WAEC Biology 2016 past questions and answers

Volvox is a hollow ball of many similar cells joined together, which is a colony. Spirogyra is a filament, and Paramecium and Euglena live as single cells.

In flowering plants the ovules are enclosed in an ovary, which becomes the fruit. Gymnosperms have no ovary, so their seeds lie exposed on cone scales.

DNA is copied (replicated) in the nucleus, where the chromosomes are found.

Plant A's leaves and stem drooped because its cells lost more water than they took in. This drooping is called wilting.

Dry (low-humidity) and hot air makes water evaporate from the leaves fastest, so the plant loses water quickly and wilts.

Hydra is made of many cells grouped into layers that do different jobs, but it has no true organs. That is the tissue level of organisation.

Diagram I is a budding yeast, a complete single-celled organism. Diagram II is a white blood cell, which is only a cell of the human body.

II is a white blood cell. White blood cells fight germs, so if their number falls the body is less able to resist infection.

When plant cells lose water they become flaccid (soft), and the leaves and stem droop: the plant wilts.

In a healthy kidney all the glucose in the filtrate is reabsorbed into the blood. Glucose in urine is a sign of diabetes.

Muscles can only pull. They work in antagonistic pairs (e.g. biceps and triceps): one contracts while the other relaxes, so the bone can be moved in both directions.

The cambium is the lateral meristem: its dividing cells make the stem and root thicker (secondary growth).

The nose, throat (pharynx and trachea), diaphragm and lungs work together to take air in and out of the body: the respiratory system.

Breathing is the movement of air into and out of the respiratory organs, which exchanges gases with the surroundings. Respiration is the release of energy inside cells.

Insulin is made by the islets of Langerhans in the pancreas. It lowers the blood sugar level.

Sneezing is a reflex: it happens automatically without our deciding to do it. The other actions are chosen.

Root hairs grow out of the piliferous layer, the outer layer of the young root just behind the tip.

Endolymph fills the inner ear (semicircular canals, utriculus, sacculus, cochlea). The tympanum (eardrum) is a membrane between the outer and middle ear.

The diagram shows a single ovule attached at the base of the ovary, which is basal placentation.

First boil the leaf in water to kill and soften it (III), then decolourise it in alcohol (I), dip it in warm water to soften it again (II), and finally add iodine (IV).

A leaf that has been in sunlight has been photosynthesising and has stored starch, so the test will show a result.

Guard cells are found in the epidermis of leaves, where pairs of them surround each stoma.

In parasitism the parasite benefits by feeding on its host, and the host is harmed.

Villi are tiny finger-like folds of the small intestine wall. They greatly increase the surface through which digested food is absorbed.

The kidney is an excretory organ. The oesophagus, pancreas and stomach all help in digestion.

Extra nutrients cause algae to bloom; when they die, bacteria use up the oxygen and fish die. This is eutrophication.

Sewage is rich in nitrates and phosphates, so dumping it into water also feeds algae and causes eutrophication.

A community is all the populations of different species living together in one habitat. Individuals of one species form a population.

A wind vane points the way the wind is blowing. An anemometer measures wind speed, and a barometer measures air pressure.

A food web is made of many food chains linked together. Because one animal can eat, or be eaten by, several others, it appears in several chains, which makes the web complex.

An adaptation is any feature of structure, function or behaviour that helps an organism survive in its habitat.

A saprophyte feeds on dead organic matter, so only one living organism is involved. The other relationships are between two living organisms.

Overcrowding leads to competition for food and space, death, and movement away (migration). Commensalism is a feeding relationship, not a result of overcrowding.

A pandemic is a disease outbreak that spreads over very large areas, across countries or continents.

Conservation means using natural resources wisely and carefully so that they last and are not wasted.

Air is everywhere and cannot be stored or kept back for later. Soil, water and wildlife can be protected and conserved.

Protecting endangered species keeps them from dying out, which is a main aim of conservation.

Differences in visible features such as height, colour or shape are called morphological variation. Physiological variation is in body processes, such as blood group.

Individuals differ because of the genes they inherit and the features they acquire from their environment. These differences together are called variation.

AB × BO gives gametes A, B and B, O, so the children can be AB, AO, BB and BO, exactly the four groups shown.

Blood group AB has both A and B antigens, so it can safely be given only to another AB person. The baby must be AB.

The offspring are X^cX, X^cX, XY and XY: two carrier females and two normal males, a ratio of 2 : 2 = 1 : 1.

I and II are X^cX females: they carry one colour-blindness allele but see normally. III and IV are normal XY males.

People who study genes and heredity are geneticists.

Mendel founded genetics, Johannsen coined the word 'gene' and Morgan studied sex linkage in fruit flies. Felix Dujardin studied protoplasm in single-celled organisms, not genetics.

Darwin's natural selection is summed up as 'survival of the fittest': the best-adapted individuals survive and pass on their features.

Ants, honeybees and termites are social insects that live in organised colonies. Cockroaches live alone, without social organisation.

Organisms that cannot adapt to their surroundings fail to survive and reproduce, and in time the species dies out (extinction).

(a)(i) Any three: as single free-living cells; as colonies; as filaments; as part of a many-celled organism (tissues).
(ii) Single: Amoeba, Euglena, Chlamydomonas, Paramecium. Colony: Volvox, Pandorina, Eudorina. Filament: Spirogyra, Ulothrix, Oedogonium. Part of an organism: cheek cell, onion epidermal cell.
(b) Diagram 6–10 cm long with a title, showing and labelling: cellulose cell wall, cell membrane, cytoplasm, large central vacuole with tonoplast, nucleus (with nucleolus), chloroplasts, mitochondria; extra marks for middle lamella, endoplasmic reticulum, Golgi body. Clean lines and ruled label lines.
(c)(i) Any three in a table: plant cell has a cellulose cell wall / animal cell has none; plant has chloroplasts / animal has none; plant has one large central vacuole / animal has small or no vacuoles; plant stores starch / animal stores glycogen; plant cell has a regular shape / animal cell irregular; plant lacks centrioles / animal has centrioles.
(ii) Any three: both have a cell membrane; both have cytoplasm; both have a nucleus; both have mitochondria, ribosomes, endoplasmic reticulum and Golgi bodies.

