• “Describes the number of species, niches, and trophic levels in the ecosystem and the complexity of its food web”
  • Factors that influence biodiversity…
  1. Climate: influences abundance and type of primary producers and number of species primary production can support
  • Climate is major factor in determining location of biomes and where terrestrial organisms live
  1. Latitude: correlated with climate but also determines solar energy exposure
  • Areas at middle/lower latitudes (closer to equator) receive more sun bcuz are tilted closer to sun
  • Also, seasonal variations are minimized at lower latitudes bcuz each day earth strikes at same angle; more constant environment (stable) can support more species
    • So tropical ecosystems are very diverse, have many species but with smaller numbers of each species; polar ecosystems have few species but with many individuals
  1. Habitat size and diversity: influence how many different kinds of organisms can be supported
  • Larger the ecosystem, likely to have more diverse habitats that can support a greater variety of species
  1. Evolutionary History: Tropical communities are generally older than temperate or polar communities, which have repeatedly “started over” after major disturbances such as glaciations.
  • So, species diversity usually highest in the tropics bcuz there has been more time for speciation to occur
  1. Elevation: temp and precipitation strongly correlated with elevation (temp decreases & rain increases as elevation increases)

Stability Of Ecosystems

  • Stability of an ecosystem increases with increases in biodiversity
    • Occurs bcuz in highly diverse system, disturbances may adversely affect only a few species which can be replaced by more unaffected species
      • In systems with low biodiversity, disturbances may have more permanent effect

Island Equilibrium Model

  • Islands closer to mainland and larger are more diverse
    • Small island = fewer resources, less diverse habitats, smaller populations, likely to already have species
  • Number of species gets larger → immigration rate decreases while extinction rate increases