Alpha ,Beta ,gama diversity

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1. Alpha diversity In ecology,  alpha diversity  ( α-diversity ) is the mean species diversity in sites or habitats at a local scale.

2. Alpha diversity Alpha diversity (α-diversity) is expressed in terms species richness or number of species in an ecosystem. It defines the biological diversity within an ecosystem, community or simply in a particular habitat. The alpha diversity can be measured by counting the distinct group of organisms such as different species, genera, and families or number of taxonomic entities (number of taxa ) within the ecosystem.

3. The term was introduced by R. H. Whittaker Whittaker's idea was that the total species diversity in a landscape is determined by two different things, the mean species diversity in sites or habitats at a more local scale (alpha diversity) and the differentiation among those habitats (beta diversity).

4. Diversity of Diversities Difference between the diversities is usually one of relative emphasis of two main envir . aspects Two key features Richness Abundance – our emphasis today Each index differs in the mathematical method of relating these features One is often given greater prominence than the other Formulae significantly differ between indices

5. Alpha Diversity Indices “Heterogeneity Indices” Consider both evenness AND richness Species abundance models only consider evenness No assumptions made about species abundance distributions Cause of distribution Shape of curve “Non-parametric” Free of assumptions of normality

6. Beta diversity Beta Diversity (between habitat diversity along environment gradient)

7. Beta diversity Beta diversity (β-diversity) is defined as the quantitative measurement of diversity of communities along environmental gradients. The species diversity that experience changing environment between ecosystems is compared to measure the beta diversity. It is given as the rate of change in species composition among communities or across different ecological habitat.

8. Conti… In 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).

9. Gamma diversity Gamma diversity (γ-diversity) is defined as the species richness or total number of species over a large region (ecological, units). Gamma diversity also called as large-scale landscape diversity, within a region is given by the quantitative measurement of overall diversity for different ecosystems. It is often expressed as the species richness of component communities.