Biodiversity and Conservation Class 12 Notes

What is Biodiversity?

• Genetic diversity — variation of genes within a species; e.g. different varieties of rice or the many breeds of dogs.
• Species diversity — the number and variety of species in a region (species richness).
• Ecological diversity — the variety of ecosystems such as forests, grasslands, deserts and coral reefs in a region.
• The rich diversity in a region is called biodiversity; the more species and genes a region holds, the more biodiverse it is.

Patterns of Biodiversity

Importance of Biodiversity

• Productive value — sources of food, fibre, medicines and other products; a huge proportion of modern medicines derive from plants and microbes.
• Ethical value — every species has a right to exist; humans are only one species among many and must not cause extinction.
• Aesthetic value — the beauty of diverse life brings happiness, pleasure and recreation.
• Option value — preserving genetic diversity keeps future options open for discovering new products, crops and medicines (an unknown future potential).

Loss of Biodiversity

• Habitat loss and fragmentation — the most important cause; clearing forests and draining wetlands destroy homes and split populations.
• Over-exploitation — excessive hunting and harvesting; e.g. the passenger pigeon and Steller's sea cow were driven extinct by humans.
• Alien species invasion — introduced species outcompete natives; e.g. the Nile perch eliminated cichlid fish in Lake Victoria, and Lantana replaced native shrubs.
• Co-extinction — when a species goes extinct, the species that depend on it (its parasites, pollinators) often go extinct too.
• The IUCN estimates that about 34,000 plant species are threatened globally, and recent extinction rates are tens to hundreds of times the natural background rate.

Biodiversity Hotspots

• India has four hotspots: the Himalayas, Indo-Burma (northeast), the Western Ghats and Sri Lanka, and Sundaland (Andaman and Nicobar Islands).
• Collectively, the world's hotspots hold 43% of all terrestrial vertebrate species and more than 50% of the world's plants, though they cover only about 2.5% of Earth's land area.
• Hotspots contain a very large fraction of endemic species and are priorities for urgent conservation.

Conservation Strategies — In Situ and Ex Situ

• National parks and wildlife sanctuaries — protect habitats and the species living in them.
• Biosphere reserves — large protected areas (India has 14) that conserve whole ecosystems.
• Sacred groves — forest patches protected and preserved by tribal communities for religious reasons; e.g. the sacred grooves of Khasi and Jaintia Hills in Meghalaya and the Aravalli Hills of Rajasthan — pristine ecosystems preserved without modern legislation.
• Pristine sites like these sacred groves show how indigenous traditions preserve biodiversity.

• Zoos and botanical gardens — maintain living populations of threatened species.
• Seed banks — store seeds of many plant varieties for future use.
• Cryopreservation — freezing of gametes, embryos and other genetic material at very low temperatures.
• Tissue culture — rapid propagation of rare or endangered plants from small tissue samples.
• Wildlife safari parks and other protected ex situ facilities complement in situ reserves.

International Efforts and Summary

The most important international effort is the Convention on Biological Diversity (CBD), signed at the Earth Summit held in Rio de Janeiro, June 1992. The CBD has three objectives: conservation of biodiversity, sustainable use of its components, and the fair and equitable sharing of benefits arising from genetic resources.

• Earth Summit (Rio, 1992) — adopted the Convention on Biological Diversity and the Agenda 21 framework.
• The World Summit on Sustainable Development (2002) and other follow-ups keep biodiversity on the global agenda.
• India is a megadiverse country and a party to the CBD, committing to conserve hotspots and reduce rates of biodiversity loss.
• Conservation is therefore both a national and an international responsibility combining in situ, ex situ and community efforts.

Solved Examples

Example: A logger's survey finds that increasing an explored area from 1 km² to 4 km² doubles the number of bird species recorded. Using S = CA^Z, what does this imply about the exponent Z for that region?

Solution: If area A quadruples (1 → 4) and S doubles, then S₂/S₁ = 2 = (A₂/A₁)^Z = 4^Z, so 4^Z = 2 gives Z = 0.5. This confirms that the island-like or continental nature of the region sets its Z value; steeper slopes (higher Z) mean richness rises faster with area.

Example: Distinguish in situ from ex situ conservation, with one example of each.

Solution: In situ conservation protects species in their natural habitat — national parks, wildlife sanctuaries, biosphere reserves and sacred groves are examples. Ex situ conservation protects species outside their habitat — zoos, botanical gardens, seed banks, cryopreservation and tissue culture are examples. Both approaches are needed for effective biodiversity protection.