All 12 questions from the West African Examinations Council (WAEC) Biology 2023 Theory paper, with the correct answer and a full explanation for each. Free, no signup needed.
[Essay Paper 2 — Section A]
1(a). What is classification of living things?
1(b). State four ways each by which the following groups of organisms are of economic importance in their habitats: (i) Fungi; (ii) plants.
1(c). Complete the table below by stating five major phyla of the Kingdom Animalia and given one example of each.
Model answer
Classification of living things is the grouping/arrangement of organisms, with similar characteristics based on structural/genetic/cellular/evolutionary trends, for easy identification.
(b)(i) Fungi are of economic importance because they: cause various plant/animal diseases; act as decomposers; recycle nutrients; bring about fermentation in breweries; are used in baking industries.
(ii) Plants are of economic importance because they: are involved in nutrient recycling; purify the environment/reduce greenhouse effects; provide shade/shelter; provide food; provide oxygen.
(c) Major phyla of the Kingdom Animalia and examples:
Porifera — Sponges/Venus flower basket
Cnidaria/Coelenterata — Hydra/Obelia/sea anemone/jellyfish/Aurelia/coral
Platyhelminthes — Liver fluke/tapeworm/Schistosoma/planaria
Nematoda — Wuchereria/whipworm/Ascaris/Guinea worm/hookworm
Annelida — Marine worm/leech/earthworm/lugworm/seaworm/bobbit worm/fireworm
Mollusca — Snail/bivalve/slug/octopus/clam/oyster/squid
Arthropoda — Scorpion/spider/cockroach/crab/crayfish/grasshopper/centipede/millipede/ant
Echinodermata — Starfish/sea lily/sea cucumber/brittle star/sea star
Chordata — Fish/frog/toad/bird/man/human/cat/lion/tiger/dog/salamander/alligator/snake/giraffe
2(a). Complete the table below by naming five elements, their functions in plants, and the effect of deficiency in plants (Iron, Molybdenum, Potassium, Copper, Nitrogen).
Model answer
Iron — Function: necessary for the synthesis of chlorophyll/protein. Deficiency effect: chlorosis/yellowing of leaves/poor growth.
Molybdenum — Function: converts nitrogen to amino acids. Deficiency effect: stunted growth/pale leaves.
Potassium — Function: protein synthesis/formation of cell membrane/crop margin turns yellow/brown; maturation/activates respiration/photosynthesis. Deficiency effect: premature death of plant leaf.
Copper — Function: activates enzymes for respiration/carbohydrate metabolism/photosynthesis. Deficiency effect: pale/wilted/spotted leaves.
Nitrogen — Function: necessary for the formation of Chlorophyll/amino acids/protein. Deficiency effect: poor/stunted growth/yellowing of leaves/poor flower formation.
2(b). Name three classes of organic foods which are essential constituents in the diet of a normal mammal.
Model answer
Three classes of organic foods essential in the diet of a normal mammal: Carbohydrate; Protein; Lipids/fats and oil (Vitamin is also acceptable as a further class).
2(c). State two roles each of the following structures of the digestive system in humans: (i) buccal cavity; (ii) duodenum; (iii) stomach.
2(d). Name the end product of adding dilute hydrochloric acid to sucrose.
Model answer
(c)(i) Buccal cavity: takes in/receives food; contains the teeth that chew/masticate food to increase the surface area of food particles; contains salivary glands that secrete saliva that moistens the food and contains the enzyme ptyalin which breaks down starch to maltose.
(ii) Duodenum: receives the food as chyme from the stomach; receives pancreatic juice from the pancreas; receives bile from the liver which reduces surface tension/emulsifies fats and oil.
(iii) Stomach: temporarily stores food; secretes dilute hydrochloric acid which destroys bacteria; churns food.
(d) The end product of adding dilute hydrochloric acid to sucrose is glucose and fructose.
3. Relationships I, II, III, IV and V exist among some organisms in an ecosystem. Use them to answer questions 3(a) to 3(e).
I: Organism A grows on dead organism B. II: Organism C feeds on the remnants of food left by organism D without affecting organism D. III: Organism E provides shelter for organism F while organism F transports organism E towards food. IV: Organism H feeds on organism J, causing organism J a disease.
(a) Name the type of relationship in: I; II; III; IV; V.
(b) In relationship IV, what is the biological term for each of organization B and G? (i) B; (ii) G.
(c) Name one example each of organisms B to J.
(d)(i) Name the relationship that is most beneficial to the ecosystem. (ii) Give one reason for the answer 3(d)(i).
