Migration of Organisms: Climate. Geography. Ecology

In the common sense, migration is considered by many authors as a mechanism for avoiding unfavorable environments by moving to expectedly more auspicious locations at different times. In other terms, migration may represent the seasonal movement of organisms from place to place owing to the change in the environmental conditions. Consequently, two important questions arise to mind, why do some animals migrate? How would migration affect the gene pool? Whatever are the answers, the cost of m...