Energy Flow in Ecosystem

Energy Flow

The chemical energy of food is the main source of energy required by all living organisms. This energy is transmitted to different trophic levels along the food chain. This energy flow is based on two different laws of thermodynamics:

  • First law of thermodynamics, that states that energy can neither be created nor destroyed, it can only change from one form to another.
  • Second law of thermodynamics, that states that as energy is transferred more and more of it is wasted.

Energy Flow in Ecosystem

The energy flow in the ecosystem is one of the major factors that support the survival of such a great number of organisms. For almost all organisms on earth, the primary source of energy is solar energy. It is amusing to find that we receive less than 50 per cent of the sun’s effective radiation on earth. When we say effective radiation, we mean the radiation, which can be used by plants to carry out photosynthesis.

Also Read: Difference between food web and food chain

energy flow in ecosystem

Most of the sun’s radiation that falls on the earth is usually reflected back into space by the earth’s atmosphere. This effective radiation is termed as the Photosynthetically Active Radiation (PAR).

Overall, we receive about 40 to 50 percent of the energy having Photosynthetically Active Radiation and only around 2-10 percent of it is used by plants for the process of photosynthesis. Thus, this percent of PAR supports the entire world as plants are the producers in the ecosystem and all the other organisms are either directly or indirectly dependent on them for their survival.

The energy flow takes place via the food chain and food web. During the process of energy flow in the ecosystem, plants being the producers absorb sunlight with the help of the chloroplasts and a part of it is transformed into chemical energy in the process of photosynthesis.

This energy is stored in various organic products in the plants and passed on to the primary consumers in the food chain when the herbivores consume (primary consumers) the plants as food. Then conversion of chemical energy stored in plant products into kinetic energy occurs, degradation of energy will occur through its conversion into heat.

Then followed by the secondary consumers. When these herbivores are ingested by carnivores of the first order (secondary consumers) further degradation will occur. Finally, when tertiary consumers consume the carnivores, energy will again be degraded. Thus, the energy flow is unidirectional in nature.

Moreover, in a food chain, the energy flow follows the 10 percent law. According to this law, only 10 percent of energy is transferred from one trophic level to the other; rest is lost into the atmosphere. This is clearly explained in the following figure and is represented as an energy pyramid.

Trophic level

The producers and consumers in the ecosystem can be arranged into different feeding groups and are known as trophic level or the feeding level.

  1. The producers (plants) represent the first trophic level.
  2. Herbivores (primary consumers) present the second trophic level.
  3. Primary carnivores (secondary consumers) represent the third trophic level
  4. Top carnivores (tertiary consumers) represent the last level.

Food Chain

energy flow in ecosystem

There are basically three different types of food chains in the ecosystem, namely –

  • Grazing food chain (GFC) – This is the normal food chain that we observe in which plants are the producers and the energy flows from the producers to the herbivores (primary consumers), then to carnivores (secondary consumers) and so on.
  • Saprophytic or Detritus food chain (DFC) – In this type of food chain, the dead organic matter occupies the lowermost level of the food chain, followed by the decomposers and so on.
  • Parasitic food chain (PFC) – In this type of food chain, large organisms either the producer or the consumer is exploited and therefore the food passes to the smaller organism.

In nature, we mostly observe food web as there are many organisms which are omnivores. As a result, they occupy multiple trophic levels.

Law of Thermodynamics in the Ecosystem

The law of thermodynamics in the ecosystem explains the flow of energy at each trophic level. The first law states that energy is neither created, nor destroyed; it can only be converted from one form to another. This is true in energy flow in the ecocystem.

The second law states that there is loss of energy at each step of energy flow. This law also stands true in ecology as their is progressive decrease in energy at each trophic level.

Also Read: Ecosystem

This was a brief idea about the energy flow in the ecosystem. For more information on energy flow, keep visiting BYJU’S website or download BYJU’S app for further reference.

Frequently Asked Questions


What do you understand by the energy flow?

The energy flow is the amount of energy that moves along the food chain. This energy flow is also known as calorific flow.


Why is the energy flow in ecosystem important?

The energy flow in the ecosystem is important to maintain an ecological balance. The producers synthesise food by the process of photosynthesis. A part of the energy is stored within the plants. The remaining energy is utilised by the plants in their growth and development. This stored energy is transferred to the primary consumers when they feed on the producers. This energy is further passed on to the secondary consumers when they feed on the primary consumers, and so on.


What is the 10 percent law of energy flow?

The 10 percent law of energy flow states that when the energy is passed on from one trophic level to another, only 10 percent of the energy is passed on to the next trophic level.


Green plants occupy the following trophic level in an ecosystem
(a)Complete food chain
(b)First trophic level
(c)Second trophic level
(d)Third trophic level

Answer: (b)First trophic level
Green plants occupy the first trophic level. They are the primary producers, manufacturing their own food through the process of photosynthesis. We depend on producers for nutrition. Herbivores occupy the second trophic level, while the third, fourth, and fifth trophic levels are occupied by carnivores.

The Y shaped energy flow model was given by?

The Y shaped energy flow model was given by H.T. Odum.

What is the single channel energy flow model?

The single channel energy flow model depicts unidirectional flow of energy which shows that at each trophic level their is a progressive decrease in the energy levels.

What is the primary or main source of energy in the ecosystem?

Sun is the primary and main source of energy in the ecosystem


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