Question

The flow of energy is always _______________ in food chains.

Answer 1

Hint:In an ecosystem different organisms from different levels live. These depend on each other for energy accepting plants.
To complete the requirement of energy or food the order of eaten and being eaten continues in the ecosystem and due to these relations among organisms a chain is made that is called a food chain.

Complete answer:
In an ecosystem, organisms are majorly divided into four groups that are producers, herbivores, carnivores, omnivores, and decomposers.
Using solar energy green plants synthesize food. Only plants are able to convert solar energy into chemical energy. So all other organisms depend on green plants for energy directly or indirectly.
Herbivores directly depend on plants for energy requirements. Like cows, grasshoppers, mice, etc.
Carnivores depend on herbivores for food. Like a mouse is eaten by a cat.
When these animals are dead their body is decomposed and it becomes the source of energy for decomposers. Most decomposers are microbes like bacteria and fungi.
So in this way energy produced by green pants is given to other animals. So the flow of energy is always from plants to heterotrophic. Energy cannot be given to plants by any other source except sunlight.

Hence the energy flow is always unidirectional.

Note: For understanding the transfer of energy we can use the rules of thermodynamics- law of conservation, the law of entropy, etc. As energy cannot be given to plants by any other source except sunlight chlorophyll-containing organisms are the only one that is able to utilize sunlight.