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Topic last updated: 09 Nov 2023
    • Biology Biology
    • Ico Science Science
    • 14-16
    • 55

Ecosystems and ecology

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Biotic and abiotic factors

The community contains both biotic and abiotic factors. The biotic factors are the living and the abiotic are the non-living. Both the biotic and abiotic factors interact with each other in an ecosystem, and any changes to the factors can influence other factors.

The table below shows how changes to biotic or abiotic factors can be important.


Biotic or Abiotic


Food availability


All animals eat organisms including animals and plants. This means that  all sources of food are biotic factors, as they are living things. If the availability of food decreases, then the number of organisms in the community will also fall as the food chain has been disrupted.



Predators eat prey. If a new predator arrives then this will make the population of the prey fall. The introduction of a new predator may also affect existing predators, as they are both competing for the same prey. Therefore, the population of the existing predator may fall too.



If a species is out competed the population will fall. If the numbers drop too low then there may not be enough individuals to allow reproduction, and the species is at risk of becoming extinct.

New pathogens


The introduction of pathogens can mean that a new infectious disease is spread. This could kill a whole population.

Light intensity


Light is needed for photosynthesis. If light intensity is too low, then the rate of photosynthesis is low, and plants do not grow as quickly. Therefore, the animals which consume the plant may not have enough food.



Temperature changes can mean that species migrate, and this alters the distribution of species. Plant species could also die out if the temperature is too high.

Moisture levels


Both plants and animals need water to be able to survive.

Soil pH and mineral content


Plants need a particular soil pH as if it is too acidic or too basic this could make the plant to die. Plants also need nutrients from the soil such as nitrate, which is needed to make amino acids and proteins.

Wind intensity and direction


Wind intensity affects plants due to transpiration. The stronger the wind, the more transpiration occurs which increases water loss.



CO2 is needed for photosynthesis. If CO2 is low, the rate of photosynthesis will fall, and the plant cannot grow as quickly.



O2 is needed for aerobic respiration. This is not usually a problem for on land species as O2 levels in the air stay consistent, but it can be an issue for aquatic organisms. Oxygen levels in the water can drop when the temperature is high, and this can affect aquatic organisms.