Question

"Energy flow in food chains is always unidirectional". Justify this statement. Explain how the pesticides enter a food chain and subsequently get into our body.

 

 

Answer 1

The producers convert solar energy into chemical energy in the form of organic compounds. The primary consumers (herbivores) derive their nutrition from the producers. According to the energy transfer law, only 10% of energy is transferred from one trophic level to the other. So, the energy that is consumed by the producers does not revert back to the Sun and the energy transferred to the herbivores does not come back to the producers. It keeps on moving to the next trophic level in a unidirectional way. Hence, the flow of energy in the food chain is always unidirectional.

A large number of pesticides and chemicals are used to protect the crops from pests and diseases. Some of these chemicals are washed down from the soil and enter the water bodies. From the water bodies, they are taken up by aquatic plants and animals. In this way, these chemicals enter the food chain. As they cannot decompose, they accumulate progressively at each trophic level. This increase in the concentration of harmful chemicals with each step of the food chain is called biomagnification. As human beings occupy the top level in any food chain, these chemicals accumulate in their bodies.