Pyramid Models

13.6 Pyramid Models

Key Concept

• Pyramids model the distribution of energy and matter in an ecosystem.

Energy Pyramid

• An energy pyramid illustrates the distribution of energy among trophic levels.
• Energy pyramids compare energy used by producers and other organisms on trophic levels.
• Between each tier of an energy pyramid, up to 90 percent of the energy is lost into the atmosphere as heat.
• Only 10 percent of the energy at each tier is transferred from one trophic level to the next.

Biomass Pyramid

• Other pyramid models illustrate an ecosystem’s biomass and distribution of organisms.
• Biomass is a measure of the total dry mass of organisms in a given area.
• Example of biomass distribution:
  • Producers: $2000 \frac{g}{m^2}$
  • Primary Consumers: $675 \frac{g}{m^2}$
  • Secondary Consumers: $150 \frac{g}{m^2}$
  • Tertiary Consumers: $75 \frac{g}{m^2}$

Pyramid of Numbers

• A pyramid of numbers shows the number of individual organisms at each trophic level in an ecosystem.
• Example of number of organisms:
  • Producers: 5,000,000
  • Primary Consumers: 500,000
  • Secondary Consumers: 5,000
  • Tertiary Consumers: 5
• A vast number of producers are required to support even a few top-level consumers.