Life is difficult to define because it is associated with numerous emergent properties that reflect a hierarchy of structural organization. Organisms are highly ordered, and other characteristics of life emerge from this complex organization. Growth and Development . Heritable programs stored in DNA direct the species-specific pattern of growth and development. Energy Utilization .
Organisms take in and transform energy to do work, including the maintenance of their ordered state.
Response to Environment . Organisms respond to stimuli from their environment. Organisms regulate their internal environment to maintain a steady-state, even in the face of a fluctuating external environment. Evolutionary Adaptation . Life evolves in response to interactions between organisms and their environment.