Chapter 15 — Biodiversity and Conservation — covers types of biodiversity, patterns, threats (HIPPO), conservation strategies, and biodiversity hotspots. Carries 4-6 marks.
Key Concepts
Levels of Biodiversity
- Genetic diversity: Variation in genes within a species (e.g., different rice varieties)
- Species diversity: Variety of species in an area
- Ecological diversity: Variety of ecosystems (forests, wetlands, deserts, etc.)
Patterns of Biodiversity
Latitudinal gradient: Biodiversity increases from poles to tropics
Tropics have highest biodiversity because: (1) More solar energy (2) More stable climate (3) More time for evolution (no glaciation) (4) More area
Species-Area relationship (Alexander von Humboldt):
log S = log C + Z log A
S = species richness, A = area, Z = slope (0.1-0.2 for small areas, 0.6-1.2 for islands), C = Y-intercept
Tropics have highest biodiversity because: (1) More solar energy (2) More stable climate (3) More time for evolution (no glaciation) (4) More area
Species-Area relationship (Alexander von Humboldt):
log S = log C + Z log A
S = species richness, A = area, Z = slope (0.1-0.2 for small areas, 0.6-1.2 for islands), C = Y-intercept
Importance of Biodiversity
- Narrowly utilitarian: Food, medicines, fibres, industrial products (25% drugs from plants)
- Broadly utilitarian: Ecosystem services — O₂, pollination, nutrient cycling, flood control
- Ethical: Every species has intrinsic right to exist; stewardship responsibility
Threats to Biodiversity — HIPPO
| Threat | Details |
|---|---|
| Habitat loss & fragmentation | Deforestation, urbanisation — #1 cause of extinction. Amazon rainforest losing huge area. |
| Invasive species | Alien species outcompete natives. E.g., Nile perch in Lake Victoria, water hyacinth |
| Pollution | Chemical contamination of air, water, soil |
| Population growth | More resources needed → more pressure on ecosystems |
| Over-exploitation | Overhunting, overfishing. E.g., Steller’s sea cow, dodo, passenger pigeon — all extinct |
Conservation Strategies
| Type | Description | Examples |
|---|---|---|
| In-situ (on-site) | Protect in natural habitat | National parks, wildlife sanctuaries, biosphere reserves, sacred groves |
| Ex-situ (off-site) | Protect outside natural habitat | Zoos, botanical gardens, seed banks, cryopreservation |
India’s Biodiversity
- India has 4 biodiversity hotspots: Western Ghats, Himalayas, Indo-Burma, Sundaland
- ~45,000 plant species, ~91,000 animal species
- 14 Biosphere Reserves, 106 National Parks, 550+ Wildlife Sanctuaries
- Mega-diversity country (one of 17 in the world)
Biodiversity Hotspots (Norman Myers): Regions with high endemism (≥1500 endemic plant species) + high threat (≥70% habitat loss). 36 hotspots globally.
Quick Revision Points
- 3 levels: genetic, species, ecological diversity
- Tropics = most biodiverse; latitudinal gradient
- Species-Area: log S = log C + Z log A
- Threats: HIPPO (Habitat loss #1); Steller’s sea cow, dodo = extinct from over-exploitation
- Conservation: in-situ (national parks, biosphere reserves) + ex-situ (zoos, seed banks)
- India: 4 hotspots, mega-diversity country, 14 biosphere reserves
- Sacred groves: traditional in-situ conservation (Khasi-Jaintia hills, Western Ghats)
Chapter Navigation
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Next: Environmental Issues Class 12 Notes
Related Chapters in Class 12 Biology
- Environmental Issues Class 12 Notes
- Organisms and Populations Class 12 Notes
- Ecosystem Class 12 Notes
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