WAEC Biology 2002 past questions and answers

A palisade cell is a plant cell, so it has a cellulose cell wall and many chloroplasts. A liver cell is an animal cell and has neither.

Euglena has chloroplasts and makes its own food like a plant, but it also moves with a flagellum and can feed like an animal.

The plant cell wall is made mainly of cellulose, which gives the cell its firm shape.

Centrioles, which help in cell division, are found in animal cells but not in the cells of flowering plants. Cell walls, large vacuoles and chloroplasts belong to plant cells.

Hair (fur) and whiskers can be seen on the outside of the body and are typical of mammals. The intestine, diaphragm and lungs are internal.

The order is organelle (mitochondrion), cell (neurone), tissue (muscle), organ (heart), system (alimentary canal) and finally the whole organism (rabbit).

When a plant loses water by transpiration faster than its roots can take it up, its cells lose turgor and the plant wilts.

Excretion is getting rid of waste made by the body's own chemical reactions (metabolism). Faeces are undigested food, so passing them is egestion, not excretion.

Most stomata are on the lower surface. Uncovered leaves (IV) lose most water, then leaves with only the upper surface covered (I), then those with the lower surface covered (II), and leaves covered on both sides (III) lose least.

Growth is a permanent increase in size or mass, measured by weight, height or leaf size. The number of fruits shows reproduction, not growth.

Synovial fluid, made by the synovial membrane, lubricates movable joints so the bone ends slide smoothly.

A large surface lets more molecules pass at once, and a thin surface gives them a short distance to travel, so diffusion is fastest.

Red blood cells contain haemoglobin, which carries oxygen from the lungs to the body cells. Engulfing bacteria is done by white blood cells.

A potometer measures how fast a leafy shoot takes up water. A hygrometer measures humidity and a hydrometer measures the density of liquids.

When we breathe in, the diaphragm contracts and flattens. It becomes dome-shaped when it relaxes during exhalation.

In the light stage, light energy trapped by chlorophyll splits water (photolysis) into hydrogen and oxygen, and the oxygen is given off.

High blood pressure in the glomerulus forces water and small dissolved substances into Bowman's capsule. This is ultrafiltration.

Adrenalin raises heart rate, breathing rate and blood sugar so the body is ready to fight or run away in an emergency.

The kidneys control the body's water content and remove excess water in urine.

Testosterone is the main male sex hormone (from the testes) and oestrogen is a main female sex hormone (from the ovaries).

The cerebellum controls balance and muscle coordination, so damage to it affects walking. Breathing is controlled by the medulla.

The semi-circular canals in the inner ear contain fluid that moves when the head moves, which tells the brain about balance.

In bright light the circular muscles of the iris contract, making the pupil smaller so less light enters and the retina is protected.

Entomophilous flowers are pollinated by insects. Grasses such as guinea grass are wind-pollinated, with small dull flowers.

Fertilization is the fusion of a male nucleus with the egg (ovum). Transfer of pollen to the stigma is pollination, and pollen tube growth comes before fertilization.

The zygote divides to form the embryo. The plumule, radicle and cotyledons are parts of that embryo.

Glucose made during photosynthesis is turned into starch and stored as starch grains inside the chloroplasts. Glycogen is stored in animals and fungi, not plants.

The small swellings on the roots of a legume are root nodules.

Root nodules contain Rhizobium bacteria, which fix nitrogen from the air into compounds the plant can use.

Polished rice lacks vitamin B1 (thiamine), and a shortage of it causes beri-beri. Rickets, night blindness and scurvy are caused by lack of vitamins D, A and C.

Sodium hydroxide plus copper sulphate is the Biuret test; a purple (violet) colour shows protein.

The ileum has many villi with a rich blood supply, giving a huge surface for absorbing digested food.

A reducing sugar gives no starch (iodine stays brown), no protein (Biuret stays blue), a brick-red Benedict's result and no fat (the ethanol test stays clear).

Ecology is the study of how living things relate to one another and to their surroundings.

In photosynthesis water molecules are split and built into food, so that water is taken out of the cycle. Transpiration and perspiration put water vapour back into the air.

Every food chain starts with a producer, an autotroph that makes its own food, usually by photosynthesis.

Insecticides also kill useful insects and other animals and can pollute soil and water. The other options are biological control, which targets the pest.

Energy enters a food chain when producers trap sunlight in photosynthesis; all other organisms get their energy from them.

