WAEC SSCE - Agricultural Science - 2008

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The correct answer is: "through the blood vessels located in the placenta". During pregnancy, the placenta is the organ that connects the developing embryo to the mother's uterus, and it acts as a source of nutrients, oxygen, and hormones for the developing fetus. The placenta develops blood vessels that allow the transfer of nutrients and oxygen from the mother's bloodstream to the developing embryo, and the removal of waste products from the embryo's bloodstream. Therefore, the developing embryo derives its nutrition from the mother through the blood vessels located in the placenta.

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The characteristic that is not true of a good pasture crop is "poor digestibility." Good pasture crops should have high palatability, meaning they are attractive to grazing animals, and high nutritive value, meaning they provide the necessary nutrients for animal growth and productivity. Resistance to trampling is also important as animals may trample the pasture as they graze. Poor digestibility means that the animal is unable to break down and utilize the nutrients in the forage, which can lead to reduced animal growth and productivity. Therefore, good pasture crops should have good digestibility to ensure that animals can efficiently utilize the nutrients available in the forage.

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The false statement about farmstead planning is "administartive blocks should not be located close to the entrance of the farmstead." Administrative blocks should be located near the entrance of the farmstead to provide easy access for visitors and administrative activities. Other options are correct; waste disposal units should be far away from the main farm area to prevent the spread of diseases, all buildings should be well ventilated with good lightings for the comfort and health of workers, and animal pens should not be located too close to the worker's house to prevent the spread of diseases and unpleasant smells.

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The aims and objectives of agricultural extension education are to provide education and training to farmers to improve their agricultural practices and increase their productivity. The option that does not fit this description is "educating farmers on government annual budgets" because it does not directly relate to agricultural practices or productivity improvement.

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Farmers who plant improved maize would harvest a high yield of maize. Improved maize varieties are developed to possess desirable characteristics such as high yield potential, resistance to pests and diseases, and tolerance to environmental stressors such as drought. Therefore, farmers who plant improved maize can expect a higher yield compared to traditional maize varieties. This can result in increased income and food security for farmers and their families.

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Liver fluke infestation causes disturbance in lipid digestion because it blocks the bile duct and reduces secretion of bile. Bile is necessary for the digestion of fats. When liver flukes infect the liver, they can block the bile ducts, preventing bile from reaching the small intestine where it is needed to digest fats. Without sufficient bile, fat digestion is compromised, and the absorption of essential nutrients like fat-soluble vitamins is impaired.

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Agricultural business is difficult to insure in West Africa mainly because agricultural production is highly risky. Agricultural production is often affected by unpredictable factors such as climate change, pests, and diseases which can lead to a significant decrease in yield and financial loss. This high level of uncertainty makes it difficult for insurers to predict potential losses and determine appropriate premiums. As a result, agricultural insurance in West Africa is often underdeveloped, and many farmers are left without adequate protection against the risks they face.

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Fertile eggs will be produced by breeders if cocks are always kept with the hens. This is because fertilization occurs when a rooster mates with a hen, and the fertilized egg can develop into a chick. Keeping the hens and roosters together allows for this natural process to occur, and results in the production of fertile eggs. While illumination of laying units, prevention of brooding, and proper storage of eggs can all impact the quality and viability of the eggs, they are not necessary for the production of fertile eggs. It is the presence of a rooster and his ability to fertilize the eggs that is the critical factor in the production of fertile eggs.

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Parasites and predators are biotic factors that are usually used to control cassava mealbugs. Parasites are organisms that live in or on a host organism and rely on the host for survival while causing harm to the host. Parasites of cassava mealbugs can be introduced into the environment to control their population. Predators are organisms that hunt and kill other organisms for food, and can also be introduced into the environment to control cassava mealbug populations. Pests, on the other hand, are organisms that cause harm to crops and are not used to control cassava mealbugs. Pathogens are disease-causing microorganisms and are also not used to control cassava mealbugs.

