Thermodynamically, a system is any part of the universe separated from the rest by a well-defined boundary. Likewise, a living organism has a boundary, the skin.
Thermodynamically, systems can be of three types:
There is neither an exchange of energy nor matter with the environment.
There is an exchange of energy but not matter.
There is an exchange of both energy and matter.
Open systems are not in thermodynamic equilibrium but in a dynamic steady state. Living systems are considered to be open.
In case of an eco-system, the boundary is not rigidly defined. The ecological system or eco-system is defined as a system where the biotic community (living organisms) and the non-biotic (non-living organisms) environment function together as one complete unit.
Thus, an eco-system includes both the living organisms and their non-living counterparts, the environment, each influencing the characteristics of the other and both are necessary for the survival and maintenance of life.
An eco-system has both structure and function. The structure tells about the diversity of species, as function involves the flow of energy and cycling of materials through the structural components.
The earth as a whole is thus a vast eco-system and the portion of the earth in which the biotic components, i.e., the living matters are present is called 'biosphere' or 'ecosphere'.
Relative to the volume of the earth, the biosphere is only a very thin surface layer that extends from 11,000 metres below sea level to 15,000 metres above