JAMB UTME - Biology - 2025

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.

This is a monohybrid cross between a heterozygous red-flowered plant (Rr) and a homozygous white-flowered plant (rr), where R (red) is dominant over r (white).

To find the probability of Rr offspring, set up a Punnett square:

The possible offspring genotypes are:

• Rr (heterozygous red) - 2 out of 4 offspring
• rr (homozygous white) - 2 out of 4 offspring

The probability of an offspring being Rr is therefore:

\[ \frac{2}{4} = \frac{1}{2} \]

This means there is a 50% chance that any given offspring from this cross will have the genotype Rr (heterozygous red). This type of cross is called a test cross, commonly used to determine the genotype of an organism showing a dominant phenotype. In a test cross of a heterozygous individual with a homozygous recessive individual, the offspring always appear in a 1:1 ratio of heterozygous dominant to homozygous recessive.

The diagram shows a bird's head with two labelled structures. Structure I is the upper mandible (upper beak), which is long, slender, and curved. Structure II is the lower mandible.

This beak shape is characteristic of nectar-feeding birds such as sunbirds and hummingbirds. The long, thin, curved beak is adapted for reaching deep into tubular flowers to extract nectar by sucking.

Other feeding adaptations in birds produce distinctly different beak shapes:

• Tearing beaks are short, strongly hooked, and powerful, as seen in raptors like eagles and hawks.
• Sieving beaks are broad and flat with comb-like lamellae along the edges, as seen in ducks and flamingos.
• Boring beaks are strong, straight, and chisel-shaped, as seen in woodpeckers.

The slender, curved beak labelled I is therefore adapted for sucking nectar from flowers.

Cholera is an epidemic disease in Nigeria. An epidemic disease is one that occurs suddenly in a population, spreads rapidly, affects a large number of people within a short period, and then subsides. Cholera outbreaks in Nigeria are typically triggered by contaminated water supplies, poor sanitation, and flooding, causing sudden, widespread infection in affected communities before being brought under control.

Malaria is endemic in Nigeria, meaning it is constantly present in the population throughout the year rather than occurring in sudden outbreaks. Schistosomiasis (bilharzia) is also endemic in many parts of Nigeria, persisting in areas where people have regular contact with freshwater snails that carry the parasite. Poliomyelitis has been largely controlled through vaccination campaigns and is not characteristically epidemic in Nigeria today.

The distinction between endemic (always present) and epidemic (sudden outbreak, then subsides) is critical in examination questions about disease classification.

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.

In ecology, organisms in a habitat are connected through feeding relationships. A food chain is a simple, linear sequence showing how energy passes from one organism to the next, for example: grass to grasshopper to frog to snake to hawk. Each organism feeds on the one before it.

However, most ecosystems are far more complicated than a single chain. A grasshopper may be eaten by both frogs and birds; a frog may eat insects other than grasshoppers; a hawk may eat snakes, mice, and birds. When multiple food chains in a habitat overlap and interconnect, the result is a food web. A food web captures the complex feeding relationships among all the organisms in the habitat, showing how energy in the form of food is transferred through many interlinked pathways.

A pyramid of numbers shows how many organisms exist at each trophic level, while a pyramid of energy shows the amount of energy available at each trophic level. Neither of these describes a feeding relationship between organisms. They are graphical representations of quantity, not of who eats whom.

The key phrase in the question is "complex feeding relationship ... that involves transfer of energy in form of food." Only a food web fits this description, because it is the model that represents the full network of interconnected feeding relationships within a habitat.

Loamy soil is the most suitable soil for crop cultivation in Nigeria and in agriculture generally. Loam is a mixture of sand, silt, and clay in roughly balanced proportions, which gives it a combination of properties ideal for plant growth:

• Good water retention and drainage: It holds enough moisture for roots to absorb but drains excess water, preventing waterlogging.
• Good aeration: The presence of sand particles creates air spaces, allowing root respiration and the activity of beneficial soil organisms.
• High nutrient content: The clay and silt fractions hold mineral ions through cation exchange, while organic matter (humus) further enriches the soil.
• Easy to work: Loam is neither too heavy nor too light, making it easy to plough and cultivate.

