JAMB Biology 2005 Past Questions & Answers

This question is based on a flawed premise as the provided correct option, 'cell wall', is incorrect. The cell wall is a rigid structure found in plant cells but is absent in animal cells. The actual correct answer should be 'plasmalemma' (cell membrane), which is a structure common to both plant and animal cells, controlling the passage of substances.

Common mistake: The most common mistake is confusing the cell wall with the cell membrane, leading students to forget that animal cells lack a cell wall.

Mitochondria are the 'powerhouses' of the cell, responsible for generating energy (ATP) through cellular respiration. The sperm cell is highly motile and requires a tremendous amount of energy to power its flagellum (tail) for swimming towards the egg. To meet this high energy demand, sperm cells are packed with a high concentration of mitochondria, particularly in their middle piece.

Common mistake: Students might mistakenly choose the egg cell because it is large, but the egg is non-motile and does not have the same high energy requirement for movement as the sperm cell.

Fungi have a cell wall that provides support and gives them a fixed shape. Unlike the cell wall of plants which is made of cellulose, the fungal cell wall is made of a strong, complex carbohydrate called chitin. This chitin is what makes the hyphae, which are the thread-like structures of a fungus, rigid and tough.

Common mistake: Students often mistakenly choose cellulose because they confuse the cell wall composition of fungi with that of plants, which they learn about more frequently.

In the classification of the plant kingdom, organisms are grouped based on shared characteristics. Both Angiosperms (flowering plants) and Gymnosperms (e.g., pine trees) are known as seed-bearing plants. The major group that contains all seed-bearing plants is called Spermatophyta, which makes 'spermatophyte' the correct classification for both.

Common mistake: Students may mistakenly choose Pteridophyta because it is another major plant division they have studied, but they forget that Pteridophytes are ferns, which reproduce with spores, not seeds.

Radial symmetry means an organism's body parts are arranged around a central axis, so it can be divided into two equal halves by any plane passing through the center. Hydra has a cylindrical body with tentacles arranged around a central mouth, which is a perfect example of radial symmetry. The other organisms listed, like planaria, tapeworm, and roundworm, all have bilateral symmetry, meaning they have a distinct left and right side.

Common mistake: Students often confuse the body plans of simple invertebrates and might select planaria, forgetting that it is a classic example of bilateral symmetry, not radial.

The leech and the earthworm are both classified under the phylum Annelida. This is because they share the major characteristic of having a body that is divided into many similar, ring-like segments. This feature, called metameric segmentation, is the defining trait of annelids, also known as segmented worms.

Common mistake: Students might confuse annelids with molluscs because both are soft-bodied invertebrates, but molluscs (like snails) have unsegmented bodies, which is the key difference.

The question requires arranging the animals based on their appearance in evolutionary history, from earliest to most recent. Fish (IV. Tilapia) are the oldest group of vertebrates, followed by amphibians (III. Bufo) which evolved from fish. Reptiles (II. Agama) evolved from amphibians, and finally, mammals (I. Rattus) are the most recently evolved and complex group in this list. Therefore, the correct order of evolutionary advancement is IV, III, II, I.

Common mistake: Students may mistakenly choose option A by arranging the animals from the most complex (mammal) to the least complex (fish), which is the reverse of the correct evolutionary timeline.

The correct option is caterpillar because this is the larval stage in the life cycle of a moth. The primary function of the larval stage is to eat voraciously and grow, which is why it consumes large amounts of plant leaves and causes significant damage to agricultural crops. The pupa is a non-feeding resting stage, and the imago (adult moth) is primarily concerned with reproduction and typically feeds on nectar.

Common mistake: Students might mistakenly choose imago (the adult moth), thinking the flying adult is the main pest, but the adult's primary role is reproduction, while the caterpillar is the voracious feeding stage.

A vector is an organism that carries and transmits a disease-causing agent to another living organism. The blackfly is the vector for the parasitic worm *Onchocerca volvulus*. When an infected blackfly bites a person, it passes on the worm, which causes the disease onchocerciasis, also known as river blindness.

