In the course of his research on digestion, pavlov encountered what problem?

 he came to demonstrate the working of a process that was clearly psychological which caused a change in the digestive system.
This finding lead to the discovery on how a change in organisms' psychological condition could influence our normal biological function, such as tendency to become constipated when we're stress, increased response when we're anxious,etc.

Urban growth invariably feeds increased commercialization and industrialization. it requires continually expanding land areas. when urbanization rates are high, and countries do not have the institutional and managerial capacities or economic wherewithal to manage such rapid growths, they exert intense pressure on the types and nature of the resulting settlements. they contribute to the development of overcrowded slums and shanty towns without adequate essential services and necessary infrastructure.-by asit k. biswas and cecilia tortajada