extinction n., the state or situation that results when something such as a plant or animal species has died out completely
generation, n., a group of individuals born and living about the same time
journal, n., a magazine that reports on things of special interest to a particular group of people
species, n. , a group of animals or plants that are similar and can produce young animals or plants: a group of related animals or plants that is smaller than a genus
fossils, n., things preserved that belonged to a plant, animal or bones that lived in ancient times.