The phenomenon of multiphasic survival curves found in drosophila is confirmed in experiments on daphnids. Mathematical modeling showed that the multiphasic nature of daphnids survival curves reflected abrupt changes in the death rate of objects during phase transition. The phase of a sharp increase in mortality observed at an early age in intact drosophila occurs in daphnids only as reaction to a negative impact. The induction of reactive changes by weak external signals resulted in decreased survival for young daphnids. A logical conclusion was made about the reaction readiness for each experimental individual. It is proven that the predisposition to reaction in daphnia persists for an indefinitely large number of generations. It is postulated that this reaction has an epigenetic nature. Earlier experimental materials suggest that a reaction of this type is widespread in natural surroundings.