The energy flow in the ecosystem is one of the major factors that support the survival of such a great number of organisms. To study the complete energy chain, we first need to know the source of the energy. For almost all organisms on earth, the primary source of energy is solar energy. It is still amusing to find that we receive less than 50 percent 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. Most of the sun’s radiation that falls on the earth is usually reflected back into space by the earth’s atmosphere. The effective radiation that we are talking about is called photosynthetically active radiation (PAR). Of the 50 percent of the energy that we receive as PAR, only 2-10 percent of it is used by plants for the process of photosynthesis. Thus, this 2-10% of the 50% supports the entire world as plants are the producers and all the other organisms are either directly or indirectly dependent on them for their survival.
The energy flow takes place via food chain and food web. Thus, the plants being the producers harness the energy from the sun in the process of photosynthesis. This energy is passed on to the primary consumers in the food chain, followed by the secondary consumers and finally to the tertiary consumers. 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 to the atmosphere. This can be shown in the following figure which represents an energy pyramid.
There are basically two 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.
- 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.
In nature, we mostly observe food web as there are many organisms which are omnivores. As a result, they occupy multiple trophic levels.
This was a brief idea about the flow of energy in the ecosystem. For more information on the ecosystem, visit Byju’s.