All animals have some kind of body covering, but only vertebrates have skin. Skin is made up of several layers, with each layer having a different function. The epidermis is the thin, waterproof top layer. Any other covering, like hair, feathers, or scales extends above this. Below the epidermis is the dermis which is a thicker layer full of blood vessels and nerves. Under the dermis is a fatty layer that keeps the body warm and acts as a layer of protection against shock.
Each animal is designed to survive in a particular environment, and the variations in skin that allow this are incredible. The hairy armadillo has its skin hardened into boney plates to protect it, and the skin between the plates is unusually flexible allowing the animal to bend. Elephant skin is wrinkly, allowing this large animal to live in hot places. When the elephant bathes and covers itself with mud, the moisture stays in the cracks and folds keeping the animal cooler for longer periods of time. The enormous ears of elephants have skin full of blood vessels which gives the animal the ability to cool itself by fanning its ears. Amphibians get part of their oxygen through their skin which also allows water to pass into the body so they never have to drink through their mouth. The glass frog has transparent skin which allows surrounding colors to camouflage it. The thorny devil from Australia has its skin pulled up into spikes which make it hard to eat and tiny grooves between its scales catch dew and raindrops and send the water straight into the animal’s mouth.
Animals keep their skin in top shape by shedding the outer layer. Mammals do this in tiny skin flakes. A human will shed over 100 pounds of skin flakes in a 70-year lifetime. Lizards lose skin in patches, but a snake will shed all of its skin at once. Some animals attract mates by brilliant colors of skin, some discourage predators by skin color, and some animals such as the chameleon express their mood or temperature by their skin color.
Skin does amazing things for animals. We are reminded that God has designed and planned every aspect of our world so that we can know there is a God through the things he has made (Romans 1:20).
Source: Ranger Rick, December 2006, page 22.
Picture credits:
Hemera