B2

Pyramids of biomass

• Used to represent feeding relationships 
• Show the dry mass of living material at each stage
  • Can be difficult to weigh as they need to be killed first
• Better way of showing trophic levels
• Each bar shows mass of living material at that stage of the food chain

Trophic level: Different levels in an ecosystem, consisting of organisms sharing the same function in the food chain and the same nutritional relationship to the primal sources of energy.

Pyramids of numbers

• Each bar on the pyramid represents the number of organisms at each stage of the food chain

NOT MASS

• Not always pyramid shaped: one oak tree could feed thousands of caterpillars, so the bottom bar would be smaller then the second bar.