Life-support systems at modern spacecrafts are based on the reserves of different components and their partial physical and chemical regeneration. This permits cosmonauts to stay for a long time under space flight conditions (Valery Polyakov - 1 year and 4 months). At the same time, in many countries works are in progress on the creation of closed ecological life-support systems involving the use of biological objects of different phylogenetic levels (Mashinsky and Nechitailo, 1996).
In the known ground-based ecological systems one to several thousands of biological species are used to support the human life functions. For instance, only Chlorella was used in the first 1-day experiment in Moscow in a closed biological system with the participation of a man, while in the two-year experiment in the Bioshere-2 complex in Arizona more than 4000 species were used (Alling and Nelson, 1993). Today, many specialists consider it possible to use a limited number of species in a closed ecological system. These are, first of all, microorganisms, plants (higher and lower), aqueous animals, birds. However, there is no closed ecological system in the world so far which could be used qt least as a prototype for a long-term space flight. This is explained by incomplete understanding of the role and function of such a system, by complexity of technical approaches for its realization, by insufficient knowledge of the behavior of biological objects in space flights in which the action of a number of specific factors (altered strength of magnetic and electromagnetic fields, cosmic radiation and its level and spectral characteristics, disturbances of circadity, etc.) is combined with the action of a factor which cannot be simulated on the Earth, namely weightlessness or microgravity when all forces affecting the body are balanced.