biomass

• Biomass is the total mass of living material in a given area at a given time. 
• Biomass is measured in grams per square meter or grams per cubic meter for volume. 
• Dry mass overcomes the problem of variable amounts of water in organisms. 
• Measuring dry mass requires the organisms to be dead. 
• Calorimetry is an estimate of the energy store in dry mass:

  • Weigh sample 
  • Burn in pure oxygen in a sealed container 
  • Water surrounding the bomb increases in temperature 
  • Specific heat capacity can be used to calculate energy released from dry mass 
  • Units are KJ kg-1 
• Not all the suns energy is converted to chemical energy in the plant. 90% is reflected back to space and not all of the wavelengths are absorbed. 1-3% of the suns energy is converted to organic matter. 
• Plants convert energy into organic matter - gross primary production
• 20-50% of organic molecules are used immediately in respiration and the rest is stored as biomass - net primary production. 
• Not all chemical energy in a plant is transferred for growth. 10% of the stored food is used by primary consumers for growth. Secondary consumers transfer 20% of the energy available from their prey. 
• Some of the organisms isn't eaten or digested. 
• Net production of consumer is calculated by: N=I-(F+R)

  • N = net production 
  • I = chemical energy store of ingested food 
  • F = energy lost in faeces and urine 
  • R = respiratory losses