Factors Affecting Populations (Edexcel International A Level Biology): Revision Note

Factors Affecting Populations

• The abundance and distribution of a species within a habitat are determined by a combination of biotic and abiotic factors

• Biotic factors are living factors that influence populations within their community; biotic factors come about as a result of the activity of other organisms e.g.

  • Predation

  • Food availability

  • Intraspecific competition, arising when individuals of the same species compete for resources

  • Interspecific competition, arising when individuals of different species compete for resources

  • Cooperation between organisms

  • Parasitism

  • Disease

The Impact of Biotic Factors on a Community Table

• Abiotic factors are non-living factors that influence populations within their community e.g.

  • Light intensity and wavelength

  • Temperature

  • Turbidity, or cloudiness, of water

  • Humidity

  • Soil or water pH

  • Soil or water salinity

  • Soil composition

  • Oxygen or Carbon dioxide concentration

The impact of Abiotic Factors on a Community Table