In the first part we present an optimal control problem for a nonlinear reaction-diffusion system modelling predator-prey interactions. We implement a semi-implicit (in time) finite element method with "mass lumping", and show the results of numerical experiments in two space dimensions. The second part regards a parameter identification problem for reaction-diffusion equations modelling pattern formation (Gierer & Meinhardt activator-inhibitor model). We will discuss how we approximate solutions and show an animation of some preliminary results. http://www.maths.usyd.edu.au/u/AppliedSeminar/abstracts/2008/trenchea.html