Biology · Ch 13 — Biodiversity and Conservation
Summary
Summary
- Life on Earth has been diversifying for nearly 3.8 billion years, since it first originated. Biodiversity is the variety of living organisms that resulted, at three levels: genetic (variation within a species), species (number of species in a region), and ecological (diversity of ecosystems). Of the species named so far, more than 70% are animals, and 70% of those are insects — while the fungi alone outnumber all vertebrate species (fishes, amphibians, reptiles and mammals) put together.
- India is one of the 12 megadiversity countries, with about 8.1% of the world's species, and is also a centre of origin for many crop plants.
- Species diversity is measured by species richness (number of species). The Species-Area relationship is S = c × A^z, where S = species richness, A = area, c = a constant, and z = the slope — typically 0.1-0.2 for smaller areas within a region, but a steeper 0.6-1.2 when plotted across entire continents.
- Roughly 1.5 million species have been described so far. Total estimates vary widely: some extreme figures range from 20 to 50 million, while a more conservative, scientifically grounded estimate by Robert May puts global species diversity at about 7 million. Latitudinal gradients show diversity peaks in the tropics and declines toward the poles.
- Communities with higher diversity tend to be more stable — less variable in productivity year to year, more productive overall, and more resistant to invasion by new species.
- Loss of biodiversity occurs due to four major causes (the Evil Quartet): habitat loss and fragmentation, over-exploitation, invasive alien species, and co-extinctions. Nearly 700 species have gone extinct in recent times, and more than 15,500 species (over 650 of them in India) currently face the threat of extinction.
- Biodiversity hotspots are regions with very high species richness and a high degree of endemism, also facing accelerated habitat loss. There are 34 global hotspots; three cover India's exceptionally high biodiversity regions: Western Ghats and Sri Lanka, Indo-Burma, and the Himalaya.
- Ecosystem services — the benefits ecosystems provide, such as pollination, pest control, climate moderation and flood control, and other processes with immense economic value, though the book gives no dollar figure for it.
- Conservation strategies are in situ (within natural habitats) and ex situ (outside natural habitats).
- In situ: Biosphere Reserves, National Parks, Wildlife Sanctuaries, Sacred Groves. India has 14 Biosphere Reserves, 90 National Parks, and 448 Wildlife Sanctuaries.
- Ex situ: Botanical Gardens, Zoos, Gene Banks, Seed Banks, Cryopreservation. …