• Interaction of biotic and abiotic components results in a physical structure that is characteristic of each type of ecosystem. 
• Identification and description of plant and animal species of an ecosystem gives its species composition.
• Vertical distribution of different species occupying different levels is called stratification. 

The components of the ecosystem are seen to function as a unit: 

• Productivity. 
• Decomposition.
• Energy flow and 
• Nutrient cycle.

Description of pond as an ecosystem:

• The abiotic components include all dissolved inorganic and organic substances and the rich soil deposit at the bottom of the pond. 
• The solar input, cycle of temperature, day length, regulates the rater of function of the entire pond.
• The producer (autotrophic) includes phytoplankton, some algae and the floating, submerged and marginal plants found in edge of pond.
• The consumers are represented by zooplankton, free swimming and bottom dwelling animals.
• The decomposers are the fungi, bacteria especially abundant at the bottom of the pond.

Basic events (in terms of function) in an ecosystem: 

• Conversion of inorganic into organic material (photosynthesis) by producers.
• Consumption of the autotrophs by heterotrophs. 
• Decomposition and mineralization of the dead organic matter to release them back for reuse by the autotrophs.
• There is unidirectional flow of energy towards the higher trophic levels and its dissipation and loss as heat to the environment.