WHEN DOES A EXTINCTION?

I am not entirely sure whether you want to know what causes a species to become extinct, or what the term extinction means. I will reply to both. There are lots of things that can wipe out a species, including loss of habitat (they live in a swamp, let us say, but people are draining the swamps to make room for new housing projects), or disease, predation, pollution, or any combination of these or other causes (dinosaurs were probably killed by a large meteor or comet striking the Earth and disrupting the global climate). And the meaning of extinction is simply that the species no longer exists; all members have died out.

WHEN THE LAST INDIVDUAL HAS DIED