Alpha diversityIn ecology, alpha diversity (α-diversity) is the mean species diversity in a site at a local scale. The term was introduced by R. H. Whittaker together with the terms beta diversity (β-diversity) and gamma diversity (γ-diversity). Whittaker's idea was that the total species diversity in a landscape (gamma diversity) is determined by two different things, the mean species diversity in sites at a more local scale (alpha diversity) and the differentiation among those sites (beta diversity).
Beta diversityIn ecology, beta diversity (β-diversity or true beta diversity) is the ratio between regional and local species diversity. The term was introduced by R. H. Whittaker together with the terms alpha diversity (α-diversity) and gamma diversity (γ-diversity). The idea was that the total species diversity in a landscape (γ) is determined by two different things: the mean species diversity at the local level (α) and the differentiation among local sites (β).
Diversity indexA diversity index is a quantitative measure that reflects how many different types (such as species) there are in a dataset (a community), and that can simultaneously take into account the phylogenetic relations among the individuals distributed among those types, such as richness, divergence or evenness. These indices are statistical representations of biodiversity in different aspects (richness, evenness, and dominance).
Urban cultureUrban culture is the culture of towns and cities. The defining theme is the presence of a large population in a limited space that follows social norms. This makes it possible for many subcultures close to each other, exposed to social influence without necessarily intruding into the private sphere. Globally, urban areas tend to hold concentrations of power, such as government capitals and corporate headquarters, and the wealthy and powerful people that are employed in them. Cities also organize people, create norms, beliefs, and values.
Urban historyUrban history is a field of history that examines the historical nature of cities and towns, and the process of urbanization. The approach is often multidisciplinary, crossing boundaries into fields like social history, architectural history, urban sociology, urban geography, business history, and archaeology. Urbanization and industrialization were popular themes for 20th-century historians, often tied to an implicit model of modernization, or the transformation of rural traditional societies.
