Final answer:
An increase in population due to migration represents a change to an ecosystem brought about by biotic factors. The increase in population can lead to changes in resource availability and competition for habitat and food, affecting the overall ecosystem.
Step-by-step explanation:
The scenario that represents a change to an ecosystem brought about by biotic factors is c) An increase in population due to migration. Biotic factors refer to the living organisms in an ecosystem, such as plants, animals, and microorganisms. In this scenario, the increase in population, which is a biotic factor, can lead to changes in the availability of resources and competition for food and habitat, affecting the overall ecosystem.