1. Domain: All living organisms are first categorized into three domains: Bacteria, Archaea, and Eukarya. Animals belong to the Eukarya domain.
2. Kingdom: Within Eukarya, there are four kingdoms: Protista, Fungi, Plantae, and Animalia. Animals are classified into the Animalia kingdom.
3. Phylum: Animals are then further divided into phyla, which are large groups based on fundamental body plan characteristics. Some examples include:
* Chordata: Animals with a backbone (vertebrates)
* Arthropoda: Animals with an exoskeleton and jointed appendages (insects, crustaceans, arachnids)
* Mollusca: Animals with a soft body and a shell (snails, clams, octopuses)
4. Class: Within each phylum, animals are categorized into classes, which are based on more specific characteristics. Examples include:
* Mammalia: Animals with fur, mammary glands, and a live birth
* Aves: Animals with feathers and wings (birds)
* Reptilia: Animals with scales and lay eggs (lizards, snakes, turtles)
5. Order: Classes are further divided into orders, which are based on shared features within a class. Examples include:
* Primates: Mammals with grasping hands and feet, large brains, and complex social structures
* Carnivora: Mammals that primarily eat meat
* Rodentia: Mammals with continuously growing incisor teeth (rats, mice, squirrels)
6. Family: Orders are divided into families, which are based on even more specific traits within an order. Examples include:
* Hominidae: Primates including humans, apes, and chimpanzees
* Felidae: Carnivores including cats, lions, tigers, and leopards
* Sciuridae: Rodents including squirrels, chipmunks, and marmots
7. Genus: Families are divided into genera, which are groups of closely related species. Examples include:
* Homo: Genus including humans
* Panthera: Genus including lions, tigers, leopards, and jaguars
* Tamias: Genus including chipmunks
8. Species: Finally, the most specific classification is the species, which is a group of organisms that can interbreed and produce fertile offspring.
In summary: The animal kingdom is organized in a hierarchical way, with each level of classification representing a shared characteristic. Taxonomists use a variety of evidence, including morphology (physical appearance), genetics, embryological development, and behavior to determine the placement of animals within this system.