The components which are involved in the transference of food energy from producers (plants) to the higher consumers (carnivorous animals) in the process of repeated eating and being eaten up is termed as food chain. A food chain is step-wise transfer of energy in the form of food.
In this one type of organism are related to another for food. It forms a chain and always small in size. Food chain is constituted by the combination of mainly three steps i.e. Producer, 1st level of consumers and 2nd level of consumers. The 1st level of consumer includes all the related herbivores and 2nd level of consumer includes omnivores.
PRODUCERS → PRIMARY CONSUMER → SECONDARY CONSUMER → TERTIARY CONSUMER → DECOMPOSER
The food chain cannot have more than five steps. The food-chain starts from the producer (Green plants). The next 2nd step is herbivores. The 3rd step is made by omnivores. The 4th step is made by the carnivores. The 5th step is the bacterial level (decomposers). The dead bodies of plants and animals are decomposed into simple forms by the decomposers i.e. bacteria. These simple forms get mixed with the soil. In this way a food chain can have not more than five steps.
Aquatic Food Chain: The food chain which occurs in aquatic water is called aquatic food chain.
e.g. Algae → Protozoa → Small Insects → Large aquatic Insects → Small fish → Large fish
In the aquatic food chain small algae is producer and zooplankton are herbivores i.e. primary consumer, small fishes are secondary consumer and large fishes are tertiary consumer.
The main function of Aquatic food chain is that:
For the aquatic food chain following amount of energy will available to big fish i.e.
Small Algae → Zooplankton → Small Fish → Big Fish
(10,000 J) (10% of 10,000 J=1000 J) (10% of 1000 J=100 J) (10% of 100 J = 10 J)
Therefore the above calculation shows that the big fish will get only 10 J energy and zooplankton get more energy.
But man is disturbing the food chain and making it short. The shortening of food chain due to man’s activities leads to imbalance in the functioning of an ecosystem and ultimately the biosphere.