WAEC Biology 2017 past questions and answers

Sponges (Porifera) are the simplest animals: their cells are loosely organised and they have no nerve cells. Cnidarians have a nerve net, and flatworms and roundworms have nerve cords.

Both organisms have a rounded (blunt) front end and a narrower, pointed back end. Paramecium moves with cilia but Euglena with a flagellum, and only Paramecium has two kinds of nuclei.

Plasmodium, the malaria parasite, can live only inside its hosts (mosquito and human). The others are free-living.

The animal is a spider (arachnid). Insects have six legs and usually wings; arachnids have eight legs and no wings.

Aerobic respiration takes place in the mitochondria, where most of the cell's ATP (energy) is made.

Root hair cells have a more concentrated cell sap than soil water, so water passes into them across the cell membrane by osmosis.

Euglena photosynthesises with its chloroplasts in light, but in the dark it can absorb food from its surroundings like an animal.

Two long bones lying side by side, with a hook-like process at one end, are the radius and ulna of the lower arm (forearm).

The notch at the elbow end of the ulna (part II) fits round the trochlea of the humerus, forming the hinge joint of the elbow.

The vascular bundles are arranged in a single ring near the edge, which is the pattern in a dicot stem. Monocot stems have scattered bundles and roots have xylem in the centre.

When we breathe out, the diaphragm relaxes and curves upwards, the ribs move down and in, the chest volume falls and the pressure inside rises, pushing air out. The diaphragm flattens only when we breathe in.

Part II is the blood vessel bringing blood to the glomerulus. Plasma proteins are too large to be filtered, so they stay in the blood and are not found in the tubule.

As the filtrate passes along the tubule, water is reabsorbed but urea is not, so urea is much more concentrated in the collecting duct (IV) than at the start of the tubule (I).

Deamination removes the amino group from extra amino acids. The amino group becomes ammonia, which the liver turns into urea.

The pancreas makes hormones (insulin, glucagon) that go into the blood, and also pancreatic juice that flows through a duct into the duodenum.

To focus a near object the ciliary muscles contract, the suspensory ligaments slacken and the elastic lens becomes thicker (fatter), bending light more.

Part I is the cap at the very tip of the sperm head: the acrosome, which holds enzymes for getting into the egg.

Part II is the tail. It lashes from side to side to push the sperm forward.

Marginal placentation occurs in an ovary made of one carpel, such as the bean pod. Axile, parietal and free central placentation occur where several carpels are fused (syncarpous).

Food is made of complex organic substances that store energy. Water, air and mineral salts are simple inorganic materials.

In photosynthesis light energy is absorbed, oxygen is given off and glucose is made. Carbon dioxide is used up, not given off.

Calcium is needed to make calcium pectate, which cements plant cell walls together in the middle lamella. Lack of calcium weakens growing tips.

Each half jaw shows 2 incisors, 1 canine, 2 premolars and 3 molars, all of similar height with no gap. This is the human (omnivore) pattern.

X is the canine, a single pointed tooth used to tear and hold food.

The milk (first) set of teeth has incisors, canines and molars but no premolars. The premolars (Y) appear only in the permanent set.

Carrying capacity is the largest population an environment can keep supplied with food, space and other needs over time.

Secondary succession happens where a community was destroyed but soil remains, such as burnt forest land. Bare rock and new sand dunes start primary succession.

A habitat is the place where an organism naturally lives. Its niche is its role in that place.

A drought means too little water for crops and wild plants to grow, so food becomes scarce.

Permeability is how fast water drains through soil. Sandy soils are very permeable; clay soils are not.

Fungi have no chlorophyll and cannot make their own food; they are all heterotrophs (mostly saprophytes or parasites).

A pyramid of energy shows how much energy actually flows from one trophic level to the next. It is never upside down, unlike pyramids of numbers and biomass.

A pyramid of energy shows energy, not how many organisms there are. Showing numbers of organisms is what a pyramid of numbers does.

Polythene is a plastic that microorganisms cannot easily break down. Cotton, leather and paper are natural materials that decay.

The sea anemone protects the hermit crab with its stinging tentacles, and it gets carried to new food and eats scraps. Both benefit.

Game reserves and national parks protect wild animals and plants in their habitat, which conserves natural resources.

Cutting down forests leaves soil bare, so rain runs off instead of soaking in, and streams dry up. Planting trees and building dams help conserve water.

Petroleum formed from buried organisms over millions of years; once used, it cannot be replaced in a human lifetime. Air, food crops and soil can be renewed.

The picture shows tongue rolling. A person either can or cannot roll the tongue, with no in-between, so it is discontinuous variation.

Morphological variations are differences in visible structure, such as nose shape, skin colour and hair colour. Tongue rolling is an ability, so it is a physiological variation.

Leaf cells are body (somatic) cells, so somatic cells have 40 chromosomes. Gametes are made by meiosis, which halves the number to 20.

A mutation is a change in the genes or chromosomes, so the genotype is always involved. Mutations can also change the phenotype and can be caused artificially (e.g. by radiation).

Mammals have pentadactyl (five-digit) limbs, which support the body and are adapted for walking, running and climbing on land. Hollow bones and fused bones are bird features for flight.

Social insects such as termites and bees are divided into castes (queen, workers, soldiers, drones) that differ in shape and job. So the members are not identical.

Organic evolution is the slow build-up of inherited changes over many generations that leads to new species.

