干旱区生态环境知识资源中心

Despite the obvious anatomical difference, both visual and digestive systems represent a typical complex system composed of subsystems, each of them in turn being complex. In different rodent species, the "buccal bristles", i.e. brushes of stiff hairs upon inner surface of the cheeks, are first described in the mouth, the part of the digestive system. They represent an additional oral cavity structure apparently bound to the feeding style of predominantly herbivorous animals. Adaptive features of mutually behavior and vision traits related to either diurnal or nocturnal lifestyle of rodents inhabiting open landscapes of arid zones are discussed in connection with ecological pressure of aerial or terrestrial danger. Cases and versions of deep regress of eye and visual system due to fossorial lifestyle among vertebrates are discussed in connection with the origin of snakes, whose extra specific eye design inspired the idea that they stem from fossorial reptiles (Walls, 1942). The range and grade of adaptive perfection of two closely related functional systems, nutritional and visual, seem to be much more dramatic in the second as compared to the first, which reflects the evident first order significance of nutrition.