Bio-optics

a branch of biology that studies the aggregate of phenomena associated with the use by living organisms of light for orientation. Bio-optics embraces a range of questions usually considered by morphology, physiology (including neurophysiology), optics, ecology, and ethology.

Definite orientation to a light source is peculiar not only to animals but to plants and protozoans; some protozoans have specialized organs for perceiving light. In highly developed animals, the eye perceives not only light but also objects. Eyes can be constructed according to different principles. Insects and crustaceans have a compound faceted eye consisting of many ommatidia. In the chambered eyes of vertebrate animals, cephalopod mollusks, spiders, and some worms, the optical elements—cornea and crystalline lens— create an image on the light-sensitive back of the eye. In the eye of a scallop, an image is created by a concave “mirror” situated behind light-sensitive elements. Important qualities characterizing the eye as a photoreceptor include its resolving power, accommodation apparatus, absolute sensitivity, and color discrimination. Besides the structure and function of the optic receptor and neural mechanisms of the eye and visual centers of animals, bio-optics studies light signals as visually perceived means of intraspecific and interspecific communications and signaling of organisms; signal coloration; language of positions, gestures, and facial expressions; preventive and repellant colors, shapes, and behavior of animals; and the attracting coloration of flowers, fruits, and berries. Optical signals play an exceedingly important role in many situations that require coordinated actions on the part of animals—in life within a flock, in the coordination of the behavior of nuptial partners, parents and offspring; and so on. The possibilities of using the visual apparatus and its properties are related to the characteristics of the habitat, such as the intensity and spectral composition of light and also the transparency of the air or water.