0 — CLASSIFICATION BOUNDARY
Before classifying energy use, define what living system is being classified and during what state.
Operational definition
Layer type: Scope-defining met layer Governs: Item 0
Formal definition
The Classification Boundary identifies the living system, organizational scale, spatial boundary, temporal interval, and physiological state to which every subsequent energetic statement applies.
It establishes what will count as:
- inside versus outside;
- input versus output;
- reserve versus environmental resource;
- autonomous metabolism versus partner subsidy;
- individual production versus transfer;
- survival versus death;
- retained biomass versus exported biomass.
Governing question
Exactly what system are we classifying, and during what interval or state?
Possible focal systems include:
- an organelle;
- a cell;
- a multicellular organism;
- a colony;
- a host–microbiome system;
- a symbiotic consortium;
- a population;
- an ecosystem;
- the biosphere.
Inclusion rule
A descriptor belongs in this layer when changing it would alter the meaning of later energetic measurements or classifications even if the underlying biological events remained unchanged.
For example, glucose transferred from gut microbes to an animal is:
- an output, if the microbial community is the focal system;
- an input, if the animal is the focal system;
- an internal transfer, if the host–microbiome consortium is the focal system.
Exclusion rule
This layer does not identify:
- the environmental conditions;
- the energy source;
- the acquisition mechanism;
- the metabolic pathway;
- the ecological role.
It only defines the reference frame within which those things are evaluated.
Operational output
Every classification should begin with a boundary statement such as:
Focal system: mature individual organism
Boundary: organismal body surface and digestive absorptive boundary
Interval: 24 hours
State: active, nonreproductive, postabsorptive
Without this layer, apparently conflicting energetic claims may simply be measurements made at different scales.
0. Unit of energetic analysis
0.1 Subcellular unit
- chloroplast
- mitochondrion
- hydrogenosome
- membrane bioenergetic system
- other organelle or intracellular compartment
0.2 Cell
- free-living prokaryotic cell
- free-living unicellular eukaryote
- differentiated cell within a multicellular organism
- dormant cell
- reproductive cell
0.3 Organism
- unicellular organism
- multicellular organism
- modular organism
- clonal organism
0.4 Collective biological system
- colony
- biofilm
- social group
- superorganism
- host–microbiome system
- symbiotic consortium
- syntrophic community
0.5 Ecological system
- population
- community
- food web
- ecosystem
- biome
- biosphere
The same entity can receive different energetic classifications at different scales. A human cell, a human organism, and the human–microbiome consortium are overlapping but energetically nonidentical systems.
0.6 Temporal state
Every energetic profile must include a time-state qualifier:
- active
- growing
- maintaining
- storing
- reproducing
- fasting
- dormant
- recovering
- senescent
- dead
- decomposing