ABSTRACT
Since the beginning of biological evolution, light has been a dominant selective force in evolution. As a consequence, there exists a remarkable array of biological adaptations to light ranging from circadian rhythms to vision. This chapter addresses how vision has evolved in the service of behavior. Visual systems are responsible for collecting and reducing visual information, sifting the important from the unnecessary. By examining hozo environmental constraints have shaped the evolution of visual signals, important selective pressures have been identified. Reproduction and predation appear to be the most important determinants of visual processes. A manifestation of these selective forces can be seen in extant eyes. Eyes must capture light and resolve it into images. Virtually all the possible optical designs can be found in existing eyes from the simplest photoreceptive pit to complex eyes with several fovea. Despite their vast differences at the level of the entire organ, all these eyes share a common photoreceptive molecule, opsin. In contrast, other features of eyes are not homologous but arise through common descent. The use of eyes to recognize and respond to visual signals is common throughout the animal kingdom. As an example, the complex array of visual signals in one species is presented and changes in the brain that result from social interactions outlined.
