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Model : popdyn2
Simile version : 3.1+
Date added : 20030620
Keywords :
Population dynamics ;
Ageclass modelling ;
Disaggregated population ;
Singlespecies population dynamics ;
This models the dynamics of a population divided into three age classes: young, mature and elderly. Each age class is represented by a single compartment, whose value is the number of individuals in that class.
The flows between the age classes represent the ageing process: the movement of individuals from one class to the next as the grow older. The flows into the first age class represents reproduction. This depends on the number of mature females, which is a fraction of the number of mature individuals. The flow out of the third age class represents mortality: in this model, we assume that only the old individuals die.
Simple proportional relationships are used for all flows:
The model uses a time step of 1 year.
Source: Andrew Ford (1999): Modelling the Environment, p.28
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p028.sml 
Compartments: elderly Initial value = 20 Rate of change = aging  deaths Comments: Number of elderly, millions mature Initial value = 30 Rate of change = maturation  aging Comments: Number of mature, millions young Initial value = 50 Rate of change = births  maturation Comments: Number of young, millions Flows: aging = aging_rate*mature Comments: Number maturing, millions per year births = births_per_mature_female_per_year*mature_females Comments: Births, millions per year deaths = death_rate*elderly Comments: Number dying, millions per maturation = maturation_rate*young Comments: Number maturing, millions per year Variables: mature females = female_fraction*mature Comments: Number of mature females, millions Parameters: aging rate = 0.1 Comments: Proportion aging, per year births per mature female per year = 0.5 Comments: Number of births per female per year death rate = 0.2 Comments: Proportion dying, per year female fraction = 0.5 Comments: Proportion of females in the population maturation rate = 0.1 Comments: Proportion of young maturing, per year

Ford, A (1999) Modeling the Environment.
Island Press. p.28
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