1. Introduction
Life is essentially connected with growth. The phenomenon of growth can be studied
scientifically from two different points of view:
(a) On the level of the cell or the organism: Here, the finely tuned cellular
(metabolic and regulatory) processes underlying the increase in length and volume,
division and replication are of interest. These processes can be studied without looking
at the population as a whole.
(b) On the population level: Here the increase of the number of individuals or the
population size and its mathematical description and modeling are of interest. Strictly
speaking, this is the study of propagation (German: Vermehrung), but nevertheless the
term growth is commonly used. This can be studied and modeled without knowledge of
the cellular mechanisms.
A basic approach in microbiology is the study of growth from viewpoint (b). This is
experimentally usually simple because growth (propagation) of bacteria can be very fast
(in comparison to higher organisms) and requires only small culture volumes (flasks).
The formulas for theoretical treatment are not really difficult.