ENERGY TRANSFER AND PRODUCTIVITY

• WHY DO PLANTS ONLY CONVERT 1-3% OF THE SUN'S AVAILABLE ENERGY INTO ORGANIC MATTER?

  • reflected back by clouds and dust
  • absorbed by atmosphere
  • not all wavelengths absorbed and used for photosynthesis
  • limiting factors (e.g. CO2 concentration) limit photosynthesis rate
• EQUATION FOR NET PRIMARY PRODUCTION?

  NPP = GPP - R
• NPP?

  net primary production

  -> energy available for growth/ reproduction/ next trophic level
• GPP?

  gross primary production

  -> total quantity of chemical energy stored in plant biomass in a given area/ volume
• R?

  respiratory losses
• WHY IS THERE SUCH A LOW ENERGY PERCENTAGE TRANSFERRED BETWEEN TROPHIC LEVELS?

  • some parts of organism not consumed
  • some parts of organism not digested and lost in faeces
  • some energy lost in excretory materials (e.g. urine)
  • loss as heat from respiration to environment
• EQUATION FOR NET PRODUCTION OF CONSUMERS?

  N = I - (F + R)
• N?

  net production of consumers
• I?

  chemical energy store of ingested food
• F?

  energy lost in faeces and urine
• R?

  energy lost in respiration
• HOW TO IMPROVE PRODUCTIVITY IN FARMING PRACTICES?

  1. Factory farming
  2. Selective breeding
  3. Genetic modification
  4. Growth hormone injections
  5. Simplifying food webs (eliminate competition)
• FACTORY FARMING?

  keeping animals in confined spaces like small enclosures, barns or cages

  • movement reduced, less energy in muscle contraction
  • environment kept warm, reduces heat loss
  • controlled feeding (optimum type/ amount with no waste) e.g. high protein food pellets
  • predators excluded