NCERT Solutions for Class 12 Biology Chapter 13 Biodiversity and Conservation
NCERT Solutions for Class 12 Biology Chapter 13 Biodiversity and Conservation covers Levels of Biodiversity, Patterns of Biodiversity, Species-Area Relationship, Loss of Biodiversity ('The Evil Quartet'), In-situ and Ex-situ Conservation Strategies, and International Summits.
Overview of Topics & Subtopics (Click to Jump)
1. Levels & Patterns of Biodiversity
Short Note:
• Levels of Biodiversity:
1. Genetic Diversity: Diversity at the genetic level within a single species (e.g., Rauvolfia vomitoria producing reserpine, >50,000 rice strains in India).
2. Species Diversity: Diversity at the species level (e.g., Western Ghats have greater amphibian species diversity than Eastern Ghats).
3. Ecological Diversity: Diversity at the ecosystem level (e.g., India has deserts, rainforests, mangroves, coral reefs).
• Species-Area Relationship (Alexander von Humboldt): Within a region, species richness increases with increasing explored area up to a limit. Equation: S = C AZ or log S = log C + Z log A.
2. Loss of Biodiversity & 'The Evil Quartet'
Short Note:
• The Evil Quartet (Four Major Causes of Extinction):
1. Habitat Loss and Fragmentation: Most important cause (e.g., Amazon rainforest reduced from 14% to less than 6% of Earth's land surface).
2. Over-exploitation: Excessive human consumption leading to extinction (e.g., Steller's sea cow, Passenger pigeon).
3. Alien Species Invasions: Introduced foreign species causing decline or extinction of indigenous species (e.g., Nile perch introduced into Lake Victoria, Lantana, Water Hyacinth / Eichhornia, Parthenium, African catfish Clarias gariepinus).
4. Co-extinctions: When a host species becomes extinct, parasites or plant-pollinator mutualists linked to it also go extinct.
3. Biodiversity Conservation Strategies (In-situ & Ex-situ)
Short Note:
• In-situ Conservation (On-site): Protecting endangered species within their natural habitat.
- Examples: Biosphere Reserves (14 in India), National Parks (90 in India), Wildlife Sanctuaries (448 in India), Biodiversity Hotspots (34 worldwide; Western Ghats-Sri Lanka, Indo-Burma, Himalayas), and Sacred Groves (e.g., Khasi and Jaintia Hills in Meghalaya).
• Ex-situ Conservation (Off-site): Protecting threatened plants and animals outside their natural habitats.
- Examples: Zoological Parks, Botanical Gardens, Wildlife Safari Parks, Cryopreservation (-196°C in liquid nitrogen), Seed Banks, Tissue Culture.
• International Conventions:
- The Earth Summit (1992): Rio de Janeiro, Brazil - aimed at conservation of biodiversity and sustainable utilization of its benefits.
- World Summit on Sustainable Development (2002): Johannesburg, South Africa - 190 countries pledged to achieve significant reduction in biodiversity loss rate.
Intext & Conceptual Questions
| Feature | In-situ Conservation | Ex-situ Conservation |
|---|---|---|
| Definition | Conservation of species within their natural habitats and ecosystems. | Conservation of threatened organisms outside their natural habitat in controlled environments. |
| Protection Scope | Protects the entire ecosystem along with all associated wild organisms. | Focuses on individual threatened or endangered plant and animal species. |
| Examples | National Parks, Wildlife Sanctuaries, Biosphere Reserves, Sacred Groves. | Zoological Parks, Botanical Gardens, Seed Banks, Cryopreservation. |
| Cost & Space | Cost-effective for large areas; preserves natural evolutionary processes. | Requires specialized infrastructure, high maintenance costs, and active management. |
Species-Area Relationship: German naturalist Alexander von Humboldt observed that within a given region, species richness increases with an increase in explored area, but only up to a specific limit.
On a logarithmic scale, the relationship forms a straight line represented by:
log S = log C + Z log AWhere:
• S: Species richness
• A: Area explored
• Z: Slope of the line (regression coefficient, typically 0.1 to 0.2)
• C: Y-intercept
Textbook Chapter End Exercise Questions
The four major causes of biodiversity loss are collectively termed 'The Evil Quartet':
1. Habitat Loss and Fragmentation: Destruction of natural habitats due to deforestation, urbanization, and land clearing isolates wildlife populations and drastically reduces living space.
2. Over-exploitation: Excessive hunting, poaching, and harvesting beyond natural replacement levels have caused species extinctions (e.g., Passenger Pigeon, Steller's Sea Cow).
3. Alien Species Invasions: Non-native species introduced accidentally or deliberately compete with and eliminate indigenous species (e.g., Nile perch in Lake Victoria, Lantana, Water Hyacinth).
4. Co-extinctions: Obligate mutualistic relationships mean that the extinction of one species inevitably leads to the extinction of another (e.g., host-parasite pairs, plant-pollinator systems).
Biodiversity Hotspots: Geographic regions characterized by exceptionally high levels of species richness, high degree of endemism (species confined exclusively to that region), and facing severe threats of habitat destruction.
Biodiversity Hotspots covering India:
1. Western Ghats and Sri Lanka
2. Indo-Burma Region
3. Himalayas
Sacred Groves: Undisturbed forest patches protected by indigenous communities due to religious beliefs, cultural traditions, and spiritual veneration.
Significance:
• They serve as sanctuary zones for rare, threatened, and endemic species of flora and fauna that have disappeared from surrounding deforested landscapes.
• Examples include the Khasi and Jaintia Hills in Meghalaya, Aravalli Hills of Rajasthan, and Western Ghat regions of Karnataka and Maharashtra.
Read More & Chapter Resources
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