Food Production
Use of Biological Resources · 3 question types
Exam Frequency Analysis
Past paper frequency (2018 to 2024)
This topic accounts for approximately 7% of your exam marks.
Microorganisms in food production (yeast, yoghurt, fermenter conditions) and glasshouse/fertiliser yield questions recur across most series.
A (greenhouse) is a building with glass walls and roof; a (polytunnel) is a curved frame covered with clear plastic sheeting. Both let growers control the environment around a crop so that photosynthesis, and therefore yield, can be pushed higher than it would be outdoors.
A glasshouse or polytunnel increases yield because it lets the grower manage the factors that limit photosynthesis and growth:
- Higher temperature. The transparent cover traps heat from the Sun (and can be topped up by heaters), so the air inside stays warmer. Warmer conditions speed up the enzyme-controlled reactions of photosynthesis and growth, and they extend the growing season into colder months.
- More light. The clear cover still lets light through, and growers can add artificial lighting to keep photosynthesis going on dull days and after dark.
- Controlled carbon dioxide. The enclosed space can be enriched with extra CO₂ (see section 2).
- Protection. Crops are shielded from frost, wind, heavy rain, and many pests and diseases, so fewer plants are lost.
- Controlled watering. Water and dissolved mineral ions can be supplied steadily so the crop never runs short.
A polytunnel is cheaper to build and cover than a glasshouse, so it is widely used for crops like strawberries and salad leaves, but it gives less precise control than a fully equipped glasshouse.