In biology the term extinct is used for species which are no longer alive. so here Ava is correct because a species has died out and is not longer alive.
Endangered species are those which are on the urge of being extinct, means they are in danger so the term "endangered"
Ava can also elaborate the terms by taking examples
Dinosaurs are extinct species. They are no longer alive or not found in any part of world. So they are called as extinct.
The term can be used for animal or plant species.