All 50 questions from the West African Examinations Council (WAEC) Biology 2018 Objective paper, with the correct answer and a full explanation for each. Free, no signup needed.
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The scientist who introduced binomial nomenclature in the classification of organisms was
Carolus Linnaeus introduced the binomial system of nomenclature for classifying organisms.
Which of the following statements is true about arthropods?
In insects, the prothorax (first thoracic segment) bears only the first pair of legs and no wings.
What level of organization is Spirogyra?
Spirogyra is a filamentous alga existing at the tissue level of organization (a chain of similar cells).
The streaming movement of cytoplasm within Paramecium is known as
Cyclosis is the term for the streaming/circular movement of cytoplasm within a cell, as seen in Paramecium.
Which of the following organelles is found only in plant cells?
Plastids (e.g. chloroplasts) are found only in plant cells, not animal cells.
Active transport differs from diffusion in that active transport
Unlike diffusion, active transport moves substances against (up) a concentration gradient and requires energy.
The diagrams below are illustrations of an experimental set-up to demonstrate a type of tropic response in plants (porous pot vs dry soil). The type of response demonstrated is
The set-up compares root growth response to water availability, demonstrating hydrotropism.
The conclusion drawn from the experiment is that
The roots grow towards the moist porous pot, showing that roots are positively hydrotropic.
The odontoid process is found on the
The odontoid process (dens) is a projection of the axis, the second cervical vertebra.
A seedling was made to stand in a solution of red ink for three hours and a transverse section of the stem was examined under the microscope. The process being investigated was the
The red ink experiment demonstrates that xylem vessels are responsible for the upward conduction (ascent) of water and dissolved minerals.
Which of the following structures would carry out respiration?
A germinating seed is alive and metabolically active, so it carries out respiration; the other options are dead/inert tissue.
Which of the following substances is not an excretory product of animals?
Oxygen is not excreted by animals as waste — it is a by-product released by plants during photosynthesis.
An example of homeostasis in living organisms is
Homeostasis is the maintenance of a fairly constant internal environment; releasing/redistributing phosphorus to maintain internal balance under deficiency is a homeostatic response.
Ultrafiltration in the kidney takes place in the
Ultrafiltration of blood occurs at the glomerulus into the Bowman's capsule.
The thyroid gland is located at the base of the
The thyroid gland is located at the base of the neck.
Which of the following statements about the response of neurons to stimulus is correct?
This follows the 'all-or-none' law: a stimulus must reach a threshold intensity before a neuron will fire.
Which of the following practices may lead to infection of the eye? Use of
Improper use/wear of contact lenses increases the risk of eye infections.
The structures for gaseous exchange in breathing roots are
Breathing (pneumatophore) roots have lenticels — small pores that allow gas exchange.
The diagram below is an illustration of the life cycle of an insect. The adult insect in this life cycle is a
The life cycle shown (egg-larva-pupa-adult, with resting/twig stage) is characteristic of a mosquito's complete metamorphosis.
The larva is also known as a
The larval stage of a mosquito/housefly-type insect is known as a maggot.
The source of energy required by plants during food production is
Sunlight is the energy source that drives photosynthesis (food production) in plants.
One major difference between plant and animal nutrition is the ability of
Plants (autotrophs) can synthesize their own food, which is then also used by animals (heterotrophs) who cannot manufacture their own food.
By what process is starch converted into maltose?
Starch is broken down into maltose by hydrolysis (enzyme amylase adds water to break glycosidic bonds).
The ascent of water in tall trees is mainly due to
Transpiration pull (the pull created by water loss from leaves) is the main force driving the ascent of water in tall trees.
The duodenum of a person was surgically removed. Which of the following substances would have their digestion affected?
The duodenum secretes/receives enzymes and bile important for digesting carbohydrates (starch), proteins, and lipids, so removing it affects digestion of all three.
Which of the following dental formulae represents the dentition in rabbits?
Rabbits (order Lagomorpha) have the dental formula I2/1 C0/0 P3/2 M3/3, matching option A.
The diagram below is an illustration of an experimental set-up to demonstrate a property of soil. The property of soil demonstrated is
The set-up with soil-filled tubes standing in water demonstrates capillarity — the rise of water through soil pores.
