65 questions. Try each one, then open the answer to check yourself and read the explanation.
A group of closely related organisms capable of interbreeding to produce fertile offspring are known as members of a
Answer: D (species.)
A species is defined as a group of organisms that can interbreed and produce fertile offspring.
Viruses are economically important because they
Answer: C (cause diseases in plants and animals.)
Economic importance is about effect on people: viruses cause diseases of crops, livestock and humans. The other options are just features of viruses.
A beaker of pond water containing few specimens of Euglena was placed in a dark room for two weeks. At the end of this period, the specimens of Euglena were still alive because they were
Answer: A (able to carry out holozoic nutrition.)
Without light Euglena cannot photosynthesise, but it can switch to feeding on organic matter (heterotrophic nutrition), so it survives in the dark.
The cytoplasm of the cell is considered a very important component because it
Answer: B (suspends all cell organelles.)
The cytoplasm is the jelly-like medium in which all the organelles are suspended and where many reactions take place.
Use the diagram (a thistle funnel containing sugar solution, with a membrane tied over the funnel, standing in distilled water) to answer this question.
After an hour, the level of water in the thistle funnel will
Answer: A (rise.)
Water moves by osmosis from the distilled water into the more concentrated sugar solution, so the level in the funnel rises.
Use the diagram (a thistle funnel containing sugar solution, with a membrane tied over the funnel, standing in distilled water) to answer this question.
The experiment above is used to demonstrate the process of
Answer: D (osmosis.)
Water passing through a selectively permeable membrane from a dilute to a concentrated solution is osmosis.
Use the diagram (a thistle funnel containing sugar solution, with a membrane tied over the funnel, standing in distilled water) to answer this question.
In plant cells the role of the membrane is played by the
Answer: C (cytoplasm.)
The membrane in the funnel is selectively permeable. In a plant cell the cell wall lets everything through; it is the lining of cytoplasm (with the cell membrane and tonoplast) that acts as the selectively permeable membrane.
Red blood cells were found to have burst open after being placed in distilled water for an hour. This phenomenon is known as
Answer: C (haemolysis.)
Water enters red cells by osmosis until they burst; the bursting of red blood cells is called haemolysis.
The overall reaction in glycolysis can be summarised as
Answer: B (C6H12O6 → 2C3H4O3 + 4H + 2ATP)
Glycolysis splits one glucose into two molecules of pyruvic acid (C3H4O3), releasing hydrogen and a net gain of 2 ATP.
The curvature movement of plants in response to the stimulus of water is called
Answer: A (hydrotropism.)
'Hydro' means water; a growth curvature in response to water is hydrotropism.
Two organelles directly involved in mitotic cell division are
Answer: D (nucleus and centriole.)
The nucleus holds the chromosomes that divide, and the centrioles form the spindle that pulls them apart.
The following statements about mitotic cell division are correct except that
Answer: A (it occurs only in young cells.)
Mitosis happens in body (somatic) cells of all ages, e.g. for repair and replacement, so it is not limited to young cells.
The longest bone in the body is the
Answer: B (femur.)
The femur (thigh bone) is the longest bone in the human body.
Which of the following structures is not a skeletal material?
Answer: D (Muscle)
Chitin, cartilage and bone all form skeletons; muscle moves the skeleton but is not a skeletal material.
The reason why the flow of blood through the capillaries is very slow is
Answer: D (to allow adequate time for exchange of materials.)
Slow flow in capillaries gives time for oxygen, food and wastes to diffuse between the blood and the tissues.
Which of the following features is not characteristic of arteries? Arteries
Answer: A (possess valves at intervals throughout their length)
Valves along the length are a feature of veins; blood in arteries is under high pressure and needs no valves except at the heart.
A group of rats placed in an air-tight box for some hours died because they
Answer: D (used up the available oxygen.)
In a sealed box no fresh air enters, so the rats used up the oxygen needed for respiration and died.
Which of the following organisms have kidney as their excretory organ?
Answer: A (Fishes, amphibians, birds, man)
Kidneys are found in vertebrates. Annelids use nephridia, insects Malpighian tubules, tapeworms flame cells and protozoans contractile vacuoles.
