Ecosystem - Notes | Class 12 | Part 1: Ecosystem- Structure and Function


An ecosystem is a functional unit of nature, where living organisms interact each other and with the physical environment.


Types of ecosystems 
  • Terrestrial ecosystem: Forest, grassland, desert etc.
  • Aquatic ecosystem: Pond, lake, wetland, river & estuary.
  • Man-made ecosystem: Crop fields and aquarium.
Entire biosphere is regarded as global ecosystem.

In an ecosystem, biotic and abiotic components interact and function as a unit.

Vertical distribution of different species occupying different levels is called stratification. E.g. in a forest, trees occupy top strata (layer), shrubs the second and herbs & grasses the bottom layers.

Pond (Aquatic ecosystem) 

A pond is a shallow, simple, self-sustainable water body that exhibits all basic components of an ecosystem.
  • Abiotic components: Water and soil deposit.
  • Climatic conditions: Solar input, cycle of temperature, day-length etc.
  • Autotrophic components: Phytoplankton, some algae and the floating, submerged and marginal plants.
  • Consumers (heterotrophs): Zooplankton, free swimming and bottom dwelling forms.
  • Decomposers: Fungi, bacteria and flagellates.
Pond performs all the functions of an ecosystem. E.g.
  • Autotrophs convert inorganic into organic material using solar radiant energy.
  • Heterotrophs consume the autotrophs.
  • Decomposition and mineralization of the dead matter to release them back for reuse by the autotrophs.
4 basic components of functioning of an ecosystem:
  1. Productivity 
  2. Decomposition
  3. Energy flow 
  4. Nutrient cycling 
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