Food supply

1. Overview

As the global human population continues to grow, the demand for food increases. To meet this demand, humans have developed various agricultural techniques to maximize yield (the amount of food produced). This topic explores the methods used to increase production and the environmental and ethical implications of large-scale farming practices.

Key Definitions

• Yield: The amount of agricultural product (crop or livestock) produced per unit area.
• Monoculture: A farming system where only one species of crop is grown in a large area.
• Intensive Farming: An agricultural system that uses high levels of input (such as fertilizers and machinery) to maximize yield from a specific area of land.
• Herbicide: A chemical substance used to kill unwanted plants (weeds).
• Insecticide: A chemical substance used to kill insects that damage crops.
• Fertilizer: A chemical or natural substance added to soil to increase its fertility by providing essential mineral ions.
• Selective Breeding: The process by which humans use animal or plant breeding to selectively develop particular phenotypic traits.

Core Content

Methods to Increase Food Production

To increase the efficiency and quantity of food, several technological and biological methods are used:

• Agricultural Machinery:
  • The use of tractors, combine harvesters, and irrigation systems allows farmers to manage much larger areas of land.
  • Efficiency: It reduces the time and human labor required for sowing, maintaining, and harvesting crops.
• Chemical Fertilizers:
  • Plants require mineral ions for growth, particularly Nitrates (for making amino acids/proteins) and Magnesium (for making chlorophyll).
  • Adding these to the soil ensures that nutrient depletion does not limit plant growth.
• Insecticides:
  • Insects can reduce yield by eating the crop or acting as vectors for plant diseases.
  • Insecticides improve the quality of the crop (less damage) and the total yield.
• Herbicides:
  • Weeds compete with crop plants for resources like light, water, and mineral ions in the soil.
  • Killing weeds reduces competition, allowing the crop to grow more successfully.
• Selective Breeding:
  • Humans choose individuals with the best characteristics (e.g., high grain yield, disease resistance, or fast growth in livestock) and breed them together. Over generations, this leads to significantly higher production.

Large-Scale Monocultures

Growing only one species (e.g., a massive field of only wheat) has specific consequences:

Advantages	Disadvantages
Highly efficient as the same machinery and techniques can be used across the whole field.	Low biodiversity: Only one species is present, reducing the variety of insects and birds.
Easier to manage and harvest, leading to lower costs for consumers.	Pest/Disease spread: If a pest or pathogen enters the field, it can spread rapidly because all plants are susceptible and close together.
Specialized for high yield.	Soil exhaustion: The same nutrients are removed from the soil year after year, requiring more fertilizers.

Intensive Livestock Production

This involves keeping large numbers of animals (e.g., chickens or cattle) in confined spaces with controlled environments.

Advantages	Disadvantages
High Yield: Produces large amounts of meat, milk, or eggs in a small space.	Ethical/Welfare concerns: Animals are often kept in crowded, unnatural conditions.
Cost-effective: Food is cheaper for the consumer.	Disease risk: Close proximity allows diseases to spread quickly, often requiring the use of antibiotics (which can lead to antibiotic resistance).
Controlled Environment: Temperature and feeding can be optimized for growth.	Pollution: Large amounts of animal waste can leak into water sources, causing eutrophication.

Extended Content (Extended Only)

There is no additional Supplement content for this specific sub-topic (20.1) in the current IGCSE syllabus.

Key Equations

While there are no specific biological formulas for this topic, you may be asked to calculate the percentage increase in yield:

$$\text{Percentage Increase} = \frac{\text{New Yield} - \text{Original Yield}}{\text{Original Yield}} \times 100$$

• New Yield: The amount produced after using a technique (e.g., fertilizer).
• Original Yield: The amount produced before the technique was applied.
• Units: Always express as a percentage (%).

Common Mistakes to Avoid

• ❌ Wrong: Saying that fertilizers are "food" for plants.
• ✅ Right: Fertilizers provide mineral ions; plants make their own "food" (glucose) via photosynthesis.
• ❌ Wrong: Confusing herbicides with insecticides.
• ✅ Right: Herbicides kill weeds; Insecticides kill insect pests.
• ❌ Wrong: Confusing selective breeding with genetic engineering.
• ✅ Right: Selective breeding involves choosing parents for natural reproduction; genetic engineering involves changing the DNA in a lab.

