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

5.4- Pesticides and Biological Control

understand the reasons for pest control and the advantages and disadvantages of using pesticides and biological control with crop plants

Monoculture: 

• Large fields with the same type of crops
• Susceptible to pests (variety of living things)--> reduces productivity of farming--> loss of food and financial impact on farmer
• Pesticides- Chemical and are designed to kill a pest
• Advantages:
• Chemicals --> Easy to obtain
• Easy to apply
• Very effective
• Disadvantages:
• Very toxic- harmful to humans
• Bio accumulation
• Mutation in the pest leads to resistance
• Pesticides may not work/ may need to be applied in a higher concentration

Biological Control: 

• Cactus flourished in Australia but there were no natural predators of it
• It needed to be removed as it was taking up agricultural land
• Moth (Cactoblastis) was introduced from another country (Alien species)
• Advantages:
• No toxic chemicals involved
• Less impact on humans and wildlife
• Disadvantages:
• Not 100% effective
• Difficult to control
• A danger that an alternative food source might be found for the alien species
• Sometimes difficult to match a predator to the prey

5.3- Fertilisers

understand the use of fertiliser to increase crop yield


Fertilisers:

• Generally take the form of nitrates, phosphates or a combination of both
• These compounds are taken up by the roots 
• Used in the leaf to form proteins (nitrates) and DNA, membrane structure (phosphates)
• Can be divided into two groups:
• Organic
• Produced from animal waste--> Cow faeces
• Goes through decomposition and fermentation
• Forms slurry which gives the plant nitrates and phosphates
• Artificial
• Chemicals which are synthetically produced
• Potassium Nitrate and Ammonium nitrate
• They will go into solution in the soil water
• Releases nitrates 
• Promotes growth in the same way as organic compounds

5.2- Crop yield

understand the effects on crop yield of increased carbon dioxide and increased temperature in glasshouses

Increased concentration of CO2:

• Substrate
• Rate of photosynthesis increases which means that there is a higher yield

Increased temperature:

• Increase in rate of photosynthesis which means that there is a higher yield
• There is an optimum temperature along the graph
• Avoiding frost damage, Constant temperature --> higher yield

Both of the conditions have limits

5.1- Glasshouses

describe how glasshouses and polythene tunnels can be used to increase the yield of certain crops

Glasshouses- Simple house structure, all surfaces are glass which allow light to pass through

1. The initial source of energy is solar radiation
2. Light goes through the glass
3. Light is absorbed by surfaces inside the glasshouse
4. Energy is re-emitted as heat
5. Heat warms the air- raising the temperature
6. Warm air is trapped inside which causes convection currents (warm air rises and moves back down after being cooled at the top of the glasshouse)

Polythene tunnels- Framework with polythene over it, allows light to pass through, cheaper and more adjustable than the glasshouse

Increasing crop yield: 

• High temperatures --> optimum temp. for enzyme reactions (photosynthesis)
• Constant temp. throughout the growing year--> constant production
• Prevention of loss of water vapour --> crops do not dry out
• Avoid frost damage (particularly seedlings)
• Glasshouses are often warmed by burning fossil fuels:
• Increase in carbon dioxide levels inside the glasshouse
• Increased concentration of substrate for photosynthesis
• Production of ethene --> Stimulate fruit ripening

2.89

Understand the sources, roles and effects of the following hormones: ADH, adrenaline, insulin, testosterone, progesterone and oestrogen.


Hormones- Chemicals released by a cell or a gland which sends out messages that affect other parts of the organism. 

• ADH- controls the amount of water in the blood. It is produced in the Pituitary gland. 
• Adrenaline- Increases heart rate and breathing rate during exercise. It is produced in the Adrenal gland.
• Insulin- Decreases the level of glucose in the blood. It is produced in the pancreas. 
• Testosterone- This hormone triggers puberty in boys. It is produced in the testis. 
• Progesterone- Controls the menstrual cycle in females. It is produced in the ovaries.
• Oestrogen- Triggers puberty in girls and stimulates growth of uterus lining. It is also produced in the ovaries. 

2.88

Describe the role of the skin in temperature regulation, with reference to sweating, vasoconstriction and vasodilation

• When the body feels that it is too hot:
• Hairs on skin lie flat (less insulating air trapped)
• Sweating starts
• Blood is diverted close to the surface of the skin (more heat radiation)
• When the body feels that it is too cold:
• Hairs on skin stand up (more insulating air trapped)
• Sweating stops
• Shivering starts, so muscles respire more, producing more heat
• Blood is diverted away from the skin (less heat radiated)
• How is blood diverted?
• Arterioles in the skin can open and close in response to nerve messages
• Vasoconstriction: Arteriole closes
• This happens when the body is cold
• Vasodilation: Arteriole opens
• This happens when the body is hot

2.87

Understand the function of the eye in focusing near and distant objects, and in responding to changes in light intensity

• Eye- Focuses light onto photo receptors
• Photo receptors- the sensory cells of the eyes known as the rods and cones
• When focussing on distant objects:
• The rays of light are almost parallel
• Lens remains flat and focussed on the retina (the inner area of the eye)
• The cilliary body relaxes
• When focussing on near objects:
• The lens has to adjust to the scattered light rays
• The cilliary body contracts which forces the Lens to become rounded
• This allows the image to be focussed on the retina

2.86- The eye

 Describe the structure and function of the eye as a receptor

• The eye is made of three coats: 
• The outermost layer consists of the Cornea and Sclera 
• The middle layer consists of the Cilliary body, Choroid and the Iris 
• The innermost layer consists of the Retina 

• The function of the eye is to receive light and send it to the brain which interprets these signals 
• The light first enters the cornea
• There are no blood vessels in the cornea as the light must be able to travel through uninterrupted 
• The aqueous humour is a nutrient filled liquid which provides nutrients to the cornea and the lens
• The pupil controls how much light passes through from the cornea to the lens
• The iris is two sets of muscle fibres that control the size of the pupil