Laterite soil is highly weathered and leached, with poor fertility and a hard, iron-rich crust that limits root penetration. Sandy soil drains too quickly and has very low nutrient-holding capacity. Clayey soil holds too much water, has poor drainage and aeration, and becomes very hard when dry, making it difficult for roots to penetrate.

Fingerprints are the variation most applicable to crime detection. Every individual (including identical twins) has a unique set of ridge patterns on their fingertips. These patterns - classified as loops, whorls, and arches - are formed during foetal development and remain unchanged throughout life. This uniqueness and permanence make fingerprints an extremely reliable tool for identifying individuals.

In forensic science, fingerprints left at a crime scene (latent prints) can be lifted, analysed, and matched against databases of known prints to identify suspects or confirm the presence of a particular person. This technique, known as dactyloscopy, has been used in criminal investigations worldwide for over a century.

The other variations listed are not suitable for crime detection:

• Tongue rolling is a genetic trait (the ability to roll the tongue into a tube shape), but it is shared by a large proportion of the population and cannot distinguish one individual from another.
• Height is a continuous variation influenced by both genetics and environment. Many people share similar heights, making it useless as a unique identifier.
• Colour (skin, eye, or hair colour) is also shared among large groups and provides no individual-level identification.

Exam tip: Fingerprints are an example of discontinuous variation - each person's pattern is qualitatively distinct, not just a point on a continuous scale. This uniqueness is what makes them forensically useful.

A burrow is an underground tunnel or hole dug by an animal to serve as a shelter, nesting site, or place to store food. Among the options given, the bush rat is the animal that creates its natural habitat in burrows.

Bush rats, like many other rodents, are well adapted for digging. They use their strong claws and compact bodies to excavate burrows in soil, where they live, breed, and shelter from predators and extreme weather. These burrows may have multiple entrances and chambers for different purposes.

The other options do not create burrows. Doves build nests in trees, on ledges, or on the ground surface using twigs and other materials. Chameleons are arboreal reptiles that live on tree branches, relying on camouflage rather than burrowing for protection. Snails carry their own protective shells on their backs and shelter under rocks, leaves, or in moist crevices rather than digging into the ground.

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.

Camouflage is an adaptation in which an organism's body colouration blends with its surrounding environment, making it difficult for predators (or prey) to detect it. The green-brown colour of a grasshopper in a dry grass field is a classic example of camouflage: the grasshopper's body matches the colours of the dried and living grass, helping it avoid being spotted by birds and other predators.

This should not be confused with mimicry, which is an adaptation where one organism resembles a different, often dangerous or unpalatable, organism. For example, a harmless hoverfly may resemble a wasp. The grasshopper is not imitating another species; it is blending into its physical habitat.

Predation refers to the act of hunting and killing other organisms for food, which is a behaviour rather than a body-colour adaptation. Mating-related colouration typically involves bright, conspicuous colours (such as the plumage of male peacocks) to attract mates, which is the opposite of what is described here.

The key distinction for examinations: camouflage = blending with the environment; mimicry = resembling another organism.

Germination is classified based on the fate of the cotyledons (seed leaves) relative to the soil surface. In epigeal germination, the hypocotyl elongates rapidly and arches upward, pulling the cotyledons above the soil. Once above ground, the cotyledons may photosynthesize briefly before the true leaves take over. Examples include beans (Phaseolus) and castor oil plant.

In hypogeal germination, the epicotyl elongates instead, pushing the plumule (young shoot) above the soil while the cotyledons remain buried underground. Maize and mango are common examples of hypogeal germination.

The prefix epi- means "above" and hypo- means "below," while -geal relates to the earth. This makes the terminology self-explanatory: epigeal means the cotyledons come above the earth, and hypogeal means they stay below.

