Topic Summaries

Biotic and abiotic factors

IGCSE > Biology > Pearson IGCSE > IGCSE Biology Topic Summaries > Ecosystems > Biotic and abiotic factors
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  • Biotic (living) factors that can affect a community include availability of food, new predators arriving, new pathogens, or one species outcompeting another so the numbers are no longer sufficient to breed.
    • A change in a biotic factor would affect a community, e.g. if a new pathogen appeared and killed an entire species, the organisms depending on this species for food or a habitat would also die.
  • Abiotic (non-living) factors that can affect a community include: light intensity (e.g. plants adapted to the shade may quickly wilt and die if they are moved into direct sunlight), temperature (e.g. some organisms like reptiles cannot regulate their own body temperature), CO2 levels in plants (a major limiting factor in photosynthesis) and O2 levels for aquatic animals (required for respiration), moisture levels, soil pH and mineral content, and wind intensity/direction.
    • A change in an abiotic factor would affect a community (e.g. cacti are adapted to survive with little water and will die if overwatered, so species that depend on cacti for a habitat or a food resource would then also die).

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