One way invertebrate in general contribute to the process of life?

I think you are talking about tiny animals without skeletons. If so, these are a/the critical component to the entire food chain. For example we are talking about the ocean's tiniest creatures such as plankton that in massive abundance feed to many species of sealife to even fatham. The greatest mammals on earth - whales - depend on this tiny creature by the ton - filtering them from the ocean waters as a rich source of nutritition.