pyramids of biomass

• Pyramids of biomass show the biomass of each tropic level in a food chain.

  • Biomass is the mass of living organisms.
• The bars get smaller as you go up the trophic levels.

  • This means that the total mass of the organisms in each level is decreasing.

  This means that, for example, there would be fewer snakes than rabbits because the snake's bar is smaller than the rabbits.

  • The total mass of snakes is lower than the total mass of rabbits.
• (1) There are 3 main reasons why only 10% of the biomass gets passed on;

  • Organisms don't normally eat every part.

  For example, birds wouldn't eat the snake's skeleton or teeth.
• (2) There are 3 main reasons why only 10% of the biomass gets passed on;

  • The bits that the organism does eat may not be absorbed if they cannot break them down properly.

  For example, the scales of a snake might not be able to be broken down.

  • These bits get egested as faeces.
• (3) There are 3 main reasons why only 10% of the biomass gets passed on;

  • Most of the nutrients the animals absorb are used to release energy through respiration rather than for growth.

  This means the biomass gets released as waste products such as carbon dioxide and urea rather than being stored within the organism forever.

  • Therefore, it doesn't pass on all the biomass that is consumed throughout it's life.
• Efficiency = biomass transferred to the next level ÷ biomass that was available on the previous level

  • Then multiply by 100 to turn it into a percentage.