He graduated from the University of Tartu in 1975. His earlier work dealt with ethology and field ecology. He has studied the mechanisms of species coexistence in species-rich communities and developed mathematical modelling in ecophysiology. Since 1975, he has been the main organiser of annual meetings of theoretical biology in Estonia. In 1992, he became a Professor of Ecophysiology in the University of Tartu. In 1997, he joined the Department of Semiotics, and became a Professor in Biosemiotics. Since 2006, he is the Head of the Department of Semiotics in the University of Tartu, Estonia. His field of interests include biosemiotics, ecosemiotics, general semiotics, theoretical biology, theory of evolution, history and philosophy of semiotics and life science.