Food chain: We know that it is the green plants which manufacture their ownfood by using the solar energy. As the green plants can prepare their own food, they are autotrophic. Green plants in the presence of sun light react with the inorganic substances (CO2 and water) and make their own food. The plant's body preserves the solar energy in the form of potential energy. Of the food manufactured by the plants, only small portion is used for its own requirement while the major portion is stored in its body. The herbivorous animals eat this stored food and the carnivorous animals eat these herbivorous animals. They are consumers. The decomposers (bacteria, fungus) use plants, herbivorous, carnivorous animals etc. as food and transforms those into humus. From inorganic components of soil the green plants again produce their food with the help of solar energy. It is now clearly understood that starting with plants, through various types of animals and decomposers, step by step, the food substances are transferred from one to another and finally return to the green plants. This cyclic transfer of food and the relation of food and its consumer are known as the food chain.
Depending on producer and different levels of consumers some examples of food chain are given below:
From the examples given above, we can understand that how the food material forms consumers of different levels of the food chain based on producers. In one food chain there may be one producer and three to four consumers.Generally the final consumer is not eaten by any other animal. His death occurs due to disease, normal or abnormal causes.
In an eco-system there maybe different types of food chains. Usually two types of food chain are found in nature.
1. Grazing food chain or Predator food chain.
2. Saprophytic food chain or Detritus food chain.
1. Grazing or Predator food chain: The food chain starts from the greenplants, goes to grazing herbivores and gradually moves from the smaller carnivores to the bigger. It is known as predator grazing food chain. e.g. deer eats grass, tiger eats the deer (this is a predator grazing food chain).
2. Saprophytic or Detritus food chain: Different micro-organisms or fungussplits up dead body of plants and animals into organic components. The splitting organisms are decomposers. The splited organic compounds are taken as food by some animals and then the decomposers are converted into foods of other animals. Such as, Dead organism-Decomposer-Amoeba -Hydra Zooplankton-Fish.