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When a piece of land is repeatedly cropped with maize, the soil nutrients may become depleted, and diseases and pests that affect maize may build up. Therefore, it is best to plant a crop that is not susceptible to the same pests and diseases and that can utilize different nutrients from the soil. Of the options given, cowpea would be the best choice because it is a leguminous crop that can fix atmospheric nitrogen into the soil and it is less susceptible to the pests and diseases that affect maize.

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The implement used for pulverizing the soil is the harrow. Harrow is a farm implement used for pulverizing soil and breaking up clods of earth after ploughing. It is commonly used for preparing seed beds for planting and for incorporation of fertilizer into the soil.

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The rabbit is able to utilize forage because it has an enlarged caecum that digests fibre. Unlike humans, rabbits are herbivores and feed on plant material that is difficult to digest. Their digestive system has a specialized structure that allows them to break down the cellulose and extract nutrients from it. The caecum is a large pouch located between the small and large intestine and is filled with bacteria and other microorganisms that break down fibre and other indigestible materials. This process produces volatile fatty acids and other byproducts that are absorbed and used as a source of energy by the rabbit. Thus, the rabbit is able to obtain nutrition from the forage it consumes.

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An illegal method of harvesting fish is by the use of potassium cyanide. This toxic substance is sometimes used by fishers to stun or kill fish, making them easier to catch. The cyanide is typically squirted into the water where the fish are, which can cause the fish to become disoriented and less able to swim. This allows the fisher to easily scoop them up with a net or by hand. However, the use of potassium cyanide is highly destructive to the marine ecosystem and can kill not only the target fish but also other marine life such as corals and invertebrates. It is illegal in most countries and is considered a serious threat to the sustainability of fisheries and marine biodiversity.

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Tomato plants are staked to produce clean fruits, reduce pest damage to fruits, and increase yield. However, staking tomato plants does not directly improve the taste of the fruits. The taste of tomatoes is influenced by factors such as the variety, ripeness, and growing conditions. Staking simply helps to keep the fruits off the ground, reducing the risk of rot or damage, and allowing for more efficient use of space and light, which can ultimately lead to a higher yield of healthy, delicious fruits.

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The main reason for removing the barks of cassava tubers before processing is to reduce the cyanide content of the products. Cassava tubers contain a toxic substance called cyanide, which can cause health problems such as goiter, ataxia, and even death. The cyanide is mainly found in the bark or outer layer of the tuber, and so by removing it, the level of cyanide in the processed products such as garri, fufu, and tapioca is reduced to safe levels. Therefore, removing the barks of cassava tubers before processing is an important step in ensuring the safety and quality of cassava-based food products.

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To calculate the depreciation of the tractor, we need to determine its annual depreciation. The tractor was bought for Le 15.0m and will be sold for Le 1.0m at the end of 10 years, so its total depreciation is Le 15.0m - Le 1.0m = Le 14.0m. To determine the annual depreciation, we divide the total depreciation by the number of years of its useful life: Annual depreciation = Total depreciation / Useful life Annual depreciation = Le 14.0m / 10 years = Le 1.4m per year Therefore, the calculated depreciation of the tractor is Le 1.4m. Answer: Le 1.4m

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The process which a farmer goes through from the time he hears about a new idea till he finally accepts it is referred to as adoption. Adoption refers to the process of taking up a new idea, technology or practice by an individual, group or society. It involves several stages which include awareness, interest, evaluation, trial, adoption, and confirmation. At the adoption stage, the farmer has decided to adopt and integrate the new idea or technology into their farming practices, and has committed resources to implement it. The successful adoption of new ideas and technologies is critical for agricultural development and productivity improvement.

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Birds store food in the crop. The crop is an expandable pouch-like organ located at the base of a bird's neck that is part of the digestive system. When a bird eats, the food is temporarily stored in the crop, where it can be moistened and softened by saliva. This allows the food to be broken down more easily by enzymes and bacteria in the bird's digestive system. After the food has been stored in the crop, it moves to the other parts of the digestive system, including the proventriculus, where digestive juices and enzymes are secreted, and the gizzard, where it is ground up into smaller pieces by muscular contractions and the presence of small stones. The cloaca is the opening at the end of the digestive system through which solid waste is eliminated.

