2021 JAMB BIOLOGY PAST QUESTIONS AND ANSWERS

Species is the taxonomic rank where organisms can interbreed to produce fertile offspring, sharing similar characteristics and genetic makeup. Kingdom, class, and family are higher taxonomic levels and encompass broader groups of organisms.

Euglena is a mixotrophic organism, capable of surviving in darkness by switching to heterotrophic nutrition, allowing it to absorb organic matter instead of relying on photosynthesis. In darkness, photosynthesis (option B) is not possible.

The cytoplasm suspends organelles and is the site for most cellular processes. It does not regulate energy (which mitochondria do), nor is it solely responsible for cell division. It also isn’t the outermost cell part, as that is the membrane.

[Diagram explanation] The thistle funnel experiment demonstrates osmosis. Water moves through the semi-permeable membrane toward the sugar solution, causing the water level to rise in the thistle funnel. This process continues until equilibrium is reached.

Osmosis is demonstrated here, as water moves across a membrane from an area of low solute concentration (distilled water) to high solute concentration (sugar solution). It is not a demonstration of diffusion, water culture, or transportation.

In plant cells, the cell wall provides structural support and plays a role similar to the membrane, helping regulate cell pressure and protect the cell. The cytoplasm, nucleolus, and mitochondria have different functions within the cell.

Haemolysis occurs when red blood cells burst due to osmotic imbalance, as water enters the cells in a hypotonic solution. Plasmolysis, diffusion, and wilting describe different processes or phenomena not involving the bursting of animal cells.

Hydrotropism is the growth movement of plants in response to water. Geotropism is a response to gravity, phototropism to light, and thigmotropism to touch.

Glycolysis involves the breakdown of glucose into two molecules of pyruvate (C3H4O3), producing ATP and hydrogen in the process. The correct equation reflects this breakdown. Other options either misstate the products or incorrectly describe the stages of the process.

The femur, located in the thigh, is the longest bone in the human body, providing support for weight-bearing and locomotion. Other bones, like the humerus, scapula, and tibia, are not as long as the femur.

Muscle tissue, while involved in movement, is not considered skeletal material. Chitin, cartilage, and bone are all structural components that provide support and protection in various organisms.

Slow blood flow in capillaries allows for adequate exchange of materials (e.g., oxygen, carbon dioxide, nutrients) between blood and tissues. Other options do not accurately describe the purpose or function of slow capillary flow.

Fishes, amphibians, birds, and humans all possess kidneys as their primary excretory organs. Annelids, insects, and protozoans have other excretory structures and do not all share the kidney as an excretory organ.

Arteries do not have valves along their length; this feature is found in veins. They do have thick, muscular walls, carry blood away from the heart, and, except for the pulmonary artery, generally transport oxygenated blood.

The graph shows that birds maintain a stable body temperature independent of environmental temperature, while lizards’ body temperature fluctuates with their environment. This illustrates endothermy in birds and ectothermy in lizards.

Poikilothermy refers to organisms that do not regulate their body temperature internally and fluctuate with environmental temperature, as seen in lizards. Homeostasis, homeothermy, and osmoregulation describe different physiological processes.

Saline solutions are isotonic to body fluids, helping to maintain fluid and electrolyte balance. Plain water would disturb this balance and could cause cell lysis. Salt as a preservative or blood cell production is unrelated to saline use in drips.

The cochlea in the inner ear contains hair cells that convert sound vibrations into electrical signals. Other structures, such as the ampulla, tympanum, and malleus, have different roles in the ear and are not directly involved in sound perception.

Convex lenses converge light rays before they enter the eye, allowing them to focus properly on the retina for those with long-sightedness. Diverging or adjusting light intensity does not address this condition.

A seed is a developed ovule, containing the embryo and sometimes an endosperm, enabling it to grow into a new plant. The ovary itself develops into the fruit, not the seed.

Photosynthesis removes carbon from the atmosphere as plants absorb carbon dioxide to produce glucose. Other processes, like putrefaction, volcanic eruption, and fuel burning, release carbon into the atmosphere.

The water cycle includes processes like precipitation, transpiration, and evaporation. Other cycles, like the carbon, nitrogen, and oxygen cycles, involve different chemical or biological processes.

Light is the critical limiting factor for plants below the photic zone, as it is required for photosynthesis. Other factors like nutrients, water, and carbon dioxide are also important but not as limiting as light in deep waters.

A quadrat is used to estimate plant populations in a specific area by counting individuals within marked sections. Other tools, like the pooter, pitfall trap, and sweep net, are used for capturing or counting animals or insects.

