Students in Ecology usually are not conscious of the origins of the terms and concepts that they are accustomed to use. Yet the terms and concepts in ecology have been developed within specific historical contingency with cultural and institutional settings. Ecology as a scientific discipline was firmly established during the early 20th century. As many other fields in biological sciences, the most conspicuous force made ecology as a well defined discipline seems to have been the scientists' conscious effort to make the field more exact and quantitative one. On the other hand, ironically, the prime mover of the effort, Frederic Clements, was also greatly influenced by the current cultural milieu in which the idea of human society as a functional whole was widely discussed. Furthermore, the early stage of ecology in this period was visibly colored by the American mid-west landscape where most of the important early ecologists lived in. The concept of ecosystem was suggested by an Englishman Tansley who had exactly same aspiration with that of Clements, namely the aspiration for a more exact and mechanical structure of the discipline. Yet, this concept became influential disciplinary tool only if it was combined with the idea of balance of nature, which was a concept heavily loaded with the organic metaphor. More interesting is that the ecology based primarily upon the concept of ecosystem became widely accepted through the thrust of research largely from the post World War II military agenda. During the late 20th century, again new trends in ecology swept through the discipline. The major impact was, as usual, from the introduction of new concepts in physical sciences, chaos theory in particular. This new trend in ecology claimed to overcome the previous two mythical bases of the discipline, namely the organic metaphor of balance in community ecology and the mechanical metaphor of linear energy flow in ecosystem ecology. This third wave of ecological paradigm, dubbed as the evolutionary ecology, seems to have been fitting well with the cultural tone of the late 20th century, and appears to be thriving into the next century through the rush of environmental discourses.