| Abstract | A four-parameter model describing mortality as the first passage of an abstract measure of survival capacity, vitality, is developed and used to explore four classic problems in biodemography: 1) medfly demographic paradox, 2) effect of diet restriction on longevity, 3) effect of early growth rate on later life survival and 4) mortality plateaus. The model quantifies the sources of mortality in these classical problems into vitality-dependent and -independent parts and characterizes the vitality-dependent part in terms of initial and evolving heterogeneities. In general, it provides an accessible tool to decompose any survival curves into four pieces: intrinsic mortality related to the senescence rate, extrinsic mortality related to the accidental rate as well as two sources of heterogeneities among a population. Through the lens of the partition, we are able to better understand the underlining biological and ecological mechanisms that shape the survival curves. |
|---|
