End of Notes

All aspects of the Biology specification (both paper one and two) has been covered. (Yay!).
Good luck!

5d) Cloning

Cloning plants using tissue culture:

1. Plant with desirable characteristics is selected to be cloned. Small pieces (explants)are taken out from the tips of the stem and the sides of the shoot
2. They are then sterilised to kill any bacteria
3. The explants are then grown in vitro - placed into a petri dish containing a nutrient medium (agar) Has all the nutrients to help it grow and austin hormone
4. Cells in explant divide and grow into a small plant
5. Small plant is taken out of medium and planted in the soil and put into greenhouses so they share the same characteristics as the original 
6. There is agar jelly inside which has nutrients (NPK, Mg, Ca, S and Auxin hormones) to help the cells to divide and grow
7. Can be used to produce commercial quantities of identical plants 

Cloning an adult mammal (dolly the sheep):

1. A body (somantic) cell of Sheep A is taken out as it is the sheep we want to clone and the nucleus is taken out (enucleated) and kept 
2. Then the egg cell of another sheep, Sheep B is taken out, because egg cells can adjust and differentiate (change into different types) and then the nucleus is taken out and thrown away 
3. Nucleus of Sheep A is put into the egg cell of Sheep B
4. This egg cell works like a normal fertilised egg and when it is stimulated with an electric shock it divides (by mitosis) and forms an embryo
5. Once it forms a small embryo it is inserted into the uterus of a different sheep, Sheep C- with a different phenotype to prove that the cloning worked
6. The embryo developed normally and was born as a Clone of the first sheep (A). 

Paper Two- Pros and Cons:

Pros-

Help cure diseases by transferring genes into food and giving it to people 

Could make it possible to have organ transplants by cloning organs 

Useful genetics are passed on to offspring 

Cons-

Cloned animals might not be as healthy as normal ones 

Might be consequences that we're not aware of

5c) Genetic modification/engineering

Restriction Enzymes - Are used to splice (cut) the DNA at the specific site- desired gene, e.g. human insulin. It can either be cut as a blunt or sticky end.

Ligases Enzymes - are used to stick pieces of DNA together

Vectors- something to transfer new DNA:
e.g. plasmids and viruses
Plasmids -

1. Isolate/ take out plasmid from bacterium using a pipette
2. cut apart the plasmid 
3. splice out the required gene using enzymes 
4. The glue using ligases the required gene and plasmid together. This is then called RECOMBINANT DNA. 
5. TRANSGENIC CELLS multiplies and starts producing (e.g. human insulin)  

Viruses-

1. Spice the required gene 
2. Add to the virus
3. Virus injects into the DNA (new organism) and RECOMBINANT DNA forms 
4. You then have a transgenic bacterium

Large amounts of human insulin can be produced by genetically modified bacteria that are grown in a fermenter 

Genetically modified plants:

• Crops can be genetically modified to increase food production in lots of different ways - one way is to make them resistant to insects, another is to make them resistant to herbicides (chemicals that kill plants) 
• Making crops insect-resistant means farmers can spray as many pesticides so wildlife isn't destroyed. It also increases crop yield. 
• Making crops herbicide-resistant means farmers can spray it to kill weeds but not the crops
• Some people are against genetic engineering altogether as they worry that a change in organisms genes might create unforeseen problems

1. Splice the DNA with desired features using the enzymes 
2. Meanwhile take plasmid out of Bacteria (Agrobacterium tumefaciems) and cut to allow space for the gene 
3. glue it together to make it a recombinant DNA 
4. Add the new DNA into a petri dish
5. There is agar jelly inside which has nutirents (NPK, Mg, Ca, S and Auxin hormones) to help the cells to divide and grow

5b) Selective Breeding

Organisms are selectively bred to develop the best features:
Best features:

• maximum yield of plants 
• good health and disease resistance 
• animals: fertility, not fatty, taste, docile (as pets) 
• plants: attractive, nice smell, shape, fresh 

How to selective breed:

1. Select organisms with desirable features (from existing stock) 
2. Breed them with one another 
3. Offspring: select the best of their offspring and breed them together
4. Repeat the process- consistent organisms 

