Less understood is the role of advection in biology, however. I plan to show that advection is in fact a crucial part of biological picture and moreover is mainly to be associated with a deterministic description. First I shall show how one can introduce these two aspects in a generic way in modelling. Then I shall refer to two important instances to illustrate the interplay of diffusion and advection in dynamical behaviour. The first example is related to biological growth and consequently the patterning and morphogenesis process in development.
Suggestive applications are in somite formation or plant growth.
The scond biological illustration is given by a new understanding of the chemotaxis cellular signalling process. Chemotaxis is well understood in biology in terms of its detailed mechanistic, biomolecular description. I shall use the example of bacterial chemotaxis to show how one can get a good insight into this interesting phenomenon again as an application of the stochastic and deterministic effects.