Assumptions of The Standard Model
- The state variables of the individual are structural mass and reserve; they have a constant composition (strong homeostasis).
- Food is transformed into reserve, which fuels all other metabolic processes
- The reserve density at birth equals that of the mother at egg formation. Foetuses develop similarly, but receive unrestricted amount of reserve from the mother during development.
- Stage transitions occur if the cumulated investment into maturation exceeds threshold values. These stages typically are: embryo, juvenile and adult.
- Somatic maintenance is proportional to structural body volume, and maturity maintenance to maturity but maturity does not increase in the adult stage. Heating costs for endotherms and osmostic work (for fresh water organsism) are somatic maintenance costs that are proportional to surface area.
- The feeding rate is proportional to the surface area; food handling time and the transformation efficiency from food to reserve are independent of food density.
- The reserves is such that weak homeostasis applies: the chemical composition of the body becomes constant during growth in a constant environment.
- A fixed fraction (called kappa) of mobilized reserve is allocated to somatic maintenance plus growth (soma), the rest on maturity maintenance plus maturation or reproduction.
- Reserve that is allocated to reproduction is first accumulated in a buffer. The rules for converting the buffer to gametes are species-specific (e.g. spawning can be once per season).
- During starvation, individuals always give priority to maintenance. After having used the reproduction buffer, they allow a species-specific amount of shrinking of structure and/or maturity
These assumptions quantify all energy and mass fluxes in an organism (including heat, dioxygen, carbon dioxide, ammonia) and imply rules for the covariation of parameter values across species (body size scaling relationships).
Read more about this topic: Dynamic Energy Budget
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