Ecosystem is defined as an functional unit of nature. Where living organisms interact with each other and with their surrounding physical environment. The word ecosystem was coined by Sir AG Tansley (1935). The size of any ecosystem various greatly from a small pond to a large forest or a sea.
Ecosystem can be classified into two main types:
- Terrestrial Ecosystem : Example forest, grassland, desert etc.
- Aquatic ecosystem: For example pond, lake, river, wet land, estuary etc.
There are some man made ecosystem e.g., Fish aquarium.
Structure of Ecosystem: Each and every ecosystem consists of biotic (living component of the ecosystem like autotrophs, herbivores and cornivores and abiotic components non living component of the ecosystem like soil, air etc. and their interactions with each other result in a physical structure, that is the characteristic for each type of ecosystem. Identification and enumeration of plant and animal species of an ecosystem gives its species composition vertical distribution of different species occupying different levels is called stratification. For example, trees occupy top vertical starta or layer of a forest, shrubs the second and herbs and grasses occupy the bottom layer. The other main functional components of an ecosystem are
- Productivity
- Decomposition
- Energy flow
- Nutrient lycling.
In an ecosystem the transfer of food energy taken place from one organism to another organism, this transfer of food making a sequence of events in unidirectional way is called food chain. The many interconnected food chains together forms food web. The specific position occupied by an organism in a food chain in an ecosystem is called trophic level. There are many trophic levels in ecosystem like:
- producer (Ist trophic level)
- Herbivores (IInd trophic level)
- Carnivore (IIIrd trophic level)
- Top carnivore (IVth trophic level)
Diagrammatic representation of trophic levels in an ecosystem is given below:
