Edexcel International A Level Biology

Revision Notes

5.12 Factors Affecting Populations

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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

Biotic factors that affect 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

Abiotic factors that affect a community table

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Author: Naomi H

Naomi graduated from the University of Oxford with a degree in Biological Sciences. She has 8 years of classroom experience teaching Key Stage 3 up to A-Level biology, and is currently a tutor and A-Level examiner. Naomi especially enjoys creating resources that enable students to build a solid understanding of subject content, while also connecting their knowledge with biology’s exciting, real-world applications.