Diversity means number and variety of species. Biodiversity is the diversity of plant and animal life in a particular region or in the world as a whole.
It is often used as a measure of the health of biological systems. The year 2010 has been declared as the International year of biodiversity.
Biodiversity represents the quality and characteristic features of life in an ecosystem. Being a combination of genes, species and the ecosystem itself, biodiversity can be considered at three levels: Genetic diversity; species diversity and ecosystem diversity.
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(i) Genetic Diversity:
Living things contain in their cells, the basic instructions (which are called genes) for their own development. Many of these instructions result in physical characteristics that affect the way organisms interact with their environment. Variations in such characteristics within the same species give rise to genetic diversity. A significant level of variation must be present for species to adapt to an ever-changing ecosystem. Domesticated species often have low levels of genetic diversity so it poses risks.
A newly-evolved virus or bacteria strand can invade a population of nearly identical organisms very rapidly. Thus, the protection that genetic diversity generally offers in wild populations is lost in such artificial selection or preferential breeding of crops and animals.
(ii) Species Diversity:
It is a measure of the diversity within an ecological community that incorporates the number of species in a community and the evenness of species abundances. Communities with more species are considered to be more diverse. Evenness measures the variation in the abundance of individuals per species within a community. Communities with greater evenness are considered to have greater species diversity.
a) Species richness: Number of species per unit area
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b) Species Evenness: Evenness of individuals in a species
To sum up, species diversity provides a quantitative idea of the number of species and the variety of species present in a particular region.
(iii) Ecosystem Diversity:
It indicates the variation in the structure and functions of the ecosystems. It tells about trophic levels, energy flow, food, and total stability of ecosystems. The ecosystems can be of various types as governed by the species composition and the physical structure.
Following are few examples:
(a) Terrestrial ecosystems,
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(b) Aquatic ecosystems,
(c) Artificial or man-made ecosystems.