WAEC SSCE - Agricultural Science - 2018 (Essay)

(a) Two examples of each class of crop

• (i) Roots and tubers: cassava, yam (also cocoyam, sweet potato).
• (ii) Oil crops: oil palm, groundnut (also coconut, soya bean).
• (iii) Grain legumes: cowpea (beans), soya bean (also groundnut, pigeon pea).
• (iv) Cereals: maize, rice (also sorghum, millet).

(b) Five differences between the digestive system of a goat and a chicken

(c) Five reasons why farmers keep records

• To determine whether the farm is making a profit or a loss.
• To plan and budget for future production.
• To use as evidence when seeking loans from banks.
• To compare the performance of the farm from one period to another.
• For tax assessment and to detect theft or losses; it also aids sound management decisions.

Reading the plan. The farmland is a trapezium with two parallel sides, the top boundary of \(70\text{ m}\) and the bottom boundary of \(90\text{ m}\), and a perpendicular distance between them (the left boundary) of \(40\text{ m}\).

(a) Area of the farmland

The area of a trapezium is half the sum of the parallel sides multiplied by the perpendicular distance between them:

The area of the farmland is \(3200\text{ m}^2\) (that is, \(0.32\) hectares).

(b) Population of banana plants

Each plant occupies a square of ground equal to the spacing:

The farm can carry a population of 200 banana plants.

(c)(i) Names of the tools

• Tool I: Ranging pole
• Tool II: Arrow / pin

(c)(ii) Two uses of each tool

I (Ranging pole)

• Marking survey stations.
• Setting out straight lines.

II (Arrow / pin)

• Marking off the length of chains measured during chaining.
• Marking survey stations and points of intersection.

(c)(iii) One general way of maintaining the tools

Clean and dry the tools after use, oil or grease the metal parts to prevent rust, and store them in a cool, dry place.

How to read the diagrams. Each drawing shows the diagnostic body plan of a crop pest. Match the visible features (mouthparts, legs, wings, body shape, feathers) to the correct group before answering.

(a) Names of the pests labelled I, II and III

(The pest labelled IV is a grain-feeding bird such as the weaver bird or quelea.)

(b) Life cycle of the pest labelled I (grasshopper)

The grasshopper undergoes incomplete metamorphosis (paurometabolous development) with only three stages: egg, nymph and adult. There is no pupa.

1. Egg stage: The fertilised female uses her ovipositor to lay batches of eggs in a pod inside moist soil. The eggs remain dormant, often through the dry season, before hatching.
2. Nymph (hopper) stage: Each egg hatches into a nymph that closely resembles the adult but is smaller, wingless and unable to reproduce. The nymph feeds on plant leaves and grows by a series of moults (ecdysis), passing through several instars. Wing buds enlarge at each moult.
3. Adult stage: After the final moult the insect emerges with fully developed wings and functional reproductive organs. It flies, feeds, mates and the females lay eggs, so the cycle begins again.

Summary: \[ \text{Egg} \;\rightarrow\; \text{Nymph (several instars)} \;\rightarrow\; \text{Adult} \]

(c) Four damages caused by the pest labelled III (shield/sucking bug) on crops

1. It pierces leaves and stems with its needle-like mouthparts and sucks the sap, causing wilting, yellowing and stunted growth.
2. It feeds on developing fruits, pods and seeds, causing them to become deformed, shrivelled or to drop prematurely.
3. It injects toxic saliva at the feeding points, producing necrotic (dead, discoloured) spots and lesions on the plant tissue.
4. It acts as a vector, transmitting viral, bacterial and fungal diseases from infected to healthy plants, thereby lowering yield and the market quality of produce.

