Saturday, 25 February 2012

5.11 Breeding Animals

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

Lets use cow as an example:
In this case the desired outcome for the cow is the milk yield. The earliest farmers would realise a few cows would be producing 50 ml of milk, while some produces 150 ml of milk, however, most of the cows would be producing 100 ml of milk.

The farmer will collect all the milk but he will only choose to cows which produce 150 ml milk as the breeding cows. In the next generation we find that a few cows are producing 100 ml, a few cows are producing 200 ml and the majority of cows will be producing 150 ml of milk.

He will then select the cows which produce 200 ml milk as the breeding cow. And in the next generation there would be a few cows producing 150 ml of milk, a few producing 250 ml of milk and the majority producing 200 ml of milk.

This shows that the milk yield would be genetic which means that the farmer can select the one with the desired characteristics to breed.

5.10 Breeding Plants

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

Lets take the rice crop as an example:
The number of rice grains is under the control of genes and if the farmer wants to improve the number of rice grains per plant; he notices that some plants have 6 grains per stem while others may have 8 grains per stem or even 10 grains per stem. So the farmer's decides to harvest the 6 grain and 8 grain plant but he will use the 10 grain ones for planting/breeding.

In the next generation of plants, he noticed that the rice plants are now producing 8 grains per stem, 10 grains per stem or 12 grains per stem. So he would harvest the 8 grain and 10 grain plants and select the 12 grain ones for breeding.

In this way the grain of the rice plant gradually increases which means the yield has increased.

Wednesday, 15 February 2012

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 intraspecific and interspecific predation, control of disease, removal of waste products, quality and frequency of feeding and the use of selective breeding.

Fish is an attractive product for farmers as they have low fat and high protein, but also that they are efficient at turning the nutrients into fish mass.

Fish farming will allow us to control the quality of water (clean), controlling the amount of predators and controlling the pests and diseases. By controlling these factors, it will result in a increase in yield of the fishes. However, where you have a high density of fish, there is a possibility that the transmission of disease will happen very fast and in some cases farmers have taken to use antibiotics which is of concern to human health. The abundance of fish within the fish farm also makes pests common and therefore some farmers will add pesticides to it which is also harmful to consumer health.


  • Aquaculture industry has provided a lot of employment opportunities
  • Fish farming may help conserve wild fish resources as it may provide a faster rate of food supply to keep up with the demand
  • Aquaculture may provide the main source of protein for people in many areas


  • The addition of antibiotics and pesticides may cause health hazards on consumers

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 microorganism.

  • The industrial fermenter is the reaction vessel in which fermentation occurs, normally made out of steel or copper. Inside of the steel jacket, there is normally another steel jacket inside, and in between the two, there will be layer of water in which it will act as a cooling jacket in order to keep the optimum temperature for the reaction to occur.
  • The fermenter will need to be cleaned and there will be a inlet where steam sterilises the fermenter between two fermentations. Steam is used to clean the tanks out.
  • Within the fermenter there will be a heating plate to raise the temperature, and the combination between the heater and the cooling jacket, provides the optimum temperature for fermentation.
  • Nutrient will also be added to the tank which will act as food for the microorganism. There would be a temperature probe in the tank in order to monitor the internal temperatures and the fermentation reaction would also require the addition of the microorganisms. The pH probe is also built in the fermenter in order to keep the conditions at the optimum rate of reaction. 
  • We will also need a way to stir the reaction and this is done by the addition of motor and this will agitate the mixture preventing the mixture to slump.
  • At the end of the reaction, we need a way to drain off the product, which also leads to a process called downstream processing which involves purification of the product
So in conclusion, the fermenter is to keep the optimum growth conditions for the conditions so it will provide the product we are looking for. 

Tuesday, 14 February 2012

5.7 Yoghurt

Understand the role of bacteria (Lactobacillus) in the production of Yoghurt.

  1. Firstly, milk is obtained from cows
  2. Then, the milk is treated in order to remove pathogens such as the TB bacillus with a process called pasteurisation
  3. The milk sugars are then converted into lactic acid. 
  4. This is done by incubating the milk to about 45-46 degree centigrade with the addition of lactobacillus
  5. Lactobacillus produces the enzymes which helps to break down the milk sugar into lactic acid
  6. The acid will result in a lower ph, and this causes milk protein to solidify and this solidification of the oft the milk product is what we call yoghurt.

5.5 Beer Production

Understand the role of yeast in the production of beer.

Beer is largely ethanol, an alcohol molecule, is produced from glucose which is broken down to ethanol and carbon dioxide.

Glucose =====Anaerobic Respiration (with the aid of yeast)==> Ethanol + Carbon Dioxide

The ethanol is often flavoured with the addition of plants such as hops which is traditionally added to change the flavour. The glucose comes from starch which is converted into maltose and maltose into glucose. The starch is converted into maltose by amylase and maltose into glucose by maltase. The starch comes from barley seeds, sometimes, wheat seeds and some other types of beer, include rice. The starch is broken down to maltase through the germination of the seed, commonly known as 'malting'.

