Food chain

Food chain is the linear network of links in a food web starting from an autotroph such as grass  and ending with predator like bear or a detrivore like earthworm at its apex. 

A food chain shows how organisms are related to each other by the food they eat. Each level of food chain represents a different trophic level. A food chain starts at trophic level 1 with primary producers such as plants, can move to primary consumer at level 2 and typically finished with secondary or tertiary consumer at levels 3, 4 or 5.

Food chain is of 2 types. They are grazing food chain and detrious food chain.

Grazing food chain start from living plants and goes to grazing herbivores and then to carnivores and predators

Some examples of grazing food chain are:

Detrious food chain start from dead organic matters and goes to decomposers and then to predators. 

A food chain can regulate and maintain the population size. As the living beings are eating and being eaten up each other, the overall population size is controlled. It is also balancing the ecology. All the nutrients are balanced equally.