The graph in Fig. 1 shows the results of a laboratory investigation which measured the body temperatures of a lizard and a bird under changing artificial conditions.
Which of the statements below is valid?
Answer: B (The body temperature of the bird varied less than that of the lizard during changes in environmental temperature)
On the graph the lizard's temperature climbs steeply from about 60°F to above 110°F, while the bird's line rises only a few degrees. So the bird's temperature varied less, but it did not stay exactly constant, and the lizard was warmer than the bird at high temperatures.
The graph in Fig. 1 shows the results of a laboratory investigation which measured the body temperatures of a lizard and a bird under changing artificial conditions.
What physiological term can be used to describe the regulation of the body temperature of the lizard?
Answer: C (Poikilothermy)
The lizard's body temperature changes with its surroundings; animals like this are poikilothermic (cold-blooded).
The reason why hospitals use saline solutions as drip instead of water is
Answer: C (to maintain the composition of body fluids.)
Saline has the same salt concentration as blood plasma, so it keeps body fluids balanced; plain water would make blood cells swell and burst.
The part of the ear which contains nerve cells sensitive to sound vibrations is the
Answer: A (cochlea.)
The cochlea in the inner ear holds the sensory hair cells that respond to sound; the ampulla senses movement for balance.
Spectacles with convex lenses correct long-sightedness by
Answer: A (converging the light rays before they enter the eye.)
A convex lens bends light rays inwards (converges them) so that near objects focus on the retina instead of behind it.
A seed of a flowering plant can best be described as
Answer: B (the developed ovule.)
After fertilisation the ovule becomes the seed and the ovary becomes the fruit.
Which of the following processes removes carbon from the atmosphere?
Answer: B (Photosynthesis)
Green plants take in carbon dioxide from the air during photosynthesis; the other processes release carbon dioxide.
Which of the following cycles involves the process of precipitation and transpiration?
Answer: A (Water cycle)
Precipitation (rain) and transpiration (water loss from leaves) are stages of the water cycle.
The mesophyll layer of a leaf consists of
Answer: D (photosynthetic parenchyma cells.)
The mesophyll (palisade and spongy layers) is made of parenchyma cells packed with chloroplasts for photosynthesis.
Which of the following treatments would increase the rate of transpiration in a potted plant?
Answer: B (Placing it under a fan in a room)
A fan blows away the humid air around the leaves, keeping the diffusion gradient steep, so water vapour is lost faster.
Pepsin is secreted as an inactive precursor called pepsinogen because
Answer: C (pepsin is a proteolytic enzyme and might attack the stomach tissues)
Pepsin digests protein, and the stomach wall is made of protein; releasing it in an inactive form protects the cells that make it.
An organism whose source of carbon is inorganic is likely to be a/an
Answer: B (autotrophic organism.)
Autotrophs make their own food from inorganic carbon (carbon dioxide); heterotrophs need organic carbon from other organisms.
Which of the following organisms is an endoparasite?
Answer: C (Ascaris)
Ascaris (roundworm) lives inside the host's intestine, so it is an endoparasite; mosquitoes and dodder feed from the outside.
Which of the following statements about ecosystems is false?
Answer: A (All the energy entering the ecosystem is passed on to decomposers)
Much of the energy entering an ecosystem is lost as heat at each level, so not all of it reaches the decomposers.
What is the critical limiting factor for plants below the photic zone in an aquatic ecosystem?
Answer: C (Intensity of light)
The photic zone is the layer light can reach; below it there is too little light for photosynthesis.
Which of the following instruments is used to estimate the number of plants in a habitat?
Answer: C (Quadrat)
A quadrat is a square frame placed in a habitat to count plants; the others are for catching small animals.
Which of the following statements is true about sandy soil? It
Answer: B (is light and easy to dig)
Sandy soil has large particles with big air spaces, so it is light, well aerated, drains fast and is easy to dig.
Which of the following organisms is a primary consumer?
Answer: B (Sheep)
A primary consumer eats plants; the sheep is a herbivore.
Study the food chain P → Q → R → S → T.
The organism designated P in the food chain above is normally sustained by energy from
Answer: A (sunlight.)
