Concept of Biodiversity – Types of biodiversity, species diversity

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Concept of Biodiversity

Biodiversity is the variety of plant and animal life in the world or in a particular habitat.

Measurement of Biodiversity

Biodiversity is measured by two major components:Species richness, and Species evenness.

Species richness : It is the measure of number of species found in a community and can be further divided into :

  1. Alpha diversity : It refers to the diversity within a particular area or ecosystem, and is usually expressed by the number of species (i.e., species richness) in that ecosystem.
  2. Beta diversity : It is a comparison of diversity between ecosystems, usually measured as the change in amount of species between the ecosystems.
  3. Gamma diversity : It is a measure of the overall diversity for the different ecosystems within a region.

Species evenness : It measures the proportion of species at a given site, e.g. low evenness indicates that a few species dominate the site.

Genetic diversity

  1. Genetic diversity is the total number of genetic characteristics in the genetic makeup of a species.
  2. A single species might show high diversity at the genetic level for E.g. Man has different genes such as : Chinese, Indian American, African etc.]. India has more than 50,000 genetically different strains of rice, and 1,000 varieties of mango.
  3. Genetic diversity allows species to adapt to changing environments. This diversity aims to ensure that some species survive drastic changes and thus carry on desirable genes.

Species diversity

  1. It is the ratio of one species population over total number of organisms across all species in the given biome. ‘Zero’ would be infinite diversity, and ‘one’ represents only one species present.
  2. Species diversity is a measure of the diversity within an ecological community that incorporates both species richness (the number of species in a c-ommunity) and the evenness of species.
    • For example, the Western Ghats have a greater amphibian species diversity than                    the Eastern Ghats. There are more than 2,00,000 species in India of which                              several are confined to India (endemic).
  3. Endemism is the ecological state of a species being unique to a defined geographic location, such as an island, nation, country or other defined zone, or habitat type; organisms that are indigenous to a place are not endemic to it if they are also found elsewhere. A particular type of animal or plant may be endemic to a zone, a state or a country. The extreme opposite of endemism is cosmopolitan distribution.
  4. Species differ from one another, markedly in their genetic makeup, do not inter-breed in nature. Closely-related species however have in common much of their hereditary characteristics. For instance, about 98.4 per cent of the genes of humans and chimpanzees are the same.
  5. According to the IUCN (2004), the total number of plant and animal species described so far is slightly more than 1.5 million, but we have no clear idea of how many species are yet to be discovered and described. A large proportion of the species waiting to be discovered are in the tropics. Estimate place the global species diversity at about 7 million.
  6. 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.
  7. Among animals, insects are the most species-rich taxonomic group, making up more than 70 per cent of the total. That means, out of every 10 animals on this planet, 7 are insects.
  8. The number of fungi species in the world is more than the combined total of the species of fishes, amphibians, reptiles and mammals.
  9. It should be noted that these estimates do not give any figures for prokaryotes. Biologists are not sure about how many prokaryotic species there might be.
  10. In general, species diversity decreases as we move away from the equator towards the poles. With very few exceptions, tropics (latitudinal range of 23.5° N to 23.5° S) harbour more species than temperate or polar areas.
  11. India, with much of its land area in the tropical latitudes, has more than 1,200 species of birds.
  12. 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.

Why tropics have greater biological diversity?

  1. Speciation is generally a function of time, unlike temperate regions subjected to frequent glaciations in the past, tropical latitudes have remained relatively undisturbed for millions of years and thus, had a long evolutionary time for species diversification.
  2. Tropical environments, unlike temperate ones, are less seasonal, relatively more constant and predictable. Such constant environments promote niche specialization and lead to a greater species diversity.
  3. There is more solar energy available in the tropics, which contributes to higher productivity; this in turn might contribute indirectly to greater diversity.

The importance of Species Diversity to the Ecosystem

  1. For many decades, ecologists believed that communities with more species, generally, tend to be more stable than those with less species.
  2. What exactly is stability for a biological community? A stable community should not show too much variation in productivity from year to year; it must be either resistant or resilient to occasional disturbances (natural or man-made), and it must also be resistant to invasions by alien species.
  3. Although, we may not understand completely how species richness contributes to the well-being of an ecosystem, we know enough to realize that rich biodiversity is not only essential for ecosystem health but imperative for the very survival of the human race on this planet.