Note that epicotyl and hypocotyl are parts of the embryonic axis, not types of germination. The epicotyl is the region above the cotyledon attachment point, and the hypocotyl is the region below it. The question asks about the type of germination, not a plant structure, so the correct answer is epigeal germination.

The haemocoel is a structure specifically associated with an open circulatory system. In an open circulatory system, found in arthropods (insects, crustaceans, spiders) and most molluscs, blood (called haemolymph) is not confined to blood vessels throughout its entire circuit. Instead, the heart pumps haemolymph through short arteries into open body cavities called haemocoels, where the fluid directly bathes the tissues and organs, allowing exchange of nutrients, gases, and waste products. The haemolymph then drains back into the heart through openings called ostia.

Veins, arteries, and arterioles are all components of a closed circulatory system, in which blood is always contained within a continuous network of vessels (as in vertebrates, annelids, and cephalopods). In a closed system, exchange between blood and tissues occurs across capillary walls, not by direct bathing of organs.

The presence of a haemocoel is one of the defining features that distinguishes an open circulatory system from a closed one.

Plants have two main vascular tissues: xylem and phloem. Xylem is responsible for transporting water and dissolved mineral salts from the roots upward to the leaves. Phloem, on the other hand, is the tissue responsible for translocation, which is the movement of manufactured food (mainly sucrose and amino acids) from the sites of production (typically leaves, where photosynthesis occurs) to sites of use or storage throughout the plant.

Phloem cells, specifically sieve tube elements and their companion cells, form a continuous pathway that carries dissolved organic nutrients bidirectionally: from leaves downward to roots, and from storage organs upward to growing tips, flowers, and fruits. This process is driven largely by pressure differences created by the active loading and unloading of sugars into and out of the sieve tubes.

The pericycle is a layer of cells in the root that gives rise to lateral roots. The endodermis is a single cell layer in the root that regulates which substances enter the vascular cylinder. Neither of these tissues is involved in the long-distance transport of food. Xylem vessels transport water, not manufactured food.

Exam tip: Remember the distinction: xylem moves water up, phloem moves food (sugars) to where the plant needs it.

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.

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.

Ferns are vascular plants (pteridophytes) that possess true roots, stems, and leaves. Their roots are the structures responsible for absorbing water and dissolved mineral nutrients from the soil, just as in flowering plants. The roots of ferns are adventitious, arising from the rhizome (underground stem), and they have root hairs that increase the surface area for absorption.

Hyphae are the thread-like filaments that make up the body of fungi and are used by fungi for absorption, not by ferns. Rhizoids are simple, root-like structures found in bryophytes (mosses and liverworts) and some algae; they anchor the plant and assist with absorption in organisms that lack true roots. A rhizome is the horizontal underground stem of a fern that functions in anchorage and vegetative reproduction, not directly in nutrient absorption.

The key distinction is that ferns, unlike simpler plants such as mosses, have evolved true roots with vascular tissue (xylem and phloem) for efficient absorption and transport.

Buccal respiration is a mode of breathing in which an animal pumps air into and out of its lungs by raising and lowering the floor of its mouth (the buccal cavity). The toad, an amphibian, uses this method. During buccal respiration, the toad lowers the floor of its mouth with the nostrils open, drawing air into the buccal cavity. The nostrils then close, and the floor of the mouth is raised, forcing air into the lungs. This buccal pumping mechanism supplements cutaneous (skin) respiration, which is also important in amphibians.

Tilapia (a bony fish) respires using gills, not buccal pumping. Birds use a highly efficient system of air sacs and parabronchi in their lungs, powered by movements of the ribcage and sternum. Grasshoppers and other insects respire through a tracheal system, a network of tubes (tracheae and tracheoles) that deliver air directly to body tissues through openings called spiracles.

Buccal respiration is a characteristic feature of amphibians, and it is commonly tested alongside cutaneous respiration as a defining amphibian trait.

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.

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.

