A branch of biology concerned with the interrelationships of organisms and their environment. Ecology is made up of two word Oikos-logos (study of the earth)


Ecosystem:

The relationship between the non-living physical environment and the living biological community is called ecosystem. All the energy transferred as organisms interact with each other and with non-living things. (physical agents). Ecosystems are the basic units of ecology. Ecosystems include oceans, ponds, farms, forests and cities. An ecosystem can be small like the surface of a leaf or widely the oceans.

Moving from the global view of Earth to a regional, national or local level we are led to the consideration of fellow human beings as an additional social component of the environment. Different types of social groups such as nations, tribes and families interact in different ways, both cooperative and aggresive and cause distinctive impacts on physical environment. In particular, they create a built, man-made environment which affects all the natural environments.One of the most common forms of these man-made environments is the city. and in this sense, urban design or "the art of building (planning) cities" is the method creating a built environment. This artificial environment fulfills man's aspirations and represents his values.

On the other hand, cities have always been focus for anxiety. moralists, philosophers, economists, city planners,industrial designers and architects and in recent decades environmentalists have all been concerned by the explosive growth of the cities and resulting urban problems.