NCERT Solutions for Class 12 Biology Chapter 13 Biodiversity and Conservation

Short Note:

• Biodiversity exists at three levels: genetic diversity (variation in genes within a species), species diversity (variety of species within a region), and ecological diversity (variety of ecosystems within a geographic area).

• A key global pattern is the latitudinal gradient, where species diversity generally increases from the poles towards the equator, with tropical regions like the Amazon rainforest showing much greater species richness than temperate or polar regions, attributed to factors such as stable climate, more solar energy, and greater ecological niche specialisation.

Short Note:

• Biodiversity provides essential ecosystem services, including pollination, nutrient cycling, climate regulation, and serves as a source of food, medicine and industrial products, in addition to its ethical and aesthetic value.

• The species-area relationship, described mathematically, shows that as the area of a habitat increases, the number of species found within it also increases, though at a decreasing rate, following a roughly logarithmic relationship.

Short Note:

• Major causes of biodiversity loss, often summarised as the 'Evil Quartet', include habitat loss and fragmentation (the most significant cause), over-exploitation of species (overharvesting or overhunting), invasion by alien/exotic species that outcompete native species, and co-extinctions (when the extinction of one species leads to the extinction of another dependent species).

Short Note:

• In-situ conservation involves protecting species within their natural habitat, through the establishment of protected areas such as national parks, wildlife sanctuaries, and biosphere reserves.

• Ex-situ conservation involves protecting species outside their natural habitat, such as in zoological parks, botanical gardens, wildlife safari parks, and through techniques like cryopreservation of gametes and seed banks, which help preserve genetic material for future use.