Ecosystem
The term ecosystem was first used in 1935 in a publication by British ecologist Arthur Tansley. Tansley devised the concept to draw attention to the importance of transfers of materials between organisms and their environment. He later refined the term, describing it as "The whole system, ... including not only the organism-complex, but also the whole complex of physical factors forming what we call the environment". Tansley regarded ecosystems not simply as natural units, but as "mental isolates". Tansley later defined the spatial extent of ecosystems using the term ecotope.
Eco-cities
An eco-city or ecocity is "a human settlement modeled on the self-sustaining resilient structure and function of natural ecosystems", as defined by the Ecocity Builders (a non-profit organization started by Richard Register who first coined the term). Simply put, an eco-city is an ecologically healthy city. The World Bank defines eco-cities as “cities that enhance the well-being of citizens and society through integrated urban planning and management that harness the benefits of ecological systems and protect and nurture these assets for future generations”. Although there is no universally accepted definition of an 'eco-city', among available definitions, there is some consensus on the basic features of an eco-city.