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To find out the percentage of potassium in the fertilizer, we need to understand what NPK means. NPK stands for Nitrogen, Phosphorus, and Potassium, which are the three most important nutrients required for plant growth. In this case, the fertilizer has an NPK ratio of 15:11:8, which means it contains 15% nitrogen, 11% phosphorus, and 8% potassium. To find out the percentage of potassium in the fertilizer, we need to divide the amount of potassium by the total amount of NPK and then multiply by 100 to convert it to a percentage. Therefore, the percentage of potassium in the fertilizer is (8 / 34) x 100 = 23.53%. Therefore, the correct option is: 23.53%

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The milk-secreting organ in cattle is called the udder. It is a specialized mammary gland that is located on the lower underside of the cow's body. The udder is made up of four separate compartments, or quarters, each containing a network of mammary glands that produce milk. During milking, a suction device is attached to the teats of the udder, which extracts milk from the cow's mammary glands. The milk is then collected in a container for processing and distribution. Cows are commonly bred for their milk, which is a nutritious source of protein, vitamins, and minerals. The milk can be consumed as a beverage or used to make dairy products such as cheese, butter, and yogurt. In summary, the udder is the milk-secreting organ in cattle. It is a specialized mammary gland that produces milk, and is located on the lower underside of the cow's body.

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The three most important physical factors that influence rock weathering are: particle size, hardness, and degree of cementation. Particle size refers to the size of the rock fragments or particles, while hardness refers to the ability of the rock to resist weathering. Degree of cementation refers to how well the rock particles are held together. The combination of these factors can influence the rate and type of weathering that occurs in a given rock. For example, rocks with smaller particle sizes and weaker degrees of cementation may weather more quickly than rocks with larger particle sizes and stronger degrees of cementation.

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Floriculture is a branch of horticulture that focuses on the cultivation of ornamental plants, such as flowers, foliage plants, and ornamental trees and shrubs. It is concerned with the production of plants for their aesthetic value, rather than for food or medicinal purposes. Floriculture is an important part of the agricultural industry and is often practiced on a large scale in commercial nurseries and greenhouses. Examples of plants commonly grown in floriculture include roses, chrysanthemums, orchids, and poinsettias.

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The correct answer is "systematic insecticides". Maize stem borers are insects that bore into the stem of the maize plant, causing damage and reducing yield. Systematic insecticides are pesticides that are absorbed by the plant and transported to all parts of the plant, including the stem. This makes them effective in controlling insects that bore into the stem, such as maize stem borers. Contact poisons, on the other hand, are pesticides that kill insects on contact with the plant surface, and may not be effective against insects that are inside the plant. Nematicides are pesticides used to control nematodes, which are not the same as stem borers. Fumigants are pesticides that are inhaled by insects and can be used to control pests in stored grains or in the soil, but may not be effective against pests that are actively feeding on the plant.

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During photosynthesis, green plants use the energy from sunlight to convert carbon dioxide and water into a type of sugar called glucose. This process takes place in special organelles in plant cells called chloroplasts, which contain a pigment called chlorophyll that gives plants their green color. The glucose produced during photosynthesis can be used by the plant for energy, stored for later use, or used to make other important molecules like carbohydrates, proteins, and fats. Therefore, the answer to the question is a carbohydrate, specifically glucose.

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The false statement about bush burning is that "the heat generated increases the population of soil organisms." Bush burning actually reduces the population of soil organisms because it destroys their habitat and food sources. The intense heat generated from the fire can kill or damage the soil organisms. The other three statements are true. Bush burning can release mineral nutrients bound in plant tissues, which can improve soil fertility. It can also encourage the growth of fresh grasses by removing dead vegetation and providing nutrients for new growth. Additionally, the heat generated from bush burning can destroy pests that may harm crops or vegetation.

