Section 5: Use of biological resources
a) Food production
b) Selective breeding
c) Genetic modification
d) Cloning
a) Food production
Crop plants
5.1 describe how glasshouses and polythene tunnels can be used to increase the yield of certain crops
Polythene tunnels
- Keep frost off
- Stops water loss
- Avoid direct effect of sunshine
- Heat doesn’t escape
5.2 understand the effects on crop yield of increased carbon dioxide and increased temperature in glasshouses
- Increase the concentration of carbon dioxide (Substrate), photosynthesis rate increases, higher crop yield up to a point (greatest yield of product)
- Increasing temperature: at first increases the reaction, then hits the peak (optimal temperature), and drops
- Using glasshouses advantages: Avoid frost damage, provide constant temperature – contributes to yield
5.3 understand the use of fertiliser to increase crop yield
You apply fertilisers to the soil to promote growth of plants. They take the form of nitrates (for proteins), phosphates (DNA, membrane structure) or both. They are taken up by the root structure and then to the leaf.
Fertilisers: organic & artificial
Organic: produced from animal wastes on farms (cow faeces collected by farmers à decomposition / fermentation à slurry applied to fields)
Artificial: chemicals, synthetically produced (potassium nitrate, ammonium nitrate, bought by the farmer à go into solution in the soil water à release nitrates à same)
5.4 understand the reasons for pest control and the advantages and disadvantages of using pesticides and biological control with crop plants
PESTICIDES
Monoculture is susceptible to pests; they use crop as their own food source. This reduces the productivity of farming. To overcome this, you may use pesticides; chemicals designed to kill the pests.
Advantages: - Easy to obtain - Easy to apply - Very effective |
Disadvantages: - Toxic - Kill other plants and animals, possibly humans - Bio accumulation: pesticide builds up through the food chains e.g. DDT - Mutation leads to resistance (higher concentration or alternative pesticides needed) |
BIOLOGICAL CONTROL
Introducing an alien species from another country that eat the pests away.
Advantages: - No toxic chemicals involved - Less impact on man/ wildlife |
Disadvantages: - Not 100% effective. It is difficult to control: introduced species are likely to find alternative prey and don’t die out after removal of pests. - Difficult to match a predator to the prey (can’t find suitable animals to remove pests) |
Microorganisms
5.5 understand the role of yeast in the production of beer
Beer is made out of ethanol, which is produced from the fermentation of yeast. Yeast supplies the enzymes to bring about this conversion. Ethanol is flavoured by flowers such as hops. Glucose comes from starch (Barley seeds, wheat seeds, rice). The process of starch converting into maltose with the help of amylase is called malting.
5.6 describe a simple experiment to investigate carbon dioxide production by yeast, in different conditions
5.7 understand the role of bacteria (Lactobacillus) in the production of yoghurt
Milk is produced from cow. It first goes through pasteurisation (heat treatment to kill off any pathogens in the milk). Incubating the milk sugars (lactose) at 45 - 46°C with the help of lactobacillus produces the enzymes that break down lactose into lactic acid. This creates acidic conditions, encouraging the milk proteins to solidify. The product of this solidification is yoghurt.
Fruit Yoghurt
1) Raw milk is heated to 90°C for 30 minutes.
- Kill bacteria. Pasteurise
2) The milk is cooled to 40°C and bacteria is added
- Added bacteria not killed or denatured.
3) The mixture is kept at 40°C for several hours until yoghurt is made.
- Optimum for enzymes. For bacteria to reproduce, Enough time for yoghurt to be made
4) Fruit is sterilised and added to the yoghurt
- kill remove bacteria so yoghurt is not spoilt or contaminated.
5.8 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 is made of copper or steel. There is another layer inside to form a cooling jacket (it contains water). The reaction will produce heat, therefore, needs to be cooled off to maintain optimal conditions. The fermenter will need to be cleaned. There is a pipe that sends steam into the fermenter. It sterilises the fermenter between fermentation. There is a heater within the fermenter to raise the temperature. The heater and the cooling jacket together produce the optimal temperature. The fermenter also requires nutrients for the microorganisms (pipe). A temperature probe is required to monitor the temperature to deploy the heater and the cooling jacket. The reaction will require additional microorganisms and the heater. It also requires a pH probe to maintain the optimal pH. One needs to be able to stir the mixture using a motor. By agitating the mixture, it will stop them from clomping. Overall, the fermenter is a reaction centre where we control the optimum growth conditions for the microorganisms. Finally, we need a way to drain off the product that will be sent for downstream processing (involves purification).
Aseptic Precautions: to avoid contamination and production of unwanted by-products
Optimum temperature – to allow for maximum yield since microorganisms are very sensitive to changes
pH – microorganisms are very sensitive to changes in pH and effect the metabolic processes so acid or alkali is added as needed
Oxygenation – needed for aerobic respiration
Agitation / Stirring – paddles (impeller) or jets of air are used to stir the culture medium to prevent microorganisms settling and maintaining an even concentration of nutrients, even temperature.
Fish farming
5.9 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 farming is very good. Fish are low in fat, but high in protein. They are also efficient at turning their nutrients into fish mass. Fish farming will allow us to control the quality of water, control predators and reduce pests / diseases. We contribute to an increase in yield of fish. However, high density of fish increases chances of transmission of disease. So fish farmers may use antibiotics.
b) Selective breeding
5.10 understand that plants with desired characteristics can be developed by selective breeding
5.11 understand that animals with desired characteristics can be developed by selective breeding.