(e)(i) Give two examples of organism A. (ii) Name the group to which organism A belongs.
Model answer
(a) Types of relationship: I: Saprophytism; II: Commensalism; III: Mutualism; IV: Predation. (Relationship V was not described in the excerpt provided.)
(b) Biological term for organisms B and G: B — prey; G — predator.
(c) Examples of organisms B to J: B: Antelope/goat/sheep/cow/rabbit/guinea pig/rat. C: Remora fish. D: Shark. E: Hermit crab. F: Sea anemone. G: Lion/tiger/leopard/cat/dog/snake/hawk/eagle. H: Tapeworm/tick/louse/Plasmodium/Ascaris. J: Human/pig/cattle/cow/sheep/dog/cat.
(d)(i) The most beneficial relationship to the ecosystem is Saprophytism. (ii) Reason: it is involved in nutrient recycling/replenishment of nutrients in the ecosystem.
(e)(i) Examples of organism A: Mushroom/Mucor/Rhizopus/Yeast/Pseudomonas/Bacillus/Clostridium/Enterobacter/Escherichia spp./E. coli/Salmonella spp. (ii) Group: Fungi/Bacteria/mold/mould.
3(d)(cont.). Complete the table below by listing four organisms involved in the nitrogen cycle and state one role each of the organisms.
Model answer
Organisms involved in the nitrogen cycle and their roles:
Animals — Excrete nitrogenous compounds/eat proteins in plant, die/decay to form ammonium compound.
Plants — Absorb nitrate from soil/die/decay to form ammonium compound.
Putrefying bacteria — Break down dead plants/animals.
Azotobacter — Converts atmospheric nitrogen to nitrate.
Rhizobium — Converts atmospheric nitrogen to nitrates.
Nitrobacter — Converts nitrite to nitrates.
Nitrosomonas — Converts ammonium compound to nitrite.
Pseudomonas — Converts amino compound to ammonium compounds.
4(a). Complete the following Punnett squares of a dihybrid cross between two rats. One has black fur (BB) and short tail (tt), the other has brown fur (bb) and long tail (TT). Give the parental gametes and the F1 offspring grid.
4(b). How many of the offspring will have: (i) black fur and short tail; (ii) brown fur and long tail; (iii) black fur and long tail; (iv) brown fur and short tail?
4(c). If there were twenty (20) chromosomes in the leaf cell of a plant, how many chromosomes would be in each of the following cells of the plant: (i) pollen grain; (ii) guard cell; (iii) ovule; (iv) root cell?
Model answer
(a) Parental gametes: horizontal (PGH): Bt; vertical (PGV): bT. All F1 offspring genotype: BbTt (black fur, short tail — since B and T are the given dominant alleles based on the cross set up).
(b) Offspring with: (i) black fur and short tail — all 16/16 (since all offspring are BbTt, heterozygous for both traits, showing the dominant phenotypes black fur and short tail); (ii) brown fur and long tail — 0; (iii) black fur and long tail — 0; (iv) brown fur and short tail — 0. (All 16 offspring show the same phenotype: black fur and short tail, since this is a cross between two pure-breeding/homozygous parents for different traits.)
(c) Number of chromosomes: (i) Pollen grain — 10 (haploid, since it's a gamete); (ii) Guard cell — 20 (diploid, a somatic cell); (iii) Ovule — 10 (haploid, gamete-forming structure); (iv) Root cell — 20 (diploid, a somatic cell).
[Essay Paper 2 — Section B]
5(a)(i). What are sense organs?
5(a)(ii). Name three sense organs that respond to the stimulus of chemicals.
5(b). List three animals each that exhibit the following courtship behaviours: (i) territoriality; (ii) pairing.
5(c)(i). State one similarity between the eggs of toads and the eggs of birds.
5(c)(ii). State three differences between the eggs of toads and the eggs of birds.
Model answer
(a)(i) Sense organs are organs with sensory receptors that detect changes from the environment and relay the impulses to the nervous system for interpretation and appropriate response sent to the effector organ.
(ii) Sense organs that respond to the stimulus of chemicals: Tongue; Nose; Skin (and Eye, in some classifications).
(b)(i) Animals that exhibit territoriality: Agama lizard/lizard; Leopard/tiger; Jaguar; Lion; Dog.
(ii) Animals that exhibit pairing: Termite; Human; Gibbon; Domestic fowl/duck/pigeon; Fish.
(c)(i) Similarity between eggs of toads and eggs of birds: both have yolk; embryo; vitelline membrane.
