The benthos (also benthon) represents the entirety of plant and animal organisms living above, on, or at the bottom or in the littoral zone of bodies of water. Since the origins of life and throughout the long evolution of the organic world, chemical signaling has remained one of the most reliable means of communication among aquatic organisms. On land, it competes with vision and hearing, but in water, under conditions of limited visibility and the density of the habitat, the advantage is entirely on its side. Aquatic inhabitants are characterized by extremely well-developed chemoreceptive organs. In lower animals, these are not yet differentiated into gustatory (taste) and olfactory (smell) senses, so chemical signals are perceived together. Higher organisms, on the other hand, possess highly specialized organs for smell and taste.