The series of organisms taking part at various biotic levels form a food chain. Food chains describe the feeding relationship between the organisms of an ecosystem. The flow of energy from one species to another at various biotic levels forms a food chain. A food chain always starts with producers.
The successive levels in the food chains of a community are called as trophic levels. From autotrophs the energy goes to the heterotrophs and decomposers. When one form of energy is change to another, some energy is lost to the environment in forms which cannot be used again. Some common food chains are mentioned below.
Plants →Deer→ Lion
Plants →Grasshopper →Frog →Snake→ Hawk
Algae →Small animal →Small fish→ Big fish →Bird
Food chains generally consist of only three or four steps. The loss of energy at each step is so great that very little usable energy remains after four trophic levels. There are generally a greater number of individuals at the lower trophic levels of an ecosystem; the greatest number is of the producers.
The length and complexity of food chains vary greatly. Each organism is generally eaten by two or more other kinds of organisms which in turn are eaten by several other organisms. The relationship can be shown as a series of branching lines called a food web. Food web is a web of cross-linked food chains.
There is a flow of energy in the form of food within an ecosystem. The flow of energy is unidirectional. The energy that is captured by the autotrophs does not revert back to the solar input and the energy which passes to the herbivores does not come back to autotrophs. Also, some harmful chemicals enter our bodies through the food chain. One of the reasons is the use of several pesticides and other chemicals to protect the crops from diseases and pests through which they enter the food chain.