(ii) Differences between eggs of toads and eggs of birds:
Eggs of toads: surrounded by jelly coat; relatively smaller; shell membrane absent; presence of black part; eggs are laid in chains.
Eggs of birds: surrounded by calcareous shell; relatively larger; shell membrane present; no black part; eggs are laid in a single piece.
[Biology Practical — Section A]
1. Study specimens A, B, C and D and answer questions 1(a) to 1(f).
(a) State three observable differences between specimens A and B.
(b) In the table below, using a tick (√), indicate the appropriate modes of reproduction of the organism that possesses each of specimens A, B and C (Type of fertilization: Internal/External; Reproductive process: Oviparous/Viviparous).
(c)(i) Name the Phylum/Division of the organisms that possess each of specimens A and D.
(c)(ii) Name the class of organisms that possess each of specimens A, B, C and D.
(d) State the biological function of specimen B to the organism that possesses it.
(e) Crack open specimen B and carefully empty its content into a Petri dish. Complete the table below by naming three observable features of specimen B and state one function each of the features named.
(f) State one habitat each of the organisms that possess specimens A, B and D.
Model answer
(a) Observable differences between A/Egg of catfish and B/Egg of domestic fowl: A has more numerous/many eggs while B has one/not numerous; A's shell is absent while B's shell is present; A is relatively small while B is relatively large; A is green/yellow/orange in colour while B is cream/white/peach/brown; A is clustered while B is single; A is round while B is oblong/oval; A is soft while B is hard.
(b) Reproductive mode table: Specimen A — Type of fertilization: External (Yes); Reproductive process: Oviparous (Yes). Specimen B — Type of fertilization: Internal (Yes); Reproductive process: Oviparous (Yes). Specimen C — Type of fertilization: Internal (Yes); Reproductive process: Viviparous (Yes) [exact fertilization/process combination depends on the actual specimen provided in the exam].
(c)(i) Phylum/Division: A — Chordata; D — Angiospermophyta/Angiospermatophyta/Magnoliophyta.
(ii) Class: A — Osteichthyes/Pisces; B — Aves; C — Mammalia; D — Dicotyledoneae/Dicotyledonae/Magnoliopsida.
(d) Biological function of specimen B (egg) to the organism: Reproduction/production of offspring.
(e) Observable features of specimen B and their functions:
Shell — Protection; Prevents dehydration/desiccation/drying up.
Shell membrane/vitelline membrane — Medium for diffusion of gases/gaseous exchange; protection.
Albumen/Egg white — Source of food for embryo; Provides water for embryo.
Yolk — Source of nutrients/food for the embryo.
Chalaza — Holds the embryo at the centre of the egg/in place.
(f) Habitats: A — Pond/river/mud/estuarine/lake/any correctly named aquatic habitat; B — House/garden/poultry/pen/farmhouse; D — Forest/garden/farmland/farm.
2. Study specimens F, G and H and answer questions 2(a) to 2(f).
(a) Name the Class to which each of specimens F and G belong.
(b) State one reason each for the answers in 2(a).
(c) Name the root system of each of specimens F and G.
(d)(i) Detach one complete leaf from specimen F and make a drawing, 8cm to 10cm long of the leaf and label fully.
(d)(ii) State one function each of three of the labelled parts of the drawing in 2(a)(1).
(e) State three ways by which specimen F is of economic importance.
(f)(i) Describe briefly four observable features of specimen H.
(f)(ii) State one biological significance of specimen H to the plant from which it was obtained.
Model answer
(a) Class: F: Monocotyledoneae/Monocotyledonae/Liliopsida (e.g. Guinea grass/Panicum sp.); G: Monocotyledoneae/Monocotyledonae/Liliopsida (e.g. Cocoyam/Caladium sp.).
(b) Reasons: F — leaves have parallel venation; leaf sheath present; presence of fibrous root system; narrow leaves/leaves with narrow lamina; circular node present. G — presence of fibrous/adventitious/contractile root system; bears tiny axillary bud at some points of the nodes; bears tiny, broad terminal buds; surrounded with relatively large scale leaves; presence of long adventitious roots.
(c) Root systems: F — Fibrous; G — Adventitious/contractile/fibrous.
(d)(i) Drawing of the complete leaf of specimen F (Guinea grass/Panicum sp.) should show and label: Apex, Margin, Midrib, Blade, Vein, Ligule, Leaf sheath. (Title, Quality — clarity of lines, size 8-10cm, neatness of labels, magnification — should all be indicated; drawn 'Not Drawn to Scale'.)
