5.11- Breeding Animals

Understand that animals with desired characteristics can be developed by selective breeding.

Using Cow as an example, the desired characteristic is milk yield.

• Some cows produced 50ml or 150 ml of milk but most cows produced 100 ml
• The farmer will collect all the milk
• The farmer chooses the 150ml milk cows as his breeding cows
• In the next generation, 
• Some cows produce 100ml or 200 ml of milk but most cows produce 150 ml
• He will then select the 200ml cows for breeding

Milk yield must be genetic for this to work. 

5.10- Breeding Plants

Understand that plants with desired characteristics can be developed by selective breeding


The number of rice grains is under the control of genes. The farmer wants to improve the no. of grains per plant and therefore increase the yield.

• The plants have 6, 8 and 10 grains per stem
• The farmer harvests the 6 and 8 stem grains
• The 10 grain stems are planted
• In the next generation:
• The plants have 8, 10 and 12 grains per stem
• The farmer harvests the 8 and 10 grain stems
• But selects the 12 grain stems for planting

The grain of rice plant gradually increases which means the yield has increased. 

5.9- Fish farming

Explain the methods which are used to farm large numbers of fish to provide a source of protein, including maintenance of water quality, control of intra specific and inter specific predation, control of disease, removal of waste products, quality and frequency of feeding and the use of selective breeding

Fish are an attractive product for farmers as they have low fat and high protein. They are efficient at turning their nutrient into fish mass. 

• Fish farming allow us to control the quality of the water, predators and reduce pests/diseases
• By controlling these factors, the yield of fish will increase
• High density of fish--> possibility of fast transmission of disease, pests
• Farmers use antibiotics in some cases which is of concern to human health
• Pesticides might also be used--> harmful to humans

5.8- Fermenter

interpret and label a diagram 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 microorganisms

• The fermenter usually has two steel jackets with water in between and this is known as the cooling jacket
• The steam which goes inside sterilises the tank in between the fermentations
• There is also a heater to raise the temperature inside the fermenter, combination of the cooling jacket and the heater allows for the optimum temperature for fermentation
• Nutrients (food for micro-organisms) are also added through a pipework
• A temperature probe inside the fermenter tells us whether to use the cooling jacket or the heater
• Requires the addition of micro-organisms through another tap
• The pH probe is built in to allow the maximum rate of reaction
• A motor is used to stir the reaction which agitates the mixture --> spreading the micro-organisms
• A way to drain off the product is required which leads to downstream processing which requires the purification of the product

The fermenter allows the optimum growth conditions for the micro-organism so it is able to produce the required product

5.7- Yoghurt

Understand the role of bacteria (Lactobacillus) in the production of yoghurt

1. Cow produces milk
2. It is then pasteurised which removes pathogens such as TB
3. This heat treatment kills of all pathogens in the milk
4. The milk sugars are then converted into Lactic acid
5. This can be done by incubating the milk at 45-46 degrees and adding  Lactobacillus
6. Lactobacillus produces enzymes which break down the milk sugar (lactose)
7. Acid will result in a lower pH which causes milk proteins which then solidify to for Yoghurt 

5.6- Experiment to investigate production of Yeast

Describe a simple experiment to investigate carbon dioxide production by yeast, in different conditions

1. Mix yeast suspension with a sucrose solution and place in a boiling tube
2. A delivery tube must be attached to collect the CO2 formed
3. The CO2 can be collected over water 
4. Or bubbled through limewater

5.5- Beer Production

Understand the role of yeast in the production of beer

• Beer is broken down from glucose into Ethanol and Carbon Dioxide (Anaerobic respiration)
• Using Yeast which provides the necessary enzymes for the reaction
•  Ethanol is flavoured using Hops (plants)
• Starch --Amylase--> Maltose --Maltase--> Glucose
• Sources of starch are Wheat, Barley seeds and rice