Commensalism (from Latin com meaning together and mensa meaning table) is a form of symbiosis, or close association between organisms of two or more species, in which one participant in the relationship benefits, and the relationship is neutral for the other participant. This type of symbiotic relationship is often symbolized as (+, 0). Commensalism is one of three recognized categories of symbiotic relationships. The other two are mutualism, in which both participants benefit, and parasitism, in which one benefits and the other is harmed. Of the three types of symbiotic relationships, commensalism seems to be the least common. In addition, some scientists think it is unlikely that one species is completely unaffected by the relationship. Thus, examples of what at first appear to be commensalism may not prove to truly be commensalism upon more in-depth study. One example of commensalism occurs in the ocean. Certain types of barnacles attach to...