- “Describes the number of species, niches, and trophic levels in the ecosystem and the complexity of its food web”
- Factors that influence biodiversity…
- 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
- 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
- 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
- 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
- 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
- Occurs bcuz in highly diverse system, disturbances may adversely affect only a few species which can be replaced by more unaffected species
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