Quote:
Originally Posted by dalem
Why, the characteristic of being alive of course. 
More seriously, one can assemble a set of characteristics that define "life", but eventually you have to draw the line somewhere. I think algae is alive and crystals aren't. What do algae do that crystals don't? Is it as simple as reproducing instead of simply growing?
-dale |
In general the line is more of a fuzzy, wideish band. Viruses, for instance. Or parasites like
Rickettsia. Reproduction is certainly a vital characteristic, but viruses are definitely capable of reproduction. One might argue that they must have a host cell in order to reproduce, but then, so must highly dependent parasitic bacteria like
Rickettsia.