by Goblinoid Games » Mon Dec 17, 2012 4:27 pm
Personally, if the need to know arises I would assign iron-based metabolisms as the default, under the assumption that this is the most common for life. The Silotrons are different since they are silicon-based life, but none-the-less it partly depends on the breathable atmosphere. If an organism uses oxygen, then hypothetically there are only a few viable options under most conditions hospitable to life. If the organism metabolizes some other gas, then there are more exotic possibilities, but it is up to you how complicated you want to make it. IMHO for most situations I'd stick to the main 3 types, assigning iron-based most often.