An organism (You're one.) is a system. As is a family, a society, or a population. Donella Meadows does a wonderful job helping us look at things and their behaviors as systems, as opposed to linear, A causes B-type explanations. Highly recommended.
Libraries are my passion in life. Before I became mayor, I used to sneak out here during lunch time...and I'd go to a corner and take a book -- any book almost -- and read it for a while, and then feel rejuvenated.