JAMB UTME - Biology - 2025

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An estuary is a partially enclosed coastal body of water where freshwater from rivers meets and mixes with saltwater from the sea. Estuarine habitats have fluctuating salinity, tidal influence, and waterlogged, often muddy substrates. Only specially adapted plants can thrive in these conditions.

Mangrove trees and shrubs are the characteristic vegetation of estuarine and coastal swamp habitats in tropical regions. They possess several key adaptations for this environment:

• Prop roots (stilt roots): Provide anchorage in soft, unstable mud and raise the plant above tidal water.
• Pneumatophores (breathing roots): Aerial roots that project above the waterlogged soil to obtain oxygen, since the anaerobic mud lacks sufficient dissolved oxygen for root respiration.
• Salt-excreting glands: Allow the plant to tolerate the high salt concentration of brackish water.
• Viviparous seeds: Seeds germinate while still attached to the parent plant, producing seedlings that can establish quickly once they drop into the water or mud.

Plantain, Gmelina, and Iroko are all terrestrial plants that grow in well-drained, non-saline soils. They lack the specialised adaptations required for survival in a saline, waterlogged estuarine environment.

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The genotype of an organism is the complete set of genes (alleles) it carries in its DNA. It represents the organism's genetic constitution, whether or not those genes are visibly expressed. Two organisms can share the same outward appearance yet differ in genotype if one carries a hidden recessive allele.

It is important to distinguish the genotype from related but different terms:

• A nucleotide is the basic building block of nucleic acids (DNA and RNA). Each nucleotide consists of a phosphate group, a five-carbon sugar, and a nitrogenous base. It is a molecular unit, not a description of an organism's overall genetic makeup.
• A karyotype is the organised visual profile of an organism's chromosomes, arranged by size and shape. It shows chromosome number and structure but does not describe the specific allele composition at each gene locus.
• The phenotype is the set of observable physical and biochemical characteristics of an organism (e.g. eye colour, height, blood group). Phenotype results from the interaction of genotype with the environment, but it is not the genetic makeup itself.

Exam tip: Remember the pair: genotype = genes you carry; phenotype = traits you display. Questions often test whether students can distinguish between the two.

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Obudu Game Reserve (also known as Obudu Cattle Ranch or Obudu Mountain Resort) is located in Cross River State, in the south-eastern part of Nigeria. It sits on the Obudu Plateau in the Sankwala Mountains, near the border with Cameroon.

Cross River State is known for its rich biodiversity and is home to several important conservation areas, including the Cross River National Park. The cool highland climate of the Obudu Plateau, at an elevation of about 1,576 metres above sea level, supports unique montane grassland and forest ecosystems that are distinct from the surrounding tropical lowlands.

The other states listed do not contain Obudu Game Reserve. Anambra State is in the south-east but lacks this highland reserve. Akwa Ibom State is a coastal state in the Niger Delta region. Rivers State, also in the Niger Delta, is distinct from Cross River State despite the similarity in names.

Exam tip: Do not confuse Rivers State with Cross River State. They are separate states with different geographical features and conservation areas.

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Spermatophytes are seed-bearing plants. They are divided into two major groups: gymnosperms (seeds not enclosed in a fruit) and angiosperms (seeds enclosed within a fruit, formed from the ovary wall).

Angiosperms are considered the most advanced spermatophytes because they possess several evolutionary innovations:

• Double fertilisation, which produces both an embryo and a nutrient-rich endosperm.
• Flowers, which allow efficient pollination by wind, water, insects, and other animals.
• Fruits, which aid in seed dispersal.
• Highly efficient vascular tissue, including vessel elements in the xylem.

Angiosperms also form the largest group in the plant kingdom, with over 300,000 known species, far exceeding the roughly 1,000 species of gymnosperms.

Ferns are not spermatophytes at all; they reproduce by spores, not seeds. Cones are reproductive structures of gymnosperms, not a plant group. Gymnosperms are spermatophytes but are less advanced and far fewer in number than angiosperms.

The correct answer is therefore angiosperm.

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Population growth is influenced by a range of factors. These are broadly categorised into factors that increase population size (such as birth rate and immigration) and factors that decrease it (such as death rate, emigration, predation, disease, and competition for resources like food).

Predators reduce a population by killing and consuming members of the prey species. Food shortage limits population growth because organisms cannot survive and reproduce without adequate nutrition. Disease causes mortality, directly reducing numbers. All three are environmental resistance factors that check population growth.

Natality refers to the birth rate of a population. It is not a factor that acts on population growth from outside; rather, it is a component of population growth itself. Natality describes how many new individuals are added to a population per unit time. While it influences population size, it is a demographic parameter rather than an environmental or ecological limiting factor.