An estuary is a partially enclosed coastal body of water where freshwater from rivers and streams meets and mixes with saltwater from the sea. Estuarine habitats are characterised by brackish water (a mixture of fresh and salt water) and fluctuating salinity.

A lagoon is a classic example of an estuarine habitat. Lagoons are shallow bodies of water separated from the open sea by sandbars, barrier islands, or coral reefs, but they maintain a connection with the sea. In West Africa, well-known examples include the Lagos Lagoon and the Ebrié Lagoon. The water in lagoons is typically brackish because freshwater from rivers drains into them while seawater enters through inlets.

The other options are not estuarine habitats:

• A river is a freshwater habitat. Although a river may flow into an estuary, the river itself is not estuarine.
• Lakes are inland freshwater bodies with no direct connection to the sea.
• The ocean is a fully marine (saltwater) habitat, not a zone of freshwater-saltwater mixing.

For examination purposes, remember that estuarine habitats are defined by the mixing of fresh and salt water. Lagoons, mangrove swamps, and river deltas are the most commonly cited examples.

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.

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.

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.

The cooling effect on the body of mammals is brought about by sweat excretion. When the body temperature rises, sweat glands in the skin produce sweat, which is secreted onto the surface of the skin. As this sweat evaporates, it absorbs latent heat of vaporisation from the skin, thereby lowering the body temperature.

This process is a key thermoregulatory mechanism in mammals. It is controlled by the hypothalamus, which detects a rise in blood temperature and triggers increased sweat production alongside vasodilation (widening of blood vessels near the skin surface) to dissipate heat.

The other processes listed do not produce a cooling effect:

• Digestion is the breakdown of food in the alimentary canal to release nutrients - it actually generates metabolic heat rather than removing it.
• Urine formation (occurring in the kidneys) is an excretory process that removes nitrogenous waste and regulates water and ion balance, but does not function as a cooling mechanism.
• Respiration is the metabolic process of releasing energy from food (glucose). It is exothermic and produces heat, which is the opposite of cooling.

The coronary artery is the artery that carries blood to the heart. Specifically, the coronary arteries branch off from the base of the aorta and supply oxygenated blood to the heart muscle (myocardium) itself. Without this blood supply, the cardiac muscle cells would not receive the oxygen and nutrients they need to function, which is why blockage of the coronary arteries leads to a heart attack (myocardial infarction).

The pulmonary artery carries deoxygenated blood from the right ventricle of the heart to the lungs for gas exchange. The renal artery carries blood from the aorta to the kidneys. The aorta is the largest artery in the body and carries oxygenated blood away from the left ventricle to the rest of the body.

A common source of confusion is thinking that "carries blood to the heart" means veins (since veins generally return blood to the heart). However, the coronary arteries specifically deliver arterial blood to nourish the heart tissue itself.

The levels of organization in living things, from simplest to most complex, are: cell, tissue, organ, organ system, and organism. An organ is a structure made up of two or more different types of tissues working together to perform a specific function.

An onion bulb is an organ. It is a modified underground stem composed of several tissue types: the fleshy scale leaves (which store food), the outer dry protective scales, the basal plate (a compressed stem), and the growing point. These different tissues work together to store nutrients and enable vegetative reproduction, which is the hallmark of organ-level organization.

Euglena and Paramecium are unicellular (single-celled) organisms. They exist at the cell level of organization because all their life processes are carried out within a single cell. They do not have tissues or organs.

Hydra is a simple multicellular organism that exists at the tissue level of organization. It has two cell layers (ectoderm and endoderm) that form simple tissues, but these tissues are not organized into distinct organs.

Exam tip: To identify the level of organization, ask whether the structure contains multiple tissue types working together. If yes, it is at least at the organ level.

The diagram shows a longitudinal section of a flower with four labelled parts. Label I points to the anther at the tip of the stamen, label II points to the stigma at the top of the style, label III points to the petals (the broad, conspicuous structures surrounding the reproductive organs), and label IV points to the sepal at the base of the flower.