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A vegetatively propagated citrus plant will produce fruits earlier than the one established from seeds because it is more advanced at the time of establishment. Vegetative propagation involves taking a cutting or a bud from an already established citrus tree and growing it into a new tree. This method ensures that the new tree is genetically identical to the parent tree and has the same desirable traits, such as early fruit production. In contrast, growing citrus trees from seeds involves genetic variation and takes a longer time to produce fruits. It may take up to six years for a seed-grown citrus tree to produce fruits, whereas a vegetatively propagated tree may produce fruits within two to three years after planting. Therefore, vegetatively propagated citrus plants have a head start in terms of growth and development, and are able to produce fruits earlier than seed-grown trees. It has nothing to do with gummosis disease, insect pests, or wind pollination.

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Excessive drainage of soil water can be checked by the addition of adequate quantities of compost manure. Compost manure is a type of organic fertilizer that improves soil structure and water-holding capacity. When added to soil, it increases the soil's ability to retain water, thereby reducing drainage. This allows plants to access water more effectively, resulting in better growth and yield. The other options mentioned in the question, N.P.K 15-15-15, sulphate of ammonia, and single superphosphate, are chemical fertilizers that do not directly affect soil water-holding capacity.

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Groundnut grows best on a well-drained, light sandy-loam soil. This is because groundnuts require a well-drained soil to prevent waterlogging, which can lead to root rot and stunted growth. Sandy-loam soils also allow for good aeration and root penetration, while also retaining enough moisture to support the growth of the plant. Additionally, this type of soil is easy to work with, which makes it ideal for planting and harvesting groundnuts.

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An incubator is a device that provides controlled conditions to hatch eggs artificially. It is important in supplying heat for embryo development, ensuring that the eggs are kept at a constant temperature, humidity and ventilation. The temperature supplied by the incubator is critical for the embryo development and survival of the chick. Therefore, an incubator is crucial in providing the right conditions for the eggs to hatch into healthy chicks. Thus, the correct option is "heat for embryo development".

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To calculate the feed efficiency, we need to divide the total amount of feed consumed by the number of eggs produced and then multiply the result by 10. Therefore, the feed efficiency of the layer would be: Feed efficiency = (Feed consumed ÷ Number of eggs produced) x 10 Feed efficiency = (26 kg ÷ 230 eggs) x 10 Feed efficiency = 0.113 x 10 Feed efficiency = 1.13 Therefore, the feed efficiency for egg production for the layer is 1.13. Answer option B is correct.

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The milk collection vessel of the mammary gland is the gland cistern. The mammary gland is made up of several lobes, which in turn are made up of smaller lobules. Each lobule contains a cluster of milk-secreting cells called alveoli. The alveoli drain into small ducts, which converge to form larger ducts. The gland cistern is a large cavity or reservoir that receives milk from the small ducts. The teat, which is the nipple-like protrusion on the udder, is connected to the gland cistern by the streak canal, which acts as a valve to regulate the flow of milk from the mammary gland.

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Among the given options, the benefit of foreign exchange is likely to be of least importance to the peasant farmer. Foreign exchange refers to the money earned by a country through the export of goods and services to other countries. Peasant farmers generally produce crops and raise animals for subsistence or for sale in local markets. Their focus is primarily on meeting their own needs and earning income to support their families. While some crops and products may be exported, the amount of foreign exchange earned is likely to be minimal compared to larger commercial farms. Therefore, foreign exchange is of least importance to the peasant farmer compared to the other benefits listed.

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The land tenure system that allows the owner the greatest freedom to dispose of the land as he wishes is the free-hold system. In this system, the owner has complete and absolute ownership of the land and can use it, sell it, or pass it on to heirs as they please. The owner has the right to determine how the land is used, as well as to benefit from any profits or losses that arise from its use. This differs from other systems such as lease-hold, communal and share-cropping, which may impose certain restrictions or limitations on the owner's use and control of the land.

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The cheapest source of energy for domestic use considering all costs is sunlight. This is because sunlight is free, abundant and does not require any infrastructure or maintenance costs to capture and utilize. Solar energy can be captured through the use of solar panels and converted into electricity, which can power homes and appliances. Additionally, sunlight can also be used for passive solar heating and lighting, which can further reduce energy costs. In comparison, electricity, biogas and water require infrastructure, maintenance and fuel costs, which can make them more expensive in the long run.

