Ecological Pyramids

• Pyramid of numbers


  • To compare the number of organisms present in each trophic level at a particular time.

  Constructing a pyramid of numbers:

  1. 1 bar for each tropic level; first trophic level at the bottom
  2. Length of the bar represents the number of organisms in each trophic level
  3. Longer bar = higher number (proportional in length; give suitable scale when given grids to plot)
  4. Height of all bars are the same

  
• Pyramid of biomass

  • To compare the dry mass of organisms present in each trophic level at a particular time.

  Constructing a pyramid of biomass:

  1. 1 bar for each tropic level; first trophic level at the bottom
  2. Length of the bar represents the mass of organisms in each trophic level
  3. Longer bar = higher mass (try to be proportional in length)
  4. Height of all bars are the same