Draw large and in pencil, keep the drawing within the size asked, and give it a title.

(a) Mouth (buccal cavity) → pharynx → oesophagus → stomach → small intestine (duodenum, ileum) → large intestine (caecum and appendix, colon) → rectum → anus.
(b)(i) Any three: bird has a beak, human has lips and teeth; bird has no teeth, human has teeth; bird has a crop, human has none; bird has a gizzard, human has none; bird has two caeca, human has one caecum and appendix; bird's gut opens into a cloaca, human's into an anus.
(ii) Any three: both have an oesophagus; both have a stomach (proventriculus in bird); both have a small intestine and large intestine; both have a liver and pancreas; both have a tongue.
(c) Incisors are sharp and chisel-like for cutting grass (upper incisors replaced by a horny pad in cattle); canines are absent or small, leaving a gap (diastema) so the tongue can move food; premolars and molars are broad with ridges for grinding; jaws move sideways for grinding; molars have open roots and keep growing.
(d) Any two: makes pancreatic juice with amylase (starch → maltose), trypsin (protein → peptides) and lipase (fat → fatty acids and glycerol); its alkaline juice (sodium hydrogencarbonate) neutralises acid chyme from the stomach.

In (b), compare the same structure in both animals on each line.

(a)(i) A habitat is the natural place where an organism lives.
(ii) Any three: break down dead plants and animals and their wastes; release mineral nutrients back into the soil or water (nutrient recycling); form humus that improves soil; clear away dead matter; release carbon (IV) oxide for photosynthesis.
(b) The sun is the source of energy. Producers (phytoplankton, algae, water plants) trap light energy in photosynthesis. Primary consumers (zooplankton, tadpoles, small fish) eat the producers; secondary and tertiary consumers (bigger fish, birds) eat them. Energy flows in one direction along the chain; at each step much is lost as heat (respiration) and in wastes, so less energy reaches each higher level. Decomposers get energy from dead matter at every level.
(c)(i) Any three: cause plant diseases (e.g. rusts, blights, mosaic); rot fruits and stored produce; lower crop yield; denitrifying bacteria remove nitrates from the soil.
(ii) Any six: decay of dead matter recycles nutrients; nitrogen-fixing bacteria enrich the soil; yeast used in baking and brewing; bacteria used in making yoghurt, cheese and vinegar; making antibiotics (e.g. penicillin) and vaccines; bacteria in the gut make vitamins (B, K); sewage treatment; making biogas; retting of fibres and tanning of leather; used in genetic engineering (e.g. insulin).

For energy flow, start from the sun and name a trophic level at each step.

(a)(i) Agglutination is the clumping together of red blood cells when the antigens on the donor's cells meet the matching antibodies in the recipient's plasma (incompatible blood).
(ii) Completed table (donor down, recipient across: A, B, AB, O):
Donor A: +, −, +, −
Donor B: −, +, +, −
Donor AB: −, −, +, −
Donor O: +, +, +, +
(b)(i) Mosquito larva: mouth brushes create water currents that sweep tiny food particles (algae, bacteria) into the mouth; it hangs at the surface breathing through a siphon while it feeds.
(ii) Dodder: a parasitic plant with no (or little) chlorophyll and no true leaves; its stem twines round the host and sends haustoria into the host's xylem and phloem to absorb water and food.
(iii) Grasshopper: biting and chewing mouthparts – strong toothed mandibles cut and grind leaves, maxillae hold and pass food, labrum and labium hold food in place, palps taste and feel food.

Remember O is the universal donor and AB the universal recipient.

(a) Any two: tactic movement is movement of the whole organism from place to place / nastic is movement of a part only; tactic movement is directed by the direction of the stimulus / nastic is not related to the stimulus direction; tactic is shown by motile organisms or cells / nastic by fixed plants.
(b)(i) Tactic: Chlamydomonas, Euglena, sperm of ferns or mosses, Paramecium.
(ii) Nastic: Mimosa pudica (sensitive plant), morning glory or other flowers that open and close, leaves of legumes that fold at night, sundew/Venus flytrap.
(c)(i) Any three: bathe regularly with soap and clean water; wear clean clothes; eat a balanced diet; avoid harmful bleaching creams; treat cuts and skin infections quickly; avoid too much sun.
(ii) Any three: heat, cold, touch, pressure, pain.
(d) Any five: increased evaporation dries the soil; plants lose more water and wilt; organisms may die of heat or dehydration; water bodies dry up; animals migrate, burrow or aestivate; enzymes may be denatured; more bush fires; faster decay of organic matter; vegetation becomes sparse (desert-like).
(e)(i) Courtship behaviour is the pattern of actions animals show to attract a mate of the same species before mating.
(ii) Any three: display of bright feathers (peacock, cock); dancing or special movements; calling or singing (frogs, birds, crickets); fighting between males; building nests or giving food; release of scents (pheromones); colour change.
(f) Any three: humans, dog, cow, Amoeba, Hydra, grasshopper, any other animal that ingests solid food.
(g) Every person has a unique fingerprint pattern that does not change. Prints left at a crime scene are lifted (with powder or chemicals) and compared with the fingerprints of suspects or with records; a match identifies the person who was there.

Section C (candidates in Nigeria only). Several short parts: give exactly the number of points asked.