In the present thesis, the multiple differences in toxic effects and research methods of toxic effects of three commonly used insecticides, organophosphates dimethoate and pirimiphos-methyl and pyrethroid deltamethrin, on different ecological categories of earthworms by using two standardized toxicity tests (filter paper contact test and artificial soil test) and microcosmic system were investigated. The results showed measurable difference in responses between earthworm biomarkers obtained in experiments conducted mainly in deterministic conditions (standardized toxicity tests) and experiments conducted mainly in stochastic conditions (microcosmic systems). From the results obtained after applying environmentally relevant concentrations of investigated pesticides, it can be concluded that the application of the investigated organophosphates in agriculture has a measurable toxicological effects on earthworms, whereas application of deltamethrin in agriculture is unlikely to affect the response of biochemical biomarkers of earthworms in the environment. The measurements showed that the occurrence of oxidative stress and changes in the activity of efflux pumps might considerably contribute to the toxic effects of investigated pesticides on earthworms. The obtained data on the recovery of biomarkers showed that the recovery of investigated biochemical biomarkers was slow, so it is necessary to take into account the recovery time when designing the monitoring studies of environmental pollution using biochemical biomarkers. Comparison of the earthworm sensitivities showed that the species-specific sensitivity was different after exposure to organophosphates using standardized toxicity tests and microcosm. The obtained differences in sensitivities point to the need of distinguishing between two types of species sensitivity, physiological and environmental sensitivity, and both sensitivities should be taken into account in the interpretation of the results of toxicological and ecotoxicological tests.