In ecology, when we refer to "factors affecting population growth," we typically mean the environmental resistance factors (biotic and abiotic) that regulate population size, such as predation, disease, food availability, and competition. Natality is part of the population's intrinsic growth rate, not an external regulatory factor.

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The rumen is the first compartment of the stomach in ruminant animals such as cattle. It houses a dense community of microorganisms, including bacteria and protozoa, that help break down cellulose and other complex plant materials that the cow cannot digest on its own.

This relationship is symbiosis (specifically mutualism), because both parties benefit. The bacteria and protozoa gain a warm, moist, anaerobic environment with a constant supply of food from the plant material the cow ingests. In return, they produce enzymes such as cellulase that digest cellulose into simpler compounds like volatile fatty acids, which the cow absorbs and uses as a major energy source. The microorganisms also synthesise vitamins (such as B-vitamins) and microbial protein that the cow digests further along the alimentary canal.

This is not commensalism, because commensalism involves one organism benefiting while the other is neither helped nor harmed. Here, both parties clearly benefit. It is not parasitism, because neither organism is harmed. It is not predation, because neither organism kills and consumes the other as prey.

Exam tip: Whenever a question describes two different organisms living together with mutual benefit, the correct ecological term is symbiosis (mutualism). The rumen of cattle is the classic JAMB example of this association.

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The carbon cycle describes how carbon moves between the atmosphere, living organisms, the oceans, and the earth's crust. The key processes in the carbon cycle include photosynthesis, respiration, decomposition, combustion, and fossilisation.

Combustion (burning) releases carbon dioxide into the atmosphere when fossil fuels (coal, oil, natural gas) or organic matter (wood, biomass) are burned. This is a major pathway by which stored carbon re-enters the atmospheric pool as CO₂. It is therefore a direct component of the carbon cycle.

The other options belong to different nutrient cycles or involve water, not carbon:

• Nitrification is a process in the nitrogen cycle, in which nitrifying bacteria convert ammonium ions (NH₄⁺) to nitrites and then nitrates in the soil.
• Evaporation is a phase of the water cycle (hydrological cycle), where liquid water changes to water vapour.
• Transpiration is also part of the water cycle. It involves the loss of water vapour from the aerial parts of plants, mainly through stomata.

Exam tip: When asked about processes in a specific nutrient cycle, focus on the element being cycled. Carbon cycle processes involve movement of carbon-containing compounds: photosynthesis, respiration, decomposition, combustion, and fossilisation.

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A reflex action is a rapid, involuntary, and automatic response to a stimulus that does not require conscious thought or decision-making from the brain. Reflex actions are mediated by a reflex arc: a stimulus is detected by a receptor, a sensory neuron carries the impulse to the spinal cord (or brainstem), a relay neuron processes it, and a motor neuron sends a response to the effector (muscle or gland), all without the cerebral cortex making a deliberate decision.

Coughing is a reflex action. When an irritant enters the airways, receptors in the throat and bronchi are stimulated, and a rapid, involuntary cough is triggered to expel the irritant. This happens automatically and does not require a conscious decision, although it can sometimes be voluntarily suppressed or initiated.

Writing, talking, and walking are all voluntary actions that require conscious thought and coordination by the cerebral cortex of the brain. Although walking can become somewhat automatic with practice, it is initiated and controlled voluntarily and involves complex motor planning, making it a learned voluntary action rather than a true reflex.

Exam tip: True reflex actions are involuntary and immediate. Common examples include coughing, sneezing, blinking, knee-jerk response, and withdrawal of the hand from a hot object.

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Hibernation is a behavioural adaptation in which an animal enters a prolonged state of dormancy during adverse weather conditions, particularly cold winters. During hibernation, the animal's metabolic rate, body temperature, heart rate, and breathing rate drop significantly, allowing it to conserve energy when food is scarce and temperatures are too low for normal activity. Examples include bears, hedgehogs, bats, and some rodents.

The key word in the question is "adverse weather conditions." Hiding is a behavioural response primarily used to escape predators, not specifically to cope with weather. Remaining motionless (freezing) is a defence mechanism against predators. Swelling up (puffing up the body) is a defensive display used by some animals to appear larger and deter predators, such as the puffer fish or the toad.

Hibernation (for cold weather) and its warm-weather counterpart, aestivation (for hot, dry conditions), are the two main behavioural adaptations specifically for surviving adverse weather.

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Flowering plants that rely on insects for pollination have evolved specific adaptations to attract insect visitors. These adaptations include brightly coloured petals, the presence of nectar (a sugary reward), sticky or spiky pollen grains that attach to insect bodies, and scented flowers that release fragrances to draw insects from a distance.

Large anthers are characteristic of wind-pollinated flowers, not insect-pollinated ones. Wind-pollinated flowers produce enormous quantities of light, smooth pollen and hang their large anthers freely so the wind can carry the pollen away. They typically lack bright colours, scent, and nectar because they do not need to attract animal visitors.

