What is a bioindicator species?

A bioindicator species is defined as a species that is used to measure the health of an ecosystem. These organisms can provide valuable information about the quality of the environment in which they live. For instance, certain species are more sensitive to pollutants or changes in habitat conditions, and their presence or absence can indicate the overall state of the ecosystem.

When a bioindicator species shows signs of stress, decline, or disappearance, it often suggests that the ecosystem is experiencing negative impacts, such as pollution, habitat destruction, or climate change. On the other hand, a thriving bioindicator species can reflect a healthy environment. This relationship makes bioindicator species crucial for monitoring environmental changes and assessing biodiversity.

The other options describe different characteristics that do not capture the essence of what bioindicator species are. Therefore, the definition that emphasizes their role in measuring ecosystem health is the accurate one.