QUICK REVISION NOTES

Class 12 Biology: Biodiversity and Conservation

MP Board

### Introduction to Biodiversity

• Biodiversity (जैव विविधता): The term was popularised by sociobiologist Edward Wilson. It refers to the immense diversity and rich variety of life-forms existing on Earth at all levels of biological organization, ranging from macromolecules within cells to biomes.
• Levels of Biodiversity:
  1. Genetic Diversity (आनुवंशिक विविधता): Diversity at the genetic level within a single species (e.g., thousands of strains of rice or varieties of mango in India).
  2. Species Diversity (जातीय विविधता): Diversity at the species level (e.g., Western Ghats have a greater amphibian species diversity than the Eastern Ghats).
  3. Ecological Diversity (पारिस्थितिकी तंत्र विविधता): Diversity at the ecosystem level (e.g., deserts, rain forests, mangroves, coral reefs, wetlands in India).

### Magnitude of Biodiversity

• According to the International Union for Conservation of Nature and Natural Resources (IUCN) 2004, the total number of plant and animal species described so far is slightly more than 1.5 million.
• Global Pattern: More than 70% of all species recorded are animals, while plants (including algae, fungi, bryophytes, gymnosperms, and angiosperms) comprise no more than 22% of the total. Among animals, insects are the most species-rich taxonomic group (making up more than 70% of the total).
• India's Biodiversity: India has only 2.4% of the world's land area, but its global species diversity is an impressive 8.1%, making India one of the 12 mega diversity countries of the world. Nearly 45,000 species of plants and twice as many of animals have been recorded from India.

### Patterns of Biodiversity

• Latitudinal Gradients: Species diversity decreases as we move away from the equator towards the poles. Tropics ($\left(23.5^{\circ}\text{ N to } 23.5^{\circ}\text{ S}\right)$ harbor more species than temperate or polar areas.
  • Reasons for greater biodiversity in tropics:
    1. Tropics had more evolutionary time undisturbed by glaciations.
    2. Constant and predictable environment.
    3. More solar energy available, contributing to higher productivity.
• Species-Area Relationship (जाती-क्षेत्र संबंध):
  • Given by German naturalist and geographer Alexander von Humboldt.
  • Within a region, species richness increases with increasing explored area, but only up to a limit.
  • Equation: log S = log C + Z log A
    • S = Species richness (जातीय समृद्धि)
    • A = Area (क्षेत्र)
    • Z = Slope of the line (regression coefficient)
    • C = Y-intercept
  • Note: The value of Z lies in the range of 0.1 to 0.2, regardless of the taxonomic group or region. However, for very large areas like entire continents, the slope is much steeper (Z values in the range of 0.6 to 1.2).

### Importance of Biodiversity (Loss of Biodiversity)

• The "Rivet Popper Hypothesis" (रिवेट पॉपर परिकल्पना): Proposed by Paul Ehrlich. In an airplane (ecosystem), all parts are joined together using thousands of rivets (species). If every passenger pops a rivet to take home (extinction of species), it may not affect flight safety initially, but as more rivets are removed, the plane becomes dangerously weak and eventually crashes. Loss of key species critical to ecosystem functioning poses a severe threat.

### Loss of Biodiversity

• Causes of Biodiversity Loss (The "Evil Quartet" / चार मुख्य कारण):
  1. Habitat loss and fragmentation (आवास क्षति और विखंडन): The most important cause driving animals and plants to extinction (e.g., tropical rainforests reducing from 14% to 8% of earth's land surface).
  2. Over-exploitation (अति-दोहन): When need turns to greed, it leads to extinction (e.g., Steller's sea cow, passenger pigeon).
  3. Alien species invasions (विदेशी जातियों का आक्रमण): Introduction of non-native species can cause decline or extinction of indigenous species (e.g., Nile perch introduced in Lake Victoria led to extinction of cichlid fish; Water hyacinth (Eichhornia crassipes); Lantana; Carrot grass - Parthenium).
  4. Co-extinctions (सह-विलuptता): When a species goes extinct, the plant and animal species associated with it in an obligatory relationship also become extinct (e.g., host fish and parasite, plant-pollinator association).

### Biodiversity Conservation

• Why Conserve Biodiversity?

  • Narrowly utilitarian arguments: Direct economic benefits like food, fodder, firewood, pharmaceuticals, and industrial products.
  • Broadly utilitarian arguments: Ecosystem services provided by nature such as oxygen production, pollination, flood control, and climate regulation.
  • Ethical arguments: Every species has an intrinsic value, and we have a moral duty to care for them and pass on our biological legacy in good order to future generations.

• Strategies for Conservation (संरक्षण की रणनीतियाँ):

### Important Biosphere Reserves, National Parks & Hotspots

• Biodiversity Hotspots: Regions with very high levels of species richness and high degree of endemism (species confined to that region and not found anywhere else). Initially 25, now 34 biodiversity hotspots are recognized globally.
• Hotspots in India:
  1. Western Ghats and Sri Lanka
  2. The Himalayas
  3. Indo-Burma
• Protected Areas in India (as of recent data):
  • National Parks (राष्ट्रीय उद्यान): E.g., Kanha National Park, Bandhavgarh National Park (Madhya Pradesh).
  • Wildlife Sanctuaries (वन्यजीव अभयारण्य).
  • Biosphere Reserves (जीवमंडल आरक्षित क्षेत्र): E.g., Pachmarhi Biosphere Reserve (Madhya Pradesh).
• Important Conventions:
  • The Earth Summit (The Convention on Biological Diversity - CBD) held in Rio de Janeiro in 1992, called upon nations to take appropriate measures for biodiversity conservation and sustainable utilization of its benefits.
  • World Summit on Sustainable Development held in 2002 in Johannesburg, South Africa, where 190 countries pledged to reduce the current rate of biodiversity loss by 2010.