Sun is considered as the ultimate source of energy. Solar radiations from sun passes through the atmosphere and are absorbed by the Earth’s surface. These radiations help to maintain the ecosystem as they:

1. Carry out the process of photosynthesis.

2. Maintain the Earth’s temperature for the survival of living organisms.

Few solar radiations are reflected by the Earth’s surface. So, only 2-10% of solar energy is captured by producers. This energy is used by the plant for the production of the biomass. This is called primary production.

Unidirectional flow of energy takes place from the sun to producers and then to consumers. When the plants are consumed by the herbivores, only 10% of the stored energy is transferred to herbivores. The remaining 90 % of this energy is utilized by plants for its own processes which includes respiration, growth, and reproduction.

Similarly, to the next tropic level i.e. carnivores, only 10% of the energy is transferred. This law is termed as ten percent law of energy flow.