Download Animal groups and their coverings

Animal Groups and Their Coverings
Mammals live on land, breathe with lungs and have fur or hair covering
their bodies. Most have 4 legs, or 2 legs and 2 arms. They give birth to live
young (with the exception of monotremes). They feed their young on milk
produced by mammary glands and are warm-blooded. Mammals are the
only animals that have hair. It grows from the outer layer of the skin. A
dense covering of hair is often called fur or wool and insulates. Glands in
the skin release oils which help to keep the fur waterproof and protects
against rain and cold. Some mammals don’t need the protection of a furry
coat e.g. elephants, rhinos and hippos have only a sparse covering of hair
over their thick, leathery skins and whales and dolphins contain a layer of
blubber under their skin that insulates, although they still possess some
sensory bristle hairs around their mouths.
Fish live in water, breathe with gills, have skin covered with scales, have
fins, lay soft eggs and are cold-blooded. They are covered in a flexible
layer of overlapping scales embedded in the inner layer of skin. They are
also protected by mucous slime that is secreted from glands in the skin,
which lubricates it and helps it to swim. Sharks and Manta rays have a different type of scale from most fish. Scales are small and tooth-like and extend into their mouth where they serve as teeth.
Young amphibians live in water, adults live on land. The young breathe
with gills while adults breathe with lungs. They have moist, scale-less skin,
have 4 legs, lay soft eggs and are cold-blooded. Most amphibians have naked skins that lack scales, feathers or fur, but the outer layer of the skin
may be tough and horny. The skin contains mucous glands that secrete
slime to lubricate the skin and prevent water logging. It must be kept moist
as it can also be used for respiration.
Reptiles mainly live on land. They breathe with lungs, have scaly skin, lay
eggs with leathery shells, are cold-blooded and can have 4 legs or zero
(snakes). The skin of reptiles contains no sweat glands and if they are in an
exposed environment, can dry out. They possess a protective layer of
horny scales that helps prevent water loss from their body. Often the outer
layer of skin is renewed and the old layer is shed.
Birds live on the land, breathe with lungs and have feathers covering their
bodies. They have 2 legs and 2 wings and most can fly. They lay eggs
with hard shells and they are warm-blooded. They possess a covering of
feathers on their body and scales over the exposed skin of their legs.
Other functions associated with some skin coverings include:
ο camouflage for protection against predators
ο recognition signal to mates or members of the same population
ο flight (contour feathers)
ο sensory organs (whiskers)
ο protection against harmful UV rays from the sun
ο waterproofing