🌍 Chapter 13: Biodiversity and Conservation πŸ“˜ Class 12 Biology | NCERT Aligned | PERSUE CLASSES
✳️ Lecture Overview
  • 13.1 Biodiversity
  • Levels, species estimates, patterns, importance, threats
  • 13.2 Biodiversity Conservation
  • Why conserve biodiversity?
  • How do we conserve it? (In situ & Ex situ methods)
πŸ”Ή 13.1 BIODIVERSITY
βœ… Definition
"Biodiversity is the variety and variability of life forms at all levels of biological organization β€” from genes to ecosystems."
πŸ”Έ Coined by: Edward Wilson
πŸ”Έ Foundation of ecosystem health, resilience, and function
🧬 13.1.1 Levels of Biodiversity
πŸ”Ή 1. Genetic Diversity
  • Variation in genes within a species
  • Helps in adaptation and evolution
πŸ§ͺ Example:
  • 50,000+ rice varieties
  • 1,000+ mango varieties in India
πŸ”Ή 2. Species Diversity
  • Diversity of species within a region
πŸ§ͺ Example:
  • Western Ghats > Eastern Ghats in amphibian species
πŸ”Ή 3. Ecological Diversity
  • Variety of ecosystems within a region
πŸ§ͺ Example (India):
  • Deserts, tropical rainforests, mangroves, coral reefs, wetlands
πŸ“Š 13.1.2 How Many Species Are There?
πŸ“Œ Estimated in India:
  • 100,000+ plant species
  • 300,000+ animal species yet undiscovered
🌍 13.1.3 Patterns of Biodiversity
πŸ”Ή A. Latitudinal Gradients
  • Biodiversity ↑ as we move from poles to equator
πŸ§ͺ Amazon rainforest:
  • 40,000+ plant species
  • 125,000+ invertebrates
πŸ“Œ Why tropics have more species?
  • Stable climate
  • Fewer seasonal fluctuations
  • Higher solar energy β†’ more productivity
πŸ”Ή B. Species–Area Relationship
  • Described by: Alexander von Humboldt
Formula:
log 𝑆 = log 𝐢 + 𝑍 log 𝐴
  • S = species richness
  • A = area
  • Z = slope (0.1–0.2 for small areas; up to 1.2 for large islands)
πŸ“Œ In NEET, Z values & curve understanding are often asked.
🧠 13.1.4 Importance of Species Diversity
βœ… Functional Importance
  • More species = more stable ecosystems
David Tilman's field studies:
  • Higher species richness β†’ less year-to-year biomass fluctuation
βœ… Rivet Popper Hypothesis – by Paul Ehrlich
  • Each species is like a rivet in an airplane β€” lose too many and the whole system fails.
πŸ”Έ Encourages protection of every species regardless of size or use
⚠️ 13.1.5 Loss of Biodiversity
πŸ“Œ Extinction Data
  • 784 species extinct in last 500 years
  • 27 species lost in past 20 years
  • 15,500+ species threatened
  • Current Mass Extinction = 6th one, human-driven, 100–1,000Γ— faster than natural rate
πŸ”΄ The Evil Quartet – Four major causes of biodiversity loss
πŸ”Ή 13.2 BIODIVERSITY CONSERVATION
❓ 13.2.1 Why Conserve Biodiversity?
βœ… 1. Narrowly Utilitarian Value
Biodiversity = Source of:
  • Food (cereals, fruits)
  • Medicines (25% drugs plant-derived)
  • Fibers, fuels, oils
βœ… 2. Broadly Utilitarian Value
Ecosystem services like:
  • Oxygen production (Amazon forest: 20% of Oβ‚‚)
  • Water purification, climate regulation
  • Pollination by bees, birds
βœ… 3. Ethical Value
  • Every species has intrinsic right to exist
  • Preserve biodiversity for future generations
🌿 13.2.2 How Do We Conserve Biodiversity?
βœ… A. In situ Conservation (On-site)
  • Protect species within their natural habitats
πŸ“Œ Methods
Biodiversity Hotspots
  • Areas of high endemism + species richness
  • 34 global; 3 in India:
  • Himalaya
  • Indo-Burma
  • Western Ghats–Sri Lanka
  • Cover <2% land, hold 30% of all species
Protected Areas in India
  • 14 Biosphere Reserves
  • 90 National Parks
  • 448 Wildlife Sanctuaries
Sacred Groves
  • Forests protected for religious/cultural reasons
  • Found in Meghalaya (Khasi), Aravallis, Western Ghats
βœ… B. Ex situ Conservation (Off-site)
  • Protect threatened species outside their natural habitat
πŸ“Œ Examples & Techniques
🌐 Global Conservation Efforts
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