ABSTRACT
In this chapter, the discrete linear time – invariant variable, fractional – order model of living organisms’ population growth is represented by percentile charts containing the rates: weight vs. age. Fractional models described by the difference equations containing fractional-order Grünwald-Letnikow backward differences of commensurate or non-commensurate orders show better matching to the measured data. A generalisation of the mentioned difference – the variable, fractional-order backward difference – is applied. In place of the fractional order, there is applied a discrete function of order. This leads to further improvement of the mathematical model. Numerical examples supporting considerations are given.