5.4b Biological Control

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

Biological Control:
One of the most famous biological control example was in Australia, where the prickly pear cactus (the pest)  of North America was first introduced into gardens and escaped into the countryside and flourished under the Australian climate system. The cactus started to cover a good deal of agricultural land and was necessary to get rid of it, however, there was no natural herbivore of the cactus so an alien specie (non-native specie) was introduced from another country which was a moth (Cactoblastis). This moth was introduced and had no competitors so they started to remove the prickly pear cactus.


  • No toxic chemicals involved
  • Less impact on man or the impact

  • Not 100% effective
  • Often difficult to control, there is often a danger that the alien specie would start preying on native species, causing native specie population to diminish
  • Difficult to match a predator to the prey which can effectively remove the pest
  • This process may last a long time

Monday, 13 February 2012

5.4a Pesticides

Understand the reasons for pest control and the advantages of using pesticides and biological control with crop plants.

Large fields of crops of the same type are called Monoculture. Monocultures tend to be really susceptible to pests which uses the crops as their own food source. By doing so, this reduces the productivity of the farm which reduces the amount of crop yield and has an financial impact on the farmer as less is produced.
To overcome this, one of the solutions is to use pesticides (chemicals used to kill the pests)


  • Pesticides are chemicals which makes it easy to obtain.
  • They are easy to apply.
  • They are very effective.

  • Many of the chemicals are toxic, they may kill other plants and animals, other than the pests which may be harmful to humans as well.
  • Bio accumulation is where the pesticides build up through the food chain causing problems for animals in the higher trophic levels. 
  • Mutation in the pest often lead to resistance so the pesticide will need to be applied at a higher level, in some cases, the pests have complete resistance to the pesticide and so the farmers have to find an alternative pesticide.

Saturday, 11 February 2012

5.3 Fertilisers

Understand the use of fertiliser to increase crop yield.

Farmers normally add fertilisers (mostly in the form of nitrates or phosphates) to the soil in order to help promote the growth of crops and increase yield. These nutrients are taken up by the root structure and then moved in the transpiration stream up to the leaves for the construction.

Nitrates will go up to form proteins which is then used by the plants to generate/repair cells.
Phosphate is involved in the DNA of plants and the membranes of the plant.

The fertilisers can be divided into two groups:


  • Made from animal manures (waste) on farms and often goes through the process of decomposition and fermentation and forms a slurry compound
  • This is applied to the fields to provide Nirates and Phosphates to promote growth

Inorganic (Artificial):

  • These take the form of chemicals (synthetically produced), well known ones are potassium nitrate and ammonium nitrate which can be bought by the farmers and applied to the fields
  • These will release the nitrates which will promote growth of the crops.

Consequences of using fertilisers:
  • Fertilisers may run-off due to excess rain and reach water sources of causes eutrophication. The fertilizers enrich the nutrient content in water sources which causes algal blooms where the algaes grow fast and multiply. When algae die they are broken down by decomposers, the process of decomposition uses up oxygen in the water sources and causes massive die-off of fishes.
  • Fertilisers may be hazardous to human health: for example, organic fertilisers might leach through to water sources and cause diseases such as E.Coli which is commonly found in cow manures. Inorganic fertilizers may also leach down to underground water sources and cause cancer and is toxic to humans.
  • Fertilisers are normally used in intensive farming techniques (when a farmer is trying to obtain as much as possible from each hectare of land) which may deplete the original soil nutrients.

5.2 Crop Yield

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

Photosynthesis: Carbon Dioxide+Water===Light & Enzyme==> Glucose+Oxygen

Increase in carbon dioxide (substrate) theoretically means that the rate of photosynthesis will increase, resulting in a increasing in crop yield up to a point where it reaches the optimum point of the rate of photosynthesis.
If we increase the temperature, the theory predicts an asymmetrical graph which means if we increase temperature, the rate of photosynthesis increases, resulting in an increase in crop yield. However, after the rate of photosynthesis reaches the optimum, the rate of photosynthesis starts to slow down, as some enzymes denature which decreases total crop yield.

Increase in temperature in a glasshouse can help avoid frost damage and provides constant temperature both of which contribute to an increased crop yield.

Wednesday, 8 February 2012

5.1 Glasshouses and Polythene Tunnels

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

Glasshouses (a.k.a. greenhouses) are basically a small house but all surfaces are made out of glass - allowing light to penetrate through to the interior of the glasshouse.

First of all, we start with solar radiation, and that is our initial source of energy, in the form of light. The light is able to penetrate through the glass to the internal surfaces. The next feature is that the light is absorbed by surfaces inside the glasshouse, which could be soil, plants etc. These surfaces will then re-emit this energy as heat which warms the hair, raising its average kinetic energy (temperature increases).

