WAEC Biology 2005 past questions and answers

Kingdom is the largest group in classification; each kingdom contains phyla, which contain classes, down to species.

Molluscs such as snails and octopuses have soft bodies that are not divided into segments, often protected by a shell.

Reproduction is a sign of life, and a virus can make copies of itself, but only inside a living host cell.

Most animals move about freely from place to place, while plants are fixed and only move parts of themselves.

Spongy, air-filled coats help fruits like coconut float, so they are an adaptation for water dispersal, not wind.

Whether made of one cell or many, every living organism carries out all the life processes such as feeding, respiration and reproduction.

Green plants make their own food from carbon dioxide and water using light energy, so they are autotrophic.

The human appendix has no clear use, but in herbivores such as rabbits the appendix and caecum help digest cellulose.

Chlamydomonas and Euglena both contain chlorophyll and make food by photosynthesis; Amoeba, Paramecium, Rhizopus and Plasmodium cannot.

Pandorina and Volvox are green algae made of many similar cells held together in a ball: a colony.

Cones give sharp, detailed (and colour) vision but need bright light; in dim light they are not stimulated, so only the less detailed rods work.

Moving against a concentration gradient means going from where there are few molecules to where there are many, which needs energy from ATP.

Osmosis is the movement of water molecules across a selectively permeable membrane; root hairs take in soil water this way.

When a plant cell loses water in a strong solution, its vacuole and cytoplasm shrink and pull away from the rigid cell wall: that is plasmolysis.

Plants build food from simple inorganic substances: carbon dioxide, water and mineral salts.

ATP stores and supplies energy for work, nerve impulses and body heat; the water of aerobic respiration is formed when hydrogen combines with oxygen, not by ATP.

Growth comes from cells dividing, getting bigger and becoming specialised; 'cell reduction' is not part of growth.

The biceps and triceps are antagonistic: the biceps contracts (triceps relaxes) to bend the arm, and the reverse straightens it.

Very salty water draws water out of most cells by osmosis, so only salt-tolerant (halophilic) microbes can live there.

Syphilis is a sexually transmitted disease caused by the spiral bacterium Treponema pallidum; the others cause tuberculosis, whooping cough and tetanus.

Every living cell of a plant respires all the time to release energy; stomata and lenticels are only openings for gas exchange.

Cobalt chloride paper turns from blue to pink with water; it changes faster on the lower surface because more water vapour escapes through its many stomata.

When humans get hot, sweat glands produce sweat that cools the skin as it evaporates, and skin blood vessels widen (vasodilation) to lose heat.

Fear makes the adrenal glands release adrenaline into the blood, preparing the body for 'fight or flight'.

Reading a verdict is done deliberately and under conscious control of the cerebrum, so it is a voluntary action.

Fertilization is the fusion of the nucleus of a male gamete with that of a female gamete to form a zygote.

Two different eggs fertilised by two different sperms give fraternal (non-identical) twins, who are no more alike than ordinary siblings.

In the light stage, light energises chlorophyll and splits water into hydrogen and hydroxyl ions, and the hydroxyl ions join to give water and oxygen. Carbon (IV) oxide is reduced by hydrogen from NADPH₂ only in the dark stage, so C is not true of the light stage.

Phosphorus is a macro-nutrient needed in large amounts; molybdenum, boron and copper are trace elements.

One gram of fat releases about 38 kJ, more than twice the energy of a gram of carbohydrate or protein (about 17 kJ).

Ptyalin is salivary amylase, the enzyme in saliva that starts turning starch into maltose in the mouth.

Savannah grass burns in the dry season, and thick corky bark shields the living tissues of the trunk from the fire.

Producers in the sea, such as phytoplankton, trap sunlight for photosynthesis, just like land plants.

A population is all the organisms of one species living in the same place at the same time.

On rocky shores waves constantly beat the rocks, so animals like barnacles and limpets cling with strong adhesives or suckers.

An ecosystem is a community of living things interacting with its non-living surroundings as a self-sustaining unit.

Edaphic factors are soil factors, which belong to terrestrial habitats; salinity, turbidity and temperature are water factors.

