Syllabus section: Ecology, Environment and Biodiversity / GS Paper III
• The term ‘Biodiversity’ refers to ‘The variety and variability among living organisms and the ecological complexes in which they occur. It can be defined as ‘the totality of genes, species and ecosystems of a region’.
Levels of Biodiversity:
• The biological diversity includes three hierarchical levels.
1. Genetic Diversity
2. Species diversity
3. Community and ecosystem diversity
1. Genetic Diversity
• The genetic variation existing within a species is called genetic diversity.
• The genetic variation may be in alleles (different variants of same genes) in entire genes (the traits determining particular characteristics) or in chromosomal structures.
• A population is able to adapt to its environment and respond to natural selection due to its genetic diversity. The evolution of new species i.e. speciation, depends upon the amount of genetic variation.
2. Species Diversity:
• Species diversity refers to the variety of species within a region. The species diversity of a region is measured on the basis of two parameters.
1. Species Richness Refers to the number of species per unit area. The number of species increases with the area of the site
2. Species Evenness Indicates the evenness in the number of individuals of a species.
3. Community and Ecosystem Diversity:
• Refers to the variations in the biological communities in which species live. There are three perspectives of diversity at the level of community.
a. Alpha Diversity
• Refers to the diversity of organisms sharing the same community or habitat.
• A combination of species richness and evenness is used to represent diversity within a community or habitat
b. Beta Diversity
• Indicates diversity between communities.
• Species frequently change when habitat or community changes. There are differences in species composition of communities along environmental gradients like latitudinal gradients, moisture gradients thereby increasing dissimilarity between communities.
c. Gamma Diversity
• Refers to the diversity of the habitats over the total landscape or geographical area