Systems, networks and circuits

Abstract

Just as we are often interested in events that are composed of many elementary (simple) events, in biology the objects under scrutiny are vastly complex objects composed of many individual molecules (the molecule is probably the most appropriate level of course graining for the systems we are dealing with). Since these components are connected together, they constitute a system. The essence of a system is that it cannot be usefully decomposed into its constituent parts. More formally, following R.L. Ackoff we can assert that two or more objects (which may be entities or activities etc.) constitute a system if the following four conditions are satisfied:

• 1. One can talk meaningfully of the behaviour of the whole of which they are the only parts;

• 2. The behaviour of each part can affect the behaviour of the whole;

• 3. The way each part behaves and the way its behaviour affects the whole depends on the behaviour of at least one other part;

• 4. No matter how one subgroups the parts, the behaviour of each subgroup will affect the whole and depends on the behaviour of at least one other subgroup.