WAEC SSCE - Agricultural Science - 1991 (Essay)

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(a) Carbon cycle

The carbon cycle is the continuous movement of carbon between the atmosphere, green plants, animals, soil organisms and the earth. The diagram below shows the main processes involved.

Description:

1. Carbon occurs in the atmosphere mainly as carbon dioxide, CO₂.
2. Green plants absorb atmospheric CO₂ during photosynthesis and use it to manufacture carbohydrates and other organic compounds.
3. Carbon passes from plants to animals when animals feed on plants or on other animals.
4. Plants, animals and microorganisms release CO₂ back into the atmosphere during respiration.
5. When plants and animals die, their remains and wastes enter the soil as dead organic matter. Decomposers act on this material and release CO₂ by decomposition.
6. Some buried organic remains may, over a very long period, form fossil fuels. Combustion of wood and fossil fuels releases CO₂ to the atmosphere.

(b) Importance of the carbon cycle to crops and animals

1. It maintains a continuous supply of atmospheric CO₂ needed by green plants for photosynthesis.
2. Photosynthesis converts CO₂ into carbohydrates such as glucose and starch, which provide food and energy for crop growth.
3. Carbon fixed by crops becomes part of proteins, fats, carbohydrates and other organic substances in plant tissues.
4. Animals obtain carbon-containing food materials by feeding on plants or other animals; these materials are needed for energy, growth, repair and reproduction.
5. Respiration by plants, animals and microorganisms, together with decomposition and combustion, returns CO₂ to the air, thereby maintaining the carbon dioxide supply for crops.
6. Decomposition of crop and animal residues adds organic matter to the soil, improving soil structure and helping to maintain soil fertility.
7. The cycle helps to maintain the balance of oxygen and carbon dioxide in the atmosphere: plants release oxygen during photosynthesis, while animals and plants release carbon dioxide during respiration.

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(a) Ovulation is the process by which a mature egg is released from the ovary into the fallopian tube, where it may be fertilized by a sperm. In humans, ovulation usually occurs once a month during the menstrual cycle.

(b) The estrous cycle, also known as the heat cycle or oestrus cycle, is the reproductive cycle that female mammals go through, which includes the period of sexual receptivity or heat. In most species, the estrous cycle is divided into four stages: proestrus, estrus, metestrus, and diestrus.

(c) Gestation refers to the period of time during which a developing fetus grows inside the uterus of a female mammal. In humans, gestation typically lasts around 40 weeks, or nine months.

(d) Parturition is the process of giving birth to a baby or offspring. During parturition, the uterus contracts to push the baby through the birth canal and out of the mother's body. After delivery, the placenta is also expelled from the uterus.

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(a) Six environmental factors affecting agricultural production in Nigeria are:

1. Climate
2. Soil type
3. Water availability
4. Topography
5. Pests and diseases
6. Land degradation

(b) Explanation of how five of the factors listed in (a) can affect agricultural production in Nigeria:

1. Climate: Climate plays a crucial role in determining the success of agricultural production in Nigeria. Extreme weather conditions such as droughts or floods can adversely affect crop growth and yield. Climate change may also result in a shift in the cropping pattern, leading to changes in the type of crops grown and their yield.
2. Soil type: Different soil types have different nutrient levels and water retention capacities, which can affect crop growth and yield. For example, sandy soil can drain water quickly, leading to drought conditions, while clay soil can retain water, leading to waterlogging and root rot.
3. Water availability: The availability of water is crucial for agricultural production in Nigeria. The availability of irrigation water can increase crop yield and quality, while water scarcity can lead to crop failure.
4. Topography: The topography of the land can affect agricultural production in Nigeria. Steep slopes can lead to soil erosion and nutrient loss, while flat lands are more conducive for crop cultivation.
5. Pests and diseases: Pests and diseases can cause significant damage to crops, leading to decreased yields and economic losses. Proper pest and disease management practices are essential to mitigate the impact of pests and diseases on agricultural production in Nigeria.

6. Land degradation: Land degradation, such as soil erosion, deforestation, and desertification, can reduce the productivity of agricultural land in Nigeria. It can also lead to loss of biodiversity, which is critical for maintaining ecosystem services and food security.

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(a) Chemical control: This method involves the use of pesticides to prevent and control the spread of crop diseases and pests. However, the overuse of pesticides can have several negative side effects such as toxicity to non-target organisms, resistance development in pests, and environmental pollution.

(b) Biological control: This method involves the use of natural enemies of pests to control their population. The side effects of biological control are generally minimal as it involves the use of natural predators and parasites. However, the success of this method can depend on the availability and effectiveness of the natural enemies.

