Exchanges continously happen in life between people or things. People give and take all the time. When we buy things for example this is quite an obvious form of exchange represented through money. Gift giving is another. Also when friends help each other though not always equally. There are other examples however relating to how we take things in the enviroment and how we give back though unfortunately people often take too much.
Even breathing is a form of exchange. It is important to see how interlinked everything really is and I think if more people recognised this then we would treat the enviroment better.