Abstract: Dissipative structure is a far-from-equilibrium new metastable state in the non-linear re gion of an cpen system, derived from and maintained by constant negentropy flow from the environment. The theory of dissipative structure, with other thermodynamic concepts, may be used to interpret ecological phenomena. Ecosystem is dissipative system and, therefore, it may be more appropriate to analyze and tackle problems such as ecological balance in terms of the theory of dissipative structure. Hierarchy theory has been developed to dea' with complex systems. The theory asserts that the organization of a system lies in the differences among its process rates. Ecological systems are medium-number, hierarchical systems. The theory of dissipative structure and the stratified stability hypothesis lay the foundation for the development of hierarchical structure of ecological systems. Hierarchy theory provides an objective conceptual framework and a practical guideline for studying the behavior and other characteristics of ecosystems. It is breaking new ground for developing unifying ecological theories. The purpose of the paper is to review and examine dissipative structure and hierarchy theory in the context of ecosystems. The relevance and applicability of the two theories in ecology are also discussed.

Key words: Dissipative structure, Stratified stability, Ecological complexity, Mediumnumber systems, Hierarchy, Ecosystem