biomass transfer through an ecosystem

• Trophic levels

  = Stage in a food chain

  1. Producer= convert light energy into chemical energy by photosynthesis.
  2. All consumers= organisms that obtain energy by feeding on other organisms.
  3. Decomposers= break down dead organisms releasing nutrients back into the ecosystem.
• Energy lost in trophic levels

  = Rarely more than 4 trophic levels as there is not sufficient biomass and stored energy left to support any further organisms.

  • Energy is lost by= movement, respiration, not all the organism is eaten or some is indigestible, lost in urine or faeces, growth. 90% lost
• Biomass

  = The mass of living material present in a particular place or in organisms.

  • To calculate biomass at each trophic level= multiply the biomass in each organism by the total number of organisms in that trophic level. (Presented in a pyramid of biomass)
  • You must calculate the dry mass by removing water content because there is varying amounts of water in different organisms. Organims must be killed so they can dried.
• Biomass efficiency

  Biomass in each trophic level is lower than the trophic level below.

  • Because biomass consists of all cells and tissues, carbon compounds in an organism.
  • When animals eat only a small proportion of food they ingest is converted into new tissue.
• Ecological efficiency

  = Efficiency which biomass or energy transferred from one trophic level to the next.

  • Efficiency= energy after transfer/ energy before transfer X100
• Efficiency at producer level

  = Producers only convert 1-3% of sunlight they receive into chemical energy because:

  • Not all solar energy available is used for photosynthesis, 90% is reflected
  • Water availability limits photosynthesis
  • Some energy is lost for photosynthetic reactions
  • Gross production= total solar energy plants convert into organic matter. Plants use 20-50% of energy for respiration, remaining energy is converted into biomass.
  • Net production= energy available to the next trophic level. Net production= gross production- respiratory losses
• Efficiency at consumer levels 


  = Consumers at each trophic level convert 10% of the biomass in their food to their own organic tissue, because:

  • not all of the biomass of an organism is eaten.
  • Some energy is transferred to the environment as metabolic heat as a result of movement and respiration.
  • Some parts of an organism are eaten but are indigestible.
  • Some energy is lost from the animal in excretory materials.
  • Only around 0.001% of the total energy originally present in the incident sunlight is embodied in a tertiary consumer.