Commensalism/kəˈmɛns(ə)lɪz(ə)m/ ~ An association between two organisms in which one benefits and the other derives neither benefit nor harm.
The comb jelly—also known as the warty comb jelly, sea walnut, or Mnemiopsis leidyi—has a disappearing butt. Sidney Tamm of the Marine Biological Laboratory in Woods Hole, Massachusetts, told New Scientist that “there is no documentation of a transient anus in any other animals that I know of. It is not visible when the animal is not pooping. There’s no trace under the microscope. It’s invisible to me.”
A self-organizing open living system has a central function, which is that of autopoiesis, a concept introduced by the Chilean biologist Humberto Maturana, who further developed it with cognitive scientist Francisco Varela. (Maturana, Biology of Cognition; Maturana and Varela, Autopoietic Systems.) Autopoiesis is the mechanism that makes living beings into autonomous systems; it is the function of continuous self-renewal through exchange with the environment and the regulation of this process in such a way that integrity of structure is maintained. Such a “dissipative structure continuously renews itself and maintains a particular dynamic regime, a globally stable space-time structure.” An autopoietic system is one primarily characterized by self-renewal, rather than being allopoietic, geared primarily toward the production of a product or function, as in the case of a machine. The human fetus is a clear example, for it continuously renews and develops itself into a coherent dynamic living system, in constant exchange with its uterine environment, a process that continues after birth with increasing autonomy. Thus an autopoietic system is one that can renew itself by constantly dissolving old structures and developing new ones, through the exchange with the environment and the metabolism of this exchange in interaction with the system’s own dynamic potentials.
Symbiosis (from Greek συμβίωσις, symbíōsis, “living together”, from σύν, sýn, “together”, and βίωσις, bíōsis, “living”) is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasitic.