WAEC SSCE - Agricultural Science - 2004

Detalhes da Resposta

Detalhes da Resposta

Pasture crops are best used in preparing hay just after seed maturation. At this stage, the plants have reached their peak nutritional content, and the stems have begun to dry up, which makes them easier to cure for hay. Curing involves removing moisture from the plants to prevent spoilage during storage. If the plants are harvested before seed maturation, they will have less nutritional value, while harvesting them after they have started to dry up excessively will lead to excessive leaf loss, making the hay less nutritious.

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The correct answer is "oestrus cycle". The oestrus cycle refers to the reproductive cycle in female animals that have a periodic sexual receptivity and ability to conceive. The interval between the beginning of one heat period (when the female is in oestrus) to the beginning of another is called the oestrus cycle. The length of the oestrus cycle varies depending on the species of animal, but it typically lasts from a few days to several weeks.

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An adult female goat is called a "doe".

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Parboiling is a term associated with the processing of rice. Parboiling involves partially boiling the rice grains in their husks, then removing the husks and allowing the grains to dry before being milled. The process helps to improve the nutritional value and shelf life of the rice, as well as making it easier to mill.

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A subsistence farmer is one who farms for the benefit of his family, while a commercial farmer farms for profit. Therefore, the factor that differentiates a subsistence from a commercial farmer is that the former produces for the benefit of his family. A subsistence farmer is not concerned with making a profit or producing for the market but rather focuses on producing enough food to sustain his family's needs. In contrast, a commercial farmer produces crops or livestock primarily for sale and profit.

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Leguminous cover crops do not reduce the soil microbial population. Leguminous cover crops such as clover, beans, and peas have root nodules that contain nitrogen-fixing bacteria. These bacteria are capable of taking nitrogen from the air and converting it into a form that can be used by plants. This process leads to an increase in soil nitrogen content, which can enhance plant growth and soil fertility. Leguminous cover crops also help to bind soil particles together through their roots, which can reduce soil erosion. Additionally, they can aid in improving the soil organic matter content, which can improve soil structure and water holding capacity. However, leguminous cover crops do not reduce the soil microbial population. In fact, they can provide a habitat for beneficial soil microorganisms, which can enhance soil health and productivity.

Detalhes da Resposta

Detalhes da Resposta

The method of fish preservation in which most of the moisture is lost is drying. Drying fish involves removing most of the moisture from the fish through exposure to the sun, smoke, or air. The reduction of moisture content in the fish prevents the growth of microorganisms that cause spoilage. The dried fish can be stored for long periods without refrigeration and can be rehydrated by soaking in water before cooking. This method of preservation is commonly used in areas where refrigeration is not readily available.

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Organic manure has several benefits when applied to the soil. It helps to improve soil fertility, enhances soil structure, promotes soil aeration, and increases the availability of essential nutrients to plants. However, one of the disadvantages of using organic manure on the soil is that it may spread diseases fast. Organic manure, especially if it is not well-treated or sterilized, may contain pathogens, weed seeds, or other harmful microorganisms that can infect plants and cause diseases. Therefore, it is essential to properly compost, sterilize, or treat organic manure before applying it to the soil to reduce the risk of disease spread.

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Detalhes da Resposta

Detalhes da Resposta

The farm implement used for planting grains is the drill. The drill is a machine used for planting crops in rows. It is designed to make evenly spaced holes in the soil, drop in a seed, and cover it up. The drill is commonly used for planting grains such as wheat, corn, and soybeans. It is an important tool for modern agriculture because it allows farmers to plant large areas quickly and efficiently.

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The main reason for not keeping birds meant for commercial egg production under the extensive system of management is that birds waste a lot of productive energy roaming about. When birds are kept under the extensive system of management, they are allowed to roam around freely in search of food and water. This requires a lot of energy and time, which could have been used for egg production. As a result, birds under this system tend to lay fewer eggs than birds kept under the intensive system of management, where food and water are provided in a concentrated area. Therefore, the extensive system is not suitable for commercial egg production as it is not efficient in terms of egg production.

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The equilibrium price of rice is the price at which its supply equals its demand. In other words, it is the price where buyers are willing to buy the same quantity of rice that sellers are willing to sell. At this price, there is no excess supply or excess demand, and the market is said to be in a state of balance. If the price is set above the equilibrium price, there will be excess supply, and if it is set below the equilibrium price, there will be excess demand. Therefore, the equilibrium price is a key determinant of the price at which rice is sold in the market.

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Milking is the management practice that is specific to dairy farming. Milking is the process of extracting milk from the udder of a lactating dairy cow, which is the primary product of dairy farming. The milk is either sold for human consumption or processed into various dairy products such as cheese, butter, yogurt, and ice cream. Deticking is the process of removing ticks from the skin of the animal. Castration is the removal of the testicles of a male animal to prevent breeding and enhance meat quality. Deworming is the administration of drugs to eliminate internal parasites in livestock.

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Detalhes da Resposta

Ananas comosus is a fruit crop, commonly known as the pineapple. It is a tropical plant that produces the juicy and sweet edible fruit called a pineapple, which is enjoyed by many people around the world. The fruit is harvested when it ripens and is commonly eaten raw or used in various culinary dishes and beverages.

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Detalhes da Resposta

Detalhes da Resposta

The viral disease described is likely to be "rinderpest". Rinderpest is a highly contagious viral disease that affects ruminants such as cattle, buffalo, and sheep. It is characterized by symptoms such as high fever, nasal and ocular discharge, and bloody diarrhea. It can be fatal in up to 90% of infected animals, making it a significant threat to livestock populations.

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Of the four options listed, sprinkler irrigation is best for a farm with an undulating landscape. This is because sprinkler irrigation can apply water to crops in a uniform manner, regardless of the terrain, by spraying water over the crops. Sprinklers can be set up on risers or towers to accommodate changes in elevation, and can be adjusted to spray water at different angles and rates to match the slope of the land. Flooding, furrow, and basin irrigation all rely on gravity to distribute water, and are therefore less effective on sloping land. Flooding, for example, can result in erosion and runoff on steep slopes, while furrow and basin irrigation can lead to uneven distribution of water on undulating land.

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Detalhes da Resposta

Detalhes da Resposta

Bacteria and fungi are the most important soil micro-organisms that cause decay and nutrient recycling. Bacteria are the most numerous micro-organisms in the soil and are responsible for the decomposition of organic matter into simple compounds. Fungi, on the other hand, are important in the breakdown of complex organic matter such as lignin and cellulose. Together, these micro-organisms are responsible for breaking down dead plant and animal matter, releasing nutrients back into the soil that can be used by other plants. This process is essential for maintaining healthy soil and sustaining plant growth.

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The best way to preserve maize grains on a large scale is by storing them in airtight containers or silos. This prevents moisture and insects from getting into the grains, which can cause spoilage or infestation. Storing maize grains under the sun or in soils may expose them to moisture and pests, while hanging them over fire places may expose them to smoke, which can affect the quality and safety of the grains. Earthen pots may not be suitable for large scale storage as they have limited capacity and may not be airtight. Airtight containers or silos can help to keep maize grains fresh and safe for a longer period of time, ensuring their availability and quality for consumption or sale.

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The land tenure system that results in fragmentation of land is inheritance. This is because when land is passed down from one generation to another through inheritance, it is often divided among the heirs of the deceased. Over time, this can result in the fragmentation of land into smaller and smaller parcels, which can be difficult to manage and cultivate efficiently. This is a common issue in many parts of the world, particularly in areas where land is a scarce resource and population growth is high.

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Igneous rocks are rocks that solidify from molten or partially molten material. Igneous rocks formed within the crust are called plutonic rocks or intrusive rocks. Plutonic rocks form when magma solidifies slowly below the Earth's surface, resulting in a coarse-grained texture. In contrast, volcanic rocks or extrusive rocks form when magma or lava solidifies quickly on the Earth's surface, resulting in a fine-grained texture. Therefore, the correct answer to the question is plutonic.

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Detalhes da Resposta

Detalhes da Resposta

Coconut is not a common staple food in West Africa. Maize, cassava, and cowpea are staple foods in West Africa, meaning they are regularly consumed in large amounts and form a significant part of the region's diet. On the other hand, coconut is not a common crop in West Africa, and it is not typically consumed in large amounts as a staple food. Therefore, the correct answer is "coconut."

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The answer is "climatic conditions". The factors necessary for siting fish pond are the availability of a reliable source of water supply, type of soil that is suitable for pond construction, and topography which should be flat or gently sloping. Climatic conditions, although important, are not necessary for siting a fish pond because the pond can be constructed in different climates provided that the temperature and humidity levels are within the acceptable range for the species of fish being reared.

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The question is asking which of the given options is NOT a function of a farm manager. The answer is "financing agricultural projects." A farm manager's primary functions are to make decisions, coordinate farm activities, and supervise farm laborers. While a farm manager may be involved in financial management, such as creating budgets or managing cash flow, their primary role is not to finance agricultural projects.

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Black pod disease of cocoa is controlled by the application of fungicide. This is because black pod disease is caused by a fungus that attacks the pods of cocoa trees, resulting in loss of yield and quality of the crop. The application of fungicide helps to prevent or reduce the spread of the disease by killing or inhibiting the growth of the fungus. Other methods like farm sanitation and fumigation of soil may also help to control the disease indirectly by reducing the spread of spores and creating a healthier growing environment, but they are not direct methods of controlling the disease like the application of fungicide.

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Maize is a very important crop because, apart from serving as a staple food for human consumption, it forms the base of most livestock feeds. This means that it is an essential component in the production of meat, dairy products, and eggs, which are important sources of protein for human consumption. Additionally, maize can be processed into various food products such as corn flakes, cornmeal, and grits. It can also be used for producing germ oil, which is used in the production of margarine, cooking oil, and salad dressings. Finally, maize residues such as stover and cobs can be used for animal bedding, fuel, and as a source of organic matter for soil improvement.

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The act of parturition in ewe is known as lambing. This is the process of giving birth to lambs in sheep. It involves the expulsion of the fetus and the placenta from the uterus of the ewe. Lambing usually occurs between the months of December and May, and the gestation period of ewes is about 145 to 155 days. During lambing, the ewe requires special care and attention to ensure the safe delivery of the lamb and the health of both the ewe and the newborn lamb.

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Detalhes da Resposta

Clay particles have excess negative charges, which makes them able to attract cations in the soil. The negative charges on the clay particles attract positively charged cations, such as calcium, magnesium, and potassium, which are important nutrients for plant growth. The attraction between the clay particles and the cations is known as cation exchange, and it helps to hold these nutrients in the soil where they can be accessed by plant roots. This is why clay soils are often very fertile, and why adding clay to sandy soils can help to improve their fertility.

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Water power can be harnessed by using turbines which convert the energy from the moving water into mechanical energy. This mechanical energy is then used to drive an electrical generator that converts the mechanical energy into electrical energy that can be used to power homes, buildings, and other electrical appliances. Therefore, the correct option is turbines.

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The soil water that is tightly held to the surface of soil particles is known as hygroscopic water. This type of water is not easily available to plants because it is held too tightly to soil particles. Hygroscopic water is attracted to the soil particles by weak electrostatic forces, and it cannot be easily removed from the soil unless it is heated. This type of water is important for soil structure because it helps to maintain the pore space in the soil.

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Mulching is a process that involves covering the soil with organic matter, such as leaves or straw, to protect it from erosion, retain moisture, and regulate soil temperature. This process helps to build up soil organic matter and nutrients, rather than depleting them. Therefore, mulching will not lead to the loss of nutrients from the soil. On the other hand, erosion, harvesting, and leaching can lead to the loss of nutrients from the soil. Erosion can cause topsoil to wash away, taking with it valuable nutrients. Harvesting removes nutrients that have been stored in crops, while leaching occurs when water carries nutrients deep into the soil or beyond the root zone, making them unavailable to plants.

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Newcastle disease is caused by a virus. The Newcastle virus is highly contagious and affects birds, particularly domestic poultry such as chickens and turkeys. The virus is spread through contact with infected birds or their secretions, or through contact with contaminated feed, water, equipment or clothing. The disease can cause respiratory, digestive and nervous system symptoms in birds, and can be fatal. Vaccination is an effective way to prevent Newcastle disease in poultry.

Detalhes da Resposta

Detalhes da Resposta

The most unreliable source of farm power is wind. This is because wind power depends on the strength and consistency of the wind. If the wind is too weak or too strong, it can't generate enough power. Also, the availability of wind energy is not constant and it can vary from one season to another. In addition, wind turbines are prone to mechanical breakdowns, which can result in extended periods of downtime. As a result, wind power is not always a dependable source of energy for farmers, especially during critical times when power is urgently needed.

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In cassava farming, the application of nitrogen fertilizer promotes rapid growth at the expense of tuber formation. Nitrogen is a macronutrient that promotes the growth of leaves and stems in plants, but when present in excess, it suppresses the development of the root system and reduces the yield of tubers in cassava. Therefore, cassava farmers need to carefully manage the use of nitrogen fertilizer to avoid promoting excessive vegetative growth at the expense of tuber formation.

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The activity that is not correct about extension agents is option C, which is training school leavers to become professional farmers. Extension agents are mainly responsible for educating farmers on modern and improved techniques in agriculture, providing them with the necessary information, and teaching them how to use new technologies, equipment, and practices to increase productivity and reduce wastage. They also teach farmers how to prepare and apply compost manure, among other things. However, it is not within their scope of duty to train school leavers to become professional farmers. This role is mainly carried out by agricultural training institutions such as colleges of agriculture and universities offering agricultural programs.

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The pregnancy hormone in female animals is progesterone. Progesterone is a hormone produced by the ovaries of female animals during pregnancy. It plays a critical role in the maintenance of pregnancy by preventing the uterus from contracting and thus maintaining a suitable environment for the developing fetus.

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Detalhes da Resposta

Out of the options provided, Tenera is a variety of oil palm. Tenera is a hybrid variety obtained by crossing Dura and Pisifera oil palm varieties. It is widely cultivated in Southeast Asia and is known for its high yield and resistance to diseases. Its fruit has a higher oil content compared to Dura and Pisifera varieties, making it suitable for commercial oil production.

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The land tenure system that encourages the establishment of permanent crops is the "freehold system." In this system, the individual or entity has the absolute ownership of the land and can use it as they wish, including planting permanent crops. They can also transfer the ownership of the land to another party, who will continue to have the same rights. Therefore, under the freehold system, farmers are more likely to invest in long-term crops such as fruit trees, which require a longer time to yield returns.

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When there is an increase in government subsidies, farmers can produce their goods at a lower cost because the government is providing financial assistance to help offset some of the expenses incurred in production. This reduction in production costs leads to an increase in the supply of goods produced by farmers, since they can now produce more for the same cost. Therefore, the correct answer is: "falls, hence supply increases".

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The most essential part of a tractor in operating a mower is the power-take-off (PTO) shaft. This is because the PTO shaft transfers the power from the tractor's engine to the mower's cutting blades, which enables the blades to rotate and cut the grass. Without the PTO shaft, the mower will not receive power and will not be able to function.

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Nitrite is oxidized to nitrate by Nitrobacter. Nitrobacter is a type of bacteria that is involved in the process of nitrification, which is a part of the nitrogen cycle. During nitrification, ammonia is first converted to nitrite by Nitrosomonas bacteria, and then nitrite is further oxidized to nitrate by Nitrobacter bacteria. Nitrate is an important form of nitrogen that plants can use for growth.

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Detalhes da Resposta

Plant breeders aim at obtaining all of the following traits mentioned in the options except "adaptation of pollination". They focus on developing crops that have tolerance to climatic extremes, resistance to pests, disease, and pathogens, and are uniform in their time of maturity. Adapting pollination is not a common objective of plant breeding as it is a natural process that occurs in the plant reproductive cycle. However, plant breeders may select for specific traits related to pollination, such as self-fertility or cross-compatibility, in order to improve the quality or yield of the crop.

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(a) Eight reasons why agriculture has not been fully mechanized in West Africa [8 marks]

• Lack of adequate capital/finance to buy expensive machines.
• High cost of purchasing, running and maintaining farm machinery.
• Small and fragmented (scattered) farm holdings that machines cannot work economically.
• The land tenure system which makes it difficult to acquire large continuous farmland.
• Shortage of trained personnel (operators, mechanics) to handle and repair machines.
• Rough topography, presence of stumps, boulders and swampy soils that hinder machine use.
• Poor rural infrastructure, that is, bad roads and lack of spare parts and repair workshops.
• Illiteracy and conservatism of farmers who prefer traditional tools and methods.

(b) Four characteristics of each [8 marks]

(i) Subsistence agriculture:

• Production is mainly for the farmer and his family, with little for sale.
• Farm size (holding) is small.
• Simple hand tools such as hoes and cutlasses are used.
• Output/yield is low and family labour is used.

(ii) Commercial agriculture:

• Production is mainly for sale and profit.
• Large farm holdings are cultivated.
• Machines and modern inputs (fertilizers, improved seeds) are used.
• Output/yield is high and hired/skilled labour is employed.

Detalhes da Resposta

(a) Two methods of calculating depreciation of farm machines [2 marks]

• Straight-line method (equal instalment method).
• Reducing (declining) balance method. (Others include the sum-of-the-years'-digits and revaluation methods.)

For example, by the straight-line method,

\[\text{Annual depreciation} = \frac{\text{Cost} - \text{Salvage value}}{\text{Estimated useful life (years)}}.\]

(b) Four roles of capital in agricultural production [4 marks]

• It is used to buy land, machinery, tools and farm buildings (fixed assets).
• It is used to purchase inputs such as seeds, fertilizers, feeds and agro-chemicals.
• It is used to pay wages to hired labour and to hire services.
• It provides working funds for storage, processing, transport and marketing of produce.

(c) Five major roles of middlemen in marketing agricultural produce [5 marks]

• Assembling/buying: they gather (bulk) produce from many scattered small farmers into large quantities.
• Transportation: they move the produce from the farms/production areas to the markets and consumers.
• Storage: they store produce and make it available throughout the year, evening out seasonal supply.
• Processing and grading: they process, grade, package and preserve the produce to add value and meet consumer needs.
• Financing and risk-bearing: they provide finance (sometimes advance money/credit to farmers) and bear the risks of price change, spoilage and loss; they also distribute the produce and pass market information to farmers.

Detalhes da Resposta

(a) Four effects of feed shortage on animal production [4 marks]

• Stunted growth and loss of body weight in the animals.
• Reduced production of milk, eggs and meat (low productivity).
• Poor reproduction, that is, reduced fertility and low birth rate.
• Lowered resistance to diseases, weakness and, in severe cases, death of the animals.

(b) Four areas of specialisation in agriculture and two contributions of each [16 marks]

• Agronomy (crop production): It develops improved crop varieties and better cultivation practices; and it increases food and raw-material production for the nation.
• Animal husbandry (livestock production): It supplies meat, milk, eggs and other animal protein for good nutrition; and it provides raw materials (hides, skin) and improved breeds of livestock.
• Agricultural engineering: It designs and provides farm machines, tools and irrigation structures that mechanise farming; and it develops soil and water conservation and storage/processing facilities.
• Agricultural economics/extension: It teaches farmers improved methods and helps them market their produce profitably; and it guides farm planning, record keeping and efficient use of resources, raising farmers' income.

Detalhes da Resposta

Practices in crop production

(a) Transplanting

Transplanting is the careful removal of young seedlings from the nursery (or seedbed) and replanting them in their permanent positions in the field. It is done when the seedlings are strong enough to survive on their own. It is best carried out in the evening or on a cloudy day and the seedlings are watered afterwards to reduce transplanting shock. It allows only healthy, vigorous seedlings to be selected, gives proper (uniform) spacing, and is used for crops such as tomato, pepper, rice and tobacco.

(b) Shading

Shading is the provision of shade (using palm fronds, mats, nets or grass) over a nursery or young transplanted seedlings to protect them from the direct heat of the sun, heavy rain and drying wind. It reduces excessive transpiration and wilting, keeps the soil moist and cool, and helps the tender seedlings to establish. Shade is gradually removed (hardening off) as the seedlings grow stronger.

(c) Supplying (filling-in)

Supplying, also called filling-in or beating up, is the replanting of seeds or seedlings in the spots (stands/hills) where the earlier planted ones failed to germinate or died. It is done soon after germination so that the new plants do not lag too far behind. It ensures a full and even plant population per unit area, thereby maintaining the expected yield.

(d) Nursery

A nursery is a specially prepared, well-protected small area of land (or containers/boxes) where seeds are first sown and the young seedlings are raised and tended until they are big enough to be transplanted to the field. It allows close attention, watering, shading and protection of the delicate seedlings, and permits selection of only the healthy ones for transplanting. It is used for crops with very small seeds or slow early growth, such as tomato, tobacco, oil palm and cocoa.

Detalhes da Resposta

(a) Effects of rural-urban migration on agricultural production

Rural-urban migration is the movement of people, especially the young and able-bodied, from the villages to the towns. Its effects on agriculture are largely negative: it causes a shortage of farm labour in the rural areas so that farms are under-cultivated; it leaves farming in the hands of the old, women and children who cannot work large farms; it lowers total food and cash-crop production and can cause food scarcity and higher food prices; it leads to abandonment of farmland and reduced use of improved practices; and it raises the cost of the few available labourers. A minor positive effect is that the migrants may send money (remittances) home to invest in farming, and reduced pressure on land can, in some cases, allow mechanisation.

(b) Effect of demand and supply on production

• (i) Demand (supply constant): When the demand for a produce rises while supply stays constant, its price rises; the higher price encourages farmers to produce more of that commodity. If demand falls, price falls and farmers reduce production.
• (ii) Supply (demand constant): When supply increases while demand stays constant, price falls, which discourages farmers and they cut back production; when supply is scarce, price rises and farmers are encouraged to produce more.

(c) Effects on farmers' income

• (i) Demand on income (price constant): a rise in demand means more produce is sold, so total income rises; a fall in demand means less is sold, so income falls.
• (ii) Supply on income (demand constant): a large supply (glut) forces prices down, which can reduce total income; a moderate/short supply raises price and can increase income per unit sold.

(d) Five roles expected of a farm manager [5 marks]

• Planning and organising the farm's activities and resources.
• Directing and supervising the farm workers.
• Keeping proper farm records and accounts.
• Making decisions on what, how and when to produce and market.
• Sourcing inputs and finance, and controlling/evaluating the farm to ensure it makes a profit.

Detalhes da Resposta

(a) Construction of a fish pond

A good site with a gentle slope, near a reliable source of clean water and on soil that holds water (clayey/loamy) is selected. The area is cleared of bush, stumps and debris and the outline of the pond is marked out. The topsoil is removed and the pond is dug to the required depth (deeper at one end so that it can be drained). An embankment (dyke) is built round the pond and compacted so that it is firm and does not leak. A water inlet (pipe or channel) is provided to let water in and an outlet/monk with a screen is provided to control the water level and to drain the pond; the screens keep fish in and predators out. The pond bottom and dykes are made watertight (a clay lining or concrete may be used), the pond is limed and manured to encourage the growth of natural fish food, then it is filled with water and stocked with fingerlings.

(b) Eight measures for efficient operation of an egg incubator

• Select and set only fertile, clean, medium-sized and well-shaped eggs.
• Maintain the correct incubation temperature (about 37.5 to 39°C / 100°F).
• Maintain the correct humidity in the incubator to prevent the eggs from drying up.
• Turn the eggs regularly (several times a day) to prevent the embryo from sticking to the shell.
• Provide adequate ventilation so that fresh air (oxygen) reaches the eggs and carbon dioxide is removed.
• Candle the eggs to detect and remove infertile or dead-in-shell eggs.
• Keep the incubator clean and disinfected to prevent disease.
• Ensure a steady, uninterrupted source of power/heat and check the thermostat and thermometer regularly for accuracy.

Detalhes da Resposta

(a) Three methods of irrigating a small nursery [3 marks]

• Watering with a watering can (hand watering).
• Sprinkler (overhead spray) irrigation.
• Drip (trickle) irrigation, or the use of a hose.

(b) Three factors considered in the choice of each method [6 marks]

(i) Surface irrigation:

• The topography of the land (it must be fairly level/gentle slope).
• The type/texture of the soil and its infiltration rate.
• The quantity of water available and the type of crop grown.

(ii) Sub-surface irrigation:

• The depth and nature of the water table.
• The soil type and its capacity to move water upward (capillarity/permeability).
• The cost of installation and the quality of the water (it must be free of salts to avoid salinity).

(c) Two advantages of sub-surface irrigation [2 marks]

• It supplies water directly to the roots with little loss through evaporation, so water is conserved.
• The soil surface stays dry, which reduces weed growth and the spread of foliar (leaf) diseases.

(d) Five ways of reducing build-up of diseases on an irrigated farm [5 marks]

• Practise crop rotation to break the life cycle of pathogens.
• Use clean, disease-free (treated) planting materials and resistant varieties.
• Ensure good drainage so that the land is not waterlogged.
• Keep the farm clean by removing and destroying infected plants and weeds (field sanitation).
• Use clean irrigation water and apply appropriate chemicals/biological control against pests and diseases.

Detalhes da Resposta

(a) Three major organs in each cavity [6 marks]

• Thoracic (chest) cavity: heart, lungs and the wind-pipe/oesophagus (also large blood vessels).
• Abdominal cavity: stomach, liver and intestines (also kidneys, spleen and pancreas).

(b) Functions of the nervous and reproductive systems [3 marks]

Two functions of the nervous system:

• It receives stimuli through sense organs and coordinates/controls the activities of the body.
• It transmits impulses (messages) and directs the response of the animal, controlling movement and involuntary body processes.

One function of the reproductive system:

• It produces sex cells (gametes) and enables the animal to reproduce and give rise to offspring, continuing the species.

(c) Importance of the following systems [importance]

• (i) Circulatory system: It transports digested food, oxygen, water and hormones to all body cells and carries away waste products (carbon dioxide, urea) to the excretory organs; it also distributes heat and helps defend the body against disease. Without it, cells would not be nourished or cleansed.
• (ii) Respiratory system: It takes in oxygen needed for the release of energy (respiration) in the cells and gives out carbon dioxide, a waste gas. This gaseous exchange keeps the animal alive and provides energy for growth, work and production.
• (iii) Digestive system: It breaks down (digests) the feed the animal eats into simple soluble substances that can be absorbed into the blood for growth, energy and body maintenance, and it removes the undigested waste. Good digestion means good use of feed and better production.

Detalhes da Resposta

(a) Budding and grafting [4 marks]

• Budding is a method of vegetative (asexual) propagation in which a single bud, cut with a piece of bark from a desired parent plant (the scion), is inserted into a slit in the bark of a rootstock so that the two unite and grow as one plant.
• Grafting is a method of vegetative propagation in which a portion of stem bearing several buds (the scion) from a desired plant is joined onto the rootstock of another plant so that their cambium layers unite and continue to grow together.

(b) Four materials required for budding [4 marks]

• A sharp budding knife.
• A healthy rootstock.
• Bud sticks (scion bearing buds) from the desired parent plant.
• Budding tape/raffia (or polythene strip) for wrapping the union, and wax to seal it.

(c) Two reasons why improvement of crops by selection may not give desired results [4 marks]

• The desirable character selected may be controlled by recessive genes, so it fails to show up in the offspring.
• Cross-pollination (out-crossing) with inferior plants nearby, and the influence of environment rather than genes, can mask or lose the selected trait in later generations.

(d) Four disadvantages of asexual and four advantages of sexual reproduction [8 marks]

Disadvantages of asexual reproduction:

• There is no genetic variation, so no improved varieties arise.
• Diseases present in the parent are passed on to the offspring.
• The offspring are all weak in the same way and can be wiped out by the same disease/pest.
• It does not allow the crop to adapt to new/changing environments.

Advantages of sexual reproduction:

• It produces variation, which is the basis for crop improvement and new varieties.
• The seeds produced are easy to store, handle and transport.
• Offspring may be more vigorous (hybrid vigour) and better adapted to the environment.
• It gives a means of surviving unfavourable conditions through resistant/dormant seeds and reduces carry-over of some diseases.

Detalhes da Resposta

(a) Definition of land [2 marks]

Land is the solid part of the earth's surface, together with all the natural resources on, above and beneath it (soil, water, minerals, air and vegetation), that man uses for agricultural and other purposes. In economics it is a free gift of nature and a factor of production.

(b) Two major classifications of land based on uses, with two examples each [4 marks]

• Agricultural land use: land used for growing crops (arable farming) and for grazing/rearing livestock. Examples: cultivating maize/yam; keeping cattle on rangeland.
• Non-agricultural land use: land used for purposes other than farming. Examples: building of houses/roads (construction) and mining/industrial or recreational use.

(c) Six factors that influence availability of land for agricultural production, explaining two [6 marks]

Six factors: (1) land tenure system, (2) population pressure/urbanisation, (3) topography and soil condition, (4) climate/rainfall, (5) government policy, (6) presence of pests and diseases (e.g. tsetse fly).

Explanation of two:

• Land tenure system: Where land is communally or fragmentally owned, a farmer cannot easily acquire a large continuous piece of land, and insecurity of tenure discourages permanent investment; this reduces the land available for serious farming.
• Population pressure and urbanisation: As population grows and towns expand, land is taken up for housing, roads, schools and industry, so less land is left for agriculture, and remaining farmland becomes overused.