Monday, February 20, 2012

5.19 Mammal Cloning

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

Dolly the sheep: 
1.  An egg cell was removed from the ovary of an adult female sheep and its nucleus removed. (enucleated)

2. The nucleus from an udder cell of a donor sheep was inserted into the empty egg cell. 

3. The fused cell then began to develop normally, using genetic information from the donated DNA 

4. The cell develops into an embryo by mitosis, and is implanted into the uterus of a foster mother sheep. 

5. Result = lamb born (Dolly) genetically identical to 'parent' sheep. 

OBJ 5.18 Commercial plant growing

Understand how micropropagation can be used to produce commercial quantities of
identical plants (clones) with desirable characteristics

1. Plant has characteristics that are commercial --> desirable --> lots of copies are wanted 

a) sexual reproduction --> variation = loss of quantities. 
2. Cloning technique --> micropropagation --> this gives us many plants of the same quality (same product) 

5.17 Micropropagation - CLONING

Describe the process of micropropagation (tissue culture) in which small pieces of plants (explants) are grown in vitro using nutrient media
Cloning = any procedure that produces genetically identical offspring. 
Micropropagation = a cloning technique(explants) = tips of stems and side shoots 

1. The tips of a stem and side root are teared off the plant under aseptic conditions. 

2. They are then placed in a petri dish agar that contains nutrients and plant hormones to encourage growth. 

3. The explants with shoots are then transferred to another culture medium containing a different balance of plant hormones to encourage root formation. 

4. When the explants have grown roots, they are transferred to greenhouses and transplanted into compost --> they then grow under normal conditions. 

5. These seedlings are genetically identical --> clones. 

  • large numbers can be produced rapidly
  • species that are difficult to grow from seeds or cuttings can be propagated 
  • can be produced at any time of the year
  • large numbers of plants can be stored easily

Saturday, February 18, 2012

5.15a Genetically Modified Plants

Evaluate the potential for using genetically modified plants to improve food production(illustrated by plants with improved resistance to pests)

Eg: maize 

a) Maize damaged by 
cork borer larvae --> reducing crop yield by 20%


a) The existence of a Bacteria called  "BT." It contains a chromosome with a gene, that when switched on it produces "Bt" toxin. 

b) BT toxin kills the cork borer 


a) The DNA from the BT gene is cut with restriction enzymes to isolate the desired gene (BT gene for the toxin)
b) It then is transferred to the cells of the maize plant by a 'gene gun.' 
c) The gene gun fires a tiny golden pellets coated with DNA that contains the BT gene (desired gene)
d) These are then 'fired' directly into young plant tissue
e) The genetically modified tissue can then be grown into new plants 
f) This gives maize the resistance against damage caused by the 
cork borer  larvae

5.14 Humulin

Understand that large amounts of human insulin can be manufactured from genetically modified bacteria that are grown in a fermenter

1. Bacterial cell transformed by recombinant DNA (with the plasmid DNA combined with the human DNA of the insulin gene.) 

2. A culture of this bacteria (large population) is injected into a fermenter 

Necessities : 

- provide nutrients
- control the temperature  + pH
- control the gases in the fermenting chamber 

Creating  the optimum  temperature for bacterial growth ---> pop will increase + bacteria will manufacture the protein Insulin. 

3. The bacteria will manufacture the insulin protein from the nutrient protein (amino acid) 

4. Then it will be necessary to remove the product --> carry out purification by downstream processing. 

5. The genetically engineered human insulin is called '

5.13b Hosting recombinant DNA

Describe how plasmids and viruses can act as vectors, which take up pieces of DNA, then
insert this recombinant DNA into other cells.

Vector = transfers the gene eg:into the plasmid 

  • Remove the nucleic acid from the virus to get just the Caspid protein shell 
  • the plasmids are taken up by the virus 
  • the virus acts as a vector of the recombinant DNA - helping us to transfer the DNA into the host cell

  • This type of virus = a PHAGE 
  • it infects bacterial cells
  • the virus is able to attach to cell membrane of the bacteria and insert the recombinant DNA into the host cell. 
  • the bacterial cell now contains the recombinant DNA and the human gene for insulin. 
  • this combination is known as 'Transgenic' 

OBJ 5.13a Recombinant DNA5.13b Hosting recombinant DNA

Describe how plasmids and viruses can act as vectors, which take up pieces of DNA, then insert this recombinant DNA into other cells.
Recombinant DNA = a section of DNA is snipped out of the DNA of one species and inserted into the DNA of another the new DNA is called the "Recombinant DNA." 