Adaptations are features that suit an organism to its environment and so help it survive.

Mangrove mud is waterlogged and short of oxygen, so mangrove plants have breathing roots (pneumatophores) that grow up into the air.

More food lets more individuals survive and breed, so the population grows. Disease, deaths and predators all reduce it.

Measles is a viral disease spread through the air, and vaccination gives children immunity against it.

Bacteria and fungi decompose dead plants and animals, releasing nutrients back into the soil for plants to use again.

Cattle dung is a good manure that adds nutrients to the soil, so it helps the farmer's vegetables grow.

Conservation means protecting wildlife, so stopping the killing of endangered species helps. The other options would harm wildlife.

A person's fingerprint pattern forms before birth and does not change for life, and no two people have exactly the same prints.

An endangered species is one with so few individuals left that it is at risk of extinction.

Height changes gradually from short to tall with many in-between values, so it is continuous. Sex and Rh factor fall into clear separate groups.

Group O people can give blood to all groups (universal donors) but can receive only group O blood, so statement C is wrong.

Round is dominant, so the F₂ has 3 round : 1 wrinkled. Wrinkled to round is therefore 1 : 3.

Morphological variations can be seen on the body (size, colour, fingerprints). Blood group can only be found by a laboratory test, so it is a physiological variation.

A mutation is a sudden change in a gene or chromosome; if it is in a sex cell it can be inherited.

Females are XX and males are XY. The father's sperm carries either X or Y, and this decides the child's sex.

Cross BO × AO gives AB, AO, BO and OO in equal numbers. Only OO (group O, the universal donor) is 1 in 4, which is 25%.

Alleles are different forms of a gene for the same trait, found at the same place (locus) on a pair of homologous chromosomes.

Few stomata, sunk in pits and only on the shaded lower surface, let out less water vapour. A tap root helps get water but does not reduce water loss.

Wasps, termites and bees live in organised colonies with castes. Cotton stainers live alone and are not social insects.

Fossils are actual remains of past organisms showing how life changed over time, so they are direct evidence. The others are indirect comparisons.

(a)(i) Parasitism: a close association between two organisms of different species in which one (the parasite) lives in or on the other (the host), gets food or shelter from it and harms it.
(ii) Commensalism: an association between two organisms of different species in which one (the commensal) benefits while the other is neither helped nor harmed.
(b)(i) Any one, e.g. Puccinia (rust) on maize or wheat; Phytophthora palmivora (black pod) on cocoa; Phytophthora infestans (blight) on potato or tomato; Ustilago (smut) on maize.
(ii) Any one, e.g. Vibrio cholerae (cholera); Mycobacterium tuberculosis (tuberculosis); Salmonella typhi (typhoid); Clostridium tetani (tetanus); Neisseria gonorrhoeae (gonorrhoea).
(c)(i) Any four: high fever; shivering/chills; headache; pains in the joints; loss of appetite; vomiting; weakness/tiredness; paleness (anaemia).
(ii) Any six: sleep under (treated) mosquito nets; put wire gauze/nets on windows and doors; drain stagnant water and remove empty cans and containers; spray stagnant water with oil to kill larvae; spray insecticides or burn mosquito coils; use mosquito repellent creams; clear bushes around homes; introduce fish (e.g. Tilapia) to eat larvae; take anti-malarial drugs to prevent or treat the disease; educate the public on malaria control.

Name each parasite with its host or disease, and give exactly the number of points asked.

(a) A receptor is a sensory cell (or group of cells) that detects a stimulus and starts a nerve impulse, which is carried by sensory neurones to the central nervous system.
(b) Made of specialised sensory cells; each is sensitive to one kind of stimulus (light, sound, touch, chemicals, heat); the free ends of the cells often bear fine hair-like processes; the cells are connected at their bases to sensory nerve fibres; they change the stimulus into nerve impulses; they are often grouped together in sense organs.
(c)(i) Diagram (title, clear lines, correct size) labelled: outer ear – pinna, external auditory canal (meatus), ear drum (tympanic membrane); middle ear – malleus, incus, stapes (ossicles), oval window, round window, Eustachian tube, middle ear cavity.
(ii) Any three: do not push sharp objects (pins, sticks) into the ear; clean only the outer ear gently, e.g. with cotton buds; avoid very loud noise and loud earphones; do not pour hot or dirty liquids into the ear; see a doctor quickly about ear pain or discharge; treat infections such as measles, catarrh or meningitis promptly.

