The term animal is a generic term covering multiple species. If you go to Dictionary.com and type in the word "animal" the definition you get is: "any member of the kingdom Animalia, comprising multicellular organisms that have a well-defined shape and usually limited growth, can move voluntarily, actively acquire food and digest it internally, and have sensory and nervous systems that allow them to respond rapidly to stimuli: some classification schemes also include protozoa and certain other single-celled eukaryotes that have motility and animal-like nutritional modes (www.dicionary.com, N.D).
The Animal Kingdoms includes the following classes:
Amphibians are Frogs, Salamanders, and Newts. Amphibians usually spend about half of their time in water and the other half on land. Their skin is moist and without any scales. They are cold-blooded and their body temperature is dependent on their environment.
The next class is that of birds, and it includes all warm-blooded vertebrates with wings and feathers. Most birds can fly, but their are some flightless species such as the ostrich's and penguin's.
Next on our list is that of fish. Most fish are cold-blooded. Fish are vertebrates and live their lives entirely in the water. Most fish breathe through their gills but their are some that can breathe oxygen through the air due different bodily adaptations.
Mammals are warm-blooded vertebrates that are covered in fur, or hair. There are three classes of mammals and these classifications are based on how they give life to their offspring. Monotremes lay eggs. Marsupials have a pouch to nurse their young, and Placentals' have a uterus that nurture and develop its young.
The last class of animals are reptiles. Reptiles are cold-blooded vertebrates and have skin covered in scales. The reptile class includes alligators, crocodiles, turtles, tortoises, lizards and snakes.