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Livestock are said to feed on the range when they eat fresh herbage directly from the pasture. This means that they graze on the plants and grasses that are growing naturally in the fields, rather than being fed harvested herbage in a stall or preserved herbage in the form of silage. The term "range" refers to the open land where these plants grow, and grazing on the range is a traditional and natural way for livestock to obtain their food. Grazing on the range can be beneficial for both the animals and the environment, as it allows the animals to eat a diverse range of plants and promotes healthy soil and plant growth through natural fertilization.

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When birds are fed on a ratio deficient in riboflavin, they may show a symptom known as curled-toe paralysis. Riboflavin, also known as vitamin B2, is an essential nutrient that is required for a wide range of bodily functions, including the growth and development of the nervous system. When birds are deficient in riboflavin, they may develop curled-toe paralysis, which is a condition where the toes on one or both feet curl up and the bird is unable to walk properly. This is due to the degeneration of the nerves that control the muscles of the feet. Other symptoms of riboflavin deficiency in birds can include poor growth, decreased egg production, and poor feather quality. However, curled-toe paralysis is one of the most noticeable symptoms and can be an indicator that the bird's diet is deficient in this essential vitamin. In summary, birds that are fed on a diet deficient in riboflavin may show symptoms such as curled-toe paralysis, poor growth, decreased egg production, and poor feather quality. The curled-toe paralysis is due to the degeneration of the nerves that control the muscles of the feet, which can make it difficult for the bird to walk properly.

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The offspring of a bull can continue to be produced long after its death by using the preserved semen for artificial insemination. Semen is collected from a bull and then frozen and stored in liquid nitrogen at very low temperatures, which helps to preserve the sperm for future use. Even after the death of the bull, the stored semen can be used to inseminate cows and produce offspring with the same genetic traits as the original bull. This is a common practice in the dairy and beef industry, as it allows farmers to continue producing high-quality offspring from a bull that may have been particularly valuable for its desirable traits such as high milk yield or lean meat. The process of artificial insemination involves thawing the stored semen and depositing it directly into the female reproductive tract, where it can fertilize the egg and produce a calf. Artificial insemination is a safe and effective way of producing offspring, and it allows farmers to select the best genetic traits for their herds without having to keep a live bull on their farm. In summary, the preserved semen of a bull can be used for artificial insemination long after its death, allowing farmers to continue producing high-quality offspring with desirable genetic traits. This is a common practice in the dairy and beef industry and is an effective way of maintaining and improving the genetic stock of a herd.

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The correct answer is grasshopper. Grasshoppers are known to be destructive pests that feed on the leaves and stems of plants, causing severe defoliation in crops. They can also cause damage to fruits and flowers. While the other options can also be damaging to crops, they do not specifically cause defoliation. - Mirids are known for sucking the sap of plants, which can cause yellowing, wilting, and stunted growth of leaves and stems. - Weevils are known for feeding on seeds, nuts, and fruits, and can cause damage to crops such as maize, soybeans, and cotton. - Aphids are also known for sucking the sap of plants, causing curling and yellowing of leaves, as well as stunted growth.

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Nitrogen is an essential nutrient for plants' growth and development, and it can come from various sources. However, one of the options mentioned is not a source of nitrogen to the soil, and that is "residues of burning activities." Lightning is a natural source of nitrogen. When lightning strikes the ground, it converts nitrogen gas in the atmosphere into nitrogen compounds that dissolve in water and reach the soil. Urea is a synthetic fertilizer that contains high levels of nitrogen. When applied to the soil, it breaks down into ammonia and other nitrogen compounds, which the plants can absorb through their roots. Blue-green algae, also called cyanobacteria, can fix nitrogen from the atmosphere and convert it into a usable form for plants. This process is called nitrogen fixation, and it is an essential way for plants to obtain nitrogen in areas where it is scarce. On the other hand, residues of burning activities do not provide nitrogen to the soil. Burning vegetation or organic matter releases carbon dioxide and other gases into the atmosphere, but it does not add nitrogen to the soil. In fact, burning can reduce the soil's nitrogen content by converting it into gas that escapes into the air. In summary, nitrogen sources to the soil include lightning, urea, and blue-green algae, while burning activities do not provide nitrogen to the soil.

