Light Sensitivity of the Biological Clock

The key to synchronization of short- and or long-term behaviours in organisms so that they happen at the most advantageous period of the day and year has inherent adaptive advantages. An organism will choose the most dependable and highly predictable environmental cues to help it anticipate the “appropriate season” through the ongoing process of natural selection. The annual variation in light-dark (LD) cycle at a given latitude is very predictable, and most organisms take advantage of it. The duration (the length of the light/dark period), the quantity (light intensity), and the quality (spectral composition) of daily light are the three crucial aspects that tell an organism about the time of day and the season. The number of hours of light that an organism perceives is known as the duration. In general, this includes the time between dawn and sunset as well as the twilight hours at each end. The quantity of photons available from a specific light source is referred to as the intensity. The colour, which is typically described as VIBGYOR, is the sensation that results from the activation of a specific class (or classes) of photoreceptors by a light wavelength from the visible light spectrum (380–760 nm). Violet, indigo, and blue are short wavelengths in VIBGYOR, while green and yellow are mid-wavelengths and orange and red are long-wavelengths. Light is available in sinusoidal form in the natural world. The change in intensity and wavelength during twilights, dawn, and dusk is also an important cue for animals, providing them with temporal information.