trophic levels in an ecosystem

• what does a food chain show

  it describes the feeding relationships between organisms and the resultant stages of biomass transfer
• what are tropic levels 


  the stages in a food chain
• how are trophic levels represented

  trophic levels are represented by numbers starting from 1.after 1 trophic levels are numbered according to far along the organism is in the food chain
• what is trophic level 1

  plants and algae which make their own food (through photosynthesis) - called producers
• what is trophic level 2


  herbivores which eat producers called primary consumers
• what is trophic level 3

  carnivores that eat herbivores called secondary consumers
• what is trophic level 4

  carnivores that eat other carnivores called tertiary consumers
• what is an apex predator


  a carnivore with no predators
• how do decomposers break down dead matter


  decomposers release enzymes which catalyse the breakdown of dead material into smaller molecules. soluble small food molecules then diffuse into the microorganisms
• what is biomass 


  the dry mass of all the living organisms in an area
• why is dry mass used for biomass

  because the wet mass varies as the volume of water in the organism varies
• how do you calculate the efficiency of biomass transfer

  efficiency= ( energy transferred/ total energy available)x 100
• what percentage of the incident energy from light for photosynthesis do producers transfer

  1%
• what percentage of the biomass from one trophic level is transferred to the level above it in feeding

  approximately 10%
• why are biomass transfers not 100% efficient

  energy is lost through:

  • egestion (removal of faeces)
  • excretion (removal of waste products)
  • respiration (loss of carbon dioxide and water) in which large amounts of glucose are used
  • the production of inedible bones and shells
• how does the efficiency of biomass transfers affect the number of trophic levels in a biomass pyramid

  the less efficient the transfers the fewer trophic levels and the fewer organisms in higher trophic levels
• what is a biomass pyramid

  a pyramid that shows the total dry mass of organisms at each trophic level

  trophic level 1 is is at the bottom of the pyramid
• what is a pyramid of numbers

  a pyramid of numbers shows the number of organisms at each tropic level
• identify the producer in this pyramid of biomass

  D is the producer
• why is this pyramid of numbers not pyramid shaped

  pyramids of numbers don't take size and mass of organisms into account