What is vision? Why is vision important for life on earth?
Vision is the ability of some living beings to perceive, to differentiate and to interpret luminous stimuli.
Vision is significant on earth mainly in the terrestrial and in the superficial aquatic habitats because our planet is intensely exposed to sunlight and thus light and colors become distinguishing factors of objects present in the environment, even at distance. This distinction gave new survival strategies for the organisms, new protection mechanisms against external dangers, new ways to search food and to communicate with other individuals, new types of courting and reproduction behaviours, etc. That is, it formed new possibilities of interaction with the surrounds and enhanced capacity to explore new ecological niches.