Biodiversity

The occurrence of different types of genes, gene pools, species, habitats and ecosystems in a particular place and various parts of earth is called biodiversity.

The term biodiversity was given by Edward Wilson.

Biodiversity is divided into three levels :-

Genetic diversity-

A single species might show high diversity at the genetic level over its distributional range. Example – The genetic variation of the medicinal plant Rauwolfia vomitoria in potency and concentration of the active chemical reserpine that the plant produces.

Species diversity –

The diversity at the species level. For example, the Western Ghats have a greater amphibian species diversity than the Eastern Ghats.

Ecological diversity –

The diversity at the ecosystem level. For example- deserts, rain forests, mangroves, coral reefs, wetlands, estuaries, and alpine meadows of India has a greater ecosystem diversity than a Scandinavian country like Norway.

Global species diversity :-

• According to the international union for conversation of nature and natural resources or IUCN (2004) The total number of plant and animal species described so far is slightly more than 1.5 million.
• Robert May places the global species diversity at about 7 million.
• More than 70 per cent of all the species recorded are animals, while plants including algae, fungi, bryophytes, gymnosperms and angiosperms comprise no more than 22 per cent of the total.
• Among animals, insects are the most species-rich taxonomic group, making up more than 70 per cent of the total.
• India has only 2.4 per cent of the world’s land area, its share of the global species diversity is an impressive 8.1 per cent and that is how makes India is one of the world.
• Nearly 45,000 species of plants ad twice as many of animals have been recorded from India.

Patterns of biodiversity

Biodiversity is not uniform through out the world because it is affected by two factors : –

Latitudinal gradients and species area relationship.

Latitudinal gradients :-

• Biodiversity increases from poles to equators.
• Tropics harbor more species than temperate or polar areas.
• Colombia located near the equator has nearly 1,400 species of birds while New York at 41° N has 105 species and Greenland at 71° N only 56 species.
• The largely tropical Amazonian rain forest in South America has the greatest biodiversity on earth- it is home to more than 40,000 species of plants, 3,000 of fishes, 1,300 of birds, 427 of mammals, 427 of amphibians, 378 of reptiles and of more than 1,25,000 invertebrates.

Tropics have greatest biodiversity because :-

• Unlike temperate regions subjected to frequent glaciations in the past, tropical latitudes have remained relatively undisturbed for millions of years.
• Tropical environments are less seasonal and more constant and predictable which promote niche specialization and lead to a greater species diversity.
• There is more solar energy available in the tropics, which contributes to higher productivity thus contributing indirectly to greater diversity.