1. Plasmid
  • found in bacterial cells 
  • small circular ring of DNA 
  • don't carry very many genes 
2. Virus = 
  • has a protein shell called a Caspid
  • contains a nucleic acid (DNA/RNA) 
  • (no cytoplasm, no nucleus etc)

    3.  Human Chromosome 
  • (length of DNA) 
  • identify a gene --> this gene codes for the protein Insulin (hormone controlling blood sugar levels) 
  • the restriction enzyme is selected to cut the DNA (to cut the gene for insulin) 
  • the gene is cut --> now isolate the plasmids and cut it with the same srestriction enzyme
  • the plasmids are now open in a structure much like a "C"
  • the opened up plasmids and the human gene insulin are mixed with a DNA ligase enzyme to create recombinant plasmids (combination of human gene + plasmid)

5.12 Restriction and Ligase enzymes

Describe the use of restriction enzymes to cut DNA at specific sites and ligase enzymes to join pieces of DNA together

1. Restriction enzymes 
  • are enzymes that cut DNA molecules at specific points
  • different restriction enzymes cut DNA at different places
  • they can be used to cut specific genes from a molecule of DNA 
2. DNA ligases 
  • are enzymes that join cut ends of DNA molecule

Friday, February 17, 2012

OBJ - 5.11 Breeding animals

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

1. Farmers breed animals for similar reasons to the breeding of crops. They have selected for animals that:
  • produce more meat, milk or eggs
  • produce more fur or better quality of fur 
  • produce more offspring
  • show increases resistance to disease and parasites 
2. Eg: Cows --> milk/meat

The farmer selects his breeding cows which are producing a high yield ---> they become the breeding population --> they are selected for the desired characteristic. 

As we progressively 'select' we change the 
desired characteristic by selective breeding. This is done under the control of genes. 

5.10 Breeding plants

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

Selective breeding 

  • decide which characteristics are important/desired
  • choose parents that show these characteristics
  • select the best offspring from parents to breed the next generation
  • repeat the process continuously. 
2. Crop plants are bred to produce strains that:

  • give higher yields 
  • are resistant to certain diseases
  • are resistant to insect pest damage
  • are hardier (so that they survive harsher climates or are productive for longer periods of the year)
  • have a better balance of nutrients in the crop 

Thursday, February 16, 2012

OBJ 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.
1. Attractive features of fish:
  • low fat
  • high protein 
  • efficient at turning their nutrient into fish mass 
2. Fish farming advantages:

  • we can control quality of water (clean) 
  • we can control predators 
  • can reduce pests 
  • can reduce bacteria/disease
3. By controlling all these factors, we can contribute to an increase in yield of fish.

4. But where there is there high density of fish --> you get a transmission of disease

5. This leads to farmers using Antibiotics ( a concern to human health) and the high density of fish also means that pests become common ---> farmers use Pesticides --> concern to human health. 

OBJ 5.8 Industrial Fermenter

Interpet and label a diagram of an industrial fermenter + explain suitable conditions 

Aseptic precautions:
- a pipe filled with steam is fed into the fermenter in between sessions to sterilize the fermenter

- at the start of the process, nutrients are fed in through pipes which can be opened or closed using valves.

Optimum Temperature and PH: (there is a sensitive prob for each)
- Fermentation produces heat, so to prevent the contents from overheating , the fermenter is surrounded by a water jacket in which water circulates, keeping the temperature at the best level for growth. 

- The PH of the contents can be adjusted by adding acid or alkali to keep it constant. 

Oxygenation and Agitation: 
- In the center of the fermenter there are stirring paddels which mix the contents - this keeps the microorganisms in suspension in the liquid so that they get more exposed to the nutrients that are fed in. And the agitation helps keep the temp even throughout the fermenter.

Wednesday, February 15, 2012

OBJ 5.5 Beer Production

Understand the role of yeast in beer production 

Beer is an alcoholic drink made by fermentation reaction that uses yeast to convert sugars to ethanol.
Fermentation also means "anaerobic respiration."

1. Sugar from plant material (barley) is converted into ethanol and carbon dioxide by fermentation. Yeast is used as a natural catalyst.

