WAEC Biology 2010 past questions and answers

Euglena has chloroplasts and makes its own food, so it is not placed with the animals; Amoeba and Paramecium are animal-like protists and Obelia is a cnidarian.

A single-celled organism has no tissues or organs; each life process is done by an organelle such as the contractile vacuole or food vacuole.

Cells of the cornified layer of the skin are dead and keratinised, so they have almost no mitochondria; muscle cells need many for energy.

Both cell types have a nucleus, cytoplasm and mitochondria; only plant cells have a cellulose cell wall and chloroplasts.

Like animals, fungi store food as glycogen rather than starch. Fungi have no gut and do not move about.

Digested food such as glucose moves from the gut, where it is concentrated, into the blood in the villi by diffusion. Water uptake and turgidity are osmosis.

When guard cells become turgid the pore opens; when they become flaccid it closes.

Energy stored in ATP is released when its end phosphate group is split off, forming ADP.

A tiny organism has a large surface compared with its volume, so wastes can diffuse out across its surface fast enough.

The axial skeleton is the central axis: skull, vertebral column, ribs and sternum. Limbs and girdles are the appendicular skeleton.

Bone's hardness comes mainly from calcium phosphate, with some magnesium salts.

Each heartbeat pushes a surge of blood that stretches the elastic artery wall; this rhythmic stretching is felt as the pulse.

The features of a good respiratory surface are large area, moist and thin surface, and a rich blood supply; 'expandable lungs' is not one of these surface features.

Mammals have two kidneys and two ureters leading into a single bladder, which empties through one urethra.

During exercise extra blood is sent to the working limbs, heart and lungs; the brain's share of the blood does not rise and falls as a proportion of the total.

The pinna (outer ear flap) is supported by flexible elastic cartilage.

The retina is the receptor for sight and sends impulses to the brain; the cochlea is the receptor for hearing and does the same.

The mother's and foetus's blood never mix; materials pass across the thin placental membrane.

V is the albumen (water and protein) and VI is the yolk (stored food); together they nourish the embryo.

III points to the twisted cord that holds the yolk in the centre of the egg: the chalaza.

Transpiration is the evaporation of water vapour from the aerial parts of a plant, mainly through the stomata of leaves.

Translocation is the movement of manufactured food in the phloem, not water in the xylem.

The underside of the leaf shelters the eggs from sun, rain and predators; laying them there is not a matter of camouflage colouring.

Carbohydrates have the general formula C_x(H₂O)_y, so hydrogen and oxygen are in the ratio 2:1, as in water.

Margarine and butter are almost pure fat, the most energy-dense food, so they should be avoided in obesity.

Boiling in water kills the cells and stops enzyme action; the chlorophyll is removed later with alcohol, not water.

Sucrose is digested by sucrase; pepsin digests protein.

The stomach is strongly acidic because of hydrochloric acid; pepsin and rennin work best at about pH 2.

Rhizobium in legume root nodules fixes atmospheric nitrogen gas into ammonia, which the plant uses.

Herbivores such as cattle lack canines (or have very small ones), which carnivores use to tear flesh.

An organism's niche is its role or 'job' in the habitat: what it eats, what eats it and how it uses resources.

An anemometer measures wind speed; a wind vane shows only its direction.

Biotic components are living things; fungi are living, while soil, rainfall and light are non-living (abiotic).

Moss spores have tough walls and can survive dry conditions, germinating when water returns.

Xerophytes live in dry places, so shortage of water is their main problem; their adaptations reduce water loss.

Carbon dioxide, CFCs and methane trap heat in the atmosphere; oxygen does not.

People move to towns for jobs and amenities; providing the same facilities in rural areas removes the reason to move.

Tendons join muscle to bone; ligaments join bone to bone.

When food is short, members of the same species compete for it: intra-specific competition.

Removing forests reduces transpiration and tends to lower rainfall, not increase it.

Wildlife conservation aims chiefly to stop species from dying out, which also helps keep the balance of nature.

Some people can roll their tongue and others cannot; this difference is a variation.

Every person's fingerprint pattern is unique, so a print can identify one individual.

Group O plasma has both anti-A and anti-B antibodies, so a group O person can receive only group O blood.

Aa × Aa gives AA, Aa, Aa and aa; only aa (1 in 4) is albino.

Each child receives genes from both parents, through the sperm and the ovum, not from one parent only.

A group O child is I^OI^O, so each parent must carry an I^O allele: father I^AI^O, mother I^BI^O.

Tt × tt gives Tt and tt in equal numbers, a 1 : 1 ratio (a test cross).

X^HY × X^HX^h: every son gets Y from the father and one X from the mother, so half the sons (X^hY) are haemophilic.

Courtship helps choose a mate of the right species, arouses the partners and times mating with ovulation; defending territory is a different behaviour.

Analogous structures, such as the wings of a bird and an insect, do the same job but are built differently, so they show diversity of structure.

Natural selection depends on variation: some individuals are better suited and survive to breed. The other statements are false.

Male agama lizards defend a territory, nodding their heads and chasing away rival males.

