Wall effect is a factor that probably plays an important role in biological evolution. It can be responsible for various evolutionary trends, for example, in process of increase of complexity of organism during evolution. If individuals can move in an arbitrary direction, the population as a whole more or less remains in one place. However, if an impermeable barrier (wall) prevents their movement in a particular direction, the population gradually moves away from it. In evolution, a barrier can be created, e.g., by the minimum complexity necessary for the functioning of a living system.