(d) Four ways of controlling the pest labelled IV (grain-feeding bird)

1. Scaring: Use scarecrows, reflective/noise-making bird scarers, or employ people to drive the birds away, especially at grain-filling stage.
2. Netting/covering: Cover maturing crops (for example seedbeds and cereal heads) with nets to physically exclude the birds.
3. Destroying nesting and roosting sites: Locate and destroy the birds' breeding colonies, nests and roosts to reduce their population.
4. Trapping or shooting: Set traps or shoot the birds where the law permits; alternatively grow bird-resistant varieties and practise uniform, early planting so the crop matures together and is exposed for a shorter period.

(a) Six problems of agricultural development in West Africa

• Inadequate finance and credit facilities for farmers.
• Poor land tenure system that limits access to large farmland.
• Inadequate storage and processing facilities causing post-harvest losses.
• Poor transportation and bad road network.
• Illiteracy and shortage of trained agricultural personnel.
• Inadequate farm inputs; pests, diseases and unfavourable weather also hinder development.

(b) Explanation of the farm practices

• (i) Crop rotation: The growing of different crops on the same piece of land in a definite order or sequence over the seasons, so that no single crop occupies the land continuously.
• (ii) Mixed farming: The growing of crops and the rearing of livestock together on the same farm at the same time.

(c) Three advantages of each practice

(i) Crop rotation

• It maintains and improves soil fertility, especially when legumes that fix nitrogen are included.
• It helps to control pests and diseases by breaking their life cycles.
• It controls weeds and makes better use of soil nutrients at different depths.

(ii) Mixed farming

• Animal manure improves the fertility of the soil for crops.
• Crop residues and by-products are used to feed the animals.
• It provides diversified income and spreads the farmer's risk.

(a) Seven ways agriculture is important to the economy of West Africa

• It provides food for the growing population.
• It is a major source of employment for the people.
• It supplies raw materials to agro-based industries.
• It earns foreign exchange through the export of cash crops.
• It is a source of government revenue through taxes and levies.
• It provides a market for locally manufactured goods such as tools and fertilizers.
• It is a source of income and capital for national development and rural livelihood.

(b) Two advantages of each source of farm power

(i) Internal combustion engine

• It is mobile and can be used anywhere, even where there is no mains supply.
• It develops high power suitable for heavy operations such as ploughing and haulage.

(ii) Electricity

• It is clean and produces no smoke or fumes.
• It is convenient, easy to control and reliable for stationary machines.

(iii) Wind

• It is a free, renewable and cheap source of power.
• It causes no pollution and is useful for pumping water and grinding in remote areas.

(c) Five poultry operations carried out with electrical power

• Brooding and heating for young chicks.
• Lighting the pen to increase egg production.
• Incubation of eggs in electric incubators.
• Grinding and mixing of feed.
• Pumping of water and ventilation of the pen with fans.

Factors hindering agricultural development in West Africa

(i) Basic amenities

• Poor road network: Feeder roads to farms are few and in bad condition. This makes it difficult and costly to move inputs to the farm and produce to markets, leading to spoilage of perishable crops and low farmer income.
• Lack of electricity: Many rural farming areas have no electricity, so farmers cannot process, store (cold storage) or pump water for irrigation, and agro-industries cannot be sited near production areas.
• Inadequate water supply: Absence of pipe-borne water and irrigation facilities limits dry-season farming and livestock watering.
• Poor storage and processing facilities: Lack of silos, cold rooms and processing plants causes heavy post-harvest losses.
• Absence of social amenities: Poor schools, hospitals and communication discourage people, especially the youth, from staying in the rural areas to farm, causing shortage of farm labour.

(ii) Farm inputs

• Inadequate improved seeds and planting materials: Farmers still use low-yielding local varieties because certified seeds are scarce and costly.
• Scarce and expensive fertilizers: Fertilizers are often unavailable, adulterated or supplied late, so soil fertility and yields remain low.
• Inadequate agrochemicals: Shortage of pesticides, herbicides and drugs leads to heavy losses from pests, weeds and diseases.
• Lack of farm machinery and implements: Farmers depend on crude hand tools, limiting the area they can cultivate and keeping output low.
• Inadequate credit: Without affordable loans, farmers cannot buy the inputs they need, so production remains at subsistence level.