Sugar --> ethanol + carbon dioxide

C6H1206 ---> (enzymes in yeast) --> 2CH5OH +2CO2

2. The starch in barley is first broken down into sugar so that the yeast cells can ferment it to ethanol.

3. When barley seeds germinate (process is called "malting", they produce the enzyme amylase which breaks down starch into maltose - this is used by the yeast as an energy source in fermentation.

4. Sugars for beer-making come from boiling the barley in water - Hops are then added to adjust the flavor of beer making it bitter, and stop bacteria growing. 

The yeast is then added and after a while it uses up all the oxygen in the mixture and startes to respire the sugars anaerobically.

5. Flow of stages in beer production

Barley seeds are germinated - they make amylase to digest starch
Seeds are killed and dreid to make malt
Malt is ground up and mixed with water in a mash turn - amylase breaks down starch into maltose
Mash is boiled and filtered
Hops are added for taste and yeast is added to ferment sugars making beer
Beer is centrifuged + filtered
Beer is put into casks or barrels

Monday, February 13, 2012

5.4b Biological control

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

1. Pest numbers can be reduced by using using another organism, rather than a toxic chemical.

2. Method examples:

a) introducing a natural predator - ladybirds control population of aphids in orange groves.

b) introducing a herbivore - moth controls the prickly pear (weed) in grazing lands of Australia.

  • no toxic chemical
  • less impact on wildlife + man

  • not 100% efficient
  • difficult to control - danger 
  • difficult to match a predator to a prey.  

5.4a Pesticides

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

1. Pests = organisms that reduce the yield of crop plants by causing economic damage to the farmer.

2. Pests = any type of organism - plants, animals, bacteria, viruses, fungi, protoctists.

3. Pests can be controlled by chemicals called pesticides 

a) Pesticides can be used to kill them or their numbers can be reduced by biological control. 
  • Chemicals = easy to obtain 
  • Easy to apply/spray on field
  • Very effective 
  •  Toxic to other plants/animals/humans 
  • Bio accumulation - pesticide builds up through the food chain causing problems to animals in the higher trohpic levels eg:DDT
  • Mutation in pest --> resistance --> Pesticides is applied in higher concentrations = more toxic

4. Monoculture:

 Involves giving over large areas of land to a single crop eg: Maize.

harvesting these vast areas of crops  in a short period time means using huge machinery and this also means that pests can spread very easily. 

If the crop becomes infested there are millions of crop plants in which the pest can spread. 

Sunday, February 12, 2012

5.3 Fertilisers

Understand the use of fertiliser to increase crop yield

1. Fertilisers contain minerals (NITROGEN, POTASSIUM AND PHOSPHORUS) - which help plants grow faster + bigger so that crop yields are increased.

Nitrogen - makes proteins
Phosphates - make DNA + membrane structure

2. They're minerals are first dissolved in water so that plants can absorb them through their roots (done by active transport)

3. Organic Fertilisers
  • made from the feaces (farmyard manure) of a range of animals mixed with straw
  • goes through a process of decomposition and fermentation --> forms a compound called "slurry"
  • applied to the fields - supplying the essentials minerals to promote growth. 
4. Inorganic Fertilisers/Artificial
  • made from inorganic compounds (potassium nitrate/ammonium nitrate) 
  • carefully formulated to yield a specific amount 
  • applied to the field in solution (water) 
  • nitrates are released and absorbed by roots of plants

5. Eutrophication

a) Occurs when farmers apply inorganic fertilisers to replace the nitrates + other mineral ions lost from removing crops.

b) The ions are very soluble --> get easliy leached (carried out by water) from the soils and can enter waterways.

c) Level of nitrates rise rapidly in these lakes and rivers --> increase in mineral ions = Eutrophication

d) Eutrophication is a natural process but the speed at which it happens due to leaching ions in fertilisers from soils is not natural and results in disaster for a waterway.