(a)(i) C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy (38 ATP)
(ii) C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ + energy (2 ATP)
(iii) C₆H₁₂O₆ → 2C₃H₆O₃ (lactic acid) + energy (2 ATP)
(b) Any four: regulating blood sugar (glucose ↔ glycogen); deamination of excess amino acids and urea formation; making bile; making plasma proteins (fibrinogen, prothrombin, albumin); detoxifying poisons and drugs; storing iron and vitamins A, D, B12; breaking down old red cells; producing heat.
(c) Diagram of a flame cell of correct size with title, showing: nucleus; cytoplasm; cell body; tuft of cilia (the 'flame'); cavity/lumen; excretory canal/tubule; (hollow cup-shaped cell).
(d)(i) Ethylene (ethene); (ii) gibberellin (or cytokinin); (iii) synthetic auxin, e.g. 2,4-D; (iv) abscisic acid (or ethylene).

Balance the equations and state the products of each type of anaerobic respiration correctly.

(a)(i) Epigeal, e.g. bean/cowpea; hypogeal, e.g. maize/pea.
(ii) Set up four flasks with moist cotton wool and seeds: A — dry cotton wool (no water), warm; B — water, but alkaline pyrogallol in the flask to absorb oxygen, warm; C — water and air, kept in a refrigerator (cold); D — water, air and warmth (control). After 3–5 days only seeds in D germinate, showing that water, oxygen and warmth are all needed.
(b)(i) Epiphytes: grow on other plants only for support/light; make their own food (have chlorophyll); do not harm the host; often have aerial roots that absorb moisture from the air.
(ii) Parasites: obtain food from a living host; harm the host; often lack chlorophyll; have haustoria that penetrate the host's tissues.
(c) Any two: dodder (Cuscuta), mistletoe (Loranthus), Striga (witchweed).

In the experiment each flask lacks one condition and a control has all three.

(a)(i) Ecological niche: the role or functional position of a species in its habitat — where it lives, what it feeds on, what feeds on it and how it affects other organisms.
(ii) Population density: the number of individuals of a species per unit area (or volume) of habitat, e.g. 20 plants per m²; = total population ÷ area.
(iii) Climax community: the final, stable community reached at the end of a succession, in balance with the climate, e.g. tropical rainforest; it changes little unless disturbed.
(b) Abiotic factors affect organisms: light controls photosynthesis and distribution; temperature and rainfall determine which plants and animals live there; soil type and pH affect plant growth; wind disperses seeds. Organisms affect abiotic factors: plants add humus and bind soil; transpiration raises humidity; shade lowers temperature and light; decomposers return minerals to the soil; organisms take in and give out O₂ and CO₂; earthworms aerate soil.

For (b) give examples in both directions: environment on organisms and organisms on environment.

(a) Any four: blood group; skin colour/albinism; tongue rolling; eye colour; height; sickle-cell trait; haemophilia; colour blindness; ear lobe shape.
(b)(i) Plants: anther (pollen mother cells) and ovule/nucellus (embryo sac mother cell). Animals: testes and ovaries.
(ii) Meiosis gives four daughter cells, mitosis two; meiosis halves the chromosome number (haploid), mitosis keeps it (diploid); meiosis has two divisions, mitosis one; in meiosis crossing over occurs, giving genetically different cells, while mitosis gives identical cells; meiosis occurs in reproductive organs, mitosis in body cells.
(c)(i) Woman I^AI^O × Mr. James I^AI^A; gametes I^A, I^O and I^A; offspring I^AI^A and I^AI^O — all blood group A. The claim is false.
(ii) A group O child must be I^OI^O, receiving one I^O from each parent; Mr. James is homozygous I^AI^A and has no I^O allele to pass on, so he cannot be the father.

Show parents, gametes and offspring in the genetic diagram.

(a)(i) Placentation is the way the placenta forms and the embryo becomes attached to the wall of the uterus (in flowering plants: the arrangement of ovules on the ovary wall).
(ii) Uterus; umbilical cord (also amnion/embryo).
(b) Any five: passes food from mother to foetus; supplies oxygen; removes CO₂ and urea from the foetus; passes antibodies to the foetus; keeps the two blood systems separate (protects from high maternal pressure); acts as a barrier to many germs and harmful substances; produces hormones (progesterone, oestrogen) that maintain pregnancy; anchors the foetus.
(c)(i) Viviparity: development of the young inside the mother's body, nourished by her through a placenta, and birth of live young, e.g. humans.
(ii) Territoriality: an animal or group claims and defends an area against others of the same species, for food, mates or breeding, e.g. the male agama lizard.
(iii) Seasonal migration: regular movement of animals from one region to another at certain seasons and back, for food, breeding or better climate, e.g. migratory birds, wildebeest.

Each short note needs a definition and an example.

(a) Adaptation is the possession of structural, physiological or behavioural features that enable an organism to survive and reproduce in its particular habitat and way of life.
(b)(i) Fleshy leaves store water for use in dry periods.
(ii) Fleshy stem stores water and photosynthesises; leaves reduced to spines cut transpiration and deter grazing animals.
(iii) Short strong beak picks up and cracks grains and seeds and digs for food.
(iv) Dark back and pale belly: seen from above the fish matches the dark water, from below the bright surface, so it is hidden from predators and prey.
(v) Small scale leaves/needles have a small surface area and thick cuticle, reducing water loss in cold or dry conditions.
(c)(i) All the organisms of one species living in a particular area at a given time.
(ii) Any five: shortage of food; competition for space and resources; overcrowding and poor housing; rapid spread of disease; more pollution and waste; unemployment and crime; shortage of water and amenities; destruction of habitats.

For each structure in (b) link the feature to the problem it solves.