The flow of energy is unidirectional. The flow of materials is cyclic. Energy enters a food chain through producers and transfer of energy takes place from producers to decomposers through the food chain on the basis of ten percent energy rule, and is unidirectional.

The flow of materials takes place in a cyclic manner. Materials like water, carbon dioxide and nitrogen are taken up by plants to make food. This food passes from producers to herbivores and carnivores. After the death of animals, these materials are returned back to the soil from where they were taken. The materials hence are re-used for growth of new plants. Hence, flow of nutrients is cyclic in food chain.