  • Nitrate levels rise and algae reproduce rapidly as they are using the nitrates to make extra proteins
  • The algae then produces an algai bloom
  • The algae prevents light penetrating into the water
  • Plants cannot photosynthesize and die 
  • Algae also dies as they run out of nitrates
  • Bacteria decay the dead plants 
  • The bacteria reproduce due to the large amount of dead matter 
  • The water becomes totally anoxic (without oxygen)
  • All life in water dies

5.2 Crop Yield

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

Carbon Dioxide 
1.  Rate of P/S (carbon dioxide + water ---> glucose + oxygen) glucose --> starch. 

 a )Increasing CO2 --> (substrate) increases the rate of reaction of P/S = a higher yield. 
b) Limit: optimum temp

2. a) Increase the temperature ---> increase the rate of reaction of P/S = yield increases.

b) Limit:
optimum temp

OBJ 5.1 Glasshouses

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

1. Source: Solar radiation (initial source of energy).

2. The transparent material allows light to penetrate through the glass 
to the internal surfaces, where it is absorbed  (this natural light allows photosynthesis to take place).

3. The short wave radiation entering the greenhouse becomes longer wave radiation as it reflects off surfaces.

4. (surfaces RE EMIT the energy as heat) the  This longer wave radiation cannot leave as easily so the greenhouse heats up.

5. This raises the average KE of air particles therefore temperature is increased.  

6. Warm air, is trapped (cools as it raises to the roof, then sinks back down to the surface and is warmed again. (convection current).


The glasshouse provides the right conditions for plants to grow: 

1. Higher temperatures lead to optimum temp for enzyme reactions + photosynthesis.

2. Provides constant temp throughout the growing year = constant production.

- Enough natural light penetrates in the glasshouse for photosynthesis during the summer months, while extra lighting gives a longer day during the winter.

3. Prevention of loss of water vapor

 - Crops dont dry out, as the vapor cannot escape to the atmosphere.
- The water vapor maintains a moist atmosphere and reduces water loss by transpiration (water evaporated from leafs)

4. Can avoid frost damage - (seedlings).

5. Burning of fossil fuels 

a) burning fuels to raise the temp when the external temp is too low also produces CO2 --> increases concentration of the substrate for photosynthesis = more product +growth.

b) Side effect: Inefficient burning = ethene  gas --> stimulates fruit ripening eg:tomato. 

Thursday, February 2, 2012

2.89 Hormones

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

Hormones are chemicals secreted by glands in te body - the bloodstream transports hormones from the glands to the target organs. 

Source: Hypothalamus (pituitary gland)
Target Organ: Kidney 
Effect: Controls water content in blood by triggering uptake of water in the kidneys. 

Adrenaline: (the 'fight or flight' hormone)
Source: Adrenal Gland (above the kidney)
Target: Vital organs eg: liver + heart 
Effect: prepares body for physical activity. 

Source: Made by cells in the pancreas 
Role: Stimulates the liver cells to take up glucose and convert it into glycogen, lowering the level of glucose in the blood. Effect: Lowers content of glucose in the blood.

Source: Testes gland
Target: Male reproductive organs 
Effect: Controls development of male secondary sexual characteristics (puberty)

Source: Ovary gland 
Target: Uterus 
Effect:  Regulates menstrual cycle - maintaining the lining of the uterus.

Source: Ovary gland
Target: Ovaries, Uterus, Pituitary gland
Effect: Controls development of female secondary sexual characteristics

Wednesday, February 1, 2012

Objective 2.86 - The Eye

Iris Reflexes: 

2.86 describe the structure and function of the eye as a receptor.


Sclera - is the tough outer coat, which is the visible white part of the eye. 

Cornea - found at the front of the eye - it is convex + transparent - it lets light into the eye. 

Iris - found behind the cornea - it is a colored ring of tissue and it is pigmented (decided the color of your eye) - its muscles contract and relax to alter the size of its pupil (controlling how much light enters the eye)

Pupil - found in the middle of the iris hole - it lets the light through - it is black because there is no light escaping from the inside of the eye. 

Choroid - is a dark layer found underneath the sclera - it is dark because it contains many pigment cells + blood vessels - the pigment stops light being reflected around inside the eye. 

Retina - is the innermost layer (found underneath the Choroid - this is where light energy is transduces into electrical energy of nerve impulses - the retina contains 2 types of photo-receptor cells, 
a) Rods - sensitive to dim light + black and white 
b) Cones - sensitive to colour 

Fovea - found in the middle of the retina - is a small area concentrated with Cones ( cones give sharper images than rods) 

Optic nerve - is a bundle of sensory nerves found at the back of the eye - they carry impulses from the eye to the brain. 

Blind spot - located where the optic nerve leaves the eye at the back of the Retina - an image cannot be formed here because there are no Rods or Cones here.