For example: ANIMAL – cow, DESIRED CHARACTERISTIC: milk yield
Various cows produce different amounts of milk. (50.100.150 à breed 150’s à 100.150.200 à and so on). By breeding the highest milk producing cows, we develop the desired characteristics by selective breeding. This works under the condition that milk yield is genetic.
c) Genetic modification (genetic engineering)
5.12 describe the use of restriction enzymes to cut DNA at specific sites and ligase enzymes to join pieces of DNA together
Restriction enzymes are able to cut the DNA at specific locations. The location identified by ATA. It is an important tool in biotechnology. DNA ligase enzymes join DNA.
5.13 describe how plasmids and viruses can act as vectors, which take up pieces of DNA, then insert this recombinant DNA into other cells
Plasmids are found in bacterial cells. They are a ring of DNA and are very small and don’t carry many genes. Virus contains a protein shell known as capsid, with a nucleic acid inside containing DNA or RNA. It has no other cellular components. The human chromosome is made of DNA.
We need to identify the gene that codes for the protein insulin (blood sugar level control). Restriction enzymes are selected to cut the DNA. Cut the plasmid with the exact same restriction enzyme. The ring structure in now broken and the insulin protein can be inserted. So human gene is inserted in plasmid and then DNA ligase is added to join the DNA. The combination of human gene and plasmid is known as a recombinant DNA.
Recombinant DNA needs to be transferred into the host cell via the virus. We remove the nucleic acid from the virus because we just want the capsid protein shell. The plasmids are taken up by the virus to form vector of recombinant DNA. This helps us transfer it into our host cell.
The type of virus used here is known as phage. It infects bacterial cells because the virus is able to attach to the cell membrane of the bacteria and insert the Recombinant DNA into our host cell. In the end, we have a bacterial cell with recombinant DNA plus its own DNA. This combination is known as transgenic. (5.16)
5.14 understand that large amounts of human insulin can be manufactured from genetically modified bacteria that are grown in a fermenter
Mutated bacterial cells injected into the fermenter along with nutrients (amino acids). Temperature, pH and gas control are compulsory. The optimal condition will result in population increase. Bacteria will be manufactured, producing more protein insulin. It is necessary to remove the product and carry out purification. There are many processes to purify for human use: downstream processing. Genetically engineered human insulin are called humulin.
5.15 evaluate the potential for using genetically modified plants to improve food production (illustrated by plants with improved resistance to pests)
Maize is damaged by the larvae of European cork borer (20% loss of crop yield). Bacteria known as BT exist. They have genes that release BT toxin when turned on. This is known to kill the cork borer larvae. By going through the steps introduced in previous objectives, you can take restriction enzymes to the genes of BT (the toxin). If you transfer these to the cells of maize plants, maize cells not have the BT genes that kill larvae. This gives maize resistance to the damage caused by the cork borer. However, it is difficult to do so. There is a method called ‘gene gon’. Tiny particles of gold are coated in BT genes. They are fired at the plant cells at high velocity to let the plant cells get the gene.
5.16 recall that the term ‘transgenic’ means the transfer of genetic material from one species to a different species.
Transgenic: transfer of genetic material from one species to a different species.
e.g. 5.13 bacterial cell of bacterial DNA + plasmids with human insulin gene
e.g. 5.15 Maize DNA + BT gene (toxin to kill larvae pests)
d) Cloning
5.17 describe the process of micropropagation (tissue culture) in which small pieces of plants (explants) are grown in vitro using nutrient media
When a plant which has characteristics that we consider desirable (commercial characteristics), we want it reproduced. Sexual reproduction will produce different plants to the parents due to genetic variation (à loss of qualities). So we use a cloning technique called micropropagation.
We can cut parts from the shoots or the roots and cut them in aseptic conditions (no contaminations). They are cut into small parts and then transferred into a petri dish containing nutrient agar. This will contain minerals that support the growth of tissue, rooting compounds and other plant hormones to encourage the growth of each of the small parts. Each will then be grown on into a seedling. Since many clones are made, they are genetically identical with the same characteristics.
5.18 understand how micropropagation can be used to produce commercial quantities of identical plants (clones) with desirable characteristics
5.19 describe the stages in the production of cloned mammals involving the introduction of a diploid nucleus from a mature cell into an enucleated egg cell, illustrated by Dolly the sheep
Dolly the sheep & original (clones)
1) Obtain genetic info from animal 1.
2) Remove diploid cell where the nucleus contains all the genetic information needed to make animal 1.
3) Animal 2 is treated with hormones like FSH (superovulation). They are encouraged to produce eggs because egg cells tend to divide.
4) We don’t want the genetic information of the egg cell, so we take the nucleus out (enucleated)
5) We fuse the cells (from animal 1 and egg cell from animal 2).
6) Cell division takes place through mitosis, which ends up as blastula (embryonic sheep).
7) The embryo is put in surrogate mother (animal 3).
8) It grows into a fetus and this was how Dolly was made.
9) Dolly the sheep is identical to animal 1 despite the age difference.
5.20 evaluate the potential for using cloned transgenic animals, for example to produce commercial quantities of human antibodies or organs for transplantation.
Cloned transgenic animals (genetically identical with 2 different DNAs mixed) can be used for commercial production of antibodies. Human antibodies can be collected by cow milk on a large commercial scale.
1) Obtain an egg cell from cow 1 and remove the cow antibody production gene.
2) Take a cell from a human and use restriction enzyme to remove a gene associated with antibody production.
3) Add human gene to the cow egg cell.
4) The cow cell is developed by mitosis to form the clone of cells and an embryo.
5) The embryo is transferred to a surrogate cow mother.
6) Genetically identical calves will be produced. They will produce milk containing human antibodies.
