Living Systems:

James Miller presents the theory that complex structures which carry out living processes can be identified at seven hierarchical levels...cells, organ, organism, group, organization, society, and supranational system. Each of these levels are open systems composed of subsystems which process inputs, throughputs and outputs of various forms of matter, energy and information. He identifies 19 critical subsystems whose processes are essential for life some of which process matter and energy. Together they make up a living system . The structure and processes of a given subsystem are more complex at a more advanced level than at the less advanced ones. The 19 critical subsystems are:

Those processing both matter and energy and information

Reproducer

Boundary

Those processing matter-energy

Ingester

Distributor

Convertor

Producer

Matter-energy storage

Extruder

Motor

Supporter

Those processing information:

Input transducer

Internal transducer

Channel and net

Decoder

Associator

Memory

Decider

Encoder

Output transducer