The absence of nectar and scentless flowers would both be disadvantages for insect-pollinated plants, since insects are guided to flowers largely by scent and the promise of a nectar reward.

Of the options provided, scented flowers is the feature specifically associated with insect pollination. The scent acts as a chemical signal that helps insects locate the flower, ensuring effective pollen transfer.

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The diagram shows an animal cell with four labelled parts. Label I points to the large, dark, roughly spherical structure located centrally within the cell. This is the nucleus, the membrane-bound organelle that contains the cell's genetic material (DNA) and controls cell activities such as growth, metabolism, and reproduction.

The other labelled structures can be identified as follows: Label II points to the cell membrane (the outer boundary), Label III indicates the cytoplasm (the gel-like substance filling the cell), and Label IV points to small, elongated organelles which are the mitochondria (responsible for cellular respiration and energy production).

The nucleus is distinguishable by its large size relative to other organelles, its dark staining (due to dense chromatin material), and its roughly circular shape. It is often the most prominent structure visible in a cell diagram.

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The diagram shows the human digestive system in a longitudinal view. The organs are labelled I through IV from top to bottom.

Label I points to the oesophagus (gullet), the muscular tube connecting the mouth to the stomach. Label II indicates the stomach, a J-shaped organ where food is mixed with gastric juices. Label III points to the pancreas, located behind the stomach. Label IV points to a large, lobed organ situated in the upper right portion of the abdominal cavity, shown with cross-hatching to indicate its dense, solid structure.

The organ labelled IV is the liver. It is the largest internal organ in the human body and plays a central role in digestion by producing bile, which is stored in the gallbladder and released into the duodenum to emulsify fats. The liver also performs functions including detoxification of harmful substances, metabolism of carbohydrates, proteins and fats, storage of glycogen and vitamins, and deamination of excess amino acids to form urea.

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A reflex action is a rapid, automatic, involuntary response to a stimulus that does not require conscious thought or decision-making from the brain. Reflex actions are coordinated by the spinal cord (or brainstem) through a pathway called a reflex arc, which consists of a receptor, sensory neurone, relay neurone (in the spinal cord), motor neurone, and effector.

Sneezing is a classic reflex action. When irritants such as dust, pollen, or strong odours stimulate nerve endings in the nasal mucosa, sensory signals travel to the sneeze centre in the brainstem, which triggers an involuntary, explosive expulsion of air through the nose and mouth. A person cannot consciously decide to sneeze or easily prevent a sneeze once it is triggered.

The other options are not reflex actions:

• Walking is a voluntary, coordinated motor activity that requires conscious initiation and control from the cerebrum, even though some aspects become semi-automatic with practice.
• Dancing is a deliberate, learned motor activity involving planning and coordination by the brain.
• Crying is an emotional response that involves higher brain centres; it is not an immediate, involuntary response to a physical stimulus in the way a true reflex is.

Exam tip: Other common reflex actions include blinking, knee-jerk response, coughing, and withdrawal of the hand from a hot surface. They are all rapid, involuntary, and protective.

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Pepsin is a proteolytic enzyme (protease) that is active in an acidic medium. It is secreted as its inactive precursor, pepsinogen, by the chief cells of the gastric glands in the stomach lining. Hydrochloric acid (HCl), produced by the parietal (oxyntic) cells of the stomach, converts pepsinogen into active pepsin and maintains the stomach contents at a pH of approximately 1.5 to 2.5. Pepsin functions optimally within this strongly acidic pH range, where it breaks down proteins into shorter polypeptide chains.

In an alkaline medium, pepsin is denatured and loses its catalytic activity. It does not function in a neutral medium either. The statement that pepsin works in both alkaline and acidic media is incorrect because the enzyme's three-dimensional structure, which is essential for substrate binding, is disrupted outside its narrow acidic pH range.

Each digestive enzyme has a specific optimum pH: pepsin requires acid (stomach), while enzymes like trypsin and pancreatic lipase require an alkaline environment (small intestine, pH approximately 7.5 to 8.5).

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Cells produce various metabolic waste products that must be stored or removed. The organelle primarily responsible for storing waste products within the cell is the vacuole.

Vacuoles are membrane-bound sacs found in cells. In plant cells, there is typically one large central vacuole that can occupy up to 90% of the cell volume. In animal cells, vacuoles tend to be smaller and more numerous. Vacuoles store a variety of substances including water, nutrients, pigments, and importantly, metabolic waste products. By sequestering waste inside the vacuole, the cell prevents these potentially harmful substances from interfering with cytoplasmic reactions.

The other options serve different functions:

• The Golgi apparatus packages, modifies, and sorts proteins and lipids for transport to their final destinations. It does not function as a waste storage site.
• The cell wall (found in plant cells) provides structural support and rigidity. It is not an organelle involved in storage.
• Lysosomes contain digestive enzymes that break down worn-out organelles, food particles, and foreign material. They destroy waste rather than store it.

