Make sure you know your biotic factors versus your abiotic factors and how those factors can affect the distribution of a species within a habitat. Changes in the distribution of just one species can affect the whole community within an ecosystem. For example the introduction of a new predator into community will not only lead to a decrease in the pre-population but it will also indirectly affect other organisms in the community that are dependent on the prey. ##sciencerevision##gcsebiology##gcs