Energy flow in ecological system 

Ecosystems are open systems, receiving energy and nutrients from outside their boundary.

Energy in Ecosystem 

The main source of energy is the sun(solar energy).

The energy of the sun comes as thermal energy (heat) and radiant energy (light).

Solar radiations with short-wavelength form the UV and X-ray regions and are very high in energy. They are not visible to us and very harmful to living organisms.
Visible light provides most of the energy required for living organisms. Larger wavelengths within the IR range having lower energy
Green plants and some photosynthetic bacteria have the potential to absorb a number of wavelengths from the visible region and fix the solar energy in the form of chemical energy as carbohydrates during photosynthesis.
A portion of the chemical energy is converted to kinetic energy during metabolic activities and yet another portion is stored as potential energy.

All forms of energy are inter-convertible.

Two laws of thermodynamics,
  1. Energy cannot be created or destroyed but can only be changed from one form to another.
  2. All forms of energy will tend to change spontaneously into a more random or less organized form. (a high energy state always tends to change into low energy state)

Flow of energy through ecosystems


All ecosystems on the earth are driven by solar energy. In the ecosystem, the plants capture solar energy during photosynthesis.
A part of organic matter is used for metabolic processes and the remaining portion is stored as carbohydrates. This chemical energy is transferred from plants to animals across the trophic levels of the ecosystem.

       Solar energy       →      Producer        →         Herbivore       →      Carnivore
                                (1st trophic level)        (2nd trophic level)       (3rd trophic level)

Significant features about energy flow,

  • The movement of energy in an ecosystem is unidirectional.
  • A continuous supply of energy should be ensured from outside to the ecosystem.
  • Energy is lost as heat during the transfer of energy from one trophic level to another in the food chain.
  • The net inflow of energy balances the net flow of energy from the ecosystem. (for maintaining dynamic equilibrium state within the ecosystem)