2017 JAMB BIOLOGY PAST QUESTIONS AND ANSWERS

During inhalation, the diaphragm contracts and flattens, increasing the volume of the thoracic cavity and reducing pressure, which draws air into the lungs. It does not restrict airflow or decrease lung volume during inhalation.

Mitosis results in the formation of two identical daughter cells, crucial for growth and tissue repair. Meiosis produces non-identical gametes, while conjugation is a sexual reproduction process in some microorganisms.

The kidneys maintain homeostasis by filtering blood, removing waste, and regulating water balance. They are not directly responsible for maintaining temperature or secreting digestive enzymes.

Desert plants develop thick waxy cuticles to reduce water loss through evaporation, helping them survive in arid conditions. This adaptation is not meant for nutrient absorption, photosynthesis, or obtaining food.

Primary consumers are herbivores that feed on producers (plants), such as rabbits and insects. Decomposers, secondary consumers, and tertiary consumers occupy different trophic levels in the food chain.

Bile emulsifies fats, breaking them into smaller droplets to aid in digestion and absorption in the small intestine. It does not digest carbohydrates or proteins directly.

Nitrogen-fixing bacteria, such as Rhizobium, reside in root nodules of leguminous plants, where they convert atmospheric nitrogen into forms usable by the plant. Leaves, stems, and flowers do not house these bacteria.

Light is an abiotic (non-living) component that affects ecosystems by providing energy for photosynthesis. Producers, decomposers, and consumers are biotic components involved in various ecological roles.

Osmosis is the movement of water molecules across a semi-permeable membrane from an area of lower solute concentration to higher solute concentration. Diffusion, plasmolysis, and transpiration involve other processes or structures.

Insulin regulates blood sugar by facilitating glucose uptake in cells. Adrenaline, estrogen, and testosterone have other functions, such as stress response and development of secondary sexual characteristics, but do not regulate blood sugar.

Blood flows from the vena cava to the right atrium, then to the right ventricle, from where it is pumped to the lungs. It returns to the left atrium, enters the left ventricle, and is finally pumped to the body. This sequence facilitates oxygenation of blood.

Mitochondria are known as the powerhouse of the cell, generating energy in the form of ATP. The nucleus stores genetic information, the cell membrane provides structure, and chloroplasts carry out photosynthesis but are not involved in ATP production in animals.

The female Anopheles mosquito is the primary vector of malaria, transmitting the Plasmodium parasite to humans. Other options, like Tse-tse flies, cockroaches, and houseflies, do not transmit malaria.

The cochlea in the inner ear contains hair cells that convert sound waves into electrical impulses sent to the brain. Other structures, like the eardrum, ossicles, and semicircular canals, contribute to hearing but do not directly convert sound waves into impulses.

The palisade mesophyll, located near the upper surface of the leaf, contains numerous chloroplasts and is the primary site for photosynthesis. Other parts, such as the spongy mesophyll and guard cells, also contain chloroplasts but are less active in photosynthesis.

The iris controls the amount of light entering the eye by adjusting the size of the pupil. The cornea, lens, and retina have different roles in focusing light and processing visual information but do not control light intake.

The epidermis, the outermost layer of skin, lacks blood vessels and relies on diffusion from underlying tissues for nutrient supply. The other options, such as muscle tissue and bone, are vascularized and contain blood vessels.

Ribosomes are the sites of protein synthesis within cells, translating genetic information into functional proteins. Other organelles like the mitochondria, nucleus, and Golgi apparatus have different functions, such as energy production, genetic storage, and modification of proteins.

Blood group O is known as the universal donor and can donate to groups A, B, and AB but cannot receive from them, as it lacks A and B antigens. Other options do not accurately describe the compatibility of blood types for transfusion.

Morphological variations refer to observable physical characteristics, such as height, skin color, and tongue rolling. Blood groups are genetic variations but not morphological, while fingerprints and body shape are morphological traits.

The Venus flytrap exhibits structural adaptation, where modified leaves are adapted to trap insects for nutrient absorption, helping the plant survive in nutrient-poor soils. Adaptive coloration, environmental adaptation, and behavioral adaptation do not specifically describe this mechanism.

[Diagram-based answer] In the diagram, part II is identified as the filament, which supports other structures within certain biological systems, such as the stamen in plants. Arch, slit, and raker serve different functions in other contexts.

Birds adapted to aquatic feeding often have long, slender, and curved beaks to access food in water environments. This type of beak differs from those adapted for cracking seeds or catching prey.

The nucleus contains DNA, which is responsible for genetic inheritance and can be used in paternity testing. The centrosome, ribosome, and mitochondria do not carry complete genetic information used for determining paternity.

