Define food chain. Explain why is the flow of energy in an ecosystem unidirectional.

                                                     (OR)

(a)  Why should National Parks be permitted to continue existing in their natural state?

(b)  Why is material reuse preferable compared to recycling?

A food chain explains which organism eats another organism in the environment. The food chain is a linear sequence of organisms where nutrients and energy is transferred from one organism to the other, and it occurs when one organism consumes another organism.

The energy flow in the ecosystem is unidirectional because the energy lost as heat from the living organisms of a food chain cannot be reused by plants in photosynthesis, and during the transfer of energy through successive trophic levels in an ecosystem, there is a loss of energy all along the path.

                                               (OR)

(a)   To protect animal and bird habitats in their natural state, reduce human intervention, and keep national parks self-sustaining, national parks should be allowed to continue in their pristine state.

(b)  Reusing is better than recycling because it saves the energy of having to dismantle and re-manufacture products. It also reduces waste and pollution because it reduces the need for law materials, saving forest and water supplies.