Pyramids of Biomass

• Pyramids of Biomass


  A handy way of illustrating the amount of biomass at each level in a food chain
• There's less energy and less biomass every time you move up a stage (trophic level) in a food chain
• There are usually fewer organisms every time you move up a level too
• Producers<|>Primary consumers<|>Secondary consumer


  • 5000 dandelions... feed... 100 rabbits... which feed... 1 fox
• This isn't always true though - for example, if 500 fleas are feeding on the fox, the number of organisms has increased as you move up to that stage in the food chain
• A better way to look at the food chain is often to think about biomass instead of number of organisms
• Pyramids of Biomass


  • Each bar shows the relative mass of living material at a trophic level
  • Biomass pyramids are practically always pyramid-shaped
• The big bar along the bottom of the pyramid shows trophic level 1, which always represents the producer (e.g. plants or algae)
• The next bar will be the primary consumer (the animal that eats the producer), then the secondary consumer (the animal that eats the primary consumer) and so on up the food chain
• Pyramids of Biomass


  Give you information about food chains
• Even if you know nothing about the natural world, you're probably aware that a tree is quite a bit bigger than an aphid
• Biomass and energy are still decreasing as you go up the levels, it's just that one tree can have a very big biomass, and can fix a lot of the Sun's energy using all those leaves
• Drawing Pyramids of Biomass

  1. Use actual numbers to draw bars of the correct scale

  2. Order of organisms must follow the order of the food chain

  3. Each bar must be labelled