(a) Aim of the experiment

To determine the moisture content (and hence the organic matter content) of a soil sample by heating and drying it.

(b) Parts labelled I to IV

• I - Evaporating dish / crucible
• II - Soil
• III - Tripod stand
• IV - Bunsen burner

(c) Calculations

Mass of fresh soil = 60 g; mass of empty dish = 35 g; mass of dish + dried soil = 80 g.

(i) Weight of the dried soil

\[80\,\text{g} - 35\,\text{g} = 45\,\text{g}\]

(ii) Weight of water lost from the soil

\[60\,\text{g} - 45\,\text{g} = 15\,\text{g}\]

(iii) Percentage of water lost from the soil

\[\frac{15}{60} \times 100 = 25\%\]

(d) Three forms in which water exists in the soil

• Hygroscopic water
• Capillary water
• Gravitational water

(a) Two types of soil water:

• Capillary water: water held in the small (micro) pores of the soil by surface tension against the pull of gravity. It is the main source of water available to plant roots.
• Gravitational water: water that drains freely downward through the large (macro) pores under the pull of gravity after rain or irrigation. It is not held long enough to be very useful to plants, and its excess causes waterlogging.

(b) Four management practices during the brooding of chicks:

1. Provide adequate warmth with a brooder (about 35 °C in the first week, reduced weekly).
2. Supply clean drinking water and good-quality chick-starter feed.
3. Provide adequate lighting, good ventilation and clean dry litter.
4. Avoid overcrowding and protect the chicks from predators (and vaccinate as scheduled).

(c) Completed table on diseases of farm animals:

The diagram is the male reproductive system of livestock (for example, a bull or ram). It shows the paired accessory glands at the top, the central bladder region, the two sperm ducts looping down to the two testes (the round bodies wrapped by coiled bands), and the penis extending below.

(a) Names of the labelled parts

(b) One function of each part

• I - Sperm duct (vas deferens): conveys mature spermatozoa from the epididymis to the urethra during ejaculation.
• II - Testis: produces spermatozoa (male sex cells) and secretes the male sex hormone testosterone.
• III - Penis: serves as the copulatory organ that deposits semen into the female reproductive tract; it also passes out urine.
• IV - Epididymis: stores the spermatozoa and provides the site where they mature and become motile.
• V - Urinary bladder: temporarily stores urine before it is passed out through the urethra.
• VI - Seminal vesicle: secretes a fluid (part of the seminal fluid) that nourishes the spermatozoa and provides the medium in which they swim.

(c)(i) Management practice

The practice is castration (the surgical removal or destruction of the testes of the male animal). By removing the source of sperm and testosterone, the male becomes sterile and loses the urge to mate, so it can no longer breed indiscriminately within the herd.

(c)(ii) The two main parts of utmost benefit

The two parts are the two testes (part labelled II and its pair on the opposite side of the diagram). Because the testes produce both the spermatozoa and the male hormone that drives mating behaviour, their removal during castration stops uncontrolled breeding in the herd.

(a) Land tenure system

Land tenure system is the system of customs and laws by which land is owned, acquired, held, controlled and used by individuals or a community. It defines the rights a person or group has over a piece of land.

(b) Weed

A weed is any plant growing where it is not wanted, that is, a plant growing out of place and competing with cultivated crops for nutrients, water, light and space.

(c) Groundnut rosette disease

• (i) Causal organism: Groundnut rosette virus (a virus complex).
• (ii) Mode of transmission: Transmitted by the aphid vector Aphis craccivora.
• (iii) Symptoms: Stunted growth; yellowing (chlorosis) and mottling of leaves; curling and reduction in leaf size giving a bushy, rosette appearance; few or no pods; drastic reduction in yield.
• (iv) Control: Plant resistant varieties; early planting; close spacing; control the aphid vector with insecticides; rogue out and destroy infected plants; practise crop rotation.

