Grey wolves have long embodied the spirit of the wilderness. Once they had the largest natural distribution of any mammal except humans. Sadly, they can no longer claim this record as they have been lost from much of their former lands. Grey wolves still occupy a range of habitats including Arctic tundra, prairies and forests.
Although melanin is found in the skin of many species, in the reptiles, the amphibians, and fish, the epidermis is often relatively colourless. Instead, the colour of the skin is largely due to chromatophores in the dermis, which, in addition to melanin, may contain guanine or carotenoid pigments.kin of a different nature exists in amphibians, reptiles, and birds. All mammals have some hair on their skin, even marine mammals which appear to be hairless. The skin interfaces with the environment and is the first line of defense from external factors.
The salt gland is an organ for excreting excess salts. It is found in elasmobranchs (sharks, rays, and skates), seabirds, and some reptiles.Sharks ' glands are found in their rectum, birds' and reptiles' in or on the skull in the area of the eyes, nostrils or mouth.These glands are lobed containing many secretory tubules which radiate outward from the excretory canal at the center. Secretory tubules are lined with a single layer of epithelial cells.he evolution of a salt gland in early reptiles and birds allowed them to eat aquatic plants and animals with high salt concentrations. This evolutionary development does not account for the gland in elasmobranchs, suggesting convergent evolution.