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Population dynamics: single species: exponential: version 1

Model : popdyn1
Simile version : 3.1+
Date added : 2003-06-20
Keywords : Population dynamics ; Single-species population dynamics ; Exponential growth ;

Description

This is the standard model of exponential population increase. The size of the population is represented by a single compartment (state variable), which has units of 'number of individuals' (absolute population size) or 'number of individuals per unit area' (population density).

The rate of change of population size is represented by a single flow, which thus incorporates all the population processes (birth, death, migration) in a single value.

The rate of population change is assumed to be proportional to population size.

Source: Andrew Ford (1999): Modelling the Environment, p.25

Files

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p025.sml

Diagram

Equations

Compartment:   population
	Initial value = 10
	Rate of change =  + growth
	Comments:
		Population size, millions 
 
Flow:   growth
	growth = growth_rate*population 
	Comments:
		Population growth, millions per year 

Variable:   growth rate
	growth rate = 0.07 
	Comments:
		Annual proportional growth rate, proportion per year 

Results

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References

Ford, A (1999) Modeling the Environment.
Island Press. p.25

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