Possible energetic changes include:
- declining acquisition efficiency
- reduced conversion efficiency
- altered mitochondrial or membrane function
- greater repair burden
- reserve loss
- altered reproductive allocation
Senescence is not reducible to energy failure alone; energetic deterioration is one component of a larger multifactorial process.
Operational definition
Life-history state.
A state characterized by age-associated decline in one or more measures of survival, physiological function, repair capacity, acquisition efficiency, or reproductive performance.
Senescence is not identical to chronological age and is not universal in the same form across life. Some organisms exhibit negligible, atypical, or modular senescence.