Exam Tips

• Command Word "Describe": If asked to describe how food production has increased, list the methods (machinery, fertilizers, etc.) and what they do.
• Command Word "Explain": If asked to explain the disadvantages of monocultures, you must give a reason (e.g., "Yield may decrease because pests spread more easily between plants of the same species").
• Real-world Context: Be prepared to see data in tables or graphs comparing "Organic Farming" vs "Intensive Farming." You will often need to interpret which method is more efficient or more damaging to the environment.
• Link to other topics: Remember that fertilizers can lead to eutrophication (covered in 21.3) and intensive farming uses antibiotics (linked to 15.1 and natural selection/resistance).

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Exam-Style Questions

Practice these original exam-style questions to test your understanding. Each question mirrors the style, structure, and mark allocation of real Cambridge 0610 Theory papers.

Exam-Style Question 1 — Short Answer [6 marks]

Question:

Intensive livestock production, such as poultry farming, aims to maximize meat production.

(a) State two advantages of intensive livestock production. [2]

(b) Describe two disadvantages of intensive livestock production, considering both the animals and the environment. [4]

Worked Solution:

(a)

1. Increased efficiency allows for higher meat production in a smaller area. Meat production is increased. Efficient use of space is a key advantage.
2. Lower production costs per animal lead to cheaper meat. Lower cost. Reduced labor costs are a factor.

How to earn full marks:

• Award 1 mark for each valid advantage stated.
• Accept answers related to higher profit margins, faster growth rates, or consistent product quality.

(b)

1. Animals are often kept in cramped conditions, restricting their natural behaviors and potentially causing stress and injury. Reduced animal welfare. Overcrowding is a welfare concern.
2. The high concentration of animal waste can lead to pollution of nearby water sources through runoff. Increased pollution. Manure contains nitrates and phosphates.

How to earn full marks:

• Award 2 marks for each disadvantage described.
• The description should include both the impact on the animals/environment AND the reason for the impact.
• Accept relevant answers related to the spread of disease, antibiotic resistance, or greenhouse gas emissions.

Common Pitfall: Students sometimes only state the disadvantage (e.g., "pollution") without explaining why it is a disadvantage in the context of intensive livestock production. Make sure you explain the link between the practice and the negative outcome to get full credit.

Exam-Style Question 2 — Short Answer [5 marks]

Question:

Farmers use various methods to increase crop yields.

(a) State two ways that agricultural machinery can increase food production. [2]

(b) Explain how the use of chemical fertilisers can improve crop yields. [3]

Worked Solution:

(a)

1. Agricultural machinery, such as tractors, can cultivate larger areas of land quickly. Larger areas cultivated. Tractors can plow more land than manual labor.
2. Combine harvesters can efficiently harvest crops, reducing losses and saving time. Efficient harvesting. Combine harvesters complete multiple tasks simultaneously.

How to earn full marks:

• Award 1 mark for each valid way stated.
• Accept answers related to planting seeds, spreading fertiliser, or irrigating crops.

(b)

1. Chemical fertilisers contain essential nutrients, such as nitrates, phosphates, and potassium. Nutrients provided. NPK are essential for plant growth.
2. These nutrients are readily available to plants, promoting faster growth and increased biomass. Faster growth. Soluble nutrients are easily absorbed by roots.
3. This results in higher crop yields, as plants are able to produce more fruits or grains. Increased yield. More biomass translates to more food.

How to earn full marks:

• Award 1 mark for stating that fertilizers provide nutrients.
• Award 1 mark for explaining that these nutrients promote faster growth.
• Award 1 mark for linking faster growth to increased crop yields.

Common Pitfall: When explaining how fertilizers work, be specific about the types of nutrients they provide (e.g., nitrates, phosphates, potassium) and how those nutrients contribute to plant growth. Don't just say "fertilizers help plants grow."

Exam-Style Question 3 — Extended Response [9 marks]

Question:

A farmer is considering switching from traditional farming methods to large-scale monoculture for growing corn.

(a) Define the term 'monoculture'. [1]

(b) Describe two advantages of large-scale monoculture. [4]

(c) Explain two disadvantages of large-scale monoculture, considering the potential impacts on the environment and crop sustainability. [4]

Worked Solution:

(a)

1. Monoculture is the cultivation of a single crop species in a given area. Single crop. Only one type of plant is grown.

How to earn full marks:

• Award 1 mark for a clear definition of monoculture, mentioning the cultivation of a single crop species in a specific area.

(b)

1. Large-scale monoculture allows for efficient use of machinery, reducing labor costs and increasing the speed of planting and harvesting. Efficient machinery use. Specialized machinery can be used effectively.
2. It simplifies crop management, as all plants require the same nutrients, water, and pest control measures. Simplified management. Fertilizer and pesticide application is standardized.
3. This can lead to higher yields in the short term, as resources are concentrated on a single crop. Higher short-term yields. All resources are focused on one crop.
4. Monoculture makes the sale of the crop easier because of the uniformity of the product. Uniform crop. The crop is easier to sell.