Nations endowed with rich biodiversity explore molecular, genetic and species-level diversity to derive products of economic importance.

Keystone species and Foundation Species

  1. Keystone species is a species whose addition to or loss from an ecosystem leads to major changes in occurrence of at least one other species.
  2. A classic keystone species is a predator that prevents a particular herbivorous species from eliminating dominant plant species. All top predators such as (Tiger, Lion, Crocodile, Jaguar ) are considered as keystone species because it regulates all other animal population indirectly. Hence top predators are given much consideration in conservation.
  3. Certain species in an ecosystem is considered more important in determining the presence of many other species in that ecosystem.
  4. If keystone species is lost, it will result in the degradation of whole ecosystem. For example certain plant species (ebony tree, Indian-laurel) exclusively depends upon bats for its pollination. If the bat population is reduced then regeneration of particular plants becomes more difficult.
  5. Foundation species is a dominant primary producer in an ecosystem both in terms of abundance and influence. Example: kelp in kelp forests and corals in coral reefs.

Flagship species

  1. A flagship species is a species chosen to represent an environmental cause, such as an ecosystem in need of conservation.
  2. These species are chosen for their vulnerability, attractiveness or distinctiveness in order to engender support and acknowledgement from the public at large.
    • Example: Indian tiger, African elephant, giant panda of China, mountain gorilla of                Central Africa, orangutan of Southeast Asia and the leatherback sea turtle.

Ecological diversity

• Ecological diversity refers to the different types of habitats. A habitat is the cumulative factor of the climate, vegetation and geography of a region.
• It includes various biological zones, like lake, desert, coast, estuaries, wetlands, mangroves, coral reefs etc.
• At the ecosystem level, India, for instance, with its deserts, rain forests, mangroves, coral reefs, wetlands, estuaries, and alpine meadows has a greater ecosystem diversity than a Scandinavian country like Norway.

Biodiversity of India

• India is a recognized as one of the mega-diverse countries, rich in biodiversity and associated traditional knowledge.
• India has 23.39% of its geographical area under forest and tree cover.
• With just 2.4% of the land area, India accounts for nearly 7% of the recorded species even while supporting almost 18% of human population.
• In terms of species richness, India ranks seventh in mammals, ninth in birds and fifth in reptiles.
• In terms of endemism of vertebrate groups, India’s position is tenth in birds with 69 species, fifth in reptiles with 156 species and seventh in amphibians with 110 species.
• India’s share of crops is 44% as compared to the world average of 11%.
India Represents
• Two ‘Realms’
• Five Biomes
• Ten Bio-geographic Zones
• Twenty five Bio-geographic provinces


  1. Biogeographic realms are large spatial regions within which ecosystems share a broadly similar biota.
  2. Realm is a continent or sub-continent sized area with unifying features of geography and fauna & flora.
  3. The Indian region is composed of two realms. They are:
    • The Himalayan region represented by Palearctic Realm and
    • The rest of the sub-continent represented by Malayan Realm
  4. In world Eight terrestrial biogeographic realms are typically recognized. They are
    • Nearctic Realm
    • Palaearctic Realm
    • Africotropical Realm
    • Indomalayan Realm
    • Ocenaia Realm
    • Australian Realm
    • Antarctic Realm
    • Neotropical Realm

Biomes of India

  1. The term biome means the main groups of plants and animals living in areas of certain climate patterns.
  2. It includes the way in which animals, vegetation and soil interact together. The plants and animals of that area have adapted to that environment.
    The five biomes of India are:
    • Tropical Humid Forests
    • Tropical Dry or Deciduous Forests (including Monsoon Forests)
    • Warm deserts and semi-deserts
    • Coniferous forests and
    • Alpine meadows.

Bio-geographic Zones

  1. Biogeography deals with the geographical distribution of plants and animals.
  2. Biogeographic zones were used as a basis for planning wildlife protected areas in India.
  3. There are 10 biogeographic zones which are distinguished clearly in India.

Bio-geographic provinces

• Bio-geographic Province is a eco systematic or biotic subdivision of realms. India is divided into 10 bio geographic zones and 25 biogeographic provinces.

List of Bio-geographic zones :


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