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.