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We consider effect of possible migration between different locations on population evolution. Examples of different rules based on preferences to live in bigger or smaller populations, (or environmental capacity, or living space available), are discussed. In the limiting case of small migration intensity, each location evolves independently according to its local rules and conditions, as expected. With increasing migration, the population distribution between locations changes, including some critical behavior of extinction of population in some locations for specific set of the rules. Then the deserted location may become populated again if the migration is still on increase as a result of a pressure to move. Presented version is devoted to the migration controlled exclusively by environmental factor, yet the model is primarily designed to describe influence of other factors which may control migrating processes such as inherited mutation load, age, or other parameters associated either with individuals or the specific location, races mixing, or recovery of environmental capacity. (C) 1999 Elsevier Science B.V. All rights reserved.