2.3.1 Biological stocks and flows
Ecology is the name coined in 1866 by Ernst Haeckel, for his study of the patterns of relations between organisms and their environment. But the study of ecology is much older than the name; its roots lie in earlier investigations of the "economy of nature." The major theme throughout the history of this science and the ideas that underlie it has been the interdependence of living things. An awareness, more philosophical than purely scientific, of this quality is what has generally been meant by the "ecological point of view." Thus, the question of whether ecology is primarily a science or a philosophy of interrelatedness has been a persistent identity problem. And the nature of this interdependence is a parallel issue. Is it a system of economic organization or a moral community of mutual tolerance and aid?
In 1927 Elton published his first major work, 'Animal Ecology', an important purpose of which was to draw together existing ecological knowledge into a new model of community. Elton was concerned with natural communities- their workings, distribution, and component populations. For Elton, the form or organization of the community became the central problem, and this has remained true of English and American ecologists up to the present.
On a systems view of the planet, there are four dynamic biochemical perspectives of materials and energy that flow through living things. These flows maintain ourselves as an integral part of a living world, which we increasingly utilise and impinge upon as we proceed with an ever increasing pace and scale of economic development. 
Ecosystems define the day to day interdependence of communities of species through flows of solar energy from plants to microbes.
Evolution denotes the flows of materials and energy that are directed by natural selection through sequences of species in time.
Gaia theory proposes that life itself is the major controlling factor in the maintenance of the planetary ocean/atmospheric balance to produce a habitable planet.
Homeostasis defines the cybernetic control of flows of materials and energy through the body surface and the internal cellular membranes via interlocking chemical reactions catalysed by proteins, the enzymes, that are specified by the genetic code residing in DNA..It is at this level that cultural ecology is taking on a new dimension through the social impact of inventions emerging from biomedical research.  These are aids to living a youthful life into what used to be described as old age.  Daily doses of drugs, such as beta blockers are now part of human ecology, working to maintaining the body as steady state.  In this sense they are a synthetic part of a healthy diet.