All living things have certain characteristics. The genetic code carries the directions for inheritance, and offspring usually resemble their parents. With , offspring have the same traits as their parents. With , offspring differ from their parents in some ways. Living organisms use energy and materials to grow, develop, and reproduce. These life processes involve a set of chemical reactions called . Organisms have means of detecting a change in their environment and responding to this . Most organisms require that their internal environments remain in a fairly constant range, and so they maintain . The ability of a group of organisms to change, or , over time is necessary for survival in an ever-changing environment.