Old exam question OCR

Fertilisers:

• Run-off from fields
• causes algal blooms
• Decreased levels of photosynthesis 
• Increased decomposition
• Oxygen levels reduced by aerobic bacteria
• organisms die due to lack of oxygen for respiration
• Increased growth of some plant species
• elimination of other species

Herbicides:

• Blows off fields
• Kill non-target species 
• Can blow into hedgerows
• Ashed into water
• Effects food chains

Prey populatin increases when theres fer imiting factors

Provides food for predator

Predator pop increases after a time lag

Prey eaten by predator

Both decline

Cycle repeated

Prey pop is at greater levels

Put line from shore to dune slack

Use suitable sized quadrat eg 25cm^2

At specific intervals

Use key to identify species

Record organism abundance

Record bare ground

Insecticides:

harmful to other organisms

Disrupts food chains

Bioaccumilates

Damages top carnivores

Pests can build up resistance

Residues can be in food

Run off causes pollution

Difficult maintaining temp

Difficult maintaining pH

Faoming

Blocking of inlet/outlet tubes

Difficulties mixing

Contamination

Conditions need to be constantly monitored

Nutrient requirement may change

Higher yield

Disease resistant

Flood resistant

Drought resistant

Improved shelf-life of product

Improved nutrient value eg goldenrice

Herbicide resistance