How does the Energy Flow in an Ecosystem?

In simplest terms, the behaviour of energy in an ecosystem is called energy flow. The flow of energy in the ecosystem is always unidirectional (linear). The energy flow obeys the first and second law of thermodynamics.

Laws of Thermodynamics (Rudolf Clausius and William Thomson)

  • 1st Law: Energy cannot be created or destroyed but can be transformed from one form to another.
  • 2nd Law: When energy is converted into different forms, its capacity to perform useful work diminishes.

To understand the above statements, let us trace the route of energy flow in the ecosystem

  • The various types of biotic components -autotrophs, heterotrophs (discussed in the earlier article)- are intimately interlinked with one another by a mutual interdependence on food energy.
  • The ecosystem derives all the energy, required for its functioning, from the Sun. The green plants then use this solar energy to convert carbon dioxide and water into glucose by the process of photosynthesis. Thus, solar energy gets converted to chemical energy. All organisms are dependent for their food on producers, either directly or indirectly.
  • The food energy flows in the ecosystem through the process of eating and being eaten. Example: The rabbit (herbivore) eats the plants and is being eaten by a fox (carnivore) and the fox is then eaten by a lion (top carnivore). So, you find a unidirectional flow of energy from the sun to producers and then to consumers.

  • In this entire process, the living organisms continuously use up a certain amount of energy to perform bodily functions (respiration, digestion, movement, etc)- and in the process releases heat.
  • Energy is always lost when transferred from one organism to another. At each step up the food chain, only 10% of the energy is passed on to the next level, while approximately 90% of the energy is lost as heat.
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