Which of the following statements would be a correct observation at the end of the experiment? Water moves
Clayey soil has the smallest particle size and highest capillarity, so water rises highest in the clayey soil column.
The most important factor(s) that influence(s) the ecological niche of an organism is/are the
An organism's ecological niche is most strongly shaped by competition for food and space with other organisms.
The diagram below is an illustration of organisms in an air-tight aquarium. The most important factor needed by the organisms is
Since the aquatic organisms rely on already-dissolved oxygen and plant photosynthesis to replenish it, light energy is the most critical factor to sustain the closed system.
Which of the following instruments is used to determine the turbidity of water?
A secchi disc is used to measure the turbidity (clarity) of a body of water.
In an ecosystem, the least efficient energy transfer link is from the
Energy transfer efficiency generally decreases at higher trophic levels; the link from secondary consumers to decomposers is the least efficient stage.
Xerophytes have the following characteristics aimed at conserving water except
Xerophytes have narrow (not broad) leaves to reduce the surface area for water loss through transpiration.
An association between living organisms in which one lives on and feeds at the expense of the other is known as
Parasitism is the relationship where one organism (the parasite) lives on/in and feeds off another (the host), harming it.
When large numbers of organisms share limited space and resources, the immediate result is
When resources are limited and shared by many organisms, the immediate consequence is competition among them.
Which of the following disease is caused by a bacterium?
Syphilis is caused by the bacterium Treponema pallidum.
Conservation of wildlife is necessary mainly because
The primary purpose of wildlife conservation is to prevent species from becoming extinct.
Two unconscious patients X and Y whose blood group genotypes are AO and AB respectively were transfused with blood from the same donor. Patient X immediately showed signs of difficulty in breathing while patient Y showed no negative reaction. Patients X and Y were likely transferred with blood of genotype
Patient X (genotype AO, blood group A) reacted badly, meaning the donor blood contained an antigen X's plasma has antibodies against (anti-B) — consistent with the donor blood being group B (genotype BO), which patient Y (group AB) could safely receive.
What should the hospital have done to prevent patient X from showing the symptom described above? Patient X should have
An agglutination (cross-matching) test before transfusion would have revealed the blood group incompatibility and prevented the reaction.
The greatest contribution to genetic studies was made by
Gregor Mendel's work on pea plants laid the foundation of modern genetics.
The exchange of genes between homologous chromosomes is called
Crossing over is the exchange of genetic material between homologous chromosomes during meiosis.
The diagrams below are illustrations of the inheritance of coat colour in mice: J, K, L, M and N are parents. The cross between two parent mice gave rise to offspring P, Q, R and S. Which parent mouse is heterozygous for coat colour?
Since black is dominant over white, for the cross to produce some white and some black mice among the offspring, parent L must be heterozygous (carrying both alleles).
Which of the offspring are all homozygous?
Since white coat colour only occurs in the homozygous recessive state, and all of offspring S are white, all of offspring S must be homozygous.
Genes that remain linked are those
Linked genes are located close together on the same chromosome (same locus region), so they tend to be inherited together.
A plant cell has 14 chromosomes prior to mitosis. What is the number of chromosomes in the daughter cells?
Mitosis produces daughter cells with the same chromosome number as the parent cell (14); it is meiosis that halves the chromosome number.
The chemical bond that holds the bases of the two strands of DNA together is a
The complementary base pairs of DNA are held together by hydrogen bonds.
The diagram below is an illustration of one of the theories of evolution. Who proposed the theory in the illustration?
The illustration (progressive change of a structure over time, e.g. gradual elongation) represents Lamarck's theory of use and disuse / inheritance of acquired characteristics.
The theory supports a
Lamarck's theory is based on the principle of use and disuse of body parts, where used parts develop further and unused parts atrophy.
In evolution, fossils are naturally preserved in
Fossils are the preserved remains or impressions of once-living organisms, naturally preserved mainly in rocks.
Which of the following insects is not a social insect?
Ants, honeybees and termites are social insects living in organized colonies; the housefly is a solitary insect.
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