Photochemistry in nature

This chapter assesses some of the ways in which photochemistry has an impact on our lives. Natural photochemical phenomena have contributed to the evolution of life as we know it, and permit its continued existence on Earth. Indeed, photochemical reactions have performed a determining role in the evolution of the Earth's atmosphere. The forms and ecology of life that have been viable at any time in the past were directly dependent on the constitution of the atmosphere during that period. Photosynthesis is perhaps the most important of the many interesting photochemical processes known in biology. Not only was the evolution of the Earth's atmosphere dependent on it, but also animal life derives energy from the Sun, via photosynthesis, by eating plants. Meanwhile, vision is stimulated by the photochemical transformation of a pigment containing a moiety related to retinal, which is the aldehyde derived from vitamin A (retinol).