Common mistake: Students often confuse the blackfly with the tsetse fly, which is the vector for trypanosomiasis (sleeping sickness), and might incorrectly choose that option.

The question describes an evolutionary change from amphibians to mammals for better adaptation to life on land. For limbs to be positioned under the body for efficient weight support and movement, the structures that attach the limbs to the axial skeleton must be modified. The pectoral girdle connects the forelimbs (arms), and the pelvic girdle connects the hindlimbs (legs), making their modification essential for this transition.

Common mistake: Students might mistakenly choose option D (vertebrae and sternum) because the backbone is central to support, but the key modification for repositioning the limbs lies in the girdles that connect them to the body.

The caudal fin is the tail fin of the tilapia. Its main job is to push the fish forward through the water. By moving its powerful tail fin from side to side, the fish pushes against the water, creating a force that propels it forward, much like how a boat's propeller works.

Common mistake: Students often mistakenly choose option B because they know fins are used for steering, but they forget that the large caudal (tail) fin's primary role is for powerful forward propulsion, while other fins like the pectoral fins handle steering and stability.

In a plant root, tissues are arranged in specific layers from the outside to the inside. The stele, which contains the transport tissues like xylem and phloem, is located in the center. The endodermis is the innermost layer of the cortex that forms a distinct, tight ring directly surrounding the stele. This layer acts as a gatekeeper, controlling the passage of water and dissolved minerals into the vascular system.

Common mistake: Students often mistakenly choose 'pericycle' because it is also very close, but the pericycle is the layer just inside the endodermis and is considered the outermost part of the stele.

In the circulatory system, veins generally carry deoxygenated blood from the body back to the heart. However, the pulmonary vein is the special exception to this rule. It is the only vein that carries pure, oxygenated blood from the lungs (where the blood picks up oxygen) to the left atrium of the heart to be pumped to the rest of the body.

Common mistake: Students often mistakenly believe all veins carry deoxygenated blood, forgetting that the pulmonary vein is the unique exception as it returns oxygenated blood from the lungs to the heart.

The pericardium is a sac that surrounds the heart, and it is filled with a special liquid called pericardial fluid. As the heart beats and pumps blood, it is constantly moving. This fluid acts as a lubricant, like oil in an engine, to reduce friction between the heart and the surrounding tissues, allowing it to beat smoothly without damage.

Common mistake: Students might mistakenly choose option B, confusing the lubricating function of the pericardial fluid with the role of the coronary arteries, which are the blood vessels that actually supply the heart muscle with oxygen and nutrients.

The pleural cavity is the space between the two membranes surrounding the lungs, and it contains pleural fluid. This fluid lubricates the lungs and creates a surface tension that keeps the lungs close to the chest wall, making them 'light' and allowing them to expand and contract easily without friction. This ensures the lungs can move freely during the process of breathing.

Common mistake: Students often mistakenly choose the diaphragm because it is the primary muscle for breathing, but its function is to change the volume of the chest cavity, not to make the lung tissue itself light.

The experiment uses alkaline pyrogallol, a chemical that absorbs oxygen, creating an oxygen-free environment. The yeast is still able to break down the glucose to produce energy, and the bubbles show that carbon (IV) oxide is being released as a waste product. This process of releasing energy from food in the complete absence of oxygen is known as anaerobic respiration or fermentation.

Common mistake: Students often choose option C because they associate respiration with using oxygen, but they fail to recognise the role of alkaline pyrogallol, which is to remove oxygen from the experiment.

The kidney produces urine through two major processes that occur in its tubules. First, ultrafiltration in the glomerulus forces water and small solutes from the blood into the tubule. Then, as this filtrate passes along the tubule, selective re-absorption occurs, where useful substances like glucose, some salts, and water are taken back into the blood, leaving waste products to form urine.

