Age-class model of population dynamics, one compartment per age class

Model : ageclass4
Simile version : 3.1+
Date added : 2003-06-20
Keywords : Age-class modelling ; Population dynamics ;

Description

This models a population of animals in terms of four age-classes. For each age-class, we use a compartment (state variable) to represent the number of individuals in that class.

In this model, there are four compartments on the model diagram. They are connected by flow arrows, which represent the aging process: the flow of individuals from one class to the next as they get older. Simile allows the same mathematical model to be represented more concisely, using a single compartment embeddedinside a multiple-instance submodel: see the links to other models below.

Files

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ageclass4.sml

Diagram

Equations

Compartments
	pop_size_1: initial value = 2
	pop size_2: initial value = 0
	pop size_3: initial value = 0
	pop size_4: initial value = 0

Flows
	ageing_1 = pop_size_1
	ageing_2 = 0.2*pop_size_2
	ageing_3 = 0.1*pop_size_3
	births   = births_2+births_3+births_4
	deaths_1 = m1*pop_size_1
	deaths_2 = m2*pop_size_2
	deaths_3 = m3*pop_size_3
	deaths_4 = m4*pop_size_4

Parameters
	m1 = 0.05
	m2 = 0.01
	m3 = 0.01
	m4 = 0.05

Intermediate variables
	births_2 = r2*pop_size_2
	births_3 = r3*pop_size_3
	births_4 = r4*pop_size_4
	pop size = pop_size_1+pop_size_2+pop_size_3+pop_size_4
	r2 = 0.05*(1-pop_size/100)
	r3 = 0.2*(1-pop_size/100)
	r4 = 0.1*(1-pop_size/100)

Results

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