5a) Food production

CROP PLANTS
You can artificially create the conditions for photosynthesis:

• enclosed 
• greenhouses and polythene tunnels increase the yield of certain crops
• artificial light ---> more photosynthesis 
• trapping heat 
• increase CO2 levels 
• increase temperature 

Greenhouses and Polythene tunnels: 

• increase CO2 levels- The more carbon dioxide present, the quicker the rate of photosynthesis and so increases the growth of crops at a faster speed 
• increase temperature- increasing the temperature raises the rate of metabolic reaction so the temperature needs to be at an optimum a very high temperature denatures the enzymes and low temperatures would reduce the metabolic rate. 
• increase of light intensity 

Fertilisers;

- replace missing elements 

- organic examples ---> nitrogen, manure and animal waste 

- most are chemically produced 

- too little has no effect 

- too much is expensive for people maintaining the crops

- Important elements are Nitrogen, Phosphorus and Potassium 

Reasons for pest control: 

cause crop damage and economic loses in high population

reduce photosynthesis and growth and damage appearance  

Pesticides:

Pros-

Kills pests

Quick results 

Increase and improve crop quality 

Prevent diseases found in fruit and vegetables 

Cons- 

Often poisonous to humans, must be used carefully 

harm other wildlife

expensive  

Biological Control:

Is alternative use of pesticides to reduce pests numbers. Introduces a predator which naturally feeds on them to reduce size.
Takes some time to fully eradicate.

Example: parasitic reduce pest numbers. They lay eggs inside whitefly egg (major pests of greenhouse gases) which prevents population increase. However can't cause crop damage.

MICRO-ORGANISMS

Yeast in the production of food:

1. Barley seeds are the main basis of beer. Seeds are germinated in large warehouses. The seeds produce an enzyme amylase during this.
2. Once the seeds have germinated they are killed and died, creating malt. The malt contains lots of amylase.
3. Malt is ground up and mixed with water in a mash tun (large container). During this time the amylase breaks down starches in the ground up seed mixture, converting it to sugars such as maltose and glucose.
4. Mash is boiled and filtered. Boiling results in denaturing of the amylase enzymes in the mixture. It must be filtered to remove residues of malt. 
5. Hops are added to the filtered solution and yeast is added. The yeast ferments sugars in the mixture creating carbon dioxide and alcohol as a result. 
6. The resulting mixture is high in alcohol and contains much carbon dioxide however it also contains yeast cells and hops. The beer is must be centrifuged, filtered and is sometimes pasteurised.
7. Beer is put into casks or barrels.  

The respiration rate of yeast:

The optimum temperature for yeast growth is 35-40C, if the temperature is too high enzymes become denatured. 

Glucose    --> Carbon Dioxide +   Alcohol 

C6H12O6 -->        2CO2        + 2C2H5OH     

Paper Two - Role of bacteria in the production of yoghurt:

• Yoghurt is made by the fermentation of milk by the bacteria called Lactic Acid Bacteria 
• This means that the bacteria respires anaerobically 
• Fermentation turns the liquid milk into a slightly sour semi solid food this is due to the lactic acid 
• Sugar in the yoghurt gives it energy and taste 
• Due to the build up of lactic acid the yoghurt has a low pH level- this prevents other micro-organisms from growing into the yoghurt 

(Lactose -->) Glucose --> Lactic Acid + Energy

                 C6H12O6 --> 2C3H6O3 (+ energy) 

Industrial Fermenter:

Containers are used to grow bacteria and fungi in large amounts 

FISH FARMING 

Problem: fish are being driven to extinction 

Cause: overfishing, high demand and sushi 

Solutions: growing fish in enclosed areas, QUOTAS, license, make fish more expensive and tax

Open and Closed Farming:

+------------------------------------+---------------------------+
| Advantages                         | Disadvantages             |
+------------------------------------+---------------------------+
| control oxygen and temperature (C) | disease spreads rapidly   |
+------------------------------------+---------------------------+
| meet demands (C+O)                 | cost of food (C)          |
+------------------------------------+---------------------------+
| introduce new breeds and fast      | pollution from faeces     |
| growth                             |                           |
+------------------------------------+---------------------------+
| fish manure well (O+C)             | fish in tanks are carniv- |
|                                    | orous and hungry          |
+------------------------------------+---------------------------+
| surviving a predator attack (C)    | fined for: traces of      |
|                                    | antibiotics               |
+------------------------------------+---------------------------+
|                                    | fined for: reduction      |
|                                    | of non-harmful organisms  |
+------------------------------------+---------------------------+