Exam tip: Distinguish between lysosomes (which digest and break down waste) and vacuoles (which store waste and other substances). Storage and digestion are different functions.

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A cypsela is a type of dry, one-seeded indehiscent fruit characteristic of plants in the family Asteraceae (Compositae), such as the dandelion and sunflower. In many species, the cypsela bears a feathery structure called a pappus, which acts like a parachute and enables the fruit to be carried long distances by wind. This is a classic example of wind dispersal (anemochory).

A schizocarp is a dry fruit that splits into single-seeded segments at maturity and may be dispersed by various means depending on the species. A caryopsis is the fruit type of grasses, where the seed coat is fused to the fruit wall; grasses are typically wind-pollinated, but the caryopsis itself may be dispersed by wind, animals, or water depending on the species. A capsule is a dry dehiscent fruit that splits open to release seeds and can be dispersed by several mechanisms (wind, shaking, explosive).

The cypsela with its pappus is the most specifically and consistently associated with wind dispersal among these options.

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Bats are mammals, while birds belong to class Aves. Although both can fly and share certain features, the question asks for a characteristic that differentiates bats from birds - something bats have that birds do not.

The distinguishing feature is that bats possess mammary glands. Mammary glands are the defining characteristic of all mammals (class Mammalia). Female bats produce milk to suckle their young, which is something no bird does. Birds instead feed their young by regurgitation or by bringing food to the nest.

The other options describe features that both bats and birds share, so they cannot differentiate the two:

• Both bats and birds possess a four-chambered heart (two atria and two ventricles), so this is not a distinguishing feature.
• While many bat species are nocturnal (active at night), some birds are also nocturnal (e.g., owls, nightjars), so nocturnal activity is not a reliable differentiating characteristic.
• Both bats and birds are warm-blooded (endothermic), maintaining a constant body temperature regardless of the environment, so this does not differentiate them.

When comparing animal groups in examinations, focus on features that are exclusive to one group. Mammary glands are exclusive to mammals and are never found in birds.

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The biosphere is the zone of the Earth that provides habitat for all living organisms. It encompasses all ecosystems on the planet and includes the parts of the atmosphere, lithosphere (land), and hydrosphere (water) where life exists. The biosphere extends from the deepest ocean trenches to several kilometres into the atmosphere, wherever conditions permit organisms to survive.

The atmosphere is the layer of gases surrounding the Earth; while some organisms live in the lower atmosphere, it is not itself a habitat zone for all life. The lithosphere is the solid outer layer of the Earth (the crust and upper mantle); it provides the physical surface on which terrestrial life exists but does not include aquatic or atmospheric habitats. "Environment" is a broader, more general term that refers to the surroundings of an organism and includes both biotic and abiotic factors; it is not the specific ecological term for the life-supporting zone.

The biosphere is the correct ecological term because it specifically denotes the global sum of all ecosystems, integrating land, water, and air wherever life is found.

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Agglutination is the clumping together of red blood cells, which can block blood vessels and be fatal. It occurs during a blood transfusion when the antigens on the donor's red blood cells react with the antibodies in the recipient's plasma. In other words, agglutination happens when the antigen-antibody combination between donor and recipient is incompatible.

In the ABO blood group system, each blood group carries specific antigens (agglutinogens) on the surface of its red blood cells and specific antibodies (agglutinins) in its plasma:

When a donor's antigen meets a matching antibody in the recipient (for example, antigen A meets anti-A antibody), the antibodies bind to the red blood cells and cause them to clump. This is agglutination.

Race has no bearing on blood compatibility. Same antibodies do not fuse with each other to cause a problem. Being in the same blood group actually ensures compatibility, not agglutination.

The key principle: always match donor antigens against recipient antibodies. Incompatibility between them is what triggers agglutination.

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The stamen is the male reproductive organ of a flower, and it consists of two parts: the filament and the anther. The filament is a slender stalk that supports the anther, holding it in a position where pollen can be effectively released or accessed by pollinators. The anther is the expanded, often bilobed structure at the tip of the filament that contains pollen sacs (microsporangia), where pollen grains (containing male gametes) are produced through meiosis and subsequently released.

The ovary and stigma are parts of the carpel (pistil), which is the female reproductive organ. The ovary contains the ovules, and the stigma is the receptive surface that captures pollen. "Filament and ovary" incorrectly combines a male part with a female part. "Sepals and petals" are accessory floral parts: sepals protect the flower bud, and petals attract pollinators. Neither is part of the stamen.

For examination purposes, remember the complete structure: a stamen = filament + anther (male), and a carpel = stigma + style + ovary (female).

