Tao Hierarchical levels

Systems, intended as analysis or synthesis of congruent elements and relationships/processes between them, are to be considered as classes/logical sets of the elements.

A key feature of any non-trivial system is the description of levels of analysis/description or synthesis/design of the system:

In this vision the system is seen as the set of classes of elements more general self-contained.
A classic description of levels of the system of life on our planet is, for example:

In real systems, existing into physical matter, level 0 is always the physical, and contains several sublevels based on the models of elementary particles and atoms.
The upper level 1 is that concerning the chemical molecular aggregates of atoms.
Level 2 is composed of aggregates of molecules to cells and cell aggregates to compose tissues and organs.
Level 3 is a set of interacting bodies and related physiologically to produce multicellular living organisms.
Once living organisms are produced there will be an interaction between them, which is the level 4, the social.

Finally, the highest level is represented by all living organisms with their environment, and that is the one of ecosystem.
In the case of artificial systems the classical example is the one of two-level physical/hardware and application/software, in turn containing many sublevels each.

A more complete representation of the various physical systems and their representational systems is:

Hierarchy of Some Systems and Domains of Knowledge
Graphics created by Marshall Clemens, NECSI