From Envirowiki

Life is a name given to a phenomena which includes plants, animals, microbes, etc. Life is characterised by an ability to self-replicate, although the line is blurry, for example, virii can only self-replicate by taking over another lifeform's cells. Another definition includes a cells which includes RNA, the precursor to DNA.

[edit] External link

• http://www.upscale.utoronto.ca/GeneralInterest/Harrison/LifeEnergy/LifeAndThermo.html - an explanation of life in relation to the second law of thermo dynamics.