Natural Selection and GM II
Pesticides
Insecticides target insects
fungicides target fungi
disadvantages
very expensive
many harmless insects are killed
pesticides can become pollutants
Biological control
Introducing a natural predator, eg: ladybirds to control th population of aphids
Using organisms to control pests
Disadvantages
can go horribly wrong
if a predator is not from there, it doesn't have an natural predator so can thrive
Fertilisers
addition of minerals to the soil
encourage crops to grow faster
nitrates,phosphates, potassium could be added
disadvantages
mineral ions are soluble
if too much is used, rain can wash fertilisers into streams and rivers
fertilisers can cause fast growth of eutrophication
eutrophication
excess nitrates cause algae on the surface of water to grown fast
they stop light getting through, so plants can't photosynthesise and die
dead plants start to decompose as micro-organisms use them as a source of food
large populations of micro-organisms remove oxygen from the water, as they respire
organisms that need oxygen for aerobic respiration die
genetic modification of crops
advantages
crops can be modified to be resistant to attacks by insects
crops are more likely to have a higher yield
farmers will have to use less insecticide so crops will be less expensive
if crops are resistant to herbicides, farmers can use herbicides to kill weeds, without killing the crops
disadvantages
Crops could cross pollinate with closely related plants
GM organisms may be bad for health
Tissue culture
When cells are grown in a artificial growth medium, usually agar jelly or a liquid broth, which contains nutrients and growth regulators
Whole plants can be produced from the cells of a single individual
The process is called micropropagation
Plant tissue culture
1) choose the plant you want to clone
2) Remove several small pieces of tissue from the parent plant, ideally the root tips and shoots
3) Grow the tissues on a growth medium containing nutrients and growth regulators. It has to be done under aseptic conditions to prevent growth of microbes that could harm the plants
4)As the tissue produces shoots and roots, they can be moved in potting compost to carry on growth
Advantages
Desirable characteristics can be maintained
Clones of GM plants can be produced
Rare plants can be saved from extinction
Disadvantages
If there is one plant susceptible to a disease, then all of them will be
Very expensive
Very susceptible to pests
In medical research
Cultures of cells can be studied to see how cells communicate with each other and how tissues develop
Used to study viruses
Cancer cells can be used to study the development and spread of the disease
Drugs can be tested on cell cultures without risking harm to animals
Genetic engineering
The transfer of a gene from the genome of one organism to the genome of another
Process
1) DNA that is going to be transferred is cut out with a restriction enzyme. Restriction enzymes recognise specific sequences of DNA and cut the DNA at these points
2)The cut leaves one of the DNA strands with unpaired bases, called sticky ends
3)The same restriction enzyme is used to cut open the vector DNA. A vector (anything that carries the new gene into a cell) is used to transfer DNA into a cell. this could be a plasmid or a virus
4)The vecotr DNA and the DNA you'e inserting are left with complimentary stciky ends. they are mixed together with ligase enzymes.
5)The ligase joins the sticky ends together to produce recombinant DNA, which is inserted into other cells
6) If the vector is a plasmid, it will be inserted into a bacterium, which can made the protein that it codes for.
Bacteria are grown in a fermenter, where they undergo binary fission. THe fermenter contains ideal conditions, like plenty of oxygen and some sort of food
Benfits
When used for crops, the yield can be increased
In medicine, treatment can be produced relatively easily and cheaply in large quantities
Risks
Hard to predict what effect modifying its genome will have on the organism
GM crops may affect the food chain
Pose a selection pressure, which could lead to increased resistance in other species, creating super weeds
Might reduce biodiversit