spermatozoon are lower in complexity.

Root structure is made of vascular bundles with specialized functions for absorption and support, which differ from stem structures.

Industrial chimneys release pollutants such as sulfur dioxide, while vehicle exhausts contribute to smog and acid rain.

Snail body structure includes a visceral mass and a muscular foot for movement, which differentiates it from other body parts.

The labelled part in the diagram conducts water and nutrients, functioning similarly to the xylem in plants.

The labeled structure II functions as xylem, a vascular tissue responsible for water transport.

Lysosomes in cells break down waste materials, earning the name ‘suicidal bags’ due to their autolytic functions.

Plasmolysis occurs when water moves out of a cell in a hypertonic solution, causing the cell membrane to pull away.

Cambium is responsible for secondary growth in plants, increasing stem thickness by producing new cells.

The vertebral structure varies by species; toads have fewer caudal vertebrae, while rats have more due to their long tails. Fish and humans have different vertebrae counts and structures, making them less likely to match this description.

Erythrocytes (red blood cells) contain hemoglobin, which binds oxygen and carbon dioxide efficiently for transport. Lymphocytes and thrombocytes do not play significant roles in gas transport, and plasma lacks the binding capacity for oxygen and CO₂.

During inspiration, intercostal muscles contract, and the diaphragm flattens, enlarging the thoracic cavity and causing air to flow into the lungs. This process does not involve exhalation, making options without inspiration steps incorrect.

Contraction of the intercostal muscles raises the rib cage, increasing chest volume and aiding in lung expansion. This is essential for inhalation, while options related to exhalation or diaphragm movement would not result directly from intercostal action.

ADH affects water balance in the kidney, glucagon influences glucose metabolism, oestrogen targets the uterus, and adrenaline affects multiple organs, fitting the given table. Incorrect options suggest effects inconsistent with these hormones’ functions.

Adrenaline, often released during stressful situations, prepares the body for “fight or flight,” which can manifest as anxiety. Hormones I, II, and III don’t have the same direct effect on stress or anxiety responses.

The Eustachian tube (labelled as the part in question) connects the middle ear to the pharynx, helping to equalize pressure. The other labeled parts do not perform this function, as they relate to hearing and balance.

The cochlea (labelled I) is part of the inner ear responsible for sound perception. Other labels correspond to structures like the external auditory meatus or ossicles, which are not responsible for detecting sound waves.

Groupings reflect ear regions: inner ear includes cochlea and semicircular canals, middle ear includes ossicles, while outer ear structures are closer to the ear canal. Misgrouped options mix structures from different ear regions.

Fertilization involves the fusion of the sperm’s head (P’s part IV) and the egg’s nucleus (Q’s part I). Other parts of P and Q are not directly involved in this fusion process that initiates embryonic development.

The union of sperm (P) and egg (Q) cells results in a new mammal, as both are gametes that combine genetic material. Asexual reproduction and plant cells are incorrect as they do not involve the fusion of these types of cells in mammals.

Gametes (P and Q) have half the chromosome number (23 each in humans) due to meiosis, allowing for restoration to 46 upon fertilization. Options with 46 chromosomes do not reflect the reduced chromosome count of gametes.

Simple sugars are produced in the chloroplast during photosynthesis, as chloroplasts contain chlorophyll which absorbs sunlight for this process. Options like vacuole and cell wall lack the biochemical machinery for sugar production.

Photosynthesis releases oxygen as a byproduct, which can be detected as evidence of the process. Carbon dioxide release and water formation are not directly observed in typical photosynthesis experiments. Fructose release is not relevant here.

Vitamin A is abundant in sources like egg yolk, carrot, and palm oil, which contain carotenoids and retinoids. Rice and green vegetables lack high concentrations of vitamin A, and options with sorghum and liver are less typical sources.

Enzymes are highly specific, meaning protease J acts on protein substrates only, matching the shape of its active site. Options suggesting denaturation or reaction stability do not address this specific enzyme-substrate interaction.

Proteases break down proteins into amino acids, which are the building blocks of proteins. Options such as fatty acids and glucose represent end products of different digestive enzymes, making them incorrect here.

Clayey soil tends to become waterlogged, impeding root growth and oxygen availability, limiting thick vegetation support. Options suggesting low water retention or porosity do not accurately describe clay’s compact structure and high water retention.

Bush burning depletes soil nutrients and negatively impacts soil structure, reducing fertility over time. Practices like soil erosion prevention and bush fallowing promote soil fertility by conserving or restoring nutrients.

A population consists of organisms of the same species in a specific area, interacting and breeding. Terms like colony and ecosystem refer to broader groupings or interactions beyond a single species group in a defined location.

Humus, the organic component of soil, forms from decomposed plant and animal matter and provides nutrients for plants. Other options like sand and clay are inorganic, lacking the necessary organic matter content.

The part labelled IV in soil diagrams typically represents humus, a dark, organic-rich layer. Silt, sand, and clay are other soil components but lack the organic material found in humus, which contributes to soil fertility.

Ecology commonly uses pyramids of energy, numbers, and biomass to represent trophic levels. “Pyramid of organisms” is not a standard ecological term and lacks the specificity of biomass or energy distribution.

Sunlight provides energy directly or indirectly to all organisms in the food chain. Green plants capture sunlight energy, forming the base of most food webs, while carbohydrates and other options are products rather than direct energy sources.

Organism L, a primary consumer, typically feeds on producers (plants). It is not a secondary consumer, nor does it act as a producer. Primary consumers play a specific role in transferring energy from plants to higher trophic levels.

Trophic levels represent each step in the food chain, classifying organisms by their feeding relationships. Terms like “energy level” or “pyramid of numbers” are not specific to this hierarchy of energy and nutrient flow.

Hairy structures reduce water loss, but flowers raised above water to attract pollinators, and spongy tissues aiding buoyancy, represent specific plant adaptations for their environments, contrasting with generalized root functions.

Competition drives succession by selecting species best suited to available resources, advancing the community structure. Predation, parasitism, and commensalism do not contribute directly to community succession.

Industrial development often disrupts natural ecosystems, contrasting with practices like recycling and wildlife reserves, which conserve resources by reducing exploitation and maintaining biodiversity.

Deforestation increases atmospheric carbon dioxide by reducing trees that absorb CO₂. Incorrect options downplay the effects of fertilizers, marine pollution, and biopesticides, which contribute to environmental degradation.