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Cross fertilization (also called cross-pollination in plants or outbreeding in animals) involves the fusion of gametes from two genetically different individuals of the same species. Its primary advantage is that it increases genetic variation in the offspring, which leads to the production of healthier, more vigorous individuals.

This occurs because cross fertilization brings together different alleles from two parents, increasing heterozygosity. Heterozygous individuals are less likely to express harmful recessive traits, a phenomenon known as hybrid vigour (heterosis). The resulting offspring tend to be more resistant to diseases, better adapted to environmental changes, and generally more robust.

The other options describe disadvantages or consequences of self-fertilization (inbreeding), not cross fertilization:

• Inbreeding depression is a reduction in fitness caused by repeated self-fertilization, which increases homozygosity and the expression of deleterious recessive alleles.
• Production of weak offspring is likewise a consequence of inbreeding, not outbreeding.
• While cross-fertilized offspring may occasionally be less adapted to a very specific local environment (because they carry new allele combinations), this is a potential trade-off, not an advantage.

For examinations, remember: cross fertilization promotes genetic diversity, hybrid vigour, and healthier offspring, while self-fertilization risks inbreeding depression.

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The diagram shows a longitudinal section of a typical animal cell (or protozoan such as Amoeba) with four organelles labelled I through IV. Label II points to the nucleus, the large, membrane-bound organelle located centrally within the cell.

The nucleus is the control centre of the cell. It contains the cell's genetic material (DNA) organised into chromosomes, which carry instructions for protein synthesis and all cellular activities. Through gene expression, the nucleus directs metabolism, growth, reproduction, and responses to stimuli.

The other options describe functions of different organelles: mitochondria produce energy for the cell through aerobic respiration, the endoplasmic reticulum transports materials within the cell, and secretory vesicles or the cell membrane transport materials outside the cell. Since the structure labelled II is the nucleus, its primary function is to coordinate the activities of the cell.

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Chlamydomonas is a unicellular, microscopic, photosynthetic organism found in freshwater habitats. It possesses a cell wall, a cup-shaped chloroplast, an eyespot (stigma), and two flagella for locomotion. Because it is a simple, unicellular organism that can both photosynthesise and move, it is classified among the most primitive plant-like organisms.

In the traditional classification system used at WAEC/JAMB level, such simple, unicellular, plant-like organisms are placed in the phylum Protophyta (meaning "first plants"). This phylum includes algae and other simple photosynthetic organisms that do not have true roots, stems, or leaves.

The other phyla listed contain more complex organisms:

• Bryophyta includes mosses and liverworts, which are small, non-vascular land plants.
• Pteridophyta includes ferns and horsetails, which are vascular plants that reproduce by spores.
• Tracheophyta refers to all vascular plants (those with xylem and phloem), encompassing ferns, gymnosperms, and angiosperms.

Chlamydomonas lacks all of these complex features. Its unicellular, flagellated, photosynthetic nature places it firmly in Protophyta.

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Poliomyelitis (polio) is a highly infectious disease caused by the poliovirus, which attacks the motor neurons of the spinal cord and brainstem. In severe cases, the destruction of these nerve cells leads to irreversible paralysis of the limbs, particularly the legs. This is why the statement that polio is capable of paralysing the limbs is correct.

Evaluating the other statements:

• Polio is a viral disease, not a bacterial one. It is caused by the poliovirus, a member of the enterovirus group.
• Effective vaccines exist against polio. The oral polio vaccine (OPV, Sabin) and the inactivated polio vaccine (IPV, Salk) have been used worldwide and have nearly eradicated the disease through mass immunisation programmes.
• While polio can technically infect people of any age, it predominantly affects children under five years old. The claim that it affects both young and old equally is misleading; it is primarily a disease of early childhood, which is why it was historically called "infantile paralysis."

Remember: polio is viral, vaccine-preventable, and primarily causes paralysis by destroying motor neurons in the spinal cord.

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Albinism is a genetic condition in which the body cannot produce normal amounts of the pigment melanin. Melanin is responsible for giving colour to the skin, hair, and eyes. The disorder is caused by inheriting two copies of a recessive gene that codes for a defective or non-functional form of the enzyme tyrosinase, which is needed for melanin synthesis.

Since albinism follows an autosomal recessive inheritance pattern, an individual must receive the defective allele from both parents (homozygous recessive, aa) to express the condition. A person who carries only one copy of the recessive allele (heterozygous, Aa) is a carrier but does not show symptoms because the dominant allele produces enough functional enzyme.

The other options are incorrect. Sebum is an oily substance produced by sebaceous glands in the skin that lubricates the skin and hair; it plays no role in pigmentation. Over-production of melanin would result in hyperpigmentation (darker skin), not albinism. The root cause is genetic, not a simple over- or under-production of a glandular secretion.

