Biology (0610) | Food supply

Biology IGCSE (0610) Study Notes: Food Supply (Human Influences on Ecosystems)

Welcome, IGCSE Biologists! This chapter is all about how we, as humans, change the world around us to get the food we need. We'll explore the methods used to boost crop and livestock yields, and critically look at the environmental and ethical costs associated with large-scale, modern farming. Understanding this topic is crucial because it connects Biology directly to real-world issues like sustainability and global resource management.

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20.1 Core Content: Increasing Food Production

The global population is huge and growing! To keep everyone fed, humans have developed many ways to increase the amount of food produced from the land. These methods aim to maximize yield (the amount of crop or meat produced) and efficiency.

A. Modern Agricultural Methods (The 'How')

We can categorize the ways food production has been increased into technological improvements and biological improvements:

1. Using Agricultural Machinery

What is it? The use of large, powerful machines (like tractors, harvesters, and mechanical planters).

Effect:

• Allows farmers to cultivate and harvest larger areas of land much faster than manual labour.
• Significantly improves efficiency (less time and fewer people needed to produce huge quantities of food).

2. Chemical Fertilisers

What is it? Artificial substances added to the soil to provide essential mineral ions.

Why it works: Plants need mineral ions, particularly nitrate ions (for making amino acids and proteins), magnesium ions (for making chlorophyll), and others like phosphate and potassium, for healthy growth. By adding these chemicals, we ensure the crops have all the nutrients they need, leading to improved yields.

Analogy: Think of chemical fertilisers as plant vitamins. If your soil is poor, adding these "vitamins" makes the plants grow bigger and stronger.

3. Insecticides and Herbicides (Pesticides)

Pesticides are chemicals used to kill unwanted organisms that compete with or harm the crops.

Insecticides:

• Used to kill insect pests (e.g., aphids, caterpillars).
• Effect: Protects the crop from damage, leading to improved quality and higher yield.

Herbicides:

• Used to kill weeds (unwanted plants growing near the crop).
• Effect: Reduces competition between the weeds and the crops for essential resources like water, mineral ions, and light, thus ensuring the crop grows optimally.

4. Selective Breeding

What is it? A process where humans intentionally select organisms (plants or livestock) with desirable characteristics and breed them together over many generations.

Effect:

• In crops: Produces varieties that give higher yields, are disease-resistant, or grow faster.
• In livestock: Produces animals that grow faster, produce more milk, or have better quality meat.

Quick Review Aid (The Tools of Modern Farming):
Modern farming relies on machines, chemicals, and clever breeding!

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B. Large-Scale Crop Production: Monocultures (Core 2)

Modern farming often involves planting only one species of crop across a very large area. This is called a monoculture.

Advantages of Monocultures

1. Efficiency: Since all plants are the same, it is easy to manage and harvest them using specialized machinery, reducing costs and labour.

2. Maximised Yield: The entire area is dedicated to producing the most economically valuable crop.

Disadvantages of Monocultures

1. Loss of Biodiversity: Monocultures replace natural ecosystems, destroying the habitat for many native plants, insects, and animals, significantly reducing the number of different species (biodiversity) in the area.

2. Vulnerability to Disease: If a pathogen (disease-causing organism) attacks one plant, it can spread extremely quickly because all plants are genetically similar (non-resistant) and grown close together. This can wipe out the entire crop.

3. Soil Depletion: Growing the same crop year after year drains the soil of the same specific nutrients, requiring heavy, constant use of artificial fertilisers.

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C. Intensive Livestock Production (Core 3)

Intensive livestock production (or factory farming) involves keeping animals in dense, high-density conditions, often indoors, to maximize the production of meat, milk, or eggs while minimizing resource use.

Advantages of Intensive Livestock Production

1. High Output: Produces a large amount of food (e.g., meat) per unit area of land.

2. Energy Efficiency: Animals are kept warm, confined, and don't need to hunt or graze. This means they use less energy on movement and maintaining body temperature, allowing more food energy to be converted into growth (biomass).

3. Easy Monitoring: It is easier to feed, medicate, and monitor the health of large numbers of animals when they are concentrated in one place.

Disadvantages of Intensive Livestock Production

1. Ethical Concerns (Animal Welfare): Many people believe keeping animals in cramped, unnatural conditions (like battery cages for chickens or small pens) causes suffering and is inhumane.

2. Disease Spread: The high density means that if one animal catches a disease, it spreads rapidly throughout the entire population.

3. Pollution: Intensive farms produce massive amounts of animal waste (manure/slurry). Managing this waste is difficult, and if it enters rivers or groundwater, it causes serious water pollution (e.g., eutrophication, which involves overgrowth of algae due to excess nutrients).

4. Antibiotic Use: Due to the high risk of disease, farmers must often use preventative antibiotics, which contributes to the global problem of antibiotic-resistant bacteria.