How to earn full marks:

• Award 2 marks for each valid advantage described.
• The description should include the advantage AND the reason for the advantage.

(c)

1. Monoculture can deplete soil nutrients rapidly, as the same nutrients are continuously extracted by the same crop. Nutrient depletion. The same nutrients are used repeatedly.
2. This can lead to reduced soil fertility and the need for increased fertiliser use, which can cause pollution. Increased fertilizer use. Pollution from fertilizer run-off.
3. Monoculture increases the risk of pest and disease outbreaks, as pests and diseases adapted to the crop can spread rapidly through the entire field. Pest/disease outbreaks. Lack of biodiversity provides no barriers to spread.
4. This reduces biodiversity, creating a less stable ecosystem that is more vulnerable to environmental changes. Reduced biodiversity. Ecosystem is more vulnerable.

How to earn full marks:

• Award 2 marks for each valid disadvantage explained.
• The explanation should include the impact on the environment/crop sustainability AND the reason for the impact.

Common Pitfall: When discussing the disadvantages of monoculture, remember to link the issue back to the environment or long-term sustainability. For example, don't just say "pests can spread easily"; explain why this is bad for the environment or the long-term viability of the farm.

Exam-Style Question 4 — Extended Response [10 marks]

Question:

A farmer uses selective breeding to improve the wool yield of his sheep. The average wool yield of his current flock is 3.0 kg per sheep per year.

(a) Define the term 'selective breeding'. [1]

(b) Describe the steps involved in selective breeding to increase wool yield in sheep. [4]

(c) After several generations of selective breeding, the average wool yield of the farmer's flock has increased to 4.5 kg per sheep per year. Calculate the percentage increase in wool yield. [2]

(d) Suggest one potential disadvantage of using selective breeding to increase wool yield in sheep. [1]

(e) The farmer also uses herbicides to control weeds in his crops. State two potential negative impacts of using herbicides. [2]

Worked Solution:

(a)

1. Selective breeding is the process of selecting individuals with desirable characteristics and breeding them together to produce offspring with those characteristics. Desirable traits. Breeding selected individuals.

How to earn full marks:

• Award 1 mark for a clear definition of selective breeding, mentioning the selection of individuals with desirable characteristics and breeding them together.

(b)

1. Identify sheep with the highest wool yield within the flock. Select best sheep. Measure and record wool production.
2. Select rams whose mothers also had high wool yields and good wool quality. Select best rams. Choose rams with desirable genes.
3. Breed the selected ewes with the selected rams. Breed selected. Natural or artificial insemination may be used.
4. Select the offspring with the highest wool yields and continue the process over several generations. Repeat process. Continue selection and breeding.

How to earn full marks:

• Award 1 mark for each step described.
• The description should be clear and logical.

(c)

1. Calculate the increase in wool yield: $4.5 \text{ kg} - 3.0 \text{ kg} = 1.5 \text{ kg}$. Increase in yield. Find the difference in wool yield.
2. Calculate the percentage increase: $(1.5 \text{ kg} / 3.0 \text{ kg}) \times 100 = 50%$ Percentage increase. Divide the increase by the original yield and multiply by 100.

How to earn full marks:

• Award 1 mark for calculating the increase in wool yield (1.5 kg).
• Award 1 mark for calculating the percentage increase correctly. $\boxed{50 %}$
• ECF allowed if the increase in wool yield is calculated incorrectly, but the percentage calculation is correct.

(d)

1. Selective breeding can reduce genetic diversity within the flock, making them more susceptible to diseases. Reduced diversity. Inbreeding can lead to genetic problems.

How to earn full marks:

• Award 1 mark for suggesting a valid disadvantage.
• Accept answers related to increased susceptibility to diseases, reduced fertility, or the development of other undesirable traits.

(e)

1. Herbicides can kill non-target plants, reducing biodiversity in the area. Kill non-target plants. Reduces plant diversity.
2. Herbicides can contaminate water sources, harming aquatic life. Water contamination. Herbicide run-off.
3. Herbicides can accumulate in the soil, affecting soil health and future crop growth. Soil contamination. Herbicides can persist in the soil.

How to earn full marks:

• Award 1 mark for each valid negative impact stated.
• Accept answers related to herbicide resistance in weeds or the disruption of natural ecosystems.

Common Pitfall: In part (c), remember to include the units (kg) in your intermediate calculation. Also, be sure to express the final answer as a percentage by multiplying by 100. In part (e), be specific about how herbicides negatively impact the environment (e.g., "contaminate water sources" instead of just "pollution").