JAMB Biology 2009 past questions and answers

A tissue is a group of similar cells doing one job. The onion bulb is built from several tissues working together to store food, which makes it an organ.

Excretion, the removal of waste made by the body's chemical reactions, happens in all living things. Not all organisms reproduce sexually, respire aerobically or move about.

Chromatin threads are the DNA in the nucleus; they coil up to form chromosomes, and the genes are sections of this DNA.

A fern has alternation of generations: the fern plant makes spores (asexual), which grow into a small prothallus that makes gametes (sexual).

The first land vertebrates were amphibians, and they evolved from lobe-finned fishes (Pisces).

Xylem and phloem are the plant's transport vessels: xylem carries water and minerals and phloem carries food, just as blood vessels carry materials in animals.

Protophytes are single-celled eukaryotes with a nucleus. Blue-green algae (cyanobacteria) have no nuclear membrane, so they belong with the bacteria in Monera.

The drawing is the head (scolex) of a tapeworm. X is one of its suckers, which, with the hooks, hold the worm onto the host's intestine wall.

The tapeworm is an endoparasite that lives attached to the wall of the small intestine of vertebrates such as man, cattle and pigs, absorbing digested food.

A streamlined body, pointed at both ends, cuts down water resistance so the fish moves through water easily.

Scratching birds such as the domestic fowl have strong, blunt claws that dig into soil without breaking. Hooked, sharp claws are for grasping prey.

Ruminants have a four-chambered stomach. They swallow grass, bring it back up as cud, chew it again and swallow it, which helps digest cellulose.

IV points to the guard cells around the stoma in the lower epidermis. They open and close the pore and so control how much water vapour escapes.

I points to the thin waxy layer on the very top of the leaf, outside the epidermis cells. This is the cuticle, which cuts down water loss.

Bladderwort is a water plant with small bladders that suck in and digest tiny animals. Hydra is an animal, yeast a fungus and Spirogyra an ordinary alga.

Bile from the liver and gall bladder breaks fat into tiny droplets (emulsification) in the small intestine (duodenum and ileum), labelled IV. The stomach (III) does not emulsify fats.

III is the stomach. Its glands secrete hydrochloric acid, which kills germs and gives pepsin the acid conditions it needs.

The gizzard has thick muscular walls and often holds grit; it grinds food because birds have no teeth. The crop only stores food.

Blood leaves the heart in arteries, which branch into smaller arterioles and then capillaries in the tissue. Veins and venules bring blood back to the heart.

Glycolysis, the first stage of respiration that splits glucose into pyruvic acid, takes place in the cytoplasm of the cell.

Malpighian tubules remove nitrogenous waste from the insect's blood. Nephridia are found in earthworms and flame cells in flatworms.

The axial skeleton is the central axis of the body: skull, vertebral column, ribs and sternum (breast bone). The humerus, clavicle, femur and ulna belong to the appendicular skeleton.

II points to the anthers on the staminal column. The anthers make pollen grains, which carry the male gametes. I is the stigma.

The flower (like hibiscus) has large showy petals and a sticky stigma, features that attract insects to carry pollen.

The male system includes the testes, the sperm ducts (vas deferens) and glands such as the prostate. Claspers are found in male sharks; the oviduct and uterus are female organs.

The micropyle is a tiny pore in the testa next to the hilum. Water first enters the seed through it, making the seed swell.

In the top drawing the rays from a near object meet behind the retina. This is long sight (hypermetropia), corrected with a converging lens as in the lower drawing.

The correcting lens is convex. It bends the rays inwards (converges them) before they enter the eye, so they focus on the retina.

On land, water is often in short supply. The amount of rainfall decides whether an area becomes desert, savanna or forest, so it controls which organisms live there.

The bacteria digest cellulose for the ruminant, and in return get food and shelter in its gut. Both benefit, so it is mutualism.

When the cytoplasm and sea water have the same concentration (isotonic), no extra water flows in by osmosis, so the protozoan needs no contractile vacuole to pump it out.

The ground of a marsh is soft, waterlogged mud with little oxygen. Plants need special roots and animals special habits to live on and in it.

Deserts get very little rain and lose heat fast at night because there are few clouds. Desert plants grow and flower quickly whenever it rains.

In zones I and III the temperature is too low or too high, so only a few individuals survive. These are the stress zones; zone II is the optimum range.

The population is largest at the peak of the curve, which is above 50 on the temperature axis.

River blindness is spread by blackflies that breed in fast streams, schistosomiasis by snails in still water, and salmonellosis by contaminated water. Meningitis spreads through air droplets.

Burning coal, oil and gas releases carbon (IV) oxide, a greenhouse gas that traps heat in the atmosphere.

Variation is the set of differences between members of the same species. It is why no two individuals are exactly alike.

Characters like height and weight show a smooth range from shortest to tallest with many in-between values. This is continuous variation.

Heredity is the passing of characters from parents to offspring. Seeds from high-yielding plants carry the genes for good yield.

Discontinuous characters fall into clear groups, such as tall or dwarf. Each is controlled by alleles of a single gene, one dominant and one recessive.

Tt × tt gives Tt, Tt, tt, tt. Half the children are Tt and can roll their tongue, so the chance is 50%.

'Meso-' means middle: mesophytes grow where water supply is moderate. Xerophytes live in dry places and hydrophytes in water.

Down feathers are soft and fluffy and lie close to the skin. They trap a layer of air, which insulates the bird.

Insects have a waxy waterproof cuticle, spiracles that can close, and they excrete almost dry uric acid, so they lose very little water.

Chromatophores are skin cells holding pigment. By spreading or bunching the pigment they let animals like chameleons and frogs change colour.

Animals like the lung fish and some snails become inactive during the hot dry season, cutting their metabolism to survive. This is called aestivation.

Darwin proposed that individuals best suited to their environment survive and reproduce more, passing on their features. This natural selection drives evolution.