Kingdom- is the highest primary division in which all objects are placed. All animals are part of the Animal Kingdom.
Phylum- Each kingdom is divided into smaller units called phyla. Example, chordates are a phylum with members possessing the nerve cord.
Class - The chordates are further divided into classes such as Mammalia, Birds, Reptilia, Amphibians. Members of each class have a characteristics that they share with the members of the same class but are not found in members of other classes.
Family - Classes are further divided into families. Families contain more than one genus.
Genus - Families are sub-divided into genera. Animals that share the same genus are very similar and probably evolved from the same common ancestor.
Species - Species is the most fundamental and contains single type of animal.
Animals are classified into two principal groups invertebrates (with-out backbone) and vertebrates (with backbone). Backbone is the observable feature which defines whether the animal is vertebrate or invertebrate.
Sponges, star fish, Obelia, worms, spiders, insects are the sub-groups of the invertebrate group, they do not have a backbone.
Fishes, birds, frogs, snakes and mammals have a backbone and are the sub-group of the vertebrate group.