(a)(i) Classification is the arranging of living things into groups based on the features they share.
(ii) Carolus (Carl) Linnaeus.
(iii) Any three: makes study and identification easier; brings order to the huge number of organisms; shows relationships between groups; shows evolutionary trends; gives each organism a unique name understood everywhere; aids reference and research.
(iv) Kingdom → Phylum (Division) → Class → Order → Family → Genus → Species.
(b)(i) Any two: contain nucleic acid (DNA or RNA) as genetic material; reproduce (inside host cells); can mutate; show heredity.
(ii) Any two: can be crystallised; have no cell structure, cytoplasm or organelles; do not feed, respire or excrete; inactive outside a living cell.
(c)(i) Any two: cassava mosaic; maize streak; tobacco mosaic; groundnut rosette; cocoa swollen shoot.
(ii) Any two: HIV/AIDS; measles; polio; smallpox; influenza; yellow fever; hepatitis; chickenpox; mumps; COVID-19; Ebola.

Learn the seven ranks in order: Kingdom, Phylum, Class, Order, Family, Genus, Species.

(a) Any four: they are proteins; they are specific (each acts on one substrate); they speed up reactions (biological catalysts) and are not used up; they work best at an optimum temperature and are destroyed (denatured) by high heat; they work best at an optimum pH; many reactions are reversible; needed in small amounts; slowed by inhibitors.
(b) Enzymes in the duodenum (from pancreatic juice), any two, with substrate and products: amylase – starch → maltose; trypsin – proteins → peptides (polypeptides); lipase – fats and oils → fatty acids and glycerol.
(c)(i) Chlorophyll traps (absorbs) light energy for photosynthesis.
(ii) Magnesium and nitrogen.
(iii) Magnesium deficiency: yellowing between the veins of older leaves (chlorosis). Nitrogen deficiency: general yellowing of leaves and stunted growth.
(d) Pick a leaf that has been in sunlight; boil it in water for about a minute to kill it and break the cell membranes; put it in alcohol (ethanol) in a test tube heated in a water bath to remove the chlorophyll; dip it in warm water to soften it; spread it on a white tile and add iodine solution; a blue-black colour shows starch is present.

For the starch test, keep the steps in order and say why each step is done.

(a)(i) Tullgren funnel (or Baermann funnel for soil nematodes).
(ii) Pooter (aspirator).
(b) Diagram of a pooter, 6–8 cm long, with title and labels: specimen tube/bottle, rubber bung (cork), inlet tube (short tube put near the insect), mouthpiece tube (sucking tube), gauze/muslin covering the inner end of the mouthpiece tube.
(c) Any three pairs, each with how both benefit: Rhizobium bacteria and legumes – bacteria fix nitrogen for the plant, plant gives food and shelter in root nodules; lichen (alga and fungus) – alga makes food, fungus holds water and gives shelter; hermit crab and sea anemone – anemone protects the crab, crab carries the anemone to food; termites and cellulose-digesting protozoa in their gut – protozoa digest wood for the termite and get food and shelter; cattle and rumen bacteria – bacteria digest cellulose, get food and a warm home.

For symbiosis, say what each partner gains in every example.

(a) The child is OO, so the mother must be BO and the father must give an O allele. The father can be AO, BO or OO.
Crosses: BO × AO → AB, BO, AO, OO; BO × BO → BB, BO, BO, OO; BO × OO → BO, BO, OO, OO. Each cross can give an OO child.
So the father's blood group could be A (AO), B (BO) or O (OO), but not AB.
Diagram must show parents, gametes, offspring.
(b)(i) Any two: sound (calls, songs, chirping); visual signals (colour, display, dances, body posture); chemical signals (pheromones, scent marking); touch (tactile).
(ii) Any two: to attract a mate; to warn of danger; to mark territory; to show where food is; to keep a group together; to identify members of the same species or colony; to frighten enemies.

The child's O allele must come from both parents, so the father cannot be AB.

(a) Chemicals (odours) in the air enter the nasal cavity and dissolve in the moist mucus lining it; they stimulate the olfactory (smell) receptor cells; impulses pass along the olfactory nerve to the olfactory lobe/cerebrum of the brain, which interprets the smell.
(b) Any: hard calcium carbonate shell protects the embryo; shell is porous for gaseous exchange; shell membranes keep out germs and reduce water loss; albumen (egg white) supplies water and protein and cushions the embryo; yolk is a store of food; chalazae hold the yolk in place so the embryo stays on top; air space provides oxygen at hatching.
(c)(i) Autotrophs are organisms that make their own food from simple inorganic substances using energy from light (or chemical reactions).
(ii) Any two: Chlamydomonas; Euglena; diatoms; Chlorella; photosynthetic bacteria.
(d) Any five: fights the spread of diseases worldwide (e.g. immunisation campaigns); sets health standards; gives health advice and education; supports research into diseases and drugs; helps countries in health emergencies and epidemics; collects and shares health statistics; helps train health workers; improves nutrition, sanitation and water supply.
(e)(i) Plants, any two: water lettuce (Pistia), water lily, Spirogyra, duckweed, water hyacinth, algae.
(ii) Animals, any two: tilapia, tadpole/frog, water snail, mosquito larva, water boatman, Hydra.
(f) Any five: skin is many cells thick / leaf epidermis is usually one cell thick; skin has hairs, sweat glands and sebaceous glands / epidermis has none (may have simple hairs); skin has sense receptors and nerves / epidermis has none; skin has blood vessels / epidermis has none; skin cells have no cell walls / epidermal cells have cellulose walls; skin has a dead keratinised outer layer / epidermis is covered by a waxy cuticle; epidermis has stomata with guard cells / skin has pores of sweat glands; skin helps control body temperature / epidermis does not; skin has pigment (melanin) / epidermis is mostly colourless.
(g)(i) Plot A: intraspecific competition (between members of the same species, maize and maize).
(ii) Plot B: interspecific competition (between different species, maize and pepper) as well as intraspecific.

Section C (candidates in Nigeria only). Read each part carefully and give only the number of points asked.