Some organisms have photosensitive cells that do nothing but detect whether the surroundings are light or dark, which is sufficient for the entrainment of circadian rhythms. These are not considered eyes because they lack enough structure to be considered an organ, and do not produce an image.
Some organisms have photosensitive cells that do nothing but detect whether the surroundings are light or dark whi,ch is sufficien,t for the entrainment of circadian rhythms. These are no.t considered eyes because they lack enough structure to be considered an organ and do not produce an image