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I've made a Youtube account!!

Would mean so much to me if you could all go and subscribe to Brendan Huo at https://www.youtube.com/channel/UClREwjuesGhD5qBoKTAgNXw?view_as=subscriber

I'm going to be making videos of my life as a student at the University of Cambridge studying Engineering (new videos coming soon!)

Biology - EDEXCEL IGCSE - Finished

So that's all there is to IGCSE Biology. Once again now all you have to do is learn these notes, memorise them and then you're done.

Good luck in your exams!

PS. I've attached a complete copy in case you're too lazy to read it from the blog (it has a mighty 31 pages).

Click here

Biology - EDEXCEL IGCSE - Use of Biological Resources

Use of Biological Resources:

Greenhouse features:

Feature	How and Why
Soil ions	Fertilisers are added to ensure minerals are present for growth. For example, nitrates are added for DNA and magnesium are added for chlorophyll
Soil pH	Adding lime to make soil more alkaline to create a more suitable pH
Carbon dioxide, light and heat	Glass of greenhouse increases light intensity as well as creating heat. All increase rate of photosynthesis. Fuels can be burnt to create carbon dioxide and heat, needed for photosynthesis.

Pest control:

Disadvantages of using pesticides:

·        Pest may develop resistance against pesticides

·        May cause bioaccumulation and biomagnification which affects the food chain

·        Not specific

Disadvantages of biological control:

·         Does not completely eradicate a pest

·         Less fast

·         More expensive

Fish Farming:

Feature	How and Why
Water quality	Temperature and oxygenation of the water can be controlled to maximize growth
Predators	Fish protected by nets to prevent predators entering
Food	Frequent and high quality feeds. Frequent to ensure that the fish always has glucose for respiration
Diseases	Antibiotics used to kill pathogens and pesticides used to kill parasites to stop fish contracting diseases
Removal of waste products	This ensures that bacteria do not breakdown the organic material and create depletion of oxygen

Use of microorganisms:

The industrial fermenter is kept in aseptic conditions. This involves using hot steam to sterilise the inside of the fermenter. This ensures that there are no microorganisms present to contaminate the product or to create competition. As well as this, the temperature, oxygen concentration, pH and carbon dioxide concentration are all controlled and monitored.

Production of beer:

1.    Barley seeds are soaked in water and laid in the Malthouse to germinate. This creates amylase to digest starch.

2.    The seeds are killed by being heated and dried to make malt

3.    Malt is ground up and mixed with water in a mash tun. The amylase breaks down starch to maltose.

4.    Mash is boiled and filtered

5.    Hops are added for taste and yeast is added to ferment sugars, making beer

6.    Beer is centrifuged, filtered and sometimes pasteurized

7.    Beer is put into casts or barrels.

Production of yoghurt:

1.    Milk is pasteurized at 90°C for 20 minutes

2.    Milk is homogenized to disperse the fat globules

3.    Bacteria is added

4.    Bacteria anaerobically respire to create lactic acid. The low pH causes the lactose to coagulate.

5.    The thickened yoghurt is stirred and cooled to 5°C

6.    Flavourings, colourings and fruit are added

Selective breeding:

Organisms can be controlled by the use of selective breeding. This is where specific organisms with the desired characteristics are chosen and bred together. This method has been able to produce crops that give higher yields, are more resistant to diseases and pests and are more nutritious. The same method can also be applied to animals, producing cows that produce more milk or animals that have an increased resistance to diseases.

Genetic Modification:

Transgenic organisms are organisms which contain the DNA from at least 2 species.

Genetic modification is used to create organisms that are capable of producing the desired proteins that we need such as insulin. This is achieved by first removing the desired gene that codes for the protein production using restriction enzyme. The same restriction enzyme is used on the plasmid of a bacteria. The plasmid and the desired gene are then joined using DNA ligase (an enzyme) to create recombinant DNA. The plasmid is then added back to a bacterium which acts as the vector. The bacteria divide by binary fusion and is eventually placed in fermenters to mass produce the required protein. Viruses can also be used as the vector.

Cloning:

Micropropagation:

First the tip of the stem of the plant is removed using a scalpel. These parts are called explants. The explants are placed in an agar medium that contains nutrients and plant hormones needed for growth. The explants with shoots are then moved to another culture medium containing a different balance of plant hormones that encourages root formation. When the explants have grown roots they are transferred to compost and kept in a greenhouse. The greenhouse is kept moist to reduce water loss. The conditions are also kept aseptic to prevent diseases.

Micropropagation is good as it can produce a large number of plants rapidly. Plants can be grown at any time of the year and plants that are difficult to grow from seeds can be propagated.

Cloning:

To clone an animal, first an egg is taken from a female and enucleated (nucleus removed). Then a body cell is taken from the animal being cloned and inserted into the enucleated egg by giving both a small electric shock. The new cell is then allowed to undergo mitosis until it becomes an embryo where it is then implanted in the uterus of the surrogate mother. The surrogate will then give birth to an animal that is genetically identical to the animal that is being cloned.

Cloning provides the opportunity to clone transgenic animals in order to produce commercial quantities of human antibodies or organs for transplantation.