The biosphere forms a thin crust of living organism on the surface of the earth. It consists of variety of organisms. The existence and well being of living-organisms depend on a system of complex interaction within and best over the components of environment. It is this interaction which satisfies all needs of living organisms.

The complex system in which interaction between the different components of environment occurs is referred to an ecosystem. The word ecosystem was introduced by A.G. Tansley in 1935. Some other terms are also used for ecosystem, which include biocoenosis by Karl Mobiuss in 1877, holocoen by Friederich, in 1930, biosystem by Thienemann in 1939 etc.

The word ‘eco’ means environment. The theme of ecosystem concept is that at any place where an organism live, there is a continuous interaction between the living and non-living components i.e., plants, animals and their environment.

The interaction between living and non­living components of an ecosystem constitutes input, transfer, storage and output of energy essential materials through the system. Each of these processes is energy dependent. The ecosystem is a system that is self regulatory.

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Types of Ecosystem :

An ecosystem can be natural or artificial, temporary or permanent, e.g. a large grassland, a forest, a village, an aquarium or a pond can all be regarded as ecosystems. The various constituent of ecosystem are summarized into following categories:

I. Natural Ecosystem

Such ecosystem operates by themselves without any major interference by man. These are further classified as:

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(A) Terrestrial Ecosystem

Forests, grassland, deserts etc.

(B) Aquatic Ecosystem these are of two types.

(i) Fresh Water Ecosystem – Fresh water ecosystem are of two types:

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(a) Lotic – Running water as springs, streams, river etc.

(b)Lentic – Standing water as lake, pond, ditch etc.

(ii) Marine Ecosystem: Water bodies which may be deep bodies as a ocean or estuary.

II. Artificial Ecosystem

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These are man-made ecosystems, which are artificially maintained by man such as
sugarcane, maize, wheat, rice fields, gardens, orchards, dams, are examples of artificial ecosystems.