Common mistake: Students may incorrectly choose option B because active transport and osmosis are involved in re-absorption, but option C correctly names the two main overall processes (ultrafiltration and selective re-absorption) that constitute the kidney's function.

Plants get rid of excess water in two main ways. The loss of water as invisible water vapour through tiny pores (stomata) on the leaves is called transpiration. When the air is very humid, plants can also push out excess water as liquid droplets through special openings called hydathodes, a process known as guttation. Therefore, the correct answer links water vapour to transpiration and droplets to guttation.

Common mistake: Students may mistakenly choose option A, confusing transpiration with respiration because both processes can involve the exchange of gases through the stomata on the leaves.

Taxis is the movement of an organism in response to an external stimulus. The prefix 'thermo' refers to temperature, so thermotaxis is movement in response to temperature changes. Since the bacteria are moving towards the warm region, it is a 'positive' response. Therefore, the movement of bacteria from a cold to a warm region is called positive thermotaxis.

Common mistake: Students may mistakenly choose negative chemotaxis because they confuse the stimulus, as 'chemo' refers to a chemical stimulus, not temperature ('thermo').

A hydrostatic skeleton is a support system that uses fluid pressure inside a closed body compartment to maintain shape and allow for movement. Oligochaetes, such as the earthworm, have this type of skeleton. They use the fluid in their body cavity (coelom) and their muscles to change shape and burrow through the soil.

Common mistake: Students often mistakenly choose arthropods, confusing the hydrostatic skeleton with the exoskeleton, which is the hard, external covering found in insects and crustaceans.

Homeostasis is the body's ability to maintain a stable internal environment, like keeping a constant body temperature. When you are in a cold environment, your body temperature starts to drop. To warm up, your brain sends signals that make your muscles contract and relax quickly, which is what we call shivering. This muscle activity generates heat and helps bring your body temperature back to normal, making it a homeostatic response.

Common mistake: Students often confuse a reflex action like pulling your hand from a hot object (Option A) with homeostasis, but a reflex action is a rapid response to protect from immediate harm, not to maintain the overall internal balance.

Cockroaches are cold-blooded insects, meaning their body temperature and activities are controlled by their environment. The optimal temperature is the most favourable condition for their life processes, including reproduction (breeding). A moderately warm temperature of about 24°C allows their metabolic enzymes to function most efficiently for successful breeding and development.

Common mistake: Students might mistakenly choose 33°C, thinking that warmer is always better for cockroaches, but extremely high temperatures can be stressful and less ideal for breeding than moderately warm conditions.

Cockroaches are poikilothermic (cold-blooded) insects, meaning their body temperature changes with the surrounding environment. They are best adapted to warm conditions, typically thriving between 25°C and 30°C. At a low temperature like 15°C, their metabolic processes slow down so much that they cannot function properly, leading to death after a prolonged period.

Common mistake: Students might mistakenly choose 33°C, thinking that very high heat is more dangerous, but cockroaches are tropical insects that are well-adapted to survive in warm conditions.

The correct answer is Taraba state. A biome is a large community of plants and animals that occupy a distinct region, and the Mambilla Plateau is a significant montane (mountain) grassland biome in Nigeria. It is known for its high altitude, cool climate, and unique biodiversity. This important ecological area is located in the Sardauna Local Government Area of Taraba State, not Plateau State.

Common mistake: Students often mistakenly choose Plateau State because the name 'Mambilla Plateau' sounds very similar, but the Mambilla Plateau is actually located in Taraba State.

Nigeria's vegetation belts are arranged in zones from south to north, based on decreasing rainfall. The rainforest belt is found in the south, and as you move northwards, it transitions into the Guinea Savanna. Further north of the Guinea Savanna, where it is drier, lies the Sudan Savanna. Therefore, the Guinea Savanna belt is bordered by the rainforests to its south and the Sudan Savanna to its north.

Common mistake: Students might mistakenly choose option A by confusing the overall sequence of vegetation belts, forgetting that the rainforest lies between the mangrove swamps and the Guinea savanna.