Life
From EvoWiki
Life is a complex phenomenon difficult to define, however see autopoiesis.
Universal features that define life are:
- replication (reproduction) leading to evolution by natural selection.
- metabolism leading to "reverse entropy".
Other common, but not necessarily universal, features of life include movement, membrane-bound cells, carbon-based1, including genes encoded in DNA.
The science concerned with life is biology.
[edit] Footnotes
- All life on Earth uses carbon, a fact which has led some scientists to speculate that carbon may be a requirement for all life, anywhere in the Universe. This is not necessarily so. If life requires an atom capable of forming complex chains with itself, silicon might be a viable alternate choice for life elsewhere. Of course, life does seem to require a certain degree of instability, and silicon compounds -- glass, quartz, etc -- tend to be too stable under Earth-normal conditions. Fortunately, molecules do tend to become less stable when you heat them up. Therefore, it seems likely that any silicon-based life which actually does exist, would have evolved on a world significantly hotter than Earth.
