5a Food Production¶
Part of 5 Use of Biological Resources.
Food production applies biology to agriculture, fermentation and fish farming. The common theme is using living systems more efficiently while controlling the conditions that limit yield or survival.
Learning Objectives¶
| ID | Route | Official specification wording | Main teaching sections |
|---|---|---|---|
5a-lo-1 |
All students | 5.1 describe how glasshouses and polythene tunnels can be used to increase the yield of certain crops 5.2 understand the effects on crop yield of increased carbon dioxide and increased temperature in glasshouses 5.3 understand how the use of fertiliser can increase crop yield 5.4 understand the reasons for pest control and the advantages and disadvantages of using pesticides and biological control with crop plants Micro-organisms |
Crop Production |
5a-lo-2 |
All students | 5.5 understand the role of yeast in the production of food including bread 5.6 practical: investigate the role of anaerobic respiration by yeast in different conditions 5.7 understand the role of bacteria (Lactobacillus) in the production of yoghurt |
Food Production by Micro-organisms |
5a-lo-3 |
All students + Biology-only detail | 5.8 understand the use of an industrial fermenter and explain the need to provide suitable conditions in the fermenter, including aseptic precautions, nutrients, optimum temperature and pH, oxygenation and agitation, for the growth of micro- organisms Fish farming 5.9B understand the methods used to farm large numbers of fish to provide a source of protein, including maintaining water quality, controlling intraspecific and interspecific predation, controlling disease, removing waste products, controlling the quality and frequency of feeding, and selective breeding |
Industrial Fermenters, Fish Farming |
Crop Production¶
Glasshouses and polythene tunnels enclose crops in a protected environment. This has several benefits:
- Weather protection: crops are shielded from harsh conditions that could damage growth.
- Carbon dioxide control: paraffin lamps or gas burners can be used to increase CO₂ concentration, ensuring that carbon dioxide is not the limiting factor in photosynthesis.
- Temperature control: the glass or plastic traps heat from sunlight, raising the temperature towards the enzyme optimum for photosynthesis. Supplementary heating can be added in cold weather.
- Pest exclusion: the enclosed space prevents many insects and other pests from reaching the crop.
Fertilisers supply the mineral ions plants need for growth: - Nitrates are needed to produce amino acids for proteins, driving growth and development. - Phosphates are required for respiration and root growth. - Potassium is needed for healthy flower and fruit development, as it supports enzyme function.
Fertilisers are water-soluble, so plant roots can absorb them by active transport.
Pest control prevents insects, fungi and weeds from damaging crops. Two main approaches exist:
| Method | Advantages | Disadvantages |
|---|---|---|
| Chemical pesticides (fungicides, herbicides, insecticides) | Quick and effective; can eliminate entire pest populations | Pests can evolve resistance; non-specific — can kill beneficial organisms; bioaccumulation along the food chain may harm other animals; must be reapplied regularly |
| Biological control (using predators/parasites of the pest) | No chemical residues; long-lasting effect | Slower; introduced species can become pests themselves; cannot eliminate a pest entirely |
Food Production by Micro-organisms¶
Yeast and bread making: Yeast is a single-celled fungus. When mixed with sugar in dough without access to oxygen, it carries out anaerobic respiration (fermentation):
glucose → ethanol + carbon dioxide
The carbon dioxide gas becomes trapped as bubbles in the dough, causing it to rise. The ethanol evaporates during baking.
Practical investigation of yeast fermentation: 1. Dissolve sugar in boiled (and cooled) water. 2. Mix yeast into the solution in a boiling tube. 3. Add a thin layer of oil on top to prevent oxygen from entering (ensuring anaerobic conditions). 4. Connect the boiling tube to a test tube containing lime water (which turns milky in the presence of CO₂). 5. Count the number of CO₂ bubbles over a set time. 6. Alter one variable — such as temperature (using a water bath) or sugar concentration — and repeat.
Yoghurt production using Lactobacillus: Lactobacillus is a bacterium that feeds on lactose (the sugar in milk), producing lactic acid: 1. All equipment is sterilised to kill unwanted microorganisms. 2. Milk is pasteurised (heated to around 72 °C for 15 seconds) to kill any bacteria present. 3. The milk is cooled and Lactobacillus is added. 4. The mixture is incubated at around 40 °C in a fermenter, where bacteria convert lactose to lactic acid. 5. The lactic acid lowers the pH, which denatures milk proteins, giving yoghurt its thick texture. 6. Flavourings, colourings or fruit are added before packaging.
Industrial Fermenters¶
Industrial fermenters are large containers used to grow microorganisms for the large-scale production of useful substances (e.g. insulin, enzymes, antibiotics or food products).
Key conditions that must be controlled:
| Condition | Reason |
|---|---|
| Aseptic conditions | Prevent contamination by unwanted microorganisms that would compete with the culture or spoil the product |
| Nutrient supply | Microorganisms need an energy source and raw materials (carbon, nitrogen, etc.) to grow and produce the desired product |
| Optimum temperature and pH | Ensures enzymes work at maximum rate without denaturing |
| Agitation (stirring) | Distributes nutrients, oxygen, microorganisms and heat evenly throughout the vessel |
Biology-Only Content: Fish Farming¶
This content is required for Biology-only students and is not required for Combined Science students.
Fish Farming¶
Large-scale fish farming uses biological management to increase yields efficiently. Key methods:
| Method | Explanation |
|---|---|
| Maintaining water quality | Water is filtered to remove waste and harmful bacteria, preventing disease |
| Controlling intraspecific predation | Fish of the same species are separated by size and age to reduce competition and cannibalism |
| Controlling interspecific predation | Different species are separated using nets or tanks to prevent predation between species |
| Disease control | Antibiotics are used to treat infections; water quality management reduces disease risk |
| Removing waste | Filtration removes faeces, which could lower oxygen levels and promote disease |
| Controlling feeding | Fish are fed frequently in small amounts to maximise growth without waste |
| Selective breeding | Fish with desirable characteristics (e.g. fast growth, disease resistance) are selectively bred |
Key Terms¶
- Fertiliser: a substance containing mineral ions (nitrates, phosphates, potassium) added to soil to support plant growth.
- Pesticide: a chemical used to kill organisms that damage crops; includes herbicides (for weeds), insecticides (for insects) and fungicides (for fungi).
- Biological control: using a living organism (predator or parasite) to control a pest species.
- Fermentation: anaerobic respiration in yeast or bacteria that produces useful products such as ethanol, CO₂ or lactic acid.
- Lactobacillus: a bacterium that converts lactose into lactic acid, used in yoghurt production.
- Pasteurisation: heating liquid (e.g. milk) briefly at a high temperature to kill harmful microorganisms.
- Fermenter: a sealed vessel used to grow microorganisms under controlled conditions for industrial production.
- Aseptic conditions: conditions that prevent contamination by unwanted microorganisms.
- Agitation: mixing or stirring in a fermenter to keep conditions uniform.
- Fish farming (aquaculture): the controlled rearing of fish in tanks or pens as a food source.
- Intraspecific predation: predation between individuals of the same species.
- Interspecific predation: predation between individuals of different species.