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Biodiversity, Conservation and Environmental Issues — Class 12 Maharashtra HSC Biology revision notes

A 7-page visual revision sheet for Biodiversity, Conservation and Environmental Issues, written for Class 12 Maharashtra HSC Biology. Formulas, diagrams and the traps that cost marks, laid out to be read the night before rather than the term before. Free, and it opens inside CapCompass.

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Biodiversity, Conservation and Environmental Issues in one look

three levels of variety, four ways it's being lost, and the pollution problem sitting alongside it

Biodiversity: Levels

  • term coined by Walter Rosen (1982), popularised by Edward Wilson
  • per IUCN/UNEP/WRI: biodiversity is the totality of genes, species and ecosystems in a region
  • the outcome of 3.5 billion years of evolutionary history
  • genetic diversity: intraspecific, variation in genes and alleles within and between populations of one species
  • underlies evolution and adaptability, e.g. ~1000 mango varieties, ~50,000 rice varieties in India
  • species diversity: interspecific, species richness (how many) and species evenness (how individuals distribute)
  • India is one of 12 megadiversity nations
  • ecological (ecosystem) diversity: variety of ecosystem types within a region
  • e.g. India: desert, rain forest, deciduous forest, wetland, estuary, grassland, vs much lower diversity in Norway

Patterns of Biodiversity

  • latitudinal gradient: species richness is highest near the equator, declines toward the poles
  • true for most plants and animals
  • tropical rain forests are richest: Amazon ~40,000 plants, 1,300 birds, 427 mammals, 3,000 fish
  • reasons proposed: long-term climatic stability, less migration between isolated populations (less gene flow)
  • abundant sunlight, warmth and rainfall favouring speciation
  • altitudinal gradient: diversity is higher at lower altitudes, falls as climate turns harsher and more seasonal

Species-Area Relationship

  • Alexander von Humboldt: species richness rises with area, but only up to a limit
  • the relationship is close to a rectangular hyperbola
  • log S = log C + Z log A
  • S is species richness, A is area, C the Y-intercept, Z the slope
  • for smaller areas, Z typically runs 0.1 to 0.2, regardless of species or region
  • for entire continents, the slope steepens toward vertical
  • meaning species count rises faster than area explored, at that scale

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