Vertebrates – Animals with
backbones.
Invertebrates – Animals without
backbones.
Amphibians – A group of
cold-blooded animals with backbones and skeletons that hatch from soft eggs in water
or moist places, then usually look like little black fish for a while before
growing legs and moving onto land. Most amphibians have smooth, moist skin that
water can pass through easily. Their skins also usually contain powerful
chemicals that can be poisonous to animals who bite them but that also can
sometimes be used as medicines for people. The amphibians include frogs and
toads, which are tailless, as well as salamanders and newts that have tails,
plus some other special types. Scientists are worried because many species of
amphibians are suffering large population losses and some are in danger of
extinction. Causes are not completely understood but include loss of habitat
and pollution caused by humans. Experts believe the fate of amphibians is a
warning of environmental damage that can one day threaten the health and
prosperity of the human race, if not our very survival.
Bird -- A type of animal
with a backbone that is covered with feathers. Most birds can fly. All birds
are warm-blooded and all birds lay eggs with shells.
Fish -- A type of
cold-blooded animal with a backbone that lives in water and swims using fins.
Almost all fish breathe oxygen from the water using gills throughout life. A
very few have lungs and breathe air. A very few are capable of leaving the
water on flipper-like fins but do not go far from water. Most fish have scaly
skins, but some have smooth skins.
Reptiles -- A group of
cold-blooded animals with backbones and skeletons that have scaly or pebbly
skin that is dry and that water does not pass through easily. Most reptiles
live all of their lives on land. Most hatch from eggs with shells that are
tough like leather; a few have egg shells that are hard like chicken eggs; and
some give birth to live babies. Reptiles include snakes, lizards, turtles,
alligators and crocodiles, and long ago they included the dinosaurs.
Mammals -- A group of
warm-blooded animals with backbones and skeletons, in which the mothers' bodies
make milk to feed their babies. Most mammals give birth to live babies, but two
unusual kinds lay eggs. Mammals have hair, and most have enough to be called
furry. Cows, lions, dogs, cats and people are all mammals.