P is the first link, the producer (a green plant), which gets its energy from sunlight.
Study the food chain P → Q → R → S → T.
Which of the following statements best describes the organism designated R? It
Answer: D (is a secondary consumer)
P is the producer, Q the primary consumer, so R, which eats Q, is the secondary consumer.
Food chains are relatively short because
Answer: C (of energy loss at each trophic level.)
About 90% of energy is lost at each level (respiration, heat, waste), so after a few links too little is left to support another level.
Which of the following organisms does not show colour adaptation to its environment?
Answer: B (Earthworm)
The chameleon, fish and toad use colour for camouflage; the earthworm lives underground and does not depend on colour.
Most tropical plants shed their leaves during dry weather conditions in order to
Answer: B (conserve water.)
Most water is lost through leaves by transpiration, so shedding leaves in the dry season saves water.
Which of the following features is not an adaptation of plants to aquatic habitat?
Answer: D (Hairy structures on the leaves to reduce water loss)
Water plants have plenty of water, so they don't need hairs to cut water loss; that is a desert-plant adaptation.
Population growth rate may be defined as the
Answer: D (net rate of natality and mortality in the habitat over a period.)
Growth rate is the balance of births (natality) against deaths (mortality) over a period of time.
In ecological succession, since lichens grow on bare rock, they are considered to be
Answer: B (pioneer organisms.)
The first organisms to colonise a bare area are called pioneers; lichens break down rock and start soil formation.
Which of the following factors will most likely lead to overcrowding within a population?
Answer: A (Absence of predators)
Predators keep numbers down; without them the population keeps growing and becomes overcrowded. Emigration and food shortage reduce numbers.
A species whose populations has become so small that it may become extinct if not protected is a/an
Answer: C (endangered species.)
An endangered species is one so reduced in number that it risks extinction without protection.
Which of the following practices does not contribute to the preservation and improvement of the environment?
Answer: D (Overgrazing)
Overgrazing strips the vegetation, exposing soil to erosion and desert formation; the others protect the environment.
Variation is important in human life and can be used for the following activities except
Answer: B (population distribution.)
Fingerprints help crime detection, and blood groups guide transfusion and paternity tests; variation is not used for population distribution.
An example of continuous variation is
Answer: D (body size.)
Body size shows a smooth range of values with many in-between forms, which is continuous variation; the others fall into clear-cut groups.
The outward appearance of an organism is referred to as
Answer: A (phenotype.)
The phenotype is the observable appearance; the genotype is the genetic make-up behind it.
The allele responsible for sickle-cell anaemia first appeared in the tropical and subtropical regions of Asia, the Middle East and Africa. It entered the United States of America when individuals were forcibly brought over from Africa. In micro-evolutionary terms this is an example of
Answer: B (gene flow.)
Gene flow is the movement of alleles from one population to another when individuals migrate, as happened here.
Which of the following diseases is not hereditary?
Answer: B (Scabies)
Scabies is caused by a mite passed by contact, not by genes; the other three are inherited.
The immediate product of meiosis in flowering plants is the
Answer: D (pollen grain.)
In the anther, meiosis of pollen mother cells directly produces haploid pollen grains (microspores).
DNA in eukaryotic cells is contained in the
Answer: B (nucleus.)
In eukaryotic cells the DNA is held in the chromosomes inside the nucleus.
A man who is heterozygous for the disease haemophilia marries a woman who is double recessive for haemophilia. What percentage of their offspring would have the disease?
Answer: C (50%)
Crossing Hh × hh gives Hh and hh in equal numbers, so half (50%) of the offspring are hh and show the disease.
A dairy farmer allowed only his best milk producing cows to mate. In succeeding generations of cows, milk production increased. This outcome is an example of
Answer: A (artificial selection.)
When humans choose which animals breed to get a desired trait, it is artificial selection.
Cytokinesis of mitosis is a process that ensures that
Answer: A (each daughter cells gets the necessary organelles.)
Mitosis has two parts: the nucleus divides first, giving each cell a full set of chromosomes, then cytokinesis divides the cytoplasm so each daughter cell gets its share of organelles.
An animal which is active during the day is known as a
Answer: B (diurnal animal.)
