ancient cities

the size of a population and the patterns of adaptation
to the environment. According to this perspective,
at the biotic level the principle of competition
operates. In their attempt to adjust to the environment,
individuals and social groups compete for
the environment’s scarce resources and develop a
social division of labor. The competition involves
some degree of cooperation, as it reflects the social
division of labor, differentiation, and specialization
of different functions in society.
In cities, the principle of competition is central
to the understanding of the differential spatial distribution
of different social groups in different
areas. Urban ecologists used the term natural areas
to describe the resulting social homogeneous areas
of the city. The natural area came into existence,
not as the result of planning efforts of the government
or real state agents but from unplanned competition
of social groups. Natural areas were believed
to come into existence through the competition of
individuals and groups for space. Once established,
these areas provided homes and services for their
inhabitants and carried out functions that contributed
to the survival of the entire community.
The cultural level of society is built upon the
biotic level. The cultural level is that part of society
based on customs, norms, and institutions. It
involves rules of social behavior, mutual social
expectations, and social interaction.
Following this conceptualization, urban ecology
has been concerned with a number of central questions
that dominated the research program through
the years. Urban ecology is concerned with the
sources and patterns of city growth, the relationship
between the spatial distribution of the city
population and the social and economic resources
of residents, the association between the distribution
of the city population and land values, and the
association between the distribution of the city
population and delinquency and deviance.
In the effort to provide answers to these questions,
urban ecology developed a number of important
concepts that were used to describe central
urban processes.
Urban Spatial Distribution
and Growth
A central concern of urban ecology is the spatial
pattern and structure of the urban community. The
Urban Ecology (Chicago School)
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central topics of interest are how different groups
are distributed in the metropolis; why the distribution
took a particular shape; and where households
of different socioeconomic, ethnic, and racial composition
were located, including the determinants
of residential segregation. The central postulate of
urban ecology is that processes of competition
regulate the overall spatial pattern of the community,
including the location of specific natural
areas. Industries and commercial institutions compete
for strategic locations, which once occupied,
enable them to exercise control over the functional
use of land in other parts of the community. The
most strategic position is found at the point of
highest accessibility, usually the center of the community.
It was here, in the industrial city, that the
largest number of people converged in their daily
journey to work, shop, and be entertained.
Consequently, land values were found to be higher
in the central business district than in the surrounding
area. On the basis of this observation
Burgess developed the concentric model of urban
structure and growth. In this model, it is assumed
that the main source of city growth is the increase
in population and that the city develops from the
center to the periphery. According to the model,
the spatial organization of the city can be described
as a series of concentric zones, emanating from the
central business district. Each zone includes natural
areas in which reside relatively homogeneous
groups according to socioeconomic status, ethnicity,
and racial composition. Adjacent to the central
business district is the transition zone, with a deteriorating
housing stock in which recent immigrants
reside. The transition zone is being invaded by
business and light manufacturing. The workers in
industries who have escaped from the area of deterioration
but who desire to live within easy access
to their work inhabit a third area. Beyond this zone
is the residential area of high-class apartment buildings
or districts of single-family dwellings. Still
farther out, beyond the city limits, is the commuters’
zone in which reside high-class individuals.
The basic argument of the concentric model
was that accessibility is the most important factor
in the location of employment and residential
activities. Competition for accessibility leads to
differential land values in the city. The central
business district was, at the beginning of the twentieth
century, the urban transportation center. As