The Effect of Farming (AQA A Level Biology): Revision Note

Farming practices & energy transfer

• Farming practices can increase production in order to increase food available for human consumption

• This can be achieved by:

  • simplifying food webs

  • reducing respiratory loss

Simplifying food webs

• Farmers can simplify food webs to reduce energy lost to non-human food chains; this can be achieved by removing pests from crops

  • Pests feed on crops, reducing crop biomass and meaning that crop plants need to expend energy on herbivory defences rather than on growth

  • This reduces the NPP of crops and therefore the energy available to humans

• Pests can be removed from crops with the use of, e.g.:

  • chemical pesticides

  • biological pest control

Reducing respiratory loss

• The net production of livestock can be increased by reducing respiratory losses; this maximises the energy available for biomass production

• Respiratory loss can be reduced by, e.g.:

  • restricting movement: keeping animals in pens reduces energy needed for muscle activity

  • keeping animals warm: heated indoor environments reduce energy used for temperature regulation

  • antibiotics: these may be given to healthy animals to prevent infection, reducing energy used by the immune system

• These practices result in higher energy outputs in less time, often at lower cost, but they do raise ethical concerns about animal welfare

Calculating percentage yield

• Modern farming strategies aim to increase the yield of crops or livestock

  • Theoretical yield is the yield that is theoretically possible under ideal conditions

  • Actual yield is the yield that is actually produced

• Percentage yield can be calculated as follows:

% yield = (actual yield ÷ theoretical yield) × 100