Diurnal animals are active by day; nocturnal animals are active at night.
Evidence for evolution include the following except
Answer: C (mutation of genes.)
Fossils, comparative anatomy and geographical distribution are lines of evidence; mutation is a cause of variation, not evidence that evolution happened.
(a) What is a sense organ?
(b) List four sense organs found in mammals.
(c) Describe the processes that will cause a person who has been spinning to feel dizzy.
(d) State two functions each of the following structures:
(i) Cerebellum; (ii) Cerebrum; (iii) Medulla Oblongata.
(a) An organ made of specialised receptor cells that detect a particular stimulus and send impulses to the nervous system.
(b) Any four: eye, ear, nose, tongue, skin.
(c) Spinning sets the fluid (endolymph) in the semicircular canals moving; when the person stops, the fluid keeps moving; it bends the sensory hairs in the ampullae; impulses go along the auditory nerve to the cerebellum/brain; the brain reads this as the body still turning while the eyes say it is still; the conflicting messages cause dizziness.
(d)(i) Cerebellum: keeps balance and posture; coordinates voluntary muscle movement.
(ii) Cerebrum: controls voluntary actions; seat of memory, intelligence, reasoning and interpretation of senses.
(iii) Medulla oblongata: controls involuntary actions such as heartbeat and breathing; controls reflexes such as coughing, sneezing and swallowing; regulates blood pressure by constricting/dilating vessels.
For (c) link the moving inner-ear fluid to the brain's wrong reading of body position.
(a) Explain why an athlete in a race would be given a glucose drink rather than a piece of bread.
(b) Outline the test for starch in a given food substance.
(c) State five reasons why water is important in human diet.
(a) Glucose is a simple sugar that needs no digestion; it is absorbed quickly into the blood and oxidised in respiration, giving energy almost at once. Bread contains starch, a complex carbohydrate that must first be digested (mouth to small intestine) before it can be absorbed, so its energy is released slowly.
(b) Crush the food and add a little water to make a suspension (or use a piece of the food); place some on a white tile or in a test tube; add a few drops of iodine solution; a blue-black colour shows starch is present (it stays brown if absent).
(c) Any five: main part of protoplasm, blood and tissue fluid; solvent for chemical reactions; transports digested food, hormones and gases; carries away excretory wastes (urine, sweat); helps regulate body temperature (sweating); lubricates joints (synovial fluid) and moistens food for swallowing; aids movement of food through the gut and prevents constipation; protects organs (e.g. cerebrospinal and amniotic fluid).
In (a) contrast 'no digestion needed' with 'must be digested first'.
(a) What is meant by the term Food chain?
(b) Draw a food chain involving four trophic levels which can be found in a terrestrial habitat.
(c) Explain (i) the flow of energy through the food chain drawn in 3(b) above;
(ii) how energy in the chain is lost to the environment.
(a) A linear feeding relationship in which energy passes from a producer through a series of organisms, each feeding on the one before it.
(b) e.g. Grass (producer) → Grasshopper (primary consumer) → Lizard (secondary consumer) → Hawk (tertiary consumer), with arrows pointing towards the eater.
(c)(i) Sun's light energy is trapped by chlorophyll in grass and stored as chemical energy in food (photosynthesis); the grasshopper gets it by eating grass; the lizard by eating the grasshopper; the hawk by eating the lizard; flow is one-way (non-cyclic), and decomposers finally obtain energy from dead remains.
(ii) At each level energy is lost as heat in respiration; in movement and other activities; in undigested food (faeces) and excretory products; parts of the organism are not eaten (bones, roots); so only about 10% passes on to the next level.
Remember: energy flows one way and decreases at each trophic level.
(a) What is variation?
(b) State five advantages of variation within a species.
(c) In a tabular form, outline four differences between continuous and discontinuous variations.
(d) Explain the following terms: (i) Sex-linked characters; (ii) Co-dominance; (iii) Hybrid vigour.
(a) The differences in features (structure, function, behaviour) between members of the same species, which may be inherited or caused by the environment.
