Ecology: Ecological Pyramids

What is an Ecological Pyramid?

• Ecological Pyramid is a graphical depiction which is meant to illustrate the relationship between different living organisms at different trophic levels in an ecosystem
• Each of the bars that make up the pyramid represents a different trophic level, and their order, which is based on who eats whom, represents the flow of energy.

Types

1. Pyramid of Numbers
   • This represents the total numbers of individuals (population) present in each trophic level. The term “pyramid of numbers” was first coined by Elton in 1972.
   • Classify into
     • Upright Pyramid
       • The numbers of organisms mostly reduce from bottom to top.
       • It usually occurs in pond and grassland ecosystems where plants occupy the base of the pyramid.

• • • Inverted
      •  It can closely be observed in the tree ecosystem, where trees are the producers and insects are the consumers.
      • The producers in the tree ecosystem are the least in numbers, and the population of consumers gradually increases at each trophic level.

1. • • Spindle-Shaped Pyramid of Number
       • Spindle-shaped Pyramid of Number is known as a partially upright pyramid, because there is neither sequential increase nor decrease in the number of individuals in an ecosystem.
       • This type of pyramid of numbers is found in the forest ecosystem without parasites.
2. Pyramid of Biomass
   • Biomass is the amount per unit area product of the living material existing in an individual or a number of individuals at a particular trophic level.
   • This pyramid indicates the total mass of organisms in a particular trophic level.
   • The pyramid is usually larger at the bottom but as it goes up it reduces in size and becomes smaller.
   • Classify into
     • Inverted
       • The aquatic ecosystem is characterised by an inverted pyramid because phytoplankton producers are located at the base of the pyramid, while consumers have larger biomass and they are located at the top
     • Upright
       • Upright pyramid example is the terrestrial ecosystem. It has a large base mainly consisting of primary consumers, the smaller trophic levels are located at the top.
3. Pyramid of Energy
   • An energy pyramid represents the amount of energy at each trophic level and loss of energy at each transfer to another trophic level.
   • It is always upright.