In paper the new aspects of action regularity of ionizing radiation of low intensity on the biophysical and biochemical characteristics of bio-objects and populations are considered. From the point of view of breaking the connection between occurrence of damages and work of systems of restoration at low intensity irradiation, are described the dose dependence of different types--from threshold up to extreme and a plateau curve, differing among themselves only by a parity of these processes. The features of action of low intensity irradiation on bio-objects and populations--change of structure of a population, sensitivity to action of external stimulus, force of connections between the elements of regulatory systems--allow to consider the low intensity irradiation as the factor capable to cause unpredictable transition of quasistationary systems in new status.