Abiotic (non-living) factors which can affect a community are:

The idea

A community is all the populations of different species living together in a habitat. Abiotic factors are the non-living physical and chemical conditions of that habitat, and they affect which species can survive there. The main abiotic factors are light intensity, temperature, moisture levels, soil pH and mineral content, wind intensity and direction, carbon dioxide levels for plants, and oxygen levels for aquatic animals. Each factor acts on organisms in a particular way. Light intensity affects photosynthesis and so plant growth; temperature affects enzyme activity and metabolic rate; moisture affects water availability; soil pH and minerals affect plant growth; wind affects transpiration and dispersal; carbon dioxide limits photosynthesis; and dissolved oxygen limits respiration in water. A change in any of these can change the community.

What earns the marks

• Name abiotic factors accurately, including light intensity, temperature, moisture, soil pH and mineral content, wind intensity and direction, carbon dioxide level and oxygen level.
• State that abiotic factors are non-living, physical or chemical conditions of the habitat.
• Link each factor to its effect on organisms, for example light intensity affects photosynthesis and temperature affects enzyme activity.
• Distinguish carbon dioxide as a factor mainly affecting plants from oxygen as a factor mainly affecting aquatic animals.
• Explain that a change in an abiotic factor can change which species survive, so the community changes.
• Use correct units or scales where data is given, such as lux for light intensity, °C for temperature or pH for soil acidity.

Common mistakes and how to put them right

• Listing biotic factors such as food supply, predators or disease as abiotic.

  Put it right: Abiotic factors are non-living, so use light, temperature, moisture, pH, wind, carbon dioxide and oxygen.

• Confusing carbon dioxide and oxygen roles.

  Put it right: Carbon dioxide is needed by plants for photosynthesis, while oxygen is needed by animals, especially aquatic ones, for respiration.

• Treating soil pH and mineral content as the same factor.

  Put it right: pH measures acidity or alkalinity, while mineral content refers to nutrients such as nitrates and phosphates.

Exam tips

• Learn the list of abiotic factors as a set and be ready to select the ones relevant to the habitat described.
• When asked to name factors, give the specific factor, such as light intensity, rather than a vague term like weather.
• Link each factor to a biological process, such as photosynthesis, enzyme activity or respiration, to gain explanation credit.