What does it mean when a species is described as extinct?

When a species is described as extinct, it means that no living members of that species can be found anywhere on Earth. This situation indicates that the species has completely disappeared from its natural habitat as well as from any other locations where it may have existed. Extinction can occur due to a variety of factors, including habitat loss, climate change, disease, and human activities.

The other options depict different statuses of species that are not accurate in defining extinction. For instance, a species "on the brink of extinction" suggests it is nearing extinction but not yet completely gone. A species that "exists in limited numbers" means it is still present but may be endangered or vulnerable. Additionally, a species "in captivity" indicates that individuals of that species may still exist but in a controlled environment, not reflecting a complete disappearance from the planet. Thus, the defining phrase for extinction is that the species is completely absent from Earth.