AP BIOLOGY

Detailed explanation-1: -Skin: the outer covering of an animal that protects it from its environment. Keratin: a type of protein that forms many of the epidermal structures in vertebrates, such as hair, nails, claws, feather, and some kinds of scales.

Detailed explanation-2: -Hair (and a coat of hairs, called fur or pelage) is uniquely mammalian. No other creature possesses true hair, and at least some hair is found on all mammals at some time during their lives. Hairs grow out of pits in the skin called follicles.

Detailed explanation-3: -Mammals have hair or fur, birds have feathers, reptiles have dry scales, amphibians have soft, moist skin, and fish have wet, slimy scales.

Detailed explanation-4: -The most important function of hair in mammals is that of insulating against cold by conserving body heat. The differing colours and colour patterns in hair coats can also serve purposes of camouflage and of sexual recognition and attraction among the members of a species.

Detailed explanation-5: -Fur is a thick growth of hair that covers the skin of mammals. It consists of a combination of oily guard hair on top and thick underfur beneath. The guard hair keeps moisture from reaching the skin; the underfur acts as an insulating blanket that keeps the animal warm.