What term describes a species that no longer has any known living individuals?

The term that describes a species that no longer has any known living individuals is "extinct." When a species is considered extinct, it means that there are no surviving members of that species in the wild or in captivity. This designation can occur due to various factors, including habitat loss, climate change, predation by invasive species, or human activities such as overhunting and pollution. The extinction of a species is a critical loss to biodiversity and can have significant ecological impacts, as each species plays a unique role in its ecosystem.

The other terms provided do not accurately describe a species with no living individuals. A species that is endangered, for example, still exists but is at risk of extinction due to a declining population. Vulnerable species are those that are facing a high risk of extinction in the wild, while threatened species are also at risk but still have some living individuals. These terms relate to species that are still present but in danger, rather than indicating total disappearance.