Only the outer and middle ear are asked for in the diagram; do not draw the inner ear.

(a) Plasma; red blood cells (erythrocytes); white blood cells (leucocytes); platelets (thrombocytes).
(b) Plasma: carries dissolved food, hormones, urea and carbon dioxide; distributes heat; carries antibodies and clotting proteins.
Red blood cells: carry oxygen as oxyhaemoglobin; help carry carbon dioxide.
White blood cells: engulf (phagocytose) germs; make antibodies/antitoxins.
Platelets: start blood clotting; help seal wounds and stop bleeding/entry of germs.
(c) Arteries | Veins:
carry blood away from the heart | carry blood to the heart;
thick, muscular, elastic walls | thin walls with little muscle;
narrow lumen | wide lumen;
no valves (except at their base) | have valves along their length;
blood under high pressure and flows in spurts | low pressure, smooth flow;
carry oxygenated blood (except pulmonary artery) | carry deoxygenated blood (except pulmonary vein);
usually deep in the body | many near the surface.
(d)(i) Pulmonary artery. (ii) Renal artery.

In (c) each difference must compare the same feature for both vessels.

(a) Sexual reproduction is the production of new individuals by the fusion of male and female gametes (fertilization) to form a zygote.
(b) Placenta (any five): lets oxygen pass from mother to foetus; lets digested food pass to the foetus; lets carbon dioxide and urea pass from foetus to mother; passes antibodies to the foetus; keeps the two blood systems apart (protects the foetus from the mother's high blood pressure and some germs); makes hormones such as progesterone; attaches the foetus to the uterus wall.
Umbilical cord (any four): joins the foetus to the placenta; umbilical vein carries oxygen and food to the foetus; umbilical arteries carry carbon dioxide and wastes to the placenta; carries antibodies to the foetus; allows the foetus to move freely in the amniotic fluid.
(c) Any four: marginal; axile; parietal; free central; basal.
(d) Water (moisture); oxygen (air); suitable (warm) temperature; a viable embryo (and end of dormancy).

Keep placenta and umbilical cord functions in separate lists.

(a)(i) Ecological succession is the gradual, orderly change in the kinds of organisms (communities) living in an area over time, until a stable climax community is formed.
(ii) Any four: it starts on bare or disturbed land with pioneer species such as lichens, mosses or grasses; each community changes the habitat (e.g. builds soil) and makes it suitable for the next; species number and variety increase over time; plants become larger and more complex; it is slow at first then speeds up; it ends in a stable climax community.
(b) Any four, explained: food supply – plenty of food raises the population, shortage lowers it; predators – more predators lower prey numbers; disease – epidemics cause many deaths; birth (natality) and death (mortality) rates – more births than deaths raise the population; immigration and emigration add or remove individuals; space/shelter and competition – overcrowding leads to competition and fewer survivors; climate/natural disasters such as floods or drought kill many.
(c) Thick cuticle resists digestion by the host's enzymes; scolex with hooks and suckers holds it to the gut wall; absorbs digested food over its whole body surface (no gut); flat, thin body gives a large surface for absorption; can respire anaerobically in the low-oxygen gut; hermaphrodite and produces very many eggs; ripe proglottids pass out with faeces to reach a new host; secretes anti-enzymes.

In (b) explain how each factor raises or lowers the population, not just its name.

(a)(i) Producer: an autotrophic organism, usually a green plant, that makes its own food from simple substances by photosynthesis and is the first link in a food chain.
(ii) Consumer: a heterotrophic organism (animal) that cannot make its own food and feeds on producers or other consumers.
(iii) Community: all the populations of different species living together and interacting in one habitat.
(iv) Decomposer: an organism such as a bacterium or fungus that breaks down dead organic matter and wastes, releasing simple nutrients back into the soil.
(b)(i) Rain forest trees (any four): very tall (often over 30 m); straight trunks with branches only near the top; thin, smooth bark; large, broad, evergreen leaves, often with drip tips; form layers and a closed canopy; buttress or stilt roots; shallow roots; many climbers and epiphytes on them.
(ii) Savanna trees/shrubs (any four): short and scattered; thick, fissured, fire-resistant bark; small or leathery leaves, often shed in the dry season; long, deep tap roots; twisted or umbrella-shaped crowns; some store water in their trunks (e.g. baobab); some have thorns.

Give clear one-line definitions, then four distinct features for each vegetation type.