What is an indicator species?

An indicator species is defined as a species whose presence, absence, or abundance reflects the overall health and condition of an ecosystem. These species are typically sensitive to environmental changes, such as pollution or habitat destruction, making them valuable for monitoring ecological health. For example, certain types of amphibians and macroinvertebrates can indicate the level of water quality in aquatic environments. When an indicator species is thriving, it often suggests that the ecosystem is functioning well, while a decline in their populations may signal environmental stress or degradation.

In contrast, the other options do not accurately capture the role of an indicator species. An extinct species does not provide information about current ecosystem health; a species that reproduces rapidly does not inherently indicate ecological conditions, and a species with a high metabolism rate may not offer functional insight into the ecosystem’s overall wellness. Thus, the definition associated with the presence of a species indicating ecosystem health is what makes it the correct choice.