Life is a characteristic that distinguishes objects that have signaling and self-sustaining processes from those that do not either because such functions have ceased ( death ), or else because they lack such functions and are classified as inanimate . Biology is the science concerned with the study of life. Any contiguous living system is called an organism . Organisms undergo metabolism, maintain homeostasis , possess a capacity to grow , respond to stimuli , reproduce and, through natural selection , adapt to their environment in successive generations. More complex living organisms can communicate through various means. A diverse array of living organisms can be found in the biosphere of Earth , and the properties common to these organisms— plants , animals , fungi , protists , archaea , and bacteria —are a carbon - and water -based...