(c) Cultural control: This method involves the use of cultural practices such as crop rotation, intercropping, and sanitation to prevent and control the spread of crop diseases and pests. The side effects of cultural control are generally positive as it promotes sustainable agriculture and reduces the reliance on chemical pesticides. However, this method may require more labor and time compared to chemical control.

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(a) Four roles of government in agricultural production are:

1. Providing agricultural subsidies and incentives to farmers to boost agricultural productivity and profitability.
2. Development and implementation of agricultural policies and programs that promote sustainable agricultural practices, food security, and rural development.
3. Providing research and extension services to farmers to improve their knowledge and skills in modern agricultural practices.
4. Investing in rural infrastructure, such as roads, irrigation systems, and storage facilities to improve access to markets and reduce post-harvest losses.

(b) Four traditional land ownership systems in Nigeria are:

1. Communal land ownership system: In this system, land is owned by the community and is available for communal use. A disadvantage of this system is that it may lead to conflicts over land allocation and use.
2. Family land ownership system: Land is owned by the family and is passed down from generation to generation. A disadvantage of this system is that it may lead to fragmentation of land holdings, making it difficult for farmers to obtain economies of scale.
3. Chieftaincy land ownership system: In this system, land is owned by the traditional ruler and is allocated to members of the community. A disadvantage of this system is that it may lead to land being allocated based on favoritism rather than merit.
4. State land ownership system: In this system, the government owns all land and allocates it to individuals or organizations. A disadvantage of this system is that it may lead to inefficient use of land as the government may not always allocate it to those who can use it most productively.

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The law of demand states that as the price of a product increases, the quantity demanded of that product decreases, and as the price decreases, the quantity demanded increases, all other factors remaining constant.

Six basic assumptions related to agricultural products are:

1. The price of the product is the only factor that influences the quantity demanded.
2. Consumers have a limited budget for spending on agricultural products.
3. The product is homogeneous, meaning that it is the same quality and has the same features across different sellers.
4. Consumer preferences for agricultural products do not change.
5. The product is a necessity, and there are no close substitutes for it.
6. Consumers have complete information about the product.

A demand schedule and demand curve can illustrate the law of demand. A demand schedule is a table that shows the relationship between the price of a product and the quantity demanded of that product. A demand curve is a graphical representation of the same relationship.

For example, let's consider the demand for apples. Suppose the price of apples is $2 per pound, and consumers are willing to buy 100 pounds of apples per week. If the price of apples decreases to $1.50 per pound, consumers may be willing to buy 120 pounds of apples per week. This relationship can be shown in a demand schedule:

The same relationship can be shown graphically in a demand curve:

[Graph showing a downward sloping demand curve]

As the price of apples decreases from $2.00 to $1.50 per pound, the quantity demanded of apples increases from 100 to 120 pounds per week. This illustrates the law of demand: as the price of a product decreases, the quantity demanded of that product increases, all other factors remaining constant.

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Proper maintenance of a tractor is essential to ensure its safe operation and longevity. Here are eight maintenance practices that tractor owners should follow, along with some precautions to keep in mind:

1. Change the engine oil regularly: Regularly changing the engine oil can help keep the tractor's engine running smoothly. It is important to follow the manufacturer's recommendations for oil type and change intervals.
2. Check and replace filters: Air, fuel, and hydraulic filters should be checked and replaced regularly to prevent contamination of the engine and hydraulic system.
3. Keep the tractor clean: Regularly cleaning the tractor can help prevent dirt and debris from building up and causing damage. It also makes it easier to inspect the tractor for any issues.
4. Inspect the tires: Check the tires regularly for wear and damage. Overinflated or underinflated tires can cause stability problems or even blowouts. Make sure the tires are properly inflated to the manufacturer's recommendations.
5. Grease fittings: Regularly lubricating the tractor's grease fittings can help prevent wear on moving parts.
6. Check the battery: Ensure the battery is charged and connections are clean and tight. A weak or dead battery can cause starting problems.
7. Inspect the brakes: Check the brakes regularly to ensure they are working properly. Faulty brakes can lead to accidents and cause damage to the tractor.
8. Store the tractor properly: When not in use, store the tractor in a dry, covered area. This can help prevent rust and damage to the tractor.

