Cell membranes do not differ in principle from medieval walled cities, the contract binding the employee to a corporation acts in much the same way as the skin surrounding the body. Barriers give shape and context to organisms and systems, determining whether one is in or out. Walls establish territory. Walls maintain identity. They keep the primary agents of diversity- known as species, apart, maintaining their separate genetic identity.
Biological barriers ensure nature's diversity.
Our policy is to break down the walls between diverse groups and cultures, to negate difference and integrate everyone and everything in the huge cannibal melting pot called monoculture. Walls are never completely open or closed. Walls are often semipermeable, allowing some agents to pass and keeping other agents in or out such as the cell membrane of the cell or the doors of a police station. A GOOD wall strikes a balance through design and programming between its internal and external environment- a GOOD wall engages in trade. There are a number of possibe outcomes to the merger of two separate entities.