Abird in the grassland

How does energy flow through an ecosystem?


Energy is the basis of the whole biosphere.

Both the living beings and the non-livings contain energy. That energy is hidden in between atoms and molecules.

As per the First Law of Thermodynamics “Energy can neither be created nor can it be destroyed”. It can only be destroyed from one form to the other.

Sun is the only source of energy in the biosphere. Every living being can get its share of energy through food only. Thus, energy is directly or indirectly obtained from green plants.

Only green plants are able to utilize the energy of sun. They absorb solar energy during the process of Photosynthesis and convert this energy into chemical energy which is retained in the form of bond energy between atoms and molecules. Since only plants can utilize and transform the solar energy in the ecosystem they are called as Transducers.

Only 1% of the solar energy can be utilized by green plants.

This energy gets stored between molecules of food they synthesize. Some part of this energy is used up in the metabolic processes of plants. The remaining energy goes to consumers when they feed on plants.

Consumers too utilize some energy in their metabolic processes. Under these conditions some energy escapes away in the form of their body heat and some energy is wasted through excretory matter from their bodies. The rest of the energy goes into the atmosphere when top consumer dies and its body is decomposed. Now we can conclude that –

(i) Energy flows in the acyclic manner in the ecosystem.

(2) Some energy is wasted at each trophic level of the food-chain

Lindeman (1942) reported that the energy available in each step of the food-chain remains 10% of the energy available at the earlier step. It means if a vegetarian animal consumes 100 kg of grass the energy that it can use will be equal to the energy contained in 10 kg of grass only. This is called as Lindeman’s 10% Law.

Loss of Energy in the Food –Chain

From Lindeman’s law it is clear that only 10% of energy is utilized at each trophic level and rest 90% goes off. This flow of energy can briefly be expressed as below –

(i) About 1000J radiant energy comes to the earth from the sun. Out of this, only 10% of the total energy is used up by green plants in the process of Photosynthesis. Remaining 990J of energy escapes away into the atmosphere. 10J of energy is stored in the form of chemical energy in starch and sugars.

(ii) The energy stored by plants reaches into the body of the Primary Consumer. Some of the energy that goes into the bodies of consumers is utilized in their metabolic processes.

(iii) The remaining energy of the bodies of primary consumers reaches into the bodies of the Secondary Consumers. There too some energy is used in the metabolic processes of their bodies. Thus, every consumer uses some of the energy it gets from the earlier consumer. In this way, every living being consumes some energy. Some energy is lost into atmosphere from the bodies of living beings. This energy is called as community heat.

(iv)When dead bodies of consumers are decomposed or burnt the energy contained in their bodies is liberated into atmosphere. Thus only 10% of the total energy is utilized and 90% energy is wasted away. The earth is an open system for energy but for substances it is a closed system.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.