Biodiversity and its Conservation — Class 12 Biology

This chapter discusses biodiversity, the variety and variability among living organisms and ecosystems, and the importance of conserving it. Biodiversity is described at three levels: genetic diversity (variation within a species), species diversity (variety of species) and ecological or ecosystem diversity (variety of habitats and communities). Patterns of biodiversity include the latitudinal gradient (diversity increases from the poles to the equator, with the tropics being richest) and the species-area relationship, expressed by Alexander von Humboldt as a rectangular hyperbola and a straight line on a logarithmic scale. The importance of biodiversity is explained through narrowly utilitarian, broadly utilitarian and ethical arguments, and the rivet-popper hypothesis illustrating ecosystem stability. Causes of biodiversity loss, the "Evil Quartet", include habitat loss and fragmentation, over-exploitation, alien species invasions and co-extinctions. Conservation strategies are classified as in situ (protection in natural habitats through biosphere reserves, national parks, wildlife sanctuaries, sacred groves and biodiversity hotspots) and ex situ (protection outside natural habitats through zoological parks, botanical gardens, seed banks, cryopreservation and in vitro fertilisation). The chapter concludes with international efforts and conventions, such as the Earth Summit and the Convention on Biological Diversity, that aim to ensure the sustainable use and equitable sharing of biological resources.