Natural Daphnia population is genetically heterogeneous by phenotypic reaction of individuals to change of food quantity by a set of quantitative morphological characters. By majority of characters, three genetically determined types of individual reaction to ecological factor were obtained, they are represented by phenotypes in which average values decrease (R₁), increase (R₂) or remain constant (St) at decreased quantity of food. It is shown that the found phenotypic reaction appears in individuals by the whole set of investigated characters independently on their functions, except cyclomorphic ones.