Food chains are the sequence of living organisms in a community in which one organism consumes another organism to transfer food energy.$^1$
Food chains are composed of tropic levels. These are the position of an organism within the food chain. OR. The various steps in the food chain at which the transfer of food or energy takes place. For example, T1(grass) → T2(Deer) → T3(Lion).$^1$
Tropic level 1 is called as producer, all subsequent levels are consumers and they rely on the producers.$^1$
It is unidirectional. The energy moves from producer to the consumers.$^1$
When a consumer eats another organism, only about 10% of the energy is transferred. The rest of the 90% is lost to metabolic activity. This limits the number of tropic levels that can exist, only about 3 or 4 tropic levels will be there.$^1$
For example:
T1(1000 Calories) → T2(100 Calories) → T3(10 Calories) → T4(1 Calories).
To understand the relationships between organisms and the energy flow in the food chain.
Due to the nature of the food chain, toxic substances will travel through the food chain. This leads to bioaccumulation and biomagnification.
A food web is the inter-connected food chain operating in an ecosystem which establishes a network of relationships between various species. In a food web, one organism may occupy a position in a more than one food chain. An organism can obtain its food from different sources and in turn may be eaten up by different types of organisms.