  • The warm air which is raising the temperature is trapped and eventually all parts in the glasshouse will be warm, this warm air makes the enzyme reaction speed nearer the optimum temperature, therefore reacting faster and producing more products. 
  • As well as this, glasshouses provide shelter for the plants inside, which allow plants to survive through climatic hazards such as strong storms and winds, allowing plants to be able to mature and be harvested.
  • Since plants are in an enclosed area in the glasshouse, they are most likely to be immune to diseases and pests outside the area which protects the plant and allows it to grow. 
  • Additionally, glasshouses provide a constant temperature all year round which means a constant production which is particularly true in high altitude areas.
  • Glasshouses also prevent a loss of water vapour through transpiration which prevents the plants from drying out.
  • Plants also avoid frost damage, especially seedlings, in the spring.
  • Glasshouses are often warmed by the burning of fossil fuels, this leads to an increase in the carbon dioxide levels in the glasshouse which means more product from photosynthesis.
  • In glasshouses, through incomplete combustion, ethene may form as the product which can help stimulate fruit ripening, particularly with the tomato.

The polythene tunnels, usually a framework with polythene over the surface which also allows light to penetrate through to the interior. Even though, both polythene tunnels and greenhouses provide warm temperature for the growth of plants, polythene tunnels provide less shelter for the plants and may be less effective which may have an effect of the output. Polythene tunnels are more common in developing countries than developed countries because of the cheaper costs but sometimes is more preferred because it is more adjustable and movable.

Monday, 6 February 2012

2.89 Hormonal Responses

Understand the sources, roles and effects of the following hormones: Anti-Diuretic Hormone, Adrenaline, Insulin, Testosterone, Progesterone and Oestrogen.

Hormonal system also coordinates the body, hormones are chemicals which are produced by glands and travel to certain parts of the body through the bloodstream.

Adrenaline glands secrete adrenaline, which increases heart rate and makes the subject more alert, this is secreted when the person is nervous, frightened or angry and helps your body cope with emergencies.

ADH controls the level of the water in your body, it controls the amount of water re-absorption in the collecting duct and is produced in the pituitary gland in the brain.

Pancreas secrets insulin and the main purpose of insulin is to lower blood sugar levels. On the other hand, pancreas also secretes, glucagon which increases blood sugar level.

Testosterone is produced in the testes in males which develops male features during puberty which matures sperm cells in males.

Ovaries produce progesterone and oestrogen in females, these control the menstrual cycle and develops female features during puberty.

2.88 Skin Response

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

There are many different types of sensors on the skin such as pain sensors, touch sensors, pressure sensors and temperature sensors which we will focus on.

Our body keeps our body temperature constant at about 37 Degrees Celsius and thermoregulates in order to keep the body temperature in this range. This is also known as homeostasis.

If the surrounding temperature is too cold:

  • Vasoconstriction happens as capillary narrows which decreases the flow of heat to the skin
  • We stop sweating as we lose heat in this process as well
  • We shiver to increase heat production in the muscles
  • Hair erects in order to trap a warm layer of air and to avoid heat from escaping.
If the surrounding temperature is too hot:
  • Vasodilation happens where the capillary is widened which carries more blood to the surface which heat can be transferred out.
  • Sweating occurs which decreases body temperature

2.87 Eye Reponse

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

Most of the bending of the light rays is done by the curved cornea but the lenses can also bend light slightly. The shape of the lens is controlled by the ciliary muscles.

When you are looking at a far object:

  • The ciliary muscles relax
  • Which tightens the suspensory ligaments
  • The lens turn into a thin shape
  • The distant object is focused on the retina
When you are looking at a close object:
  • The ciliary muscles contract
  • This slackens the suspensory ligaments
  • Elastic lens becomes fatter
  • The near object is focused on retina
image courtesy of michelle biology

If there is bright light:
  • Circular muscles contract
  • Radial muscles relax
  • Pupils become smaller and less light enters the damage (to decrease damage that can be caused by strong light intensity)
If there is dim light:
  • Circular muscles relax
  • Radial muscles contract
  • Pupil enlarges and more light can enter the eyes, which helps us see in dark places

2.86 Eyes

Describe the structure and function of the eye as a receptor.

Our eyes is the body's receptor to light and gives us the sense of sight, which most of us depend upon. It detects changes in light intensities.

At the front of the eye is the cornea where the light enters the eyes. The light then passes through the pupil which is surrounded by the coloured iris. The light focuses on the fovea and the optic nerve receives the image perceived and projects it our brains.

Parts - Functions

Cornea - allows light in and is the main refractive surface of the eye
Pupil - The pupil either dilates or contracts with the help of the iris. This controls the amount of light entering the eye so that the lens doesn't get damaged.
Iris - Muscle surrounding the pupil which helps in dilating and making the pupil smaller. The logitudinal muscles contract and the radial muscles relax to make he pupil big and vice versa.
Lens - Helps with the refraction of the light onto the retina.
Optic Nerve - Carries impulses generated by the retina to the brain and turns into vision.