4d) Human influences on the environment

Pollution of the air by sulfur dioxide and carbon monoxide:
Sulfur Dioxide-

1. Burning fossil fuels releases harmful gases like CO₂ and SO₂ 
2. The sulfur dioxide comes from sulfur impurities in the fossil fuels 
3. When this gas mixes with rain clouds it forms dilute sulfuric acid 
4. Then acid rain falls 
5. Internal combustion engines in cars and power stations are the main causes of acid rain

Carbon Monoxide- 

1. When fossil fuels are burnt without enough air supply they produce the gas carbon monoxide 
2. CO is a poisonous gas and when combined with red blood cells it prevents them from carrying oxygen 
3. Carbon monoxide's mostly released in car emissions. Most modern cars are fitted with catalytic converters that turn the carbon monoxide into carbon dioxide, decreasing the amount of CO that's released into the atmosphere. 

Greenhouse gases:
Some gases in the Earth's atmosphere prevent heat radiating into space from the Earth. This is called the greenhouse effect and the gases that are involved are called the greenhouse gases.
They include:

• water vapour 
• carbon dioxide 
• nitrous oxide 
• methane 
• CFC 

Human Activity and Greenhouse gases:

Carbon Dioxide:

- released into the atmosphere all the time as part of our everyday lives, in; car exhausts, industrial processes and as we burn fossil fuels 

- cutting down large forest areas (deforestation) can also effect the levels of carbon dioxide in the atmosphere 

Methane:

- produced from natural sources 

- also from cattle 

Nitrous Oxide: 

- released naturally by bacteria in soils and the ocean 

- a lot more is released from soils after fertiliser is used 

- also released from vehicle engines and industry 

CFCs:

- man-made chemicals that were once used in aerosol sprays and fridges 

- very powerful greenhouse gases 

- most countries no longer produce them as it damages the ozone layer (part of the upper atmosphere where ozone is found in higher concentrations) which then prevents UV radiation from reaching the Earth 

- some still remains from old fridges and are released through leaks 

Greenhouse gas results in an enhanced greenhouse effect and this may lead to global warming, which is a gradual increase of the Earth's overall temperature and consequences, examples are change in crop growth patterns or flooding due to polar ice caps melting.   

For Paper Two- Biological consequences of pollution of water by sewage:

• increases the number of micro organisms which then leads to the depletion of oxygen 
• causes eutrophication which is when the environment becomes enriched by nutrients 

Eutrophication:

When fertilisers leach into the water, it can cause eutrophication.

If too much fertiliser is applied into fields (like nitrates and phosphates) and it rains afterwards, nitrates can be easily washed through the soil into nearby rivers and lakes. 

1. Fertilisers enter the water, adding extra nutrients 
2. The extra nutrients cause algae to grow quickly and block out the sunlight 
3. Then plants in the water can not photosynthesise due to the lack of light and start to die 
4. With more food available, micro-organisms that feed on dead plants increase in number and deplete (use up) all the oxygen in the water 
5. Organisms that need oxygen, like fish, then start to die due to the lack of oxygen 

Deforestation Effects:

1. Leaching 
• when trees are removed nutrients get leached away, but don't get replaced so it leaves infertile soil 
2. Soil Erosion 
• when trees are removed, soil can be washed away by the rain (eroded), which can leave infertile ground 
3. Disturbing the water cycle
• Rainwater can run straight into the rivers which can lead to flooding 
• Makes the local climate drier when trees are cut down 
4. Disturbing the balance of carbon dioxide and oxygen
• When trees are cut down and burnt the stored carbon is released at once as Carbon Dioxide, this contributes to global warming.
• Fewer trees mean that less photosynthesis occurs releasing less oxygen. This causes the oxygen level in the atmosphere to drop 

Section 5

Use of biological resources