Extinction
. Extinction (biology), the end of existence of a group of organisms, caused by their inability to adapt to changing environmental conditions. Extinction affects individual species—that is, groups of interbreeding organisms—as well as collections of related species , such as members of the same family, order, or class (see Classification ). The dodo, for example, a species of flightless pigeon formerly living on the island of Mauritius, became extinct in 1665. About 10,000 to 12,000 years ago, the most of the woolly mammoths and the last of the mastodons , both members of the elephant family, died. And about 245 million years ago at the end of the Paleozoic Era, an entire class of primitive marine animals called trilobites disappeared forever. Fossils , the remains of prehistoric plants and animals buried and preserved in sedimentary rock or trapped in amber or other deposits of ancient organic matter, provide a record of the history of life on Earth. Scientists who study this foss...