Pyramids of biomass

• a pyramid of biomass shows the biomass at each trophic level, rather than the population.
• Other than a few unique examples, the pyramid goes down from one trophic level to next, just like the amount of energy, so the bars always get narrower towards the top.
• I can ne difficult to get valid data for a pyramid of biomass because:

  -measuring dry biomass means that all the water has to be removed from the organisms

  -an organism may belong to more than one trophic level, so it cannot easily be represented by one bar.
• in a food chain only around 10 percent of the energy is passed on to the next trophic level
• the rest of the energy passes out f the food chain in a number of ways:

  -respiration results in thermal energy transfer to the environment. the more active an organism id the higher its respiratory loss will be.

  -not all of the organisms is consumed

  -some parts of an organisms cannot be digested and are passed out of the body as feces (egestion)

  -waste products are lost during excretion.
• less energy is transferred at each level of the food chain so the biomass gets smaller. as a result, there are usually fewer that five trophic levels in food chains.
• the percentage efficiency of energy transfer between trophic levels can be calculated using:

  (biomass available after the transfer/biomass available before the transfer) *100
• Trophic levels describe the position of an organism in a food web, chain or pyramid.