All 50 questions from the West African Examinations Council (WAEC) Biology 2025 Objective paper, with the correct answer and a full explanation for each. Free, no signup needed.
Advertisement
The Genus into which man is classified is
Taxonomically, humans belong to Kingdom Animalia, Phylum Chordata, Class Mammalia, Order Primates, Family Hominidae, Genus Homo, Species sapiens.
The organism illustrated below is a stage in the
The diagram shows a nymph, an immature stage of insects with incomplete metamorphosis (hemimetabolous), such as grasshoppers.
The growth process that would occur in the organism before it becomes an adult is
The nymph undergoes moulting (shedding of the exoskeleton) several times to grow into an adult, allowing it to increase in size and develop adult features like wings.
The parts labelled I, II, III and IV respectively are
I = Apex (tip of the leaf), II = Midrib (central vein), III = Lamina (broad leaf surface), IV = Axil (point where leaf joins stem).
The part that contains the phloem and xylem is labelled
Phloem and xylem are vascular tissues located in the midrib and veins of a leaf. From the diagram, III (lamina, which contains the midrib/veins) corresponds to this.
The functions of vacuoles in plants are storage and
Vacuoles store water, salts, minerals, sugars and waste products, and help maintain internal (turgor) pressure, which pushes the cell membrane against the cell wall, helping the plant maintain rigidity and support (turgidity).
Four cells each with osmotic potential of about 3% salt solution were immersed respectively into solutions of different concentrations as follows: I - 1% salt solution, II - 3% salt solution, III - 6% salt solution, IV - 10% salt solution. Which of the solutions would cause an increase in osmotic pressure within the cell?
Osmotic pressure increases when water moves into the cell due to the concentration gradient of solutes. Solution I (1%) is hypotonic relative to the cell's internal solution (3%), so water moves into the cell, increasing osmotic pressure.
If the cells are plant cells, what would happen to the cell in solution III?
Solution III (6% salt) is hypertonic relative to the cell's internal solution (3%), causing water to move out of the cell, resulting in the cell shrinking and the plasma membrane pulling away from the cell wall - plasmolysis.
How many molecules of oxygen are required for the aerobic respiration of three molecules of glucose?
C6H12O6 + 6O2 -> 6CO2 + 6H2O + Energy. One glucose molecule takes 6 oxygen molecules, so for three glucose molecules: 3 x 6 = 18 molecules of oxygen.
Sclerenchyma tissues in plants is for
The primary function of sclerenchyma is to provide mechanical support and strength to the plant, helping it remain rigid. It is not involved in conduction or storage.
The process illustrated below (bacterium being engulfed by a cell) is referred to as
This process involves a cell engulfing a bacterium. The correct term for this is phagocytosis, where a cell surrounds and ingests large particles such as bacteria or dead cells.
The biological system that contains cells that carry out the illustrated biological process in humans is
The process shown involves the engulfment of a bacterium, a task performed by white blood cells. White blood cells belong to the circulatory system.
Which of the following statements is not correct about respiration in plants?
Photosynthesis is the process that requires light and chlorophyll, not respiration. Respiration occurs in all living plant tissues, produces energy, and (aerobic respiration) requires oxygen.
Urine when compared with blood in mammals is hypertonic because
Urine is hypertonic compared to blood because much water has been removed from the urine in the kidneys. The kidneys filter the blood, reabsorb water and useful substances, and excrete the remaining waste and water as urine.
The naturally produced auxin in plants is
The primary naturally occurring auxin in plants is Indole Acetic Acid (IAA). Auxins are plant hormones that play a significant role in growth regulation.
The sympathetic nervous system causes
The sympathetic nervous system is responsible for the 'fight-or-flight' response, which prepares the body to react to stress or danger. One of its effects is vasoconstriction (constriction of blood vessels).
Long sightedness could be corrected using a
Long-sightedness (hypermetropia) is corrected with a convex (converging) lens. Short-sightedness (myopia) is corrected with a concave (diverging) lens.
During the process of hearing in mammals, the structure in the middle ear which receives the first vibration is the
The malleus is the first bone in the middle ear that receives the vibrations from the eardrum. The vibration is passed through the malleus to the incus and then to the stapes, which transmits it to the oval window.
An important characteristic of fruits dispersed by water is the presence of
Fruits dispersed by water typically have a fibrous covering to help them float and be carried away by water.
Plants which grow and produce fruits within a year are called
Plants that complete their life cycle, including fruit production, within a single year are known as annuals.
Chemical digestion in organisms is the
Chemical digestion involves the breakdown of complex molecules into simpler molecules. For example, starch is broken down into sugars.
Excessive bleeding from an injury could be due to the lack of vitamin
Vitamin K is essential for blood clotting. A deficiency in vitamin K can result in excessive bleeding because the blood cannot clot properly.
Enzymatic digestion of protein begins in the part labelled
The digestion of protein begins in the stomach, where pepsin (an enzyme) breaks down proteins. The part labelled III represents the stomach.
The parts that secrete substances involved in the digestion of fats are labelled
The pancreas (II) produces pancreatic juice containing enzymes, including pancreatic lipase for the digestion of lipids (fats and oils). The liver (III) produces bile, which aids in the emulsification of fats.
If the small intestine of an organism does not have villi, the organism will have a problem with
The villi in the small intestine are essential for nutrient absorption. They dramatically increase the surface area for absorption of nutrients from digested food. Without villi, the surface area for absorption is drastically reduced.
Which of the following statements is not correct about the dental formula of humans?