(ii) Functions of three labelled parts: Lamina/leaf blade — photosynthesizes to make food for the plant/site for gaseous exchange. Leaf sheath — supports the lamina/attaches the lamina to the stem. Vein — contains xylem which conducts water and mineral salts through the leaf/contains phloem to transport manufactured food out of the leaf/gives structural support to the leaf/contains supporting tissues. (Other parts: Leaf ligule — allows movement of the lamina. Apex — allows water drop off the leaf/prevents water retention. Midrib — supports the blade.)
(e) Economic importance of specimen F (Guinea grass/Panicum sp.): used as feed/fodder for cattle; used as fuel; for roofing houses/structures; for making baskets; has medicinal purposes; used as rope; used for mulching; for generating income.
(f)(i) Observable features of specimen H (corm of cocoyam): vertical/swollen stem; brown in colour; bears concentric rings of nodes; bears tiny brown scale leaves at some points of the nodes.
(ii) Biological significance of specimen H to the plant: Vegetative propagation/storage of food/for anchorage.
[Biology Practical — Section B]
3(a)(i). State the Type of fruit of specimens L/orange fruit, M/coconut and N/chilli pepper.
3(a)(ii). State the life cycle of specimens L, M and N.
3(b). State the observable structural differences between: (i) specimens L and M; (ii) specimens L and N.
3(c). State three observable similarities between specimens L and N.
3(d). Make a drawing/diagram of the L.S. of specimen N/chilli pepper and label fully.
3(e)(i). State the mode of dispersal of specimen L/orange fruit.
3(e)(ii). State the placentation of specimen L/orange fruit.
3(f). State one economic importance of specimen N/chilli pepper.
Model answer
(a)(i) Type of fruit: L (orange fruit): Berry/hesperidium; M (coconut): Drupe; N (chilli pepper): Berry.
(ii) Life cycle: L: perennial; M: perennial; N: biennial/perennial.
(b)(i) Differences between L (orange) and M (coconut): L is succulent/fleshy while M has fibres/hard fibres; L has more than one seed/many seeds while M has one seed/one seeded; L is soft/succulent while M is stony/hard endocarp; L has many chambers/locules while M has one chamber/locule; L is soft to touch while M is hard to touch; L's mesocarp is soft/leathery while M's mesocarp is fibrous; L has axile placentation while M has basal placentation; L has glands present while M has glands absent.
(ii) Differences between L (orange) and N (chilli pepper): L has succulent fleshy fibres while N's succulent fibres are absent; L has bigger seeds while N has smaller seeds; L has less seeds while N has more seeds; L is spherical/round while N is elongated; L has axile placentation while N has free central placentation; L has scattered seeds while N has seeds clustered; L is juicy/has juice present while N is not juicy/dry; L has glands present while N has glands absent; L has calyx absent while N has calyx present.
(c) Similarities between specimens L and N: both possess seeds; both have two scars; both have pericarp (epicarp, mesocarp and endocarp).
(d) Drawing of the L.S. of specimen N (chilli pepper) should show and label: Pedicle/Pedicel, Calyx/Sepal, Epicarp, Mesocarp, Endocarp, Placenta, Seed, Loculus/Locule, Apex. (Drawn 'Not Drawn to Scale', with Title, Quality — clarity of lines, size 8-10cm, neatness of labels, magnification, and details such as thin epicarp shown with double lines, at least two seeds shown, elongated end with tapering apex.)
(e)(i) Mode of dispersal of specimen L (orange fruit): Animal/Man.
(ii) Placentation of specimen L (orange fruit): Axile.
(f) Economic importance of specimen N (chilli pepper): used for cooking/used as spice; source of food; for medicinal purposes; source of income.
4. Study specimens L, M and N and answer questions 4(a) to 4(f).
(a) Classify each of specimens L, M and N based on: (i) type of fruit; (ii) life cycle.
(b) Make a longitudinal section of specimen L and M, and state four observable differences between specimens L and M.
(c) State three observable similarities between specimens L and N.
(d) Make a drawing, 8cm-10cm long of specimen N and label fully.
(e) Name the mode of dispersal of specimen L.
(f) State one economic importance of specimen N.
Model answer
(This section revisits and extends specimens L, M and N covered under Practical Section B Q3 above; the classification, structural differences/similarities, drawings and economic importance follow the same details already outlined for specimens L (orange fruit), M (coconut) and N (chilli pepper) in Q3(a) to 3(f).)
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