I'm not sure if this question is okay to be posted to ell.se, as I don't know if it is obvious for native speakers or not, that:
physics and mathematics both ends with '-ics', while sociology and psychology end with '-logy'.
definition from dictionary.com:
-logy: a combining form used in the names of sciences or bodies of knowledge;
-ics: a suffix of nouns that denote a body of facts, knowledge, principles, etc.
My current conclusion is that '-ics' is for subjects that involve more practical works, whereas '-logy' is for those who deal with theoretical knowledges.
But 'biology', seemingly, doesn't fit in my conclusion.