What does extinction refer to?

Extinction refers to the complete disappearance of a species from Earth, indicating that there are no living individuals of that species left. This can occur for various reasons, including habitat loss, climate change, or competition with other species. When a species goes extinct, it means that it can no longer be found in any ecosystem, leading to the loss of biodiversity and potential impacts on the surrounding environment.

The other options represent different biological processes but do not capture the concept of extinction accurately. The reappearance of a species after it has disappeared, for example, implies that the species was not completely lost, which contradicts the definition of extinction. Introducing a new species into an ecosystem refers to species migration, and this can lead to various ecological consequences, but it does not involve the concept of a species completely disappearing. Similarly, the migration of species to new habitats does not denote extinction, as the species still exists, just in a different location. Understanding extinction is crucial for conservation efforts aimed at preserving the diversity of life on our planet.