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Temperature is an important factor in fish ponds because it affects the metabolic processes in fish. Fish are ectothermic animals, meaning they cannot regulate their internal body temperature. Therefore, the temperature of their environment has a significant impact on their biological processes, including digestion, respiration, and immune response. Different species of fish have different optimal temperature ranges for growth and survival, and temperature fluctuations outside of these ranges can cause stress and even death. Additionally, temperature can affect the dissolved oxygen levels and nutrient availability in the pond, which further impacts the health and growth of the fish.

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Swollen shoot disease of cocoa is caused by a virus. More specifically, it is caused by a group of viruses called Cocoa swollen shoot virus (CSSV). These viruses are transmitted to cocoa plants by mealybugs, which are small insects that feed on the sap of the plant. The virus then infects the plant, causing its shoots to swell and become distorted. Over time, the infected plant becomes stunted, and its yield is significantly reduced. The disease is a major problem in many cocoa-growing regions, and there is currently no cure for it.

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(a)(i) Farm surveying

Farm surveying is the process of measuring and mapping out a piece of farmland to determine its size, shape, boundaries, position and the relative levels of points on it, so that a plan of the farm can be drawn.

(a)(ii) Four reasons why farm surveying is important

• It shows the exact size, shape and boundaries of the farmland.
• It helps in proper planning and layout of the farm, structures and roads.
• It helps to settle boundary disputes and provides proof of ownership.
• It helps in determining the slope of the land for drainage, irrigation and erosion control.

(b) Six problems facing agricultural development in West Africa

• Inadequate capital and poor access to credit.
• Use of crude/simple tools and low level of mechanisation.
• Poor storage, processing and transportation (marketing) facilities.
• Land tenure problems that limit access to large farmland.
• Pests, diseases and unfavourable/unreliable weather.
• Inadequate improved inputs (seeds, fertilizer) and poor extension services.
• (Also: illiteracy of farmers and rural-urban migration of youths.)

(c) Four factors that affect the efficiency of draught animals

• The health and physical condition of the animal.
• The age and breed/size of the animal.
• The feeding and nutrition of the animal.
• The nature/type of the soil and the load or implement being pulled.
• (Also: the weather/temperature and how well the animal is trained.)

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(a) Definition of soil erosion

Soil erosion is the gradual wearing away and removal of the fertile top layer of the soil from the land surface by natural agents such as running water, wind, or by the activities of humans and animals.

(b) Four factors that influence nutrient availability in the soil

1. Soil pH (degree of acidity or alkalinity)
2. Soil moisture content
3. Soil texture and structure
4. Organic matter (humus) content

(c) Two roles of each factor in soil formation

(i) Climate

• Rainfall causes chemical weathering (leaching, hydration and solution) that breaks parent rock into soil particles.
• Alternate heating and cooling (temperature change) causes expansion and contraction of rocks, leading to physical breakdown.

(ii) Living organisms

• Burrowing animals such as earthworms and termites mix and aerate the soil and bring lower materials to the surface.
• Decomposition of dead plants and animals by micro-organisms adds humus and enriches the forming soil.

(iii) Topography

• Steep slopes encourage rapid run-off and erosion, producing shallow, stony soils.
• Gentle or flat land allows water to sink in and materials to be deposited, producing deep, well-developed soils.

(d) Four problems associated with overhead irrigation

1. High cost of installation and maintenance of the equipment.
2. It wets the foliage and so encourages the spread of fungal and other leaf diseases.
3. Wind causes uneven distribution of water over the field.
4. Much water is lost through evaporation before reaching the soil.

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(a) Four methods of identification in cattle production

1. Ear tagging
2. Branding (hot or freeze branding)
3. Ear notching
4. Tattooing

(b) Three reasons for each practice

(i) Culling of poultry

1. To remove unproductive or poor-laying birds and cut feeding costs.
2. To remove sick or diseased birds and check the spread of disease.
3. To improve the general quality and productivity of the flock.

