First I would start to talk about functionality arising in the Form of a simple "reaction" to special circumstances. On the most primitive level, you have direct physical causation satisfying this Form. Then you have rigid "self-enforcing" chains of physical events forming that "automatically react" following the From; those chains that better enforce their own existence (say, because their interesting effects fit better into diverse longer such chains) would tend to persist and occur more frequently. Gradually, the Form becomes identifiable as "perception/reaction" cycle. Brain neurons are of the same Form! Event patterns would network themselves, with ever more meaningful functionality, etc.