AQA A Level Biology

Revision Notes

7.4.2 Abiotic & Biotic Factors

Abiotic & Biotic Conditions


  • The place where a species lives within an ecosystem is its habitat
  • The role that a species plays within its habitat is known as its niche, including:
    • The biotic interactions of the species (e.g. the organisms it feeds on and the organisms that feed on it)
    • The abiotic interactions (e.g. how much oxygen and carbon dioxide the species exchanges with the atmosphere)
  • A niche can only be occupied by one species, meaning that every individual species has its own unique niche
  • If two species try to occupy the same niche, they will compete with each other for the same resources
    • One of the species will be more successful and out-compete the other species until only one species is left and the other is either forced to occupy a new, slightly different niche or to go extinct from the habitat or ecosystem altogether
  • For example, the three North American warbler species shown below all occupy the same habitat (spruces and other conifer trees) but occupy slightly different niches as each species feeds at a different height within the trees
    • This avoids competition between the three species, allowing them to co-exist closely with each other in the same habitat

Warbler niches, downloadable AS & A Level Biology revision notes

Although these birds niches seem identical, they spend their time eating in different parts of spruces and other conifer trees

Adaptations to abiotic and biotic conditions

  • Adaptations are features of organisms that increase their changes of surviving and reproducing. These adaptations can be:
    • Anatomical (e.g. structural features such as horns, claws or feathers)
    • Behavioural (e.g. courtship of defensive behaviours)
    • Physiological (e.g. processes inside the body such as venom production or the ability to digest cellulose)
  • A species must be adapted to both the biotic and abiotic factors within its habitat in order to use this habitat in a way no other species can (i.e. in order to occupy its unique niche)
  • Examples of adaptations to biotic conditions could include:

Adaptations to biotic conditions, downloadable AS & A Level Biology revision notes

  • Examples of adaptations to abiotic conditions could include:

Adaptations to abiotic conditions, downloadable AS & A Level Biology revision notes

The Effect of Abiotic Factors on Biodiversity

  • The changes that species produce in their abiotic environment can actually result in a less hostile environment
    • As a result, this can change or sometimes increase the biodiversity within that environment
  • Dung beetles are an example of a group of organisms that can create significant and beneficial changes in their abiotic environment
    • Dung beetles occupy a very specific niche within ecosystems
    • Dung beetles have learned to exploit the dung of animals as a resource and they have a characteristic behaviour of rolling the dung into balls before transporting it to their underground burrow for storage as food
    • Their behaviour within their ecosystem has many knock-on effects on the environment and other organisms living in it
    • The burrows and tunnels that they create turns over and aerates the soil (i.e. increases oxygen levels) and the buried dung releases nutrients into the soil, both of which can benefit other organisms like plants
    • The transportation of the dung underground by the beetles also helps to keep fly populations under control
  • Earthworms play a similar role but instead of transporting dung underground they pull dead leaves and other dead organic matter down into the soil
  • These types of organisms are sometimes referred to as ‘ecosystem engineers‘ as they have significant effects on the ecosystems in which they are found


Alistair graduated from Oxford University in 2014 with a degree in Biological Sciences. He has taught GCSE/IGCSE Biology, as well as Biology and Environmental Systems & Societies for the International Baccalaureate Diploma Programme. While teaching in Oxford, Alistair completed his MA Education as Head of Department for Environmental Systems and Societies.

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