Biodiversity is the total variety of life on earth. It encompasses the total number, variety, and variability of life forms, levels and combinations existing within the living world. This includes diversity within species, between species and of ecosystems. Biodiversity can also be defined as the all types of species of plants, animals and other living beings present on earth. It consists of three fundamental and hierarchical categories: Ecosystem diversity, species diversity and genetic diversity.
1. Ecosystem diversity:
It comprises a variety of habitats, dynamic complexity of plant, animal and micro-organism communities and their non-living environment which interact as a functional unit. Non-living components include sunlight, air, water, minerals and nutrients.
2. Species diversity:
A species may be defined as a group of individuals or as a population of organisms which resemble each other very closely and can interbreed with each other successfully for reproducing their own kind.
Species diversity refers to the frequency and variety of species (wild or domesticated) within a geographical area. Species diversity is usually measured in terms of the total number of species within discrete geographical boundaries. The total number of species in the globe has been estimated by World Conservation Monitoring Center to range from 5 to 30 million and approximately 17 million living species of all kinds of organisms have been described till date (WCMC 1992).
3. Genetic diversity:
Genetic diversity refers to variation of genes and or genomes within living organisms, that is the genetic differences among populations of a single species and among individuals within a population. In other words, this covers distinct populations of the same species such as hundreds of traditional rice varieties in Nepal.
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