(d) Characteristics of the factors of production

(i) Land

• It is a free gift of nature.
• It is fixed in supply and immobile.
• It is heterogeneous, varying in quality and fertility.
• It is subject to the law of diminishing returns; its reward is rent.

(ii) Capital

• It is a man-made factor of production.
• It is mobile and its quantity can be increased or decreased.
• It depreciates or wears out with use.
• It is used to produce other goods; its reward is interest.

(a) Colostrum

Colostrum is the first milk secreted from the udder of a dam (mother mammal) within the first few days (about five days) after parturition (birth). Its main features are:

• It is thick and yellowish in colour.
• It is rich in antibodies (immunoglobulins), which give the newborn passive immunity against disease.
• It is rich in nutrients, protein, vitamins and minerals.
• It has a laxative effect that helps clear the newborn's gut of the first faeces (meconium).

(b) Transverse section of an egg

The labelled diagram of the section of a hen's (chicken) egg is shown below.

The parts labelled, from the outside inwards, are: the shell, the shell membranes (outer and inner), the air cell (air space) at the broad end, the thin albumen, the thick albumen, the chalaza (twisted cords that hold the yolk in position), the vitelline membrane surrounding the yolk, the yolk, and the germinal disc (blastoderm) on the surface of the yolk.

(c) Completing the table on the Law of Diminishing Returns

Marginal product (MP) is the extra output obtained from each additional unit of the variable input:

Applying this relationship to the figures supplied in the question, the completed table is:

Working for each missing entry:

• (i) Unit 1 has no preceding unit, so its marginal product cannot be computed → – (dash).
• (ii) Total product at unit 1 = 3 kg (the base output).
• (iii) \( TP_2 = TP_1 + MP_2 = 3 + 8 = \mathbf{11\text{ kg}} \).
• (iv) \( TP_3 = TP_2 + MP_3 = 11 + 17 = \mathbf{28\text{ kg}} \).
• (v) \( TP_4 = TP_3 + MP_4 = 28 + 12 = \mathbf{40\text{ kg}} \).
• (vi) \( MP_2 = TP_2 - TP_1 = 11 - 3 = \mathbf{8\text{ kg}} \).
• (vii) \( MP_5 = TP_5 - TP_4 = 41 - 40 = \mathbf{1\text{ kg}} \).
• (viii) \( MP_6 = TP_6 - TP_5 = 41 - 41 = \mathbf{0\text{ kg}} \).

Check (running the TP column back through \( TP_n = TP_{n-1}+MP_n \)): \(3+8=11\;\checkmark\), \(11+17=28\;\checkmark\), \(28+12=40\;\checkmark\), \(40+1=41\;\checkmark\), \(41+0=41\;\checkmark\).

Interpretation (Law of Diminishing Returns): the marginal product rises to a maximum of 17 kg at the 3rd unit and then falls (12 → 1 → 0). Diminishing returns therefore set in after the 3rd unit of the variable input. Total product reaches its maximum of 41 kg at units 5 and 6, where marginal product has fallen to 0 kg.

(a) Cultivation of cassava:

• (i) Soil requirement: a deep, well-drained, loose sandy-loam soil that is fairly rich in organic matter, with a pH of about 5.5 to 6.5; cassava also tolerates fairly poor soils.
• (ii) Land preparation: clear the land, plough and harrow, then make ridges, mounds or heaps to give the developing tubers room to expand.
• (iii) Spacing: plant stem cuttings at 1 m \( \times \) 1 m, giving about 10,000 stands per hectare.
• (iv) Weed control: weed by hoe two to three times during early growth, and use pre-emergence herbicides or mulching to suppress weeds.
• (v) Fertilizer requirement: apply NPK (for example 15:15:15) or organic manure, with adequate potassium for good tuber formation, about 8 weeks after planting.
• (vii) Harvesting: harvest 9 to 12 months after planting, when the lower leaves yellow, by loosening the soil and lifting the tubers.
• (viii) Storage: leave the tubers in the ground until needed, or store fresh roots briefly in moist soil or silos; for long storage, process into gari, flour or dried chips.

