Question

a)Energy flow in a food chain is unidirectional. Justify.
b)How do pesticides enter the food chain and subsequently get into the human body?Explain

Answer 1

a) Producers convert solar energy into chemical energy in the form of organic compounds. The primary consumers derive nutrients from the producers. Therefore, energy passes to the next trophic level from the producers. The process continues from one trophic level to another. The energy that is captured by the autotrophes passes to the consumers and decomposers and it never goes back. So flow of energy is unidirectional as it goes in one direction.

b) A large number of pesticides and chemicals are used to protect crops from several pests and diseases. These pesticides reach the soil because of rain or sprinkling of water on crops and are absorbed by plants along with water and minerals from the soil.

Due to rain, these chemicals enter the water sources and bodies of aquatic plants and animals. This is how these chemicals enter the food chain.

Since these chemicals cannot decompose, they accumulate continuously at each trophic level. As the food chain proceeds, concentrations of the pesticides also increase. When human beings depends on the herbivores or other animals(secondary consumers) then the pesticides enter the human bodies.