Some aspects of biology, for example the Hardy-Weinberg simulation of population genetics or modelling heat flow in lizards, have an undeniable mathematical basis. Students can find the level of mathematical skill required to deal with such concepts to be an insurmountable hurdle to understanding. If not used effectively, spreadsheet models designed to help to overcome such mathematical difficulties present a further hurdle in terms of IT skills. This paper describes examples of how spreadsheet simulations can be designed to reduce the problem of the IT interface obscuring real subject teaching. Two sets of questions designed to help students to meet learning outcomes associated with the Hardy-Weinberg model and with thermoregulation in lizards are presented together with suggested answers. This approach has been successfully used on an introductory genetics course and a control systems course within a Biosciences degree at Canterbury Christ Church University College. (Contains 2 figures.)