Exam tip: Albinism is a classic example of a condition caused by homozygous recessive alleles. Remember that the underlying mechanism involves a faulty enzyme (tyrosinase) leading to absence or severe reduction of melanin.

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The mosquito possesses a piercing and sucking type of mouthpart. Its mouthparts are modified into a long, needle-like proboscis composed of six stylets enclosed within the labium (lower lip). The stylets include the mandibles and maxillae, which pierce the skin of the host, and the labrum-epipharynx, which forms a channel through which blood is sucked up. The hypopharynx delivers saliva containing anticoagulants into the wound. This arrangement allows the mosquito to penetrate skin and feed on blood.

The cockroach has biting and chewing mouthparts, adapted for cutting and grinding solid food. The butterfly and moth both have siphoning (sucking only) mouthparts: a long, coiled proboscis used to sip nectar from flowers. Their mouthparts are not designed for piercing; they can only access liquid that is already exposed.

In examinations, distinguish carefully between "piercing and sucking" (penetrates tissue, e.g. mosquito, tsetse fly, aphid) and "siphoning/sucking" (draws exposed liquid, e.g. butterfly, moth).

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The calyx is the outermost whorl of a flower, made up of individual units called sepals. When the sepals of the calyx are fused (joined together), the condition is described as gamosepalous.

The prefix gamo- means "united" or "fused," while sepal- refers to the sepals. So gamosepalous literally means "united sepals."

To distinguish the other terms:

• Polysepalous describes a calyx in which the sepals are free (separate from each other). The prefix poly- here indicates "many separate" units.
• Gamopetalous refers to fused petals (the corolla), not sepals. An example is the trumpet-shaped corolla of Datura.
• Polypetalous describes a corolla in which the petals are free and separate.

A helpful memory aid: terms beginning with gamo- always indicate fusion, while those beginning with poly- indicate separate parts. The second half of the word tells you which floral part is involved: -sepalous for sepals, -petalous for petals.

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Niche differentiation (also called niche partitioning) occurs when members of the same species exploit different parts of the environment or use different resources at different times, thereby reducing direct competition among themselves. The question specifically asks about intraspecific competition, meaning competition within the same species.

The toad is the classic example used in WAEC/JAMB biology. Toads undergo metamorphosis: the larval stage (tadpole) is aquatic, breathing through gills and feeding on algae and plant matter in water, while the adult toad is terrestrial, breathing through lungs and moist skin and feeding on insects. Because the juvenile and adult stages occupy entirely different ecological niches - one aquatic and herbivorous, the other terrestrial and carnivorous - they do not compete with each other for food, space, or oxygen. This is niche differentiation within the same species.

Deer, pigeons, and tilapia do not show this pattern as distinctly. Adults and juveniles of these species occupy essentially the same habitat and feed on similar resources, so there is no dramatic niche shift between life stages that would reduce intraspecific competition.

Exam tip: Organisms with distinct larval and adult stages (such as toads, frogs, and many insects) are the standard examples of niche differentiation reducing intraspecific competition.

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Plant nutrients are classified into two groups based on the quantities required:

• Macronutrients (needed in large amounts): nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulphur (S).
• Micronutrients (needed in trace amounts): iron (Fe), boron (B), zinc (Zn), manganese (Mn), copper (Cu), molybdenum (Mo), and chlorine (Cl).

Calcium is a macronutrient. It is required in relatively large quantities by plants and plays essential roles in cell wall structure (as calcium pectate in the middle lamella), membrane stability, cell signalling, and root development.

Boron, iron, and zinc are all micronutrients (trace elements). Although they are essential for plant health, they are needed only in very small quantities. A common examination mistake is to confuse macro- and micronutrients. Remember: macronutrients include the six elements listed above (N, P, K, Ca, Mg, S), and most other mineral elements fall into the micronutrient category.

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Hypogeal germination is the type of seed germination in which the cotyledons remain below the soil surface. During hypogeal germination, the epicotyl (the part of the embryonic axis above the cotyledon attachment point) elongates and pushes the plumule (young shoot) upward through the soil, while the hypocotyl (the part below the cotyledon attachment) does not elongate significantly. As a result, the cotyledons stay underground, where they continue to supply stored food to the developing seedling until it becomes self-sufficient through photosynthesis. Examples include maize, rice, mango, and most monocots.

In epigeal germination, the hypocotyl elongates rapidly, pulling the cotyledons above the soil surface, where they may turn green and photosynthesise temporarily. Examples include beans and groundnuts.

The plumule is the embryonic shoot, not a type of germination. The micropyle is the tiny pore in the seed coat through which water enters during imbibition, not a germination type.

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Camels have broad, two-hoofed toes connected by a thick, leathery pad. When the camel steps on sand, the toes spread apart, creating an enlarged foot surface area. This increased surface area distributes the camel's body weight over a wider area, reducing the pressure exerted on the sand and preventing the animal from sinking into the loose desert substrate.

