Detailed Notes CHAPTER 13 BIODIVERSITY AND CONSERVATION

CHAPTER 13 BIODIVERSITY AND CONSERVATION

Introduction

• Enormous Diversity of Life

  • Amazes alien visitors due to the vast variety of life forms on Earth.

• Astonishing Species Numbers

  • Over 20,000 species of ants, 300,000 species of beetles, 28,000 species of fishes, and nearly 20,000 species of orchids highlight the diversity.

• Variety Across Different Taxa

  • Diversity is observed across insects (ants, beetles), fishes, and plants (orchids).

• Ecological and Evolutionary Questions

  • Scientists study biodiversity to answer crucial questions about the Earth’s ecosystems and evolutionary processes.

• Why So Many Species?

  • Investigates the reasons behind the abundance of species, including evolutionary and ecological factors.

• Historical Diversity

  • Explores whether Earth has always had such rich diversity or if it has changed over time.

• Diversification Mechanisms

  • Studies how species diversify through processes like natural selection and speciation.

• Importance to the Biosphere

  • Examines the vital role of biodiversity in ecosystem stability, resilience, and functioning.

• Functionality with Less Diversity

  • Considers hypothetical scenarios to understand ecosystem dynamics with reduced biodiversity.

• Human Benefits

  • Highlights the direct benefits humans derive from biodiversity, such as ecosystem services, medicines, and cultural values.

13.1 BIODIVERSITY

• Levels of Biological Organization

  • Diversity exists at all levels, from macromolecules within cells to entire biomes.

• Definition of Biodiversity

  • Term popularized by Edward Wilson to describe diversity across all levels of biological organization.

• Important Components of Biodiversity

  • Genetic Diversity
    • Variation within a species at the genetic level, e.g., different strains of rice and varieties of mango in India.
  • Species Diversity
    • Diversity at the species level, e.g., comparing amphibian diversity in the Western Ghats and the Eastern Ghats.
  • Ecological Diversity
    • Diversity at the ecosystem level, showcasing different ecosystems like deserts, rain forests, mangroves, coral reefs, etc., in India compared to countries like Norway.

• Time Frame and Accumulation of Diversity

  • It has taken millions of years of evolution to accumulate the current rich diversity in nature.

• Threats to Biodiversity

  • Present rates of species losses could lead to a significant loss of biodiversity in a relatively short time frame, emphasizing the urgency of conservation efforts.

• Importance of Biodiversity Conservation

  • Vital environmental issue of international concern due to its critical importance for human survival and well-being on the planet.

13.1.1 How Many Species are there on Earth and How Many in India?

• Difficulty in Determining Total Species

  • Recorded species: More than 1.5 million species described.
  • Uncertainty: Difficult to determine total species on Earth due to undiscovered species.
  • Estimates: Vary widely, with conservative estimates around 7 million species.

• Factors Influencing Species Discoveries

  • Completeness: Inventories more complete in temperate regions than tropical regions.
  • Tropical biodiversity: Majority of undiscovered species likely in tropical regions.

• Current Species Distribution

  • Animal vs. plant diversity: More than 70% of recorded species are animals, while plants make up about 22%.
  • Insects dominance: Insects represent over 70% of animal species.

• Fungi and Microbial Diversity

  • Fungi vs. other groups: Fungi species outnumber combined species of fishes, amphibians, reptiles, and mammals.
  • Prokaryotic diversity: Unknown due to difficulties in identification; might be in the millions if using biochemical or molecular criteria.

• Global and Indian Biodiversity

  • India’s biodiversity: Impressive diversity with 8.1% of global species diversity.
  • Recorded species in India: Around 45,000 plant species and twice as many animal species.

• Estimates for Undiscovered Species

  • Proportion of discovered vs. undiscovered: Only about 22% of total species may have been recorded globally.
  • Indian estimate: Potential for more than 1,00,000 plant species and over 3,00,000 animal species yet to be discovered.

• Challenges and Conservation

  • Completing inventory: Requires significant time and trained personnel (taxonomists).
  • Extinction threat: Many species face extinction before discovery, highlighting the urgency of conservation efforts.

13.1.2 Patterns of Biodiversity

• Latitudinal Gradients

  • Diversity distribution: Not uniform globally, shows an uneven distribution.
  • Latitudinal gradient: Species diversity decreases from the equator towards the poles.
  • Tropical diversity: Tropics (23.5° N to 23.5° S) have more species than temperate or polar regions.
  • Examples: Colombia near the equator has more bird species than New York or Greenland.
  • India’s biodiversity: With much of its land in the tropics, India has high species diversity.

• Special Characteristics of Tropics

  • Speciation time: Tropics have had long undisturbed periods, allowing for more evolutionary time and species diversification.
  • Environmental stability: Less seasonal and more constant environments in tropics promote niche specialization and species diversity.
  • Solar energy and productivity: More solar energy in tropics contributes to higher productivity, indirectly supporting greater biodiversity.

• Species-Area Relationships

  • Observations by Humboldt: Species richness increases with explored area but only up to a limit.
  • Relationship pattern: Rectangular hyperbola on a logarithmic scale.
  • Equation: log S = log C + Z log A (where S = Species richness, A = Area, Z = slope).
  • Similarity across taxa: Slope values (Z) are similar across different taxonomic groups and regions.
  • Continent-scale relationships: Steeper slopes (higher Z values) observed for larger areas like entire continents.

• Interpretation of Steeper Slopes

  • Larger areas: Steeper slopes indicate a faster rate of species accumulation with increasing area.
  • Example: Tropical forests show steeper slopes in species-area relationships, suggesting higher species richness with larger areas, especially for frugivorous birds and mammals.