10 Self and the Phenomenon of Life
b2726 Self and the Phenomenon of Life: A Biologist Examines Life from Molecules to Humanity “9x6”multiply in number? Does it consume energy? Does it put out waste
products?
The objects manifest some of the signs of life, but not all, and
you still cannot be certain. As you are in no immediate danger of being
devoured, you have a few minutes to think. You then reach into your
pocket and take out a copy of Guidebook for Intergalactic Travelers and
look up the definition of life. This is what you find:
(1) Life is an object capable of adaptation by natural selection (biologi-
cal definition).
(2) Life is a series of chemical reactions carried out in a stepwise, non-
equilibrium energy flow (general chemical definition).
(3) Life is a series of carbon-based reactions capable of sustaining itself
(organic chemical definition).
(4) Life is a series of enzyme-catalyzed reactions capable of sustaining
itself (biochemical definition).
(5) Life is a collection of cells capable of dividing and increasing in num-
ber (cell biological definition).
(6) Life is a system of self-replicating macromolecules (molecular-
biological definition).
Fig. 2.1. UFO (unidentified foreign objects).