This principle follows the physics of pressure: \( P = \frac{F}{A} \), where P is pressure, F is force (body weight), and A is the contact area. By increasing the area, the pressure per unit area decreases, making it easier for the camel to walk on soft sand.

A narrow foot surface would cause the animal to sink deeper into the sand. "Elongated" and "long" foot surfaces do not accurately describe the adaptation; the critical feature is the widening or enlargement of the foot's contact area, not its length.

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The relationship between a fungus and an alga in a lichen is an example of mutualism. In this association, both organisms benefit. The alga (or cyanobacterium) is photosynthetic and produces organic food (sugars) through photosynthesis, which nourishes both itself and the fungus. The fungus, in return, provides a protective structure, retains moisture, and anchors the lichen to substrates such as rocks, tree bark, or soil, creating a stable microenvironment for the alga.

Parasitism involves one organism benefiting at the expense of the other (the host is harmed). Commensalism is a relationship in which one organism benefits while the other is neither helped nor harmed. Predation involves one organism (the predator) killing and consuming another (the prey). None of these accurately describes the lichen relationship, where both partners derive a clear benefit.

Lichen is one of the most commonly cited examples of mutualism in biology examinations. It is also a pioneer organism in ecological succession, colonising bare rock surfaces.

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The savanna biome is characterised by distinct wet and dry seasons, with prolonged dry periods that bring drought and frequent bush fires. Plants that thrive in this habitat must possess adaptations that help them survive water scarcity and fire damage.

The baobab tree (Adansonia digitata) has a thick bark that serves as a critical adaptation to the savanna. The thick, fire-resistant bark insulates the living cambium tissue beneath it from the intense heat of bush fires, allowing the tree to survive fires that would kill thinner-barked species. The bark also helps reduce water loss from the trunk, which is important during the long dry season.

While the baobab does shed its leaves during the dry season (deciduous habit) and has a deep root system, among the options given, the presence of thick bark is the most distinctive and widely recognised savanna adaptation for this species. Broad leaves would actually be a disadvantage in the savanna because they increase the surface area for water loss through transpiration. Tap roots help access deep water but are common to many trees in various biomes and are not unique to the baobab's savanna adaptation in the way thick bark is.

Exam tip: Savanna plant adaptations centre on surviving fire and drought. Thick bark (fire resistance), water-storing trunks, deep roots, and deciduous leaves are all relevant, but thick bark is the hallmark adaptation most frequently tested.

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UNICEF (the United Nations Children's Fund) is the United Nations agency specifically mandated to provide emergency assistance and long-term developmental support to children and mothers worldwide. Originally established in 1946 as the United Nations International Children's Emergency Fund, UNICEF works in over 190 countries to deliver healthcare, nutrition, clean water, education, and emergency relief to children affected by crises such as conflicts, natural disasters, and disease outbreaks.

WHO (the World Health Organization) focuses on international public health for all populations, not specifically children. It coordinates global health responses, sets health standards, and monitors disease outbreaks, but its mandate covers all age groups rather than targeting children's emergency needs.

NMA (the Nigerian Medical Association) is a national professional body for medical practitioners in Nigeria. It is neither a global organization nor one specifically focused on children's emergency needs.

UNIDO (the United Nations Industrial Development Organization) promotes industrial development in developing countries. Its focus is on economic and industrial growth, not on children's welfare or emergency relief.

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Rhizopus (commonly known as bread mould) is a saprophytic fungus. Saprophytes are organisms that obtain their nutrition by secreting digestive enzymes onto dead or decaying organic matter and then absorbing the resulting soluble products. Rhizopus grows on stale bread, decaying fruits, and other dead organic substrates, breaking them down extracellularly and absorbing the nutrients.

The other organisms listed obtain nutrition by different means. Bladderwort (Utricularia) and sundew (Drosera) are both carnivorous (insectivorous) plants that trap and digest small insects to supplement the mineral nutrients they cannot obtain from their nutrient-poor habitats. Mistletoe (Viscum) is a parasitic plant that grows on host trees and extracts water and nutrients from the host's vascular tissue using specialised structures called haustoria.

To distinguish modes of nutrition in exams, remember: saprophytes feed on dead matter, parasites feed on living hosts, and carnivorous plants trap living prey.

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When a soil sample is mixed with water, shaken vigorously, and allowed to stand, the particles separate into distinct layers based on their size and density. This process is called sedimentation.

During sedimentation, the heaviest and largest particles (gravel and coarse sand) settle first and form the bottom layer. Medium-sized particles (fine sand and silt) settle above them, and the finest particles (clay) settle on top of the mineral layers because they are the lightest solid particles. Decaying organic matter (humus) has a lower density than the mineral particles and water, so it floats on the surface of the water rather than sinking.