Dental formula of humans: i=2/2, c=1/1, p=2/2, m=3/3, giving 2 pairs of incisors, 1 pair of canines, 2 pairs of premolars and 3 pairs of molars on both the upper and lower jaws. Statements A, B and D correctly describe this arrangement, so C is the statement that is NOT correct.
The relationship between a bean plant and a Tridax plant on a farmland is
Competition occurs when two organisms vie for the same resource. In this case, both the bean plant and the Tridax plant would be competing for nutrients, light and space in the soil of the farmland.
The following ecological factors affect all habitats except
The effect of pressure is not significant in all habitats. It mainly affects aquatic habitats and high-altitude environments, unlike temperature, humidity and light which affect all habitats.
The ecological instrument illustrated below is a
The instrument shown is a Secchi disc, a circular plate lowered into a body of water.
The instrument is used to measure the
A Secchi disc is lowered into a body of water; the depth at which the disc is no longer visible is recorded as an indicator of water clarity (turbidity).
When tilapia population in a pond reaches the carrying capacity, the population
Carrying capacity is the maximum number of individuals that an environment can support sustainably with its available resources. When the tilapia population reaches this point, births and death rates balance out, meaning there is no further increase or decrease in population.
Which of the following statements about the pyramid of energy is correct?
The pyramid of energy represents the flow of energy through an ecosystem. At each trophic level, energy is lost primarily as heat due to metabolism and other biological processes, so energy decreases from the base to the apex.
Which of the following sequences represents the trend in eutrophication?
Eutrophication is the process in which a body of water becomes enriched with nutrients (like nitrates and phosphates), leading to excessive algal growth. As the algae die and decompose, oxygen is consumed, resulting in oxygen depletion in the water, which can lead to the death of aquatic organisms.
Which of the following statements correctly describes the term population?
A population refers to all individuals of a single species in a specific area at a given time - such as the number of tilapia in a lake.
What is the population density of Ageratum sp. of frequency 1,850 on a land area measuring 100m²?
Population density is calculated by dividing the total number of individuals by the area they inhabit: 1850 individuals / 100m² = 18.5 individuals per m².
Which of the following activities does not control pathogens?
Eating a balanced diet is important for maintaining general health and supporting the immune system, but it does not directly control pathogens. Ultraviolet radiation, disinfectants and destroying habitats are direct methods used to control and reduce pathogens.
Which of the following diseases could be prevented by a BCG vaccination?
BCG (Bacillus Calmette-Guerin) is a vaccine specifically developed to prevent tuberculosis, especially severe forms in children.
The main effect of deforestation is
Trees and vegetation play a crucial role in protecting soil from erosion. When trees are removed, the soil becomes more vulnerable to erosion by wind and water, leading to loss of fertile topsoil.
Which of the following resources cannot be conserved?
Domestic wastes are by-products of human activities (e.g. garbage, sewage). They are managed or recycled but not conserved because they are not useful natural resources.
Which of the following activities is not suitable for forest conservation?
The felling of trees (cutting down trees) is not suitable for forest conservation. This activity leads to the destruction of forests, negatively impacts biodiversity and accelerates soil erosion. Forest conservation efforts focus on maintaining or increasing tree cover.
Which of the following pairs of features is an example of discontinuous variation?
Sex, fingerprint and blood group are discontinuous variations. Height, weight and colour are continuous variations.
The ability of some individuals to taste phenylthiocarbamide is
Phenylthiocarbamide (PTC) tasting ability is a physiological variation, not a morphological one, since it relates to how the body functions rather than form/structure.
Alleles are found on
Alleles are different versions of a gene. Genes are located on chromosomes, which are found in the nucleus of cells. Each gene occupies a specific position (locus) on a chromosome.
A couple heterozygous for albino genes have normal skin colour. What is the probability that their child will be an albino?
Albinism is caused by a recessive allele. A heterozygous parent (Aa) has one dominant (normal pigment) allele and one recessive (albino) allele. In a cross of Aa x Aa, only 1 out of 4 (1/4) offspring would be albino (aa); the closest matching option provided is B.
The process occurring in the illustrated molecules below is
The image depicts the unwinding of the DNA double helix, which is characteristic of DNA replication, where the DNA makes an exact copy of itself before cell division.
If the percentage of adenine in the DNA of a human is 32%, what will be the percentage of thymine in the DNA?
In DNA, adenine (A) pairs with thymine (T) in a 1:1 ratio (Chargaff's rule). So if Adenine = 32%, then Thymine = 32%.
Which of the following statements is not correct about colour blindness?
Colour blindness is X-linked, and males express the trait if they inherit the allele. In other words, males cannot be carriers - they are either normal or they suffer from the trait. Females (with two X chromosomes) are carriers if they have one X with the colour blindness allele, or sufferers if both X chromosomes are defective. This makes 'males are often carriers' the incorrect statement.
Lamarck's theory of evolution states that
In his theory of evolution, Lamarck proposed that organisms can acquire characteristics as a result of use or disuse of organs, and that these acquired traits are then transmitted to their offspring. This concept is referred to as the inheritance of acquired characteristics (now considered incorrect, since acquired characteristics do not alter DNA and cannot be passed on).
The castes of the organisms found in a beehive are
In a beehive, there are three main castes: Queen (the reproductive female), Drones (males, whose only role is to mate with the queen), and Workers (sterile females who gather food, clean and protect the hive).
The theory of natural selection in evolution was formulated by
Charles Darwin developed the theory of natural selection, stating that organisms with favourable traits are more likely to survive and reproduce. (Jean Baptiste Lamarck instead propounded the theory of use and disuse.)
Advertisement
…and/or go further with premium services and No Ads.