(b) Any five: produces new varieties; allows natural selection (survival of the best-adapted); some individuals resist diseases; population can adapt to environmental change; reduces competition by using different resources; allows breeders to select desired traits; helps identification (fingerprints, blood groups).
(c) Table — Continuous: shows a range of intermediate forms / Discontinuous: clear-cut groups with no intermediates; Continuous: controlled by many genes (polygenic) / Discontinuous: one or few genes; Continuous: strongly affected by environment / Discontinuous: little or not affected; Continuous: gives a normal distribution curve / Discontinuous: bar chart of distinct classes; Continuous: e.g. height, weight / Discontinuous: e.g. blood group, tongue rolling. (Answer must be in a table.)
(d)(i) Characters whose genes are carried on the sex chromosomes (usually the X), e.g. haemophilia, colour blindness, so they show different patterns in males and females.
(ii) Both alleles in a heterozygote are fully expressed, neither dominant, e.g. AB blood group or roan coat in cattle.
(iii) The increased vigour, yield or disease resistance of offspring from crossing two genetically different (unrelated) parents.
Part (c) earns no marks unless it is in a table.
(For candidates in Nigeria only)
(a) With the aid of annotated diagrams only, outline the water cycle.
(b) Describe an experiment to show that water is conducted in the xylem tissue of flowering plants.
(a) Labelled/annotated diagram showing: evaporation from seas, rivers and lakes; transpiration from plants; evaporation from soil; respiration, sweating and excretion by animals; water vapour rising and condensing into clouds; precipitation (rain) falling; run-off into streams and water bodies; infiltration into underground water; absorption by plant roots; drinking by animals; decay returning water.
(b) Cut a young herbaceous shoot (e.g. balsam) under water; wash the roots/stem; stand it in a beaker of dilute dye (eosin or red ink) in sunlight for a few hours; remove, wash, and cut thin transverse sections of the stem; view under a microscope: only the xylem is stained red, showing water travels up in the xylem.
For (a) the marks are in the arrows and labels on the diagram, not in written paragraphs.
(For candidates in Nigeria only)
(a) What is growth?
(b) State two differences each between:
(i) growth in plants and animals; (ii) metamorphosis in housefly and toad.
(c) Name two hormones each involved in:
(i) plant growth; (ii) animal growth.
(d) State the effects of the hormones named in 8(c) above.
(e) Name the type of germination which takes place in:
(i) monocotyledonous plants; (ii) dicotyledonous plants.
(f) In a tabular form state four differences between the forms of germination named in 8(e) above.
(a) A permanent (irreversible) increase in size or dry mass of an organism due to the addition of new protoplasm.
(b)(i) Plants: growth restricted to meristems (tips) / animals: growth occurs all over the body; plants grow throughout life / animals stop growing at maturity; plants have an indefinite number of parts / animals a definite number.
(ii) Housefly: complete metamorphosis with a pupa (egg-larva-pupa-adult) / toad: no pupa (egg-tadpole-adult); housefly develops on land / toad's young develop in water; housefly is quicker.
(c)(i) Any two: auxin (IAA), gibberellin, cytokinin. (ii) Any two: growth hormone (somatotrophin), thyroxine, testosterone/oestrogen.
(d) Auxin: cell elongation, tropisms, root formation; gibberellin: stem elongation, breaks seed dormancy, larger fruits; cytokinin: cell division, growth of lateral buds. Growth hormone: growth of bones and muscles (too little causes dwarfism, too much gigantism); thyroxine: controls metabolic rate, growth and development (lack causes cretinism); sex hormones: development of secondary sexual features.
(e)(i) Hypogeal germination. (ii) Epigeal germination (most dicots, e.g. bean).
(f) Table — Hypogeal: cotyledons stay below ground / Epigeal: cotyledons are carried above ground; Hypogeal: epicotyl elongates / Epigeal: hypocotyl elongates; Hypogeal: cotyledons do not become green or photosynthesise / Epigeal: cotyledons turn green and photosynthesise; Hypogeal: plumule emerges first, protected by coleoptile (maize) / Epigeal: hypocotyl hooks out of the soil first; e.g. maize / e.g. bean.
Note some dicots (e.g. pea) germinate hypogeally; give the common case for each group.