Iteration is doing something over and over again
In population growth, reproduction is iterated.
Simple Population Growth Model (NetLogo)
n is population
n_0 is initial population (1)
n_1 is population at year 2 (2)
n_2 is population at year 3 (4)
n_t is population at year t
birthrate = number of offspring produced per year from 1 rabbit (2)
n_1 = birthrate x n0
n_2 = birthrate x n1
n_t+1 = birthrate x n_t
Exponential population growth: year 0 is 1 year 1 is 2 year 2 is 4 year 3 is 8 year t is 2^t
Exponential growth is unrealistic in the long term.
Population vs. time is an exponential function.
This year vs. last year is a linear function yielding a straight line:
n_t+1 = birthrate * n_t
y = slope * x
Independence in a system causes linear growth.