In article the questions connected with studying of species structure of communities of symbiotic microorganisms of a biofilm of thick intestines of healthy and sick children from various age groups are considered. The statistical analysis of distinctions on number of representatives of intestinal microflora of a biofilm of thick intestines at sick and healthy children from different age groups is carried out. Dependence of accumulation of species riches of microflora on volume of the investigated sample of children is described by sedate dependence that testifies to self-similarity of specific structure of community of microorganisms of a biofilm of thick intestines. With application of indexes of species structure the ecological characteristic of communities of symbiotic microorganisms of a biofilm of thick intestines of healthy and sick children of various age groups is given.

The monofractal analysis has been carried out of the species structure of enterobacterial communities inhabiting honeybee (Apis mellifera L.) intestines and various components of anthills (Formica aquilonia and F. protensis). It is shown that the dependence of the accumulation of the number of enterobacterial species on the sample size is described by a power law, which testifies to self-similarity of the species structure of enterobacterial communities of the social insects studied

Evidence has been obtained of the fractal structure of recent and fossil biotic communities of free-living and symbiotic organisms dwelling in terraneous and aqueous ecosystems. The developing idea of fractality or self-similarity in communities' structural organization is not just a suitable or attractive mathematical abstraction but has a backbone principle in considering nonlinear aspects of complex systems' dynamics.