Current Levels Biodiversity, Phytophagy, Parasitism, Microorganisms, Nomenclature, Biological Species, Taxonomic groups, Arthropoda, Marine Water

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Biodiversity and its Conservation
Biodiversity and its Conservation Introduction
Current Levels of Biodiversity
Alpha (α) and Beta(β) Biodiversity
Extinction and Endangered Species
Reasons of Concern for Loss of Biodiversity
Ethical and Aesthetic Rewards
Economic Benefits
Essential Services Provided by Natural Ecosystems
Steps to Preserve Biodiversity
In Situ and Ex Situ Conservation Gene Banks
In Situ Conservation
Ex Situ Conservation
Ex Situ Conservation Efforts at International Level
Ex Situ Conservation Efforts by G-15 Countries
Ex Situ Conservation Efforts in USA

	Current Levels of Biodiversity The life on the planet Earth still remains largely unexplored at the species and intraspecies level. Therefore, a complete knowledge of the world fauna and flora is not available even to the systematists, who are responsible for the taxonomic description and nomenclature of all biological species.
It is estimated that the total number of species available on this planet may be close to 100 million (108), although earlier estimates gave a figure of either 10 million or 30 million. From such a large number of species, only about 1.4 million species of plants, animals and microorganisms have so far been given scientific names. It has been shown that the diversity of fauna and flora varies in different ecosystemsta habitats, geographical regions and also among different taxonomic groups. Following are some examples: (i) Diversity is greater in terrestrial and fresh water species than in marine species. (ii) In marine water, all the 33 known living animal phyla' are available, while only 17 are found on land. and fresh waters. (iii) Arthropoda among phyla, and Insecta among arthropods have more species diversity than other groups; similarly nematodes, mites and fungi are highly diverse, the number of species approaching hundreds of thousands or millions. (iv) Among mammals, rodents have more species than other groups. (v) Among monocotyledons, orchids have more diversity.
(vi) Among squirrels (Sciuridae), the genus Sciurus has more species than other genera. (vii) More diversity occurs in tropics (tropical rain forests and coral reefs) than elsewhere. For instance, 300 tree species occur in single - hectare plots in Peru, while only 700 tree species are found in whole of North America (only 20-30 tree species per hectare). In the same area, a single tree yielded 43 species of ants belonging to 26 genera, a level of diversity found in whole of British' Isles. Hyperdiversity in certain habitats or geographical regions or among certain taxonomic groups, depends on special adaptations which allow penetration of multiple niches by them. (It has also been shown to depend on available energy and, therefore, on productivity).
Following are some examples of these adaptations. (i) Ants appear to expand due to fungistatic secretions, series-parallel work operations and a highly altruistic worker caste. (ii) In insects, size metamorphism and wings are adaptations that allowed development of hyperdiversity. (iii) Some other adaptations common to many groups include small size, phytophagy, parasitism with specialization on host's specialized life stages, greater dispersal ability, etc.