Ch 15 covers biodiversity — its levels (genetic, species, ecosystem), patterns, importance, causes of loss, and conservation strategies (in situ and ex situ).
Three levels: genetic (within species), species (number of species), ecosystem (habitat diversity). ~1.5 million species described, estimated 5-50 million. Species-area relationship: log S = log C + z log A (z ≈ 0.1-0.2 for small areas, 0.6-1.2 for large areas). Latitudinal gradient: tropics have most species. Explanations: more solar energy, stable climate, more speciation time.
Causes of loss (HIPPO): Habitat loss (most important), Invasive species (Nile perch in Lake Victoria), Pollution, Population growth/overexploitation, climate change (Others including co-extinction). Conservation: In situ (protecting in natural habitat — national parks, wildlife sanctuaries, biosphere reserves, biodiversity hotspots — 36 globally, India has 4). Ex situ (outside habitat — zoos, botanical gardens, seed banks, cryopreservation). IUCN Red List categories.
Download: https://ncert.nic.in/textbook/pdf/lebo115.pdf | Complete book: https://ncert.nic.in/textbook/pdf/lebo1ps.zip
A biodiversity hotspot is a region with: (1) at least 1,500 endemic plant species, and (2) having lost ≥70% of its original habitat. There are 36 hotspots globally, covering only 2.5% of Earth's land area but containing >60% of species. India has 4 hotspots: Western Ghats/Sri Lanka, Indo-Burma, Himalaya, and Sundaland. Hotspots are conservation priorities due to their high endemism and severe threat.
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