(ii) Dehorning of cattle

1. To prevent injury to other animals and to the handlers.
2. To make the animals docile and easy to manage.
3. To reduce the space required per animal at the feeding trough.

(c) Botanical names of four pasture legumes grown in West Africa

1. Centrosema pubescens
2. Stylosanthes gracilis
3. Pueraria phaseoloides
4. Calopogonium mucunoides

(d) Four ways of preserving harvested fish

1. Smoking
2. Salting
3. Sun-drying
4. Freezing or refrigeration

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(a)(i) Definition of crop rotation

Crop rotation is the practice of growing different types of crops in a planned and definite sequence on the same piece of land over successive cropping seasons or years, in order to maintain soil fertility and reduce the build-up of pests and diseases.

(a)(ii) A four-year crop rotation using yam, cassava, maize and groundnut

The land is divided into four plots so that every crop is grown each year, and each plot carries a different crop in turn. The legume (groundnut) is placed to restore nitrogen, and the heavy-feeding root crops are separated.

Note: Groundnut, a legume, is always followed by the heavy-feeding yam so that the nitrogen it fixes is used by the next crop.

(b) Four reasons why weeds are difficult to control

1. They produce very large numbers of seeds within a short time.
2. Their seeds can remain dormant but viable in the soil for many years.
3. They have efficient means of seed dispersal (wind, water, animals).
4. Many reproduce vegetatively from rhizomes, stolons and tubers even after the tops are removed.

(c) Two effects of diseases on crop production

1. They reduce the yield and quality of the crop produce.
2. They may kill the plants or increase the cost of production through control measures.

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(a) Definitions

(i) Demand: Demand is the quantity of a commodity that consumers are willing and able to buy at a given price over a given period of time.

(ii) Price elasticity of demand: It is the degree of responsiveness of the quantity demanded of a commodity to a change in its price. It is expressed as:

(b) Why the demand curve slopes downwards

The demand curve slopes downwards from left to right because of the law of demand: the quantity demanded rises as price falls and falls as price rises, showing an inverse relationship between price and quantity demanded. This is due to the income effect (a fall in price raises the consumer's real income) and the substitution effect (a cheaper good replaces more costly substitutes).

(c) Four agents of agricultural marketing

1. Wholesalers
2. Retailers
3. Middlemen or brokers
4. Cooperative marketing societies

(d) Two advantages and one disadvantage of each teaching method

(i) Newspapers

Advantages:

1. They can reach a large number of literate farmers at once.
2. The information can be kept and referred to again later.

Disadvantage: They are of little value to illiterate farmers who cannot read.

(ii) Television

Advantages:

1. It combines sound and moving pictures, so practices can be demonstrated clearly.
2. It reaches a very large audience at the same time.

Disadvantage: It is expensive and needs electricity, so many rural farmers cannot afford or use it.

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(a) Definition of soil

Soil is the thin, loose, uppermost layer of the earth crust made up of weathered mineral particles, organic matter, water, air and living organisms, in which plants grow and obtain support and nutrients.

(b)(i) Four components of soil

1. Mineral matter (weathered rock particles).
2. Organic matter (humus).
3. Soil water (soil solution).
4. Soil air.

(b)(ii) Percentage of each component by volume

(c) Making compost by the pit method

(i) Materials

• Plant remains (grasses, crop residues, leaves, weeds), animal dung/droppings, wood ash, top soil, and water; a pit is dug for the process.

(ii) Preparation

• Dig a pit of a suitable size in a well-drained site.
• Spread the first layer of chopped plant materials (about 30 cm) at the bottom.
• Add a layer of animal dung, then a sprinkling of wood ash and a thin layer of top soil.
• Water each set of layers to keep it moist and repeat the layering until the pit is filled above ground level.
• Insert a stick or provide vents to aid aeration, and cover the heap.
• Turn the heap at intervals (about every two to three weeks) to aid decomposition; it is ready in about three to four months when it becomes dark, crumbly and odourless.

(iii) Storage

• The finished compost is removed, kept in a cool, shaded and dry place (or bagged) and protected from rain and sun until it is applied to the farm.

