Pub. date: 2006 | Online Pub. Date: September 15, 2007 | DOI: 10.4135/9781412952453 | Print ISBN: 9780761930297 | Online ISBN: 9781412952453 | Publisher:SAGE Publications, Inc.About this encyclopedia
Life, Characteristics of
The concept of life belongs to the basic cognitive endowment of every human. This deep anchoring makes it difficult to define life. Everyone has an intuitive understanding of how a living object should look and how it should behave, but for scientific purposes it is necessary to make this implicit and vague knowledge explicit and clear. How else should we identify extraterrestrial life on other planets—or artificial life in the computer? A classical strategy of defining life, which can be traced back to Aristotle, involves listing characteristics of living beings. A modern biologist would enumerate at least three essential properties: metabolism, self-reproduction, and mutability. Organisms metabolize . There is a permanent exchange of matter and energy going on between organisms and their physical environment to build and preserve their physical structure. Organisms reproduce themselves . Organisms transmit at least a part of their genetic information to their offspring. This information ...