(b) Completed disease table:

(a) Four management practices in poultry production

• Vaccination against diseases such as Newcastle and fowl pox.
• Debeaking to prevent cannibalism and egg eating.
• Culling of unproductive, sick or weak birds.
• Provision of balanced feed and clean water; brooding of chicks, regular cleaning and disinfection of houses are also carried out.

(b) Four advantages of dehorning in cattle production

• It prevents animals from injuring one another and their handlers.
• It reduces fighting and bullying, so timid animals can feed calmly.
• It allows more animals to be kept in a given space and makes handling and transportation easier.
• It reduces damage to hides and to housing/feeding equipment.

(c) Five marketing services in agricultural production

• Buying and selling (exchange).
• Transportation of produce from farm to market.
• Storage to make produce available all year round.
• Processing to add value and reduce perishability.
• Grading, standardization and packaging; financing and market information are also provided.

(d) Five problems of agricultural marketing in West Africa

• Poor transportation and bad road network.
• Inadequate storage facilities leading to spoilage of produce.
• Perishable nature of most farm produce.
• Price fluctuation and instability.
• Presence of too many middlemen who reduce the farmer's share of the price; lack of market information and grading also hinder marketing.

(a) Four functions of soil water to crops

• It acts as a solvent, dissolving mineral nutrients in the soil so that plant roots can absorb them.
• It is the medium by which dissolved nutrients are transported into and within the plant.
• It supplies the water needed as a raw material for photosynthesis.
• It maintains the turgidity of plant cells, keeping the plant firm and erect; it also helps to regulate soil and plant temperature and is needed for seed germination.

(b) Five factors that could cause low soil pH (acidity)

• Leaching of basic cations (calcium, magnesium, potassium) by heavy rainfall.
• Continuous use of acid-forming fertilizers such as ammonium sulphate.
• Decomposition of organic matter which releases organic acids.
• Acidic parent material from which the soil is formed.
• Accumulation of acidic ions such as hydrogen, aluminium and iron; acid rain and continuous cropping that removes bases also contribute.

(c) Life cycle of the liver fluke (Fasciola)

1. The adult fluke lives in the bile ducts of the liver of a ruminant (sheep or cattle) and lays eggs.
2. The eggs pass out with the animal's faeces onto pasture.
3. In moist conditions or water, each egg hatches into a ciliated larva called a miracidium.
4. The miracidium enters the intermediate host, a mud snail (Lymnaea).
5. Inside the snail it develops in stages: sporocyst, then redia, then cercaria.
6. The cercariae leave the snail, swim and encyst on grass or vegetation as metacercariae.
7. A grazing animal swallows the metacercariae with the herbage.
8. The young flukes bore through the gut wall, migrate to the liver and bile ducts, mature into adults, and the cycle begins again.

(a) Four characteristics of igneous rocks:

1. They are formed from the cooling and solidification of molten magma or lava.
2. They are hard and crystalline.
3. They are non-porous (impervious) and do not hold water.
4. They contain no fossils and are not arranged in layers (non-stratified).

(b) Combined demand and supply schedule for maize:

(b)(i) Equilibrium: Plot both curves with price on the vertical axis and quantity on the horizontal axis. They intersect where quantity demanded equals quantity supplied, that is at a price of ₦8 with a quantity of 200 kg. This is the equilibrium price and quantity.

(b)(ii) Excess demand at ₦4 = quantity demanded - quantity supplied = \( 350 - 130 = 220 \) kg.

(b)(iii) Excess supply at ₦12 = quantity supplied - quantity demanded = \( 250 - 125 = 125 \) kg.