A float is timed as it travels a known distance downstream, giving the speed of the water; a Secchi disc measures turbidity.

Producers (green plants) trap light energy in photosynthesis and store it as chemical energy in food.

Denitrifying bacteria turn nitrates into nitrogen gas, which escapes to the air, so denitrification lowers soil nitrogen.

The mosquito has piercing and sucking mouthparts for feeding on blood and plant juices; the others have biting mouthparts.

A fire kills organisms whether the population is crowded or not, so it is density-independent; food, disease and competition get worse as density rises.

Measles is caused by a virus, and antibiotics do not kill viruses; typhoid and tetanus are bacterial and ringworm is treated with antifungal antibiotics.

Raw sewage adds nitrates and phosphates that make algae grow rapidly; when they die, decomposers use up the oxygen in the water.

The main aim of wildlife conservation is to protect species so they do not die out completely.

Burning vegetation destroys plants, animals and soil organic matter, so it wastes natural resources instead of conserving them.

A mutation is a change in the genes or chromosomes, so it always changes the genotype; it can also be caused by radiation or chemicals.

Continuous variation, such as height, shows a smooth range of values with tiny steps between individuals.

Blood groups depend on chemicals in the blood, an inner body feature; skin colour, fingerprints and height are visible (morphological) variations.

Blood group B can be given to people of group B and to group AB, who have no anti-B antibodies.

All F1 plants get one pink and one white allele; pink is dominant, so all the flowers are pink.

A carrier has one normal and one sickle allele, Hb^AHb^S, so both parents are Hb^AHb^S.

The haemophilia gene is on the X chromosome; males have only one X, so one faulty copy gives them the disease.

Genes, the factors of inheritance, are carried on the chromosomes in the nucleus.

DNA pairs adenine with thymine and cytosine with guanine; uracil is found only in RNA.

Honey bees live in organised colonies with a queen, drones and workers sharing the work: they are social insects.

Territorial behaviour is shown mainly by male animals that defend an area and the females in it from rival males.

A worker bee does a round or waggle dance in the hive to show the direction and distance of food.

Fossils, comparative embryology and comparative anatomy are classic evidences of evolution; polymorphism is just having several forms within one species.

(a) Mammals are large and complex, so their surface area to volume ratio is small and diffusion alone is too slow.
Materials are taken in or made in one part (oxygen in the lungs, digested food in the gut, hormones in glands) but needed in all cells.
Wastes made in cells must be carried to the kidneys, lungs and skin for removal.
So a transport system (blood, heart, vessels and lymph) is needed to move materials quickly round the body.
(b) Any eight: carries digested food from the intestine to cells; carries oxygen from lungs to tissues; carries carbon(IV) oxide to the lungs; carries urea and other wastes to the kidneys; carries hormones to target organs; distributes heat and keeps body temperature steady; white cells engulf germs (phagocytosis); antibodies give immunity; clotting stops bleeding and keeps germs out; carries water and mineral salts.
(c) Any four: water; mineral salts (e.g. nitrates, phosphates); manufactured food (sugars, amino acids); hormones/auxins; oxygen; carbon(IV) oxide; latex and other secretions; waste products.

Link (a) to surface area to volume ratio.

(a) Any four, each with a part: support/shape – vertebral column, pelvic girdle; protection – skull protects brain, ribcage protects heart and lungs, vertebrae protect spinal cord; movement/locomotion – limb bones at joints; making blood cells – red marrow of long bones, ribs, sternum; storage of calcium and phosphorus – bone matrix; breathing – ribs; attachment of muscles – any limb bone.
(b) The elbow is a hinge joint moved by two antagonistic muscles.
The biceps is attached to the scapula and radius; the triceps to the scapula (and humerus) and ulna.
Biceps contracts and triceps relaxes: the forearm bends (flexion).
Triceps contracts and biceps relaxes: the forearm straightens (extension).
(c)(i) Herbaceous: turgid parenchyma cells full of water; collenchyma with walls thickened at the corners; xylem vessels.
(ii) Woody: lignified xylem (wood); sclerenchyma fibres; secondary thickening that forms much wood and bark.
(d) Vitamin D (calciferol); calcium or phosphorus.

