There are billions of different kinds of living things (or organisms) on earth. To help study them, biologists have devised ways of naming and classifying them according to their similarities and differences.

The system most scientists use puts each living thing into seven groups (or taxons), organized from most general to most specific. Therefore, each species belongs to a genus, each genus belongs to a family, each family belongs to an order, etc.

From largest to smallest, these groups are:

• Kingdom
• Phylum
• Class
• Order
• Family
• Genus
• Species

Kingdoms are huge groups, encompassing millions of kinds of organisms each. All animals are in one kingdom (called Kingdom Animalia); all plants are in another (Kingdom Plantae). There are five kingdoms, which are animals, plants, fungi, prokaryotes, and protoctists, which are one-celled organisms.

Species are the smallest groups. A species consists of all the animals of the same type, who are able to breed and produce young of the same kind. For example, while any two great white sharks are in the same species, as are any two makos, great whites and makos are in different species (since they can't interbreed).

The lion belongs to the following groups:

• Kingdom Animalia (includes all animals)
• Phylum Chordata (includes all vertebrate animals, as well as some other more primitive ones)
• Class Mammalia (includes all mammals)
• Order Carnivora (includes carnivorous mammals, from bears to raccoons to harbor seals)
• Family Felidae (includes all cats)
• Genus Panthera (includes the great roaring cats: lions, tigers, jaguars, and leopards)
• Species leo (lions!)

Provided by Infoplease.com.