Subsystems and Functions

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Living Systems Internal Structure
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A living system is made up of a set of functional subsystems, a governance mechanism, various physical organizational units, and an array of components.
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Subsystems define the life functions that must be performed to sustain the living system's internal health and existence in its changing environment.
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Governance monitors the living system's situation, both in the living system's external environment as well as its internal conditions, initiating functional action as-needed for survival and to maintain internal homeostasis.
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Organization Units interpret governance functional directions and collectively translate them into the specialized component actions that are required to fulfill them.
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Components perform the actual specialized work, as prescribed by their roles and current assignments within the organization units.

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Governance has no direct contact with the components. Instead, governance functional strategies, initiatives and directions are played out across the organization units which, in turn, translate them into specific physical work assignments for the components to perform.
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System View versus Object View
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Living System as a System Entity: This is an "external" conceptual perspective that focuses on the living system's existence and how it must function to sustain itself. The subsystems structure defines the living system's functions within this conceptual frame of reference.
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Living System as a Physical Aggregate Object: This is an "internal" physical perspective that focuses on the entity's organization unit structure and component actions. The living system is seen as a complex aggregate object whose functional properties emerge from the nature of its components and the constraints that have been imposed on their behavior. The aggregate object's internal structure of organization units defines these constraints, allocates components with the necessary specialization, and orchestrates their behavior.
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At this time, the discussion will examine subsystems and functions of living systems from a conceptual system view, leaving the more detailed physical view for later.
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Life Functions
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In a living system, governance operates through intermediate organization units to harness its components to perform the functions that are necessary for life. Within the three-level living system hierarchy, all actions performed by components are, by definition, related to life functions.
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It is relatively easy to give examples of life functions for a particular level and kind of living system. For example, in an organism, its organs ingest and process food, distribute the results where needed in the body, gather and extrude of waste material, etc. Without an architectural schema, it would be very difficult to provide a complete categorization of all such functions in a generalized way that applies to all living systems. The discovery that all living systems have the same architectural structure provides that schema.
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The list of standardized subsystem functions shown in following table has been adapted from the original work on living systems by James Grier Miller. Although subject to further refinement, it is presented here to illustrate what a comprehensive list of the functionality necessary for life looks like. For each subsystem function, three examples of participating organization units are shown, one each from the cell, organism, and superorganism levels of living system.
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. Living System Life Functions .
Subsystem Function	Purpose	Participating Organization Unit Examples (three levels)
Awareness:	Maintain sensory awareness of external and internal conditions.	membrane, eye, reporting system
Perimeter:	Maintain barrier to protect from environment.	membrane, skin, border patrol
Structure:	Maintain proper relationships among organization units.	cytoskeleton, skeleton, infrastructure
Ingestion:	Bring in material from environment.	membrane vesicle, mouth, entry port
Storage:	Store material within system for later use.	vacuole, skin layer, warehouse
Distribution:	Transport material (matter-energy) within system.	endoplasmic reticulum, artery, shipping company
Conversion:	Transform ingested material into useful form.	chloroplast, stomach, refinery
Production:	Construct needed materials within system.	ribosome, bone marrow, manufacturing company
Extrusion:	Send out material from within system.	membrane vesicle, anus, sewer system
Movement:	Change location of system and/or move its parts.	flagellum, legs, transporter
Defense:	Protect organization units and components from harm.	membrane bacterial toxins, immune system, army
Enforcement:	Police rogue components who fail to follow laws and rules.	lysosome, lymph node, police department
Repair:	Fix structural damage or malfunction.	lysosome, organ's healing mechanism, disaster recovery team
Reproduction:	Create similar offspring.	chromosomes, genitalia, colonization team

Each subsystem shown it this table defines a living system function that must be performed as-needed by the work of specialized component entities. This work is orchestrated by organization units that harness and focus the capabilities of component living systems.
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For example, a human organism is made up of cells that are organized within organs. Each organ is an intermediate structure that marshals the work of its member cells to perform part or all of one or more organism-level functions. Similarly, a cell is made up of biomolecules that are organized within organelles, and a superorganism is made up or organisms that are organized within organizations (non-profit and businesses).
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Point of clarification: Organization units (organizations, organs, organelles) are intermediate structures, and not living systems. When life is perpetuated across generations, the thing being sustained is a living system design, not the organization unit structures that it produces. To perpetuate their designs, superorganisms, organisms, and cells reproduce themselves. Organization units do not reproduce themselves.
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Point of clarification: The Second Law of Thermodynamics (entropy) acts on all physical structures, including the physical embodiments of living systems. It does not, however, constrain the evolution and increasing complexity of living system non-physical designs (this is sometimes thought of as a form of negentropy). These designs are manifested in genetic code, together with its resulting systems and subsystems.

Work and Constraints looks beyond life functions to examine what living systems do, and why they do it.