Name the part for each function in (a).

(a) Enzymes are organic catalysts, made of protein by living cells, which speed up chemical reactions without being used up.
(b) Any six: protein in nature; specific – each acts on one substrate; needed in small amounts; unchanged at the end of the reaction; work best at an optimum temperature (about 35–40°C) and are denatured by high temperature; inactive at low temperature; work best at a particular pH; many reactions are reversible; slowed by poisons/inhibitors; some need co-enzymes; can work outside the cell that made them.
(c) Pancreatic juice enters the duodenum and is alkaline, giving the right pH for its enzymes.
Amylase (amylopsin) changes starch to maltose.
Trypsin changes proteins (and peptones) to polypeptides/peptides.
Peptidases (e.g. carboxypeptidase) change polypeptides to amino acids.
(d)(i) Glycogen (in liver and muscle) – also stored as fat; (ii) starch (also sucrose).
(e) Rhizopus grows on dead organic matter such as moist bread.
Its hyphae penetrate the food and secrete digestive enzymes onto it.
The food is digested outside the hyphae (extracellular digestion) into soluble products.
The hyphae absorb the soluble food and use it for growth and energy.

Name each enzyme with its substrate and product in (c).

(a)(i) Asexual reproduction is the production of new individuals from one parent without the formation and fusion of gametes.
(ii) Any two with matching example: binary fission – Amoeba, Paramecium; budding – Hydra; fragmentation/regeneration – Planaria, sponges; parthenogenesis – aphids, honey bee drones; multiple fission/schizogony – Plasmodium.
(b) Asexual vs sexual: one parent vs two parents; no gametes vs gametes formed; no meiosis vs meiosis; no fertilisation vs fertilisation forms a zygote; offspring identical to parent vs offspring vary; fast, many offspring vs slower, fewer offspring.
(c) Diagram 8–10 cm, bold lines, labelled: head, acrosome, nucleus, middle piece, mitochondria (spiral), tail/flagellum; title.
(d) Acrosome – has enzymes that dissolve the ovum membrane so the sperm can enter; nucleus – carries the haploid set of chromosomes (genes); mitochondria – release energy for swimming; tail – lashes to move the sperm.

Diagram must be large, labelled and titled.

(a)(i) Trait: an inherited characteristic, controlled by a pair of genes, e.g. height or eye colour.
(ii) Recessive gene: the allele whose effect is hidden when the dominant allele is present; it shows only when two copies are present.
(iii) Test cross: crossing an individual showing the dominant trait with a homozygous recessive one to find out its genotype.
(iv) Heterozygous: having two different alleles for a trait, e.g. Tt.
(b) Man OO gives only O gametes; woman AB gives A or B gametes.
Cross OO × AB gives AO and BO children: blood groups A or B only (half each).
No child can be AB, so the man cannot be the father of an AB child.
(c)(i) Mate the brown male with a white (homozygous recessive, bb) female.
If all the offspring are brown, he is homozygous (BB).
If about half are white, he is heterozygous (Bb).
(ii) A gamete has the haploid number (n), half the chromosomes; a body cell has the diploid number (2n).

Show the cross with parents, gametes and offspring.

(a)(i) Habitat: the natural place where an organism lives, e.g. a pond, the soil, a forest; it provides food, shelter and breeding sites.
(ii) Ecological niche: the role an organism plays in its habitat – what it eats, what eats it, where it lives and how it affects other organisms; no two species share exactly the same niche.
(b) Any three, each with its use: thermometer – temperature; rain gauge – rainfall; hygrometer/wet-and-dry bulb – relative humidity; wind vane – wind direction; anemometer – wind speed; Secchi disc – turbidity of water; light meter/photometer – light intensity; pH meter/indicator – acidity; quadrat – plant population; hydrometer – density/salinity of water.
(c)(i) Any three: elephant grass, guinea grass, shea butter tree, locust bean (Parkia), baobab, acacia, Isoberlinia, Daniellia.
(ii) Any two: lion, antelope, giraffe, zebra, elephant, grasshopper, termite, cattle egret.

Pair each instrument with the factor it measures.