Biodiversity and Conservation Class 12 Notes Biology Chapter 15

Chapter at a Glance

  • Biodiversity or biological diversity is the occurrence of different types of ecosystem, different species of organisms with their biotypes & genes adapted to different climates, environments along with their interactions & processes.
  • Biodiversity includes three inter-related hierarchial levels. These are genetic diversity, species diversity & community/ecosystem/ecological diversity.
    • Genetic diversity refers to variation of genes within species both among geographically separated populations and among individual of single population. These differences can be in between alleles, in entire genes or in chromosomal structures.
    • Species diversity refer to variety of species within a region from micro­ organisms such as virus, bacteria and protist to the multicellular kingdom of plants, animals and fungi.
    • Ecosystem (ecological) diversity describes number of niches, trophic levels and various ecological processes that sustain energy flow, food web and recycling of nutrients, E.g., India with desert, rain forest, mangrove, coral reef, wetland has greater ecosystems diversity than scandinavian country like Norway.
  • Diversity at community and ecosystem has 3 perspectives: alpha diversity, beta diversity, and gamma diversity.
  • The terms alpha, beta, and gamma diversity were all introduced by R. H. Whittaker to describe the spatial component of biodiversity.
    • Alpha diversity refers to the diversity of organism sharing the same community or habitat. It is dependent on species richness and species evenness.
    • The rate of replacement of species along a gradient of habitat or community is called beta diversity.
    • Diversity of habitat over total landscape or geographical area is called gamma diversity.
  • Biodiversity varies with change in latitude or altitude. Biodiversity increases, as we move from high to low latitude as (i.e., from poles to equator).
  • The relation between species richness and area having wide variety of taxa is rectangular hyperbola.
  • The number of species per unit area is called species richness and the number of individuals of different species represents species evenness.
  • If individuals of a species remain alive only in captivity or other human controlled conditions, the species is said to be extinct in wild.
  • A species is said to be locally extinct if it is no longer found in area, once it inhabited, but is still found somewhere else in wild.
  • A species is said to be ecologically extinct if it persists at such reduced numbers that its effect on other species in community are negligible. For instance, few tigers remain in wild that their impact on prey population is insignificant.
  • Loss of biodiversity or biodiversity loss is the extinction of species (plant or animal) worldwide, and also the local reduction or loss of species in a certain habitat.
  • The International Union for Conservation of Nature (IUCN) was established in the year 1964 to maintain Red Data Book.
  • Red data book is a source document which maintains the record of all the rare and endangered species of animals, plants and fungi as well as some local subspecies that exist within the territory of the state or country.
  • IUCN (Red list, 2004) documents the extinctions of784 species in which 338 are vertebrates, 359 are invertebrates and 87 plants in the last 500 years.
  • Major causes of loss of biodiversity are – habitat destruction, habitat fragmentation, habitat degradation & pollution, introduction of exotic species, over exploitation and co-extinction.
  • Introduction of exotic species, increased levels of diseases, and excessive exploitation of particular species causes significant biodiversity losses.
  • Disease causing micro-organisms, if introduced to new virgin areas may cause epidemics and native species are eliminated completely.
  • Over exploitation includes the activities like over hunting, over fishing, illegal trade of wildlife and excessive logging. It threatens 113rd of endangered vertebrates in the world, as well as other species. Such as whales, steller’s sea cow and passenger pigeon. Even if a species is not completely eliminated by over exploitation, the population size may become too small that the species is unable to recover.
  • Presently, 12% of all bird species, 23% of all mammal species, 32% of all amphibian species and 31% of all gymnosperm species in the world face the threat of extinction.
  • The current species extinction rates are estimated to be 100-1,000 times faster than in pre-human times.
  • Threatened Species= Endangered+ Vulnerable+ Rare
  • Species with small world population that are not presently endangered or vulnerable but are at risk, are called rare species. E.g., Venus fly trap only in Savannah of coastal plains of Carolina in East U.S.A.


  • Biodiversity conservation is basically aimed at protection, enhancement and scientific management of the biodiversity.
  • It is important to conserve biodiversity because of its several benefits it offers that are essential to live. It provides biological resources, ecosystem services, social and spiritual benefits.
  • IUCN and WWF are leading International Organisations concerned with biodiversity conservation.
  • “The earth Summit” held in Rio de Jeneiro in 1992 called upon all nations to take appropriate measures for conservation of biodiversity and sustainable utilisation of its benefits.
  • There are 2 basic methods of biodiversity conservation: In situ (on site) and Ex situ (off site).

In situ conservation

  • In situ method provides protection to total ecosystem. It includes protection of a group of typical ecosystems through a network of protected areas.
  • Example of protected areas are national park, wild life sancturies and biosphere reserve.
  • The first national park in India is Hailey national park. It was set up in 1935 in the foot hills of Himalayas in Uttar Pradesh.
  • Hot spots are the richest and most threatened reservoir of plants and animals life on earth.
  • The concept of hot spot of biodiversity was developed by Norman Myers (in 1988) to designate priority area for in situ conservation.
  • 25 terrestrial hot spots for conservation of biodiversity have been identified worldwide.
  • Among 25 hot spots of world, 2 are located in India, which are Western Ghat and Eastern Himalayas. These are regions of accelerated habitat loss.
  • Biodiversity hotspots region have very high levels of species richness and high degree of endemism (species are confined to that region and are not found anywhere else).

Ex – situ conservation

  • It a set of conservation techniques which involves the transfer of a target species away from its native habitat.
  • Concept of ex situ conservation was developed earlier before its official adoption under the Convention on Biological Diversity signed in 1992 in Rio de Janeiro.
  • It includes botanical gardens, zoos, conservation stands and gene, pollen seed, seedling, tissue culture and DNA banks.
  • India has 10 biogeographical regions, 89 national parks, 500 wild life sanctuaries, 14 biosphere reserves, 6 wetlands and 35 world heritage sites.

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