Applied Biology
This domain tests how biological principles are used in agriculture, food production, pest control and resource management. Expect fertiliser calculations, comparisons of pest-control methods, food preservation and fermentation.
Crop production
Plant growth depends on water, light, CO₂ and mineral ions. Nitrogen supports leaf and protein growth, phosphorus supports roots and energy transfer, and potassium supports water regulation and enzyme activity. Fertilisers supply these ions, but excess application causes nitrate leaching and eutrophication. Crop rotation reduces soil depletion and pest build-up; monoculture increases vulnerability to disease.
Pest control
Chemical pesticides act quickly but can harm non-target species and select for resistance. Biological control uses predators, parasites or pathogens and is more targeted but slower and harder to manage. Integrated pest management combines resistant varieties, crop hygiene, monitoring and selective pesticide use.
Food and fermentation
Preservation methods include refrigeration, drying, salting, canning and fermentation. Fermentation uses microorganisms such as yeast to produce ethanol and CO₂, or bacteria to produce acids that lower pH and inhibit spoilage.
Worked example
A crop requires 120 kg of nitrogen per hectare. Urea contains 46% nitrogen by mass, so urea needed = 120 ÷ 0.46 ≈ 261 kg per hectare. Applying extra urea wastes money and increases nitrate leaching and eutrophication.
Traps
Do not confuse the roles of N, P and K. Biological control is not risk-free; introduced agents may affect non-target species. Over-fertilisation pollutes rather than simply improving yield. State that fermentation products inhibit competitors.
Animal production
Selective breeding improves yield and disease resistance but reduces genetic diversity. Aquaculture requires careful water quality and disease management.