The part of a flower that is brightly coloured to attract pollinating agents such as insects, birds and butterflies is the petal (collectively called the corolla). Petals produce pigments such as anthocyanins and carotenoids that give them vivid colours, and in some species they also produce nectar guides visible under ultraviolet light. These visual signals help pollinators locate the flower and its nectar or pollen rewards, facilitating cross-pollination.

In the diagram, the petals correspond to the structures labelled III.

The diagram shows the arrangement of teeth in the human jaw, with four distinct types labelled I through IV. Label I indicates the incisors, which are flat, chisel-shaped teeth at the front used for cutting and biting. Label II indicates the canines, the pointed, conical teeth located just behind the incisors. Label III indicates the premolars, which have two cusps and are used for crushing. Label IV indicates the molars, the broad, multi-cusped teeth at the back used for grinding.

The teeth used for tearing in humans are the canines. Canines have a single, sharp, pointed cusp that is well-suited for gripping and tearing food, particularly meat. They are the longest teeth in the human dentition and are homologous to the prominent fangs seen in carnivorous mammals. In the diagram, the canines are labelled II.

The question asks which feature is unique to photosynthesis and not shared with respiration. To answer this, compare the two processes:

Now examine each option:

• "Food is usually broken down" describes respiration, not photosynthesis. It does not differentiate photosynthesis from respiration; it describes respiration itself.
• "Oxygen is usually liberated" is characteristic of photosynthesis only. In photosynthesis, water molecules are split and oxygen is released as a by-product. Respiration does the opposite: it consumes oxygen. This is a clear differentiating feature.
• "It occurs both during the day and night" describes respiration, which is continuous. Photosynthesis requires light and occurs mainly during the day.
• "It occurs in both plants and animals" again describes respiration. Photosynthesis occurs only in organisms with chlorophyll, not in animals.

The liberation of oxygen is the feature that belongs to photosynthesis and sets it apart from respiration.

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.

Countershading is a form of adaptive colouration in which an animal's dorsal (upper) surface is darker and its ventral (lower) surface is lighter. This colour gradient counteracts the natural shadowing effect caused by overhead light, making the animal appear flatter and less three-dimensional. The result is that the animal blends more effectively into its background and becomes harder for predators (or prey) to detect.

Countershading is widespread in nature. Many fish are dark on top and light on the belly, so they blend with the dark water below when viewed from above and with the bright sky when viewed from below. Deer, sharks, penguins, and many birds also display countershading.

The other options are not forms of colouration at all:

• Hibernation is a behavioural adaptation in which an animal enters a prolonged state of dormancy during cold seasons to conserve energy.
• Aestivation is a similar dormancy response to hot, dry conditions (e.g. lungfish burying in mud during drought).
• Migration is the seasonal movement of animals from one region to another in search of favourable conditions.

None of these three involves body colouration. The question specifically asks about adaptive colouration that helps animals remain unnoticed, which directly describes countershading.

The equation shown is:

\[ \text{Glucose} \rightarrow \text{Ethanol} + \text{CO}_2 \]

This is the summary equation for anaerobic respiration in yeast, commonly called fermentation (specifically, alcoholic fermentation). In this process, glucose is partially broken down in the absence of oxygen to produce ethanol (an alcohol) and carbon dioxide.

This reaction is distinct from the other processes listed:

• Oxidation in the biological sense usually refers to the complete breakdown of glucose in the presence of oxygen to yield carbon dioxide and water, releasing far more energy.
• Glycolysis is only the first stage of glucose breakdown, converting glucose into pyruvate. It does not directly produce ethanol. In yeast under anaerobic conditions, the pyruvate from glycolysis is then converted to ethanol and carbon dioxide in a subsequent step, but the overall process is called fermentation, not glycolysis.
• Photosynthesis is the reverse direction: it uses light energy to build glucose from carbon dioxide and water, rather than breaking glucose down.

Alcoholic fermentation is exploited commercially in bread-making (the carbon dioxide causes dough to rise) and in brewing (the ethanol is the desired product).

