Adaptation (eye) opsin photopigment. The various cone cells are maximally sensitive to either short wavelengths (blue light), medium wavelengths (green light), or long wavelengths (red light). Rod photoreceptors only contain one type of photopigment, rhodopsin, which has a peak sensitivity at a wavelength of approximately 530 nanometers which corresponds to blue-green light. A minor mechanism of adaptation is the pupillary light reflex, adjusting the amount of light that reaches the retina. In response to varying ambient light levels, rods and cones of eye function both in isolation and in tandem to adjust the visual system. Changes in the sensitivity of rods and
Evolution of the eye behaviors have been identified, in two primary groups: Below 450 nm, associated with direct light, and above 450 nm, associated with reflected light. As opsin molecules were tuned to detect different wavelengths of light, at some point color vision developed when the photoreceptor cells used differently tuned opsins. This may have happened at any of the early stages of the eye's evolution, and may have disappeared and reevolved as organisms became predator or prey. Similarly, night and day vision emerged when photoreceptor cells differentiated into rods and cones, respectively. As discussed earlier, the properties of light under water differ from