A keystone species is a species that has a disproportionately large effect on its environment relative to its abundance. Such species are described as playing a critical role in maintaining the structure of an ecological community, affecting many other organisms in an ecosystem and helping to determine the types and numbers of various other species in the community.
Extinction is the end of an organism or of a group of organisms (taxon), normally a species.
Endemic species is one that is only found in that region and nowhere else in the world. They are of conservation concern because they are not widespread and may be confined to only one or two protected areas.
Certain life forms, often a keystone species, are sacred to indigenous peoples because they present a body of knowledge and ways leading to balanced relationship with life.