Sandy soil is light and easy to dig due to its large particle size and low density. It has high drainage capacity and is poorly suited to retain nutrients, so options about limited air space and slow drainage are incorrect.

A primary consumer, like a sheep, feeds directly on producers (plants). Dogs are secondary consumers, and fungus is a decomposer, not a primary consumer. Grass is a producer.

In the food chain, P is a producer, sustained by sunlight, which it uses for photosynthesis to produce food. Other options like carbohydrates and mineral salts are incorrect sources of energy for a primary producer.

Organism R in the food chain is a secondary consumer because it feeds on primary consumers. It is not a producer or a primary consumer.

Scabies is a contagious skin disease caused by mites and is not hereditary. Albinism, haemophilia, and color blindness are genetic disorders passed from parents to offspring.

Meiosis in flowering plants produces gametophytes, which will eventually develop into gametes. Zygotes and pollen grains are not immediate products of meiosis; the zygote forms after fertilization.

In eukaryotic cells, DNA is housed in the nucleus, where it controls cellular activities and hereditary traits. Other cell structures like the central vacuole, lysosome, and Golgi body are not involved in DNA storage.

Given that haemophilia is an X-linked recessive disorder, 50% of their offspring would inherit the disease since the mother is homozygous recessive and the father is heterozygous.

Cytokinesis ensures that each daughter cell receives a full set of organelles and sufficient cytoplasm to function independently. It does not involve genetic combinations or exclusion of worn-out organelles.

Diurnal animals are active during the day, as opposed to nocturnal animals, which are active at night. Terrestrial refers to land-dwelling animals, and homoatomic is not a relevant classification in this context.

Mutation of genes is a mechanism of genetic change, but it is not direct evidence of evolution. Fossil records, comparative anatomy, and geographical distribution provide observable evidence for evolutionary relationships.

The diagram indicates that the organisms are oviparous, meaning they lay eggs. Hermaphrodite, viviparous, and ovoviviparous describe different reproductive methods that are not relevant to the diagram shown.

Amplexus is the mating posture in amphibians, where the male clasps the female to facilitate external fertilization. Other terms like mating, courtship display, and reproductive swimming are less specific in describing this behavior.

DNA analysis provides a reliable means of identifying individuals due to its unique genetic information. RNA analysis, blood group tests, and behavioral traits do not provide the same level of accuracy in personal identification.

Schistosomiasis, also known as bilharzia, is caused by parasitic worms found in freshwater. The symptoms include blood in the urine. Onchocerciasis, poliomyelitis, and salmonellosis are not typically acquired through swimming and do not cause blood in urine.

Convergent evolution occurs when unrelated species develop similar traits due to similar environmental pressures. Whale flippers and fish fins are examples of this, as both serve similar functions in aquatic environments but evolved independently.

An ecosystem is made up of biotic (living organisms) and abiotic (non-living components like water, sunlight, soil) elements interacting with each other. Only considering living organisms or physical features ignores the balance and interactions in ecosystems.

Osmosis causes water to move into the thistle funnel’s concentrated solution from the surrounding water, increasing the liquid level in the funnel.

The membrane acts as a selectively permeable barrier, allowing only water molecules to pass through by osmosis while preventing solute movement. This helps demonstrate osmotic processes.

Chlorophyll absorbs sunlight, which is essential for converting carbon dioxide and water into glucose in photosynthesis. Other functions like nutrient absorption, water transport, or leaf structure maintenance are unrelated to chlorophyll’s role.

Mitochondria produce energy in the form of ATP through cellular respiration, powering various cellular functions. They are not directly involved in protein synthesis, cell division, or waste removal.

Photosynthesis is the process by which green plants produce food, converting sunlight, water, and carbon dioxide into glucose. Respiration and transpiration are different processes, and synthesis is too broad to describe photosynthesis specifically.

The medulla oblongata regulates involuntary actions like heart rate and respiration. The cerebrum, cerebellum, and hypothalamus serve different functions related to voluntary actions, balance, and homeostasis.

Red blood cells transport oxygen from the lungs to body tissues using hemoglobin. Other options, like blood clotting, producing antibodies, or fighting infections, are functions of other cell types or processes.

The skin is the largest organ in the human body, covering the entire body and performing multiple functions like protection and temperature regulation. The brain, liver, and lungs are large organs but smaller than the skin.

The cochlea converts sound waves into nerve impulses through hair cells. The pinna, malleus, and tympanic membrane do not perform this function but are part of the sound conduction pathway.

Insects have an exoskeleton, an external structure made of chitin that supports and protects their bodies. Endoskeletons are internal, hydrostatic involves fluid-filled cavities, and cartilaginous is a type found in some vertebrates.