13.2 - Energy transfer + productivity

• What’s gross primary production (GPP) ?

  The chemical energy store in plant biomass, in a given area or volume
• What’s the net primary production (NPP) ?

  The chemical energy store in plant biomass after respiratory losses to the environment have been taken into account
• What’s the equation for NPP ?

  $NPP\ =$$\ GPP-R$
• 4 reasons why light that hits the leaf may not be used in photosynthesis ?

  • Lost as heat
  • Reflected from leaf surface
  • Light transmitted through leaf and doesn’t hit chlorophyll
  • Not all wavelengths are absorbed by chlorophyll
• What is the NPP used for ?

  Plant growth and reproduction, by other trophic levels like herbivores and decomposers
• 4 reasons why a low % of energy is transferred between each trophic level ?

  • Some parts of the organism aren’t consumed
  • Some parts are consumed but not digested so are lost in faeces
  • Some energy lost in excretory materials, eg urine
  • Some energy lost as heat from respiration and lost to environment
• What’s the equation for the net production of consumers (N) and what does each letter stand for ?

  • N = I - (F-R)
  • I - Chemical energy in ingested food
  • F - Chemical energy lost in faeces and urine
  • R - Respiratory losses to the environment
• What’s primary production measured in ?

  Biomass in a given area in a given time eg kJ per m per year