The stick insect's slender, elongated, twig-like body shape is a classic example of cryptic coloration and form (camouflage). This structural adaptation serves the purpose of protection and defence against predators.

By closely resembling twigs or branches in both shape and colour, stick insects become extremely difficult for predators such as birds, lizards, and spiders to detect among vegetation. This form of passive defence does not require the insect to fight or flee; instead, the insect avoids detection altogether by blending into its surroundings. This strategy is a type of protective mimicry known as crypsis.

The stick-like shape has nothing to do with water conservation, which typically involves physiological or behavioural adaptations such as waxy cuticles or burrowing. It is also unrelated to securing a mate, which involves courtship displays or pheromone signalling. While escaping predators is related to defence, the term "escaping adaptation" does not accurately describe what the body shape achieves. The insect's shape is primarily about avoiding detection rather than facilitating escape once spotted.

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.

Population replacement among species in a given habitat under competition is a core outcome of natural selection. Natural selection is the process where organisms better adapted to their environment (including competition for limited resources) are more likely to survive, reproduce, and pass on their advantageous traits to the next generation, eventually leading to the replacement of less-adapted species or populations over time. The concept of "survival of the fittest" is often associated with natural selection, but natural selection is the formal, broader mechanism of evolution that explains this phenomenon. 

A. survival of the fittest: While related, "survival of the fittest" is a phrase used to describe the result (the fittest survive), but natural selection is the actual mechanism or law that causes this differential survival and reproduction, leading to population changes.

B. climax community: is the stable, final stage of ecological succession in an area, where the species composition remains relatively constant over time because they are well-adapted to the local conditions, not the cause of population replacement during the competitive process itself.

D. dominant population: is one that outcompetes others, but this dominance is a result of the underlying process (natural selection), not the fundamental mechanism explaining the replacement across species generally

The nervous system is divided into two main parts: the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord. The PNS consists of all the nerves and neurones that connect the CNS to the rest of the body.

The components of the peripheral nervous system include:

• Sensory neurones (afferent neurones), which carry impulses from receptors (such as those in the skin, eyes, and ears) to the CNS.
• Motor neurones (efferent neurones), which carry impulses from the CNS to effectors (muscles and glands).
• Cranial nerves (12 pairs emerging directly from the brain) and spinal nerves (31 pairs emerging from the spinal cord).
• Ganglia (clusters of nerve cell bodies located outside the CNS).

The cerebellum is a part of the brain responsible for coordinating movement and balance, so it belongs to the CNS. The brain itself is the main organ of the CNS, and the spinal cord is the other major CNS structure. None of these three are components of the PNS.

Of the options given, sensory neurones are a component of the peripheral nervous system, as they form the pathways that carry information from the body's receptors to the central nervous system.

The Sahel savanna is a semi-arid belt stretching across West Africa just south of the Sahara Desert. It is characterised by low, erratic rainfall (typically 250-500 mm per year), sandy soils, and high temperatures. Plants that thrive here must be drought-resistant and adapted to hot, dry conditions.

The date palm (Phoenix dactylifera) is one such plant. It is well adapted to arid and semi-arid climates, with deep root systems that reach underground water and the ability to tolerate extreme heat. In Nigeria, the Sahel zone covers the northernmost states, including Borno, Yobe, Sokoto, Zamfara, and Katsina.

Borno State sits squarely within the Sahel belt, bordering the Lake Chad Basin. Its climate is characteristically Sahelian, making it the most representative location for date palm cultivation among the options given. Katsina also lies partly in the Sahel, but Borno is the classic example used in Nigerian biology curricula for Sahel vegetation, including the date palm.

Plateau State has a cooler, highland climate unsuitable for date palm cultivation, and Taraba State lies in the Guinea savanna zone with higher rainfall, neither of which matches the arid conditions the date palm requires.

Exam tip: Associate the date palm with the driest vegetation zones in Nigeria (Sahel savanna) and the states in the far northeast, particularly Borno.

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.

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).