Abiotic & Biotic Factors (OCR GCSE Biology A (Gateway))

Abiotic & Biotic Factors

• The environment in which communities of plants and animals live changes all the time

• These changes are caused by abiotic (non-living) and biotic (living) factors

• These factors affect communities in different ways, for example

  • For some species, certain factors may cause their population size to increase, whereas for other species, that same change may cause their population size to decrease

  • For some species, certain factors may cause the distribution of their populations (i.e. where they live) to change

Abiotic factors

• In Biology, ‘abiotic’ means non-living

• An abiotic factor is a non-living factor within an environment such as temperature, light intensity and water availability

• An example of an abiotic factor is a high soil pH which is unsuitable for wild azaleas to grow

  • Wild azaleas prefer a soil pH of 4.5 to 6.5

  • Azaleas would need to find another habitat

• The table below explains how these abiotic factors may affect a community of organisms

  • One abiotic factor not included in this table is the presence and levels of pollutants, which can change the size and distribution of populations of certain species

  • For example, some lichen species are very sensitive to air pollution and are not able to grow if the concentration of sulfur dioxide (an air pollutant) rises above a certain level

Abiotic Factors that Affect Communities Table

Biotic factors

• In Biology, ‘biotic’ means living

• A biotic factor is a living factor in the environment such as competition, predation, camouflage and disease

• An example of a biotic factor is the chameleon, whose camouflaged skin makes it a very effective predator of insects, thus reducing the insect species' populations

• More examples of biotic factors are shown in the table below

Biotic Factors that Affect Communities Table