In this lecture, we have covered the structural definition of urban ecosystems, distinguishing them from natural systems through their dominance by human-made structures and anthropogenic forces. We have also detailed the specific components of the urban environment, categorizing them into the Socio-Economic Environment (including political, social, and economic factors) and the Biophysical Environment (comprising the built system, pedosphere, hydrosphere, biosphere, and atmosphere), all interconnected via the anthroposphere.