premise: Life is only applicable to inanimate objects.
hypothesis: Life is a characteristic distinguishing physical entities having biological processes , such as signaling and self-sustaining processes , from those that do not , either because such functions have ceased , or because they never had such functions and are classified as inanimate . Various forms of life exist , such as plants , animals , fungi , protists , archaea , and bacteria . Biophysicists have proposed many definitions based on chemical systems ; there are also some living systems theories , such as the Gaia hypothesis , the idea that the Earth itself is alive . Death is the permanent termination of all biological functions which sustain an organism , and as such , is the end of its life .