What Are Abiotic and Biotic Factors in an Ecosystem?
Learn the difference between abiotic and biotic factors in an ecosystem, with GCSE Biology examples and a simple tip for classifying factors in exam questions.
Abiotic factors are the non-living parts of an environment, such as temperature and light intensity. Biotic factors are living things or changes involving them, such as the arrival of a new predator. Both can affect which organisms live in an ecosystem and how many there are.
What is an ecosystem?
An ecosystem is a community of living organisms interacting with the non-living parts of their environment. For example, plants and animals in a pond interact with one another, while also being affected by light, temperature and the water available.
Abiotic factors
Abiotic factors include light intensity, temperature, moisture levels, soil pH and mineral content, and wind intensity and direction. Carbon dioxide levels can affect plants, while oxygen levels can affect aquatic animals.
Suppose a shaded area receives less light. Plants growing there may photosynthesise less and grow less well. Animals that depend on those plants for food may then also be affected. The initial change in light is abiotic, even though it has consequences for living organisms.
Biotic factors
Biotic factors include food availability, new predators, new pathogens and competition between species. A pathogen is a microorganism that causes disease.
For example, if a new predator enters a habitat, it may eat more of a particular prey species. The number of those prey animals could fall, which may affect other organisms that eat them. The predator is a biotic factor because it is living.
Exam tip: Classify the factor causing the change, not the organism affected. A change in water availability is abiotic even if it changes a plant population. A new predator is biotic even if it affects the same population.