The correct statement is that decaying organic matter remains afloat. This is because humus particles are light and often contain trapped air, giving them a density lower than that of water.

The statement that the largest and medium-sized particles settle at the bottom is partially true (the largest do settle at the bottom), but it is imprecise because it groups two different size classes without noting that they form separate layers. The claim that decaying organic matter settles at the bottom contradicts what actually happens - humus floats. The claim that the largest soil particles remain suspended in water is incorrect because large particles are the first to settle due to their greater weight.

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The cortex is the region of a plant stem located between the epidermis and the vascular bundles. In a herbaceous (non-woody) stem, the cortex is composed of two main tissue types:

• Collenchyma occupies the outer part of the cortex, just beneath the epidermis. It consists of living cells with unevenly thickened cell walls that provide flexible mechanical support, allowing the young stem to bend without breaking.
• Parenchyma makes up the bulk of the inner cortex. These are thin-walled, living cells with large vacuoles. They function in storage of food, water, and waste products, and they also carry out photosynthesis when chloroplasts are present (chlorenchyma).

Xylem is a vascular tissue found in the stele (vascular cylinder), not in the cortex. Sclerenchyma, which consists of dead cells with uniformly thickened lignified walls, is characteristic of woody stems and mature tissues rather than the cortex of a typical herbaceous stem.

The correct combination is therefore parenchyma and collenchyma, as these are the ground tissues that together constitute the cortex of a herbaceous stem.

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Oxygen is transported from the lungs to all parts of the body by haemoglobin in red blood cells, forming oxyhaemoglobin. Once oxygen reaches the body's cells, its primary biological function is to serve as the final electron acceptor in aerobic cellular respiration, the process by which cells break down glucose to release energy in the form of ATP.

The overall equation for aerobic respiration is:

\[ \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{energy (ATP)} \]

Without oxygen, cells cannot carry out aerobic respiration efficiently and must rely on anaerobic respiration, which yields far less ATP. The energy released is used for all life processes, including growth, movement, active transport, and maintaining body temperature.

The removal of waste products is a function of the excretory system, not a direct use of oxygen. Growth and development of cells depend on the energy that respiration provides, but oxygen is not directly "used for" growth - it is used for respiration, which powers growth. The formation of carboxyhaemoglobin (not "carboxyl") occurs when carbon monoxide binds to haemoglobin, which is a toxic event, not a normal physiological function of oxygen.

Exam tip: The key phrase is "used for." Oxygen is specifically used in cells for the release of energy from food (aerobic respiration). Other processes like growth are downstream consequences of that energy release.

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Carbon monoxide (CO) is a colourless, odourless gas produced by the incomplete combustion of carbon-containing fuels. Its primary danger to humans lies in its effect on the blood's ability to transport oxygen.

Haemoglobin in red blood cells normally binds with oxygen to form oxyhaemoglobin, which is then transported to body tissues. Carbon monoxide has an affinity for haemoglobin that is approximately 200-250 times greater than that of oxygen. When inhaled, CO binds tightly to haemoglobin to form carboxyhaemoglobin, a stable compound that does not release CO easily. This effectively blocks haemoglobin from binding with oxygen, thereby reducing the oxygen-carrying capacity of the blood.

Carbon monoxide does not cause respiratory tract infections (those are caused by pathogens such as bacteria and viruses), does not prevent blood clotting (that involves platelets and clotting factors), and is not known to cause gene mutations (that is associated with mutagens such as certain chemicals, UV radiation, and ionising radiation).

For examinations, remember that carbon monoxide is dangerous specifically because it competes with oxygen for binding sites on haemoglobin, and its much higher affinity means even small amounts can significantly impair oxygen delivery to tissues.

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Each kidney receives blood through a renal artery. Inside the kidney, the renal artery branches into smaller and smaller arterioles. Within each nephron (the functional unit of the kidney), an afferent arteriole enters the cup-shaped structure called the Bowman's capsule (or Bowman's capsule / renal capsule) and splits into a dense, tangled ball of capillaries. This capillary tuft is called the glomerulus.

The glomerulus is the site of ultrafiltration: the high blood pressure inside these capillaries forces water, salts, glucose, urea, and other small molecules out of the blood and into the cavity of the Bowman's capsule, forming the glomerular filtrate. Large molecules such as proteins and blood cells are too big to pass through the capillary walls and remain in the blood.

The other structures named in the question serve different roles. The tubule (renal tubule) is the long tube leading away from the Bowman's capsule where selective reabsorption occurs. The pelvis (renal pelvis) is the funnel-shaped cavity that collects urine before it drains into the ureter. The nephron is the entire functional unit comprising the Bowman's capsule, glomerulus, and tubule together, not the capillary mass alone.

Remember: the glomerulus is specifically the knot of capillaries inside the Bowman's capsule where filtration begins.