FOOD CHAIN:

•The transfer of food energy from the producers through a series of organisms(herbivores to carnivores to decomposers) with repeated eating and being eaten is known as the food chain.
•The individuals of each group is known as trophic level according to their eating mechanism like producers, herbivores, carnivores and decomposers.

Types of Food Chain:
•The food chains are mainly of 3 types.

(I) Grazing food chain
(II) Detritus food chain
(III) Parasitic food chain

(I) Grazing food chain:
•This type of food chain starts with living green plants and moves to the grazing herbivores and then to the carnivores.

•In aquatic ecosystem zooplankton, in grassland ecosystem grasshopper and in forest ecosystem rabbit is the primary consumer.
•In aquatic ecosystem small fish, in grassland ecosystem frog is the secondary consumer.
•Usually 50% of the Net Primary Production is grazed by the grazers and the remaining 50% goes to the decomposers as dead organic matter.
•Therefore this type of food chain is herbivore based. Hence it is known as Grazing food chain.
•This may be an aquatic food chain or terrestrial food chain.

e.g.: Aquatic food chain:
Phytoplankton -> Zooplankton -> Small fish -> Big fish

e.g.: Terrestrial food chain:
Grass -> Grasshopper -> Frog -> Snake -> Vulture -> Plant -> Rabbit -> Fox -> Lion

(II) Detritus food chain:
•This type of food chain starts from dead organic matter which gets decomposed by the microorganisms. Thus the decaying organic matter goes into the microorganisms and then to the organisms feeding on detritus and predators.

•This system is less dependent on direct solar energy and it mainly depends upon the influx of organic matter produced in another system.
e.g: dead organic matter -> microorganisms -> detritivores -> predators (microorganisms eaters)
•The detritus food chain exists in each and every ecosystem and is most important for the circulation of materials in the ecosystem.

(III) Parasitic food chain:
•A parasitic food chain operates in the same ecosystem where the other two are prevalent.

•In this type of food chain the food energy passes through the host and parasite link.
e.g.: Plants -> Cow -> Tick

Significance of Food Chain:

•The food chain helps to understand the food and feeding relationship and the interaction between organisms in an ecosystem.
•The size of population is determined by the number of trophic levels in the food chain. If the food chain is short, then the wastage of energy is less.
•Food chain must always begins with plants and end with decay.
•It also helps to comprehend the energy flow mechanism and material circulation in ecosystem.
•The movement of toxic substances and the related problems of biomagnification can also be elucidated from the study of food chain.