Agricultural ecosystems

• Made up of domesticated animals/plants
• Make food for humans
• Energy is usually lost as humans are 3rd-4th trophic level
• Eradicate other species
• Considerable energy losses must be prevented
• Ensure as much energy as possible is channelled into human food chains
• Away from other food chains
• Increases productivity of food chain

• Rate at which something is produced
• Producers convert light energy into chemical energy
• Rate at which this is absorbed/digested is GROSS PRODUCTIVITY
• 20% energy used in respiration of plant
• Remainder is NET PRODUCTIVITY
• Net productivity= gross productivity(kJm  year  )x respiratory losses
• Net productivity is affected by:
  • Efficiency of crop at carrying out photosynthesis
  • Area of ground covered by crop leaves

Natural Ecosystems  Agricultural Ecosystems

• No additional energy input- only solar energy
• Lower productivity
• More species diversity
• More genetic diversity
• Natural recycling of nutrients
• Populations are controlled by natural means (competition and climate)
• Natural climax community
• Solar energy+Fossil fuels+labour= Additional enrgy input
• Higher productivity
• Less species diversity
• Less genetic diversity
• Limited natural recycling of nutrients- supplemented by fertilisers
• Populations are controlled by use of pesticides as well as natural means
• Prevented from reaching natural climax