The atlas and axis vertebrae enable the skull to move in various directions, including nodding and rotation. Other combinations of vertebrae, like thoracic or cervical vertebrae, support other types of movement but not specifically nodding and rotation.

Overcrowding in a habitat increases competition for resources, leading some organisms to emigrate to less crowded areas. It generally does not result in reduced competition or mortality.

In the provided diagram, the part labeled III functions as an exchange surface, allowing substances like gases to pass through. Other options, such as water outlet, food strainer, and blood transporter, do not align with the typical function of such structures in biological systems.

A hummingbird has a long, slender, and slightly curved beak that allows it to reach deep into flowers for nectar. Other beak shapes do not suit nectar feeding.

Sandy soil has the least nutrient retention capacity due to its large particle size and low water retention. Clay, loam, and clay loam soils retain nutrients better.

Dryopteris, a type of fern, is more advanced than the other options as it possesses vascular tissues and a more complex structure. Marchantia, Chlamydomonas, and Spirogyra are simpler, non-vascular plants or algae.

The color change helps grasshoppers escape detection, blending into green vegetation during the season and charred areas after a fire. This color adaptation aids in predator avoidance.

Savanna plants often have fissured bark to protect against fire and reduce water loss. Fewer grasses and tall trees are less common, while long lifespans do not specifically adapt to savanna conditions.

Xylem transports water, while phloem transports manufactured food (sugars) from leaves to other parts of the plant. Tracheids are specialized xylem cells, but they are not directly responsible for food transport.

The epidermis is the outermost layer of herbaceous roots, providing protection and aiding in absorption. The cuticle, pericycle, and endodermis are located deeper within plant tissues.

Colour blindness is a sex-linked trait, typically carried on the X chromosome, affecting mostly males. Dwarfism, albinism, and tongue rolling are not commonly sex-linked.

Population density is calculated by dividing the total number of Tridax (400) by the area sampled. With each quadrant representing 1.6m² and used 50 times, total area = 1.6 * 50 = 80m², so density = 400/80 = 5 Tridax per m².

Termites and earthworms improve soil structure by increasing porosity and aeration, which aids water retention and root growth. Acidity is not directly influenced by these organisms.

Humus percentage is calculated by finding the difference in mass before and after burning, which represents organic matter. The calculation would be: (7.5g−(25g−20g))/7.5g×100(7.5g – (25g – 20g)) / 7.5g times 100(7.5g−(25g−20g))/7.5g×100 = 33.3%.

Meiosis is the process of cell division that produces gametes with half the genetic material of the parent cell. Mitosis is for general cell division, while fertilization and implantation occur after gamete formation.

[Diagram-based answer] The structure labeled in the diagram that conserves water most efficiently is likely related to desert-adapted or succulent plants.

Wind-pollinated flowers usually lack nectar since they do not need to attract pollinators. They are generally inconspicuous and produce large amounts of pollen for dispersal by wind.

Binary fission is the simplest form of reproduction, where a single organism divides into two identical offspring. Other forms, like budding, spore formation, and conjugation, are more complex and typically found in multicellular organisms or fungi.

Hydra viridis is organized at the organ level, where different tissues form organs that perform specific functions. Other organisms like Volvox and Paramecium are unicellular or colony-based, and the onion bulb is a plant structure, not an organ system.

Chlorofluorocarbons (CFCs) are released primarily from cooling systems such as refrigerators and air conditioners. They contribute to ozone depletion. Crude oil refining, coal mining, and vehicle exhaust do not release significant CFCs.

In the dark stage (Calvin cycle) of photosynthesis, carbon dioxide is reduced to form glucose. Photolysis of water and oxidation are part of the light-dependent reactions, not the Calvin cycle.

Vibrio species, specifically Vibrio cholerae, cause cholera, an infectious disease resulting in severe diarrhea and dehydration. Clostridium, Shigella, and Salmonella typhi are associated with other diseases.

Freshwater habitats are characterized by low salinity, which differentiates them from marine habitats with high salinity levels. High turbidity, density, or current are not universal characteristics of freshwater habitats.

The remora and shark relationship is commensalism, where the remora benefits by attaching to the shark for transport and food scraps, while the shark is unaffected. Parasitism, amensalism, and mutualism do not accurately describe this relationship.

After decolourising the leaf with alcohol, it is dipped in hot water to soften it and make it easier to handle during the iodine test for starch presence. Killing the leaf or removing chlorophyll are steps taken before this stage.

Rainfall is a key determinant of vegetation type, influencing plant growth and diversity in an area. Temperature, light, and wind also affect vegetation but are not as significant as rainfall in determining major vegetation zones.