Energy Transfers

• biological mass in an ecosystem at any given time
• presence of varying amounts of water makes measurements unreliable
• must measure dry/carbon mass in small samples
• samples must be small as the samples must be killed
• measured in grams per square meter for flat sample areas (gm-2)
• measured in grams per cubic meter for aquatic environments (gm-3)

• 1 calorie = amount of energy required to raise the temperature of one gram of water by 1•C 
• sample of dry mass is weighed
• sample is burned in pure oxygen in a sealed chamber (bomb)
• burning needs a reactor and ignition source

• is insufficient
• over 90% of the sun's energy is reflected
  • deflected by dust/particles/clouds
  • absorbed by the atmosphere
    
    

• not all wavelengths can be absorbed by leaves
• lightwave (photon) may not be hitting the chlorophyll molecule
• carbon dioxide and other factors limit photosynthesis
• 1-3% of light is fixed by photosynthesis
  • 20-50% is used for respiration
  • remaining is used for biomass

• measured in percentage of energy efficiency
• between trophic levels
• measured per m2 per year
  • Kj m-2 year-1
  • kilojoules per meter-squared per year

• (energy after transfer/energy before transfer) x 100

• measure of energy productivity
• GPP
• total quantity of chemical energy store in biomass
  • in area/volume
• before respiration/other factors

• NPP = GPP - R
• chemical energy in plants' biomass after respiratory losses
• lose energy to the environment
• available to the organism for growth, reproduction, repair of tissues/organs
• available for other organisms

Consumers

• I = chemical energy of ingested food
• only 10% is transferred from plants to primary consumers
• only 20% is transferred from primary to secondary consumers

Energy Loss

• faeces and urine (F)
• respiration and heat (R)
• movement, growth and reproduction (R)
• not eaten/digested (F)

Formula

NPC = I - (F + R)