The subject of ecology is the detailed study of the basic structure of the functioning of natural and human-made systems using quantitative methods. The wildlife around us is not a disorderly, random combination of living things. It is a stable organized system of the organic world that has developed in the course of the evolution of the organic world. The central place in ecology is occupied by the problem of the dynamics and size of populations and the mechanisms of its regulation. It reveals the importance of the participation of population (competition for food) and biocenotic (predators, parasites, pathogens) mechanisms.