Answer to Question 1
Answer: The multiple nuclei model was developed by geographers C. D. Harris and E. L. Ullman in 1945. According to the multiple nuclei model, a city is a complex structure that includes more than one center around which activities revolve. Examples of these nodes include a port, neighborhood business center, university, airport, and park.
The multiple nuclei theory states that some activities are attracted to particular nodes, whereas others try to avoid them. For example, a university node may attract well-educated residents, pizzerias, and bookstores. An airport may attract hotels and warehouses. On the other hand, incompatible land-use activities will avoid clustering in the same locations. Heavy industry and high-class housing, for example, rarely exist in the same neighborhood.
Answer to Question 2
Answer: The concentric zone model was created by sociologist W.W. Burgess in 1923. According to the model, a city grows outward from a central area in a series of five concentric rings, like the growth rings of a tree.
- The innermost zone is the CBD, where nonresidential activities are concentrated.
- A second ring, the zone in transition, contains industry and poorer-quality housing. Immigrants to the city first live in this zone in high-rise apartment buildings.
- The third ring, the zone of working-class homes, contains modest older houses occupied by stable, working-class families.
- The fourth zone has newer and more spacious houses for middle-class families.
- A commuters' zone beyond the continuous built-up area of the city is inhabited by people who work in the center but choose to live in dormitory towns for commuters.
Leaf structure and its relationship to the C4 cycle
(A) Internal anatomy of the spinal cord. (B) Ascending spinal tracts.
Type of Interactions, Model, Examples and Dependence of Energy on Distance
A model of the 70 ribosome, with mRNA and tRNA bound
Internal Renal Anatomy
DNA double helix model