Precautions:

• Always read the owner's manual and follow the manufacturer's recommendations for maintenance and safety precautions.
• Always wear appropriate safety gear, such as gloves, safety glasses, and steel-toed boots.
• Use caution when working around moving parts, hot surfaces, or electrical components.
• Always use the proper tools and equipment for the job.
• Never attempt maintenance or repairs while the tractor is running.
• Always shut off the engine and engage the parking brake before performing maintenance or repairs.
• Never remove safety guards or shields.
• If unsure about a maintenance task, seek the advice of a qualified mechanic.

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(a) Agricultural marketing refers to the process of selling and distributing agricultural products from the farm to the consumers. The four channels of marketing farm produce are:

1. Direct marketing: This involves the farmer selling directly to the consumer, usually at a local market or roadside stand.
2. Auction marketing: This involves the farmer taking his products to an auction market, where buyers bid on the products.
3. Cooperative marketing: This involves farmers pooling their resources to form a cooperative, which then markets the products on behalf of the members.
4. Commission marketing: This involves the farmer hiring a commission agent or broker to sell the products on their behalf, usually in larger markets.

(b) Four problems associated with marketing of farm produce by small-scale farmers are:

1. Lack of access to markets: Small-scale farmers often face challenges in getting their products to market due to poor infrastructure, inadequate transportation, and limited market information.
2. Price instability: Small-scale farmers are vulnerable to price fluctuations in the market, which can result in unstable income and financial insecurity.
3. Lack of bargaining power: Small-scale farmers often lack bargaining power in the market due to their limited production capacity and lack of organization, resulting in lower prices for their products.
4. Poor quality control: Small-scale farmers may lack the resources and expertise to ensure consistent quality of their products, which can result in lower prices and reduced demand.

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a) Five management methods adopted in the forest area to ensure a continuous timber supply are:

1. Selective logging: This method involves harvesting only mature trees while leaving younger trees to grow and regenerate, ensuring a continuous timber supply in the long term.
2. Plantation forestry: This involves planting and managing trees in a specific area to ensure a continuous supply of timber for commercial purposes.
3. Silviculture: This is the practice of controlling the growth, composition, and quality of forest stands to ensure that they meet the desired objectives, such as timber production.
4. Forest certification: This is a process of verifying that the forest management practices meet a set of environmental and social standards.
5. Forest regeneration: This involves ensuring that the forest is regenerated after harvesting, either naturally or by planting new trees.

b) Six benefits derived from forestry and range are:

1. Economic benefits: Forestry and range provide timber and other forest products such as fuelwood, charcoal, and non-timber forest products like mushrooms, honey, and medicinal plants. These products contribute to the livelihoods of millions of people worldwide and generate significant revenue for local and national economies.
2. Environmental benefits: Forests and ranges play a crucial role in maintaining ecological balance by regulating climate, conserving soil and water resources, preserving biodiversity, and preventing soil erosion.
3. Social benefits: Forests and ranges are a source of recreation, tourism, and cultural values. They also provide habitat for wildlife and support the livelihoods of indigenous and local communities.
4. Carbon sequestration: Forests and ranges absorb carbon dioxide from the atmosphere, thus mitigating the effects of climate change.
5. Water regulation: Forests and ranges act as natural water filters, regulating the quality and quantity of water available for human consumption and agricultural purposes.
6. Disaster prevention: Forests and ranges act as natural barriers, protecting communities from natural disasters like floods and landslides.

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a) A balanced ration is a type of animal feed that provides all the necessary nutrients, in the right proportions, to support the growth, reproduction, and maintenance of an animal's health. It contains a mix of carbohydrates, protein, fats, vitamins, minerals, and water in the right amounts that are needed to meet the animal's nutritional requirements.

b) The other feed ingredients that are essential for birds at the point of lay are as follows:

• Calcium: This is an essential nutrient for the formation of eggshells. Birds at the point of lay require high levels of calcium in their diet to ensure they produce strong, well-formed eggs.
• Phosphorus: This mineral is essential for bone growth and maintenance, as well as for energy metabolism and other cellular processes.
• Salt: This is an important mineral that helps maintain fluid balance in the body, and is also necessary for proper nerve and muscle function.

The maize meal, groundnut cake, fish meal, and brewers' grain in the given ration already provide a good source of carbohydrates, protein, and fats. However, the ration is lacking in essential minerals, especially calcium and phosphorus, which are necessary for the formation of strong eggshells and bone growth. Salt is also needed to ensure proper fluid balance in the body.

In summary, a balanced ration is essential to ensure that animals receive all the necessary nutrients for optimal growth, reproduction, and maintenance of their health. The specific ingredients required in a balanced ration may vary depending on the species of animal and their nutritional requirements.