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(a) Four factors that cause a change in supply of agricultural produce

1. Change in the cost of production (prices of inputs).
2. Change in technology used in production.
3. Weather and climatic conditions.
4. Government policy (taxes and subsidies).

(b) Fixed cost and variable cost distinguished

Two examples of fixed cost: rent on land; depreciation of machinery.

Two examples of variable cost: cost of seeds and fertilizers; wages of casual labour.

(c) Explanation of the agricultural extension teaching methods

(i) Posters: A poster is a printed visual aid, usually a sheet or chart carrying a short message with bold pictures and very few words, displayed in public places such as markets and clinics. It quickly attracts the attention of passers-by and passes a single agricultural idea to many farmers at a glance.

(ii) Field trips: A field trip is an organised visit by a group of farmers to a farm, research institute or demonstration site so that they can see improved practices being carried out and learn at first hand. It is a group teaching method that lets farmers observe results directly before adopting them.

Antwortdetails

(a)(i) Definition of agriculture

Agriculture is the art and science of cultivating crops and rearing of animals for man use, and for the production of food, fibre and other useful products, as well as the processing and marketing of these products.

(a)(ii) Six branches of agriculture

1. Crop production (agronomy).
2. Animal production (livestock/husbandry).
3. Horticulture.
4. Fishery.
5. Forestry.
6. Agricultural economics and extension.
7. (Also: soil science and agricultural engineering.)

(b) Five differences between commercial and subsistence agriculture

(c) Three merits of using animal power on the farm

• It is cheaper than buying and running machines.
• The animals provide manure (dung) for the farm.
• The animals can later be sold or used for meat, and they can work where tractors cannot reach.

Three demerits of using animal power

• Animals work slowly, so large areas take a long time.
• Animals need feeding, housing and veterinary care even when not working.
• They may be affected by diseases and are unsuitable for very heavy or deep cultivation.

Antwortdetails

(a) Four breeds of rabbits

1. New Zealand White
2. Californian
3. Chinchilla
4. Flemish Giant

(b) Two reasons why oestrus detection is important

1. It shows the right time to mate or artificially inseminate the female for successful conception.
2. It helps the farmer to identify infertile or non-cycling animals for culling or treatment.

(c) Four functions of each hormone

(i) Androgen (e.g. testosterone)

1. Brings about the development of male secondary sexual characteristics.
2. Stimulates the production and maturation of sperm (spermatogenesis).
3. Promotes libido or sexual drive in the male.
4. Promotes growth of the male reproductive organs and general body/muscle growth.

(ii) Oestrogen

1. Brings about the development of female secondary sexual characteristics.
2. Induces heat (oestrus) in the female.
3. Prepares the reproductive tract (uterus) for mating and implantation.
4. Stimulates the development of the mammary glands for milk production.

(d)(i) Two viral diseases of poultry

1. Newcastle disease
2. Fowl pox

(d)(ii) Two ecto-parasites of poultry

1. Lice
2. Mites (e.g. red mite)

Antwortdetails

(a) Crop improvement is the application of genetic and agronomic principles (selection, hybridization, mutation and modern biotechnology) to produce new or better crop varieties that possess desirable qualities such as high yield, early maturity, resistance to pests and diseases, and improved nutritional or market quality.

(b) Completed dihybrid Punnett square for the cross TtCc \( \times \) TtCc (gametes TC, Tc, tC, tc):

Counting the 16 offspring gives the classic dihybrid ratio 9 : 3 : 3 : 1: 9 Tall coloured (T_C_), 3 Tall white (T_cc), 3 Dwarf coloured (ttC_) and 1 Dwarf white (ttcc).

(c) Percentage of each phenotype (each box represents \( \frac{1}{16} \) of the plants):

• (i) Tall coloured = \( \frac{9}{16}\times100 = 56.25\% \)
• (ii) Tall white = \( \frac{3}{16}\times100 = 18.75\% \)
• (iii) Dwarf coloured = \( \frac{3}{16}\times100 = 18.75\% \)
• (iv) Dwarf white = \( \frac{1}{16}\times100 = 6.25\% \)