What Are the Classifications of Living Creatures?
Classifying living creatures is something most of us start practicing when we are very young. Children learn to group animals based on what they look like, what they eat, and even how they behave. Eventually we learn the names and traits associated with major animal groups, like mammals, birds, reptiles, and insects.
But how do scientists group living things? They use something called “taxonomy”, which involves classifying organisms into categories based on similarities and differences. In its most basic form, it’s not so different from the classification we did as children, except that scientists look at more in-depth traits like internal anatomy, evolutionary history, and genetics.
The seven scientific categories of living things are Kingdom, Phylum, Class, Order, Family, Genus, and Species. You can remember these names with the acronym King Phil Came Over For Grape Soda. Each descending category becomes more specific, until you get down to a category that only contains a single species.
To give an example of how this categorization system works, we’ll explore which group domestic dogs (Canis lupus familiaris) would be placed into at each taxonomical level.
Kingdom is the broadest category, with six groups. These groups are Animalia (animals), Plantae (plants), Fungi (mushrooms and mold), Protista (protists), Archaea (archaebacteria), and Bacteria (eubacteria). Organisms are divided into kingdoms based on very general factors like whether their cells have a nucleus and where they get their energy.
As you have probably guessed, dogs fall into the Kingdom Animalia because their cells have a nucleus, they are multicellular, are able to move independently, and must consume other organisms to survive. Dogs also fall into the Phylum Chordata because they have a backbone. Other animals in this category include fish, birds, reptiles, and other mammals.
Going down another rung of the taxonomic ladder, dogs belong to Class Mammalia. Most animals in this class are hairy and warm-blooded and all of them produce milk from special glands to feed their offspring. This is the most specific category that dogs share with us humans.
The next step down is the Order Carnivora, which includes meat-eating mammals with claws and teeth used for killing other animals. Animals in this category include big cats, hyenas, raccoons, weasels, bears, wolves, and even seals and sea lions. Dogs are differentiated even further into the Class Canidae, which is made up of “dog-like” carnivores such as foxes, wolves, and coyotes with long legs and relatively small ears.
The last two categories--genus and species--are especially important because they make up an organism’s scientific name. For example, a dog’s scientific name is Canis lupus, because it falls into the Genus Canis and the Species Lupus. We also add on the subspecies familiaris to differentiate domesticated dogs from their grey wolf ancestors, though not all organisms belong to a subspecies.
Scientific names are extremely important for scientists, because they let us know exactly which species we are talking about. A species may have many common names, but must only ever have a single, unique scientific name. For example, many big cats have the common name “panther”. Without using scientific names, we could have no idea if someone using the word “panther” is talking about a leopard, a jaguar, or a mountain lion.
Cocoparisienne (photographer). (2016). Collage Dogs Animals Dogs [photography]. Retrieved from https://pixabay.com/illustrations/collage-dogs-animals-dog-puppies-1588416/