Tags allow organisms to send signals and recognize signals sent by others.
Predators evolve elaborate systems to recognize their prey. Flows of information and organisms assure that entities that can interact to create new order or value collide. Boundaries or membranes filter out extraneous flows, to create environments in which only certain kinds of reactions can occur. Catalysts provide active, temporary binding sites that facilitate reactions and interactions that might not otherwise occur. Active models provide representations of the external world that guide an organism, based on its internal structure, to seek valuable interactions and avoid harmful ones.