Taxonomy: History, Definition, Classification, and Taxonomy Mnemonic

Cougar. Mountain Lion. Puma. What do these animals all have in common? Believe it or not, they are actually all names for the same animal! Because this feline spans such a large area, different areas call it different names. As you might think, this could get confusing if scientists try to discuss the same animal, so what do they do? They use taxonomy.

Taxonomy is the science and process of organizing organisms into categories and naming them. Every species of animal has a unique taxonomic, or scientific, name. A species is a group of organisms that reproduce among itself and produce offspring. The scientific name is used by scientists all over the world for ease of communication. After all, it is very important to be specific in science. For example, the scientific name of the cougar/mountain lion/puma is Puma concolor. The name cougar/mountain lion/puma refers to the animal’s common name. Organisms can have many common names used by the public, but when scientists are referring to them, they use the scientific name.

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History of Taxonomy

To understand a bit more about this process, let’s take a look back to the origins of taxonomy. The first person to explore the organization of living things was Aristotle. He was a Greek philosopher who lived from 384 B.C. to 322 B.C. His system of organization first involved splitting all living things into two groups: plants and animals. From there, he split plants into three categories based on their size, either small, medium or large. As for animals, he split them into categories based off if they inhabited the land, water, or air. As we now know, Aristotle’s system was flawed and did not account for the other types of organisms. For example, his system meant that he categorized bats and most birds as the same type of animal, as they both fly, but not penguins, who are flightless.

After Aristotle, newer forms of classification began emerging. As scientists discovered more organisms, they endeavored to classify and name them. Using Latin words, scientists cam up with names that were descriptive, but at times very lengthy. Scientists were also giving multiple names to the same organism, which caused confusion. Eventually, a Swedish scientist by the name of Carolus Linnaeus standardized his own system taxonomy, which helped create the system that we use today.

Born in 1707, Carolus Linnaeus is often dubbed the father of modern taxonomy. He split organisms into six different levels that progressively got more specific: kingdom, class, order, genus, species, and variety. Kingdom was the broadest level, consisting of plants or animals. However, improving upon Aristotle’s ideas, he narrowed down the organization in different levels, based off of description. Ultimately, each organism had a unique, Latin-sounding name consisting of its genus and species. We will discuss this further as we look into the taxonomy system that we currently use.

Modern Taxonomy

In the system that scientists use today, there are eight taxonomic categories. From least specific to most, there is domain, kingdom, phylum, order, family, genus, and species. A good mnemonic to remember the order is “Did King Philip Come Over For Good Soup?”, with the first letter of each word corresponding to the order of the taxonomic groups.


The domain is the broadest categorization. There are three domains: Bacteria, Archaea and Eukaryota. They differentiate between eukaryotes, which have more complex cells with enclose nuclei, and prokaryotes, whose cells are less complex and lack membrane-bound nuclei. The domains Bacteria and Archaea refer to prokaryotes, while Eukaryota refers to eukaryotes.


The next level down is the kingdom. There are six different kingdoms. Two of them correspond to members of the Bacteria and Archaea domains, and the other four are under the Eukaryota domain. The six kingdoms are Eubacteria (for the domain Bacteria), Archaebacteria (for the domain Archaea), Plantae, Animalia, Fungi, and Protista.

Eubacteria and Archaebacteria are similar in that they are both single-celled prokaryotes. However, they are separate kingdoms because Archaebacteria have special cell walls that let them survive in harsher environments. Archaebacteria can be found in the extreme temperatures of hot springs and thermal vent, where Eubacteria cannot survive.

The eukaryotic kingdoms are Plantae, Animalia, Fungi, and Protista. The kingdom Plantae refers to organisms that we know as plants. These organisms produce oxygen for the environment via photosynthesis. Organisms we know as animals belong in the kingdom Animalia. They are multicellular eukaryotic organisms that gain energy by consuming other organisms. Fungi is the kingdom for organisms that get energy by decomposing organic matter and recycling it back into the earth. Finally, the kingdom of Protista includes everything else. Often called the “junk drawer” kingdom, the one defining factor that all members share is that they do not belong in any other kingdom.


Kingdoms are split into many different phylum. For example, all vertebrates, under the kingdom Animalia, are put into the Chordata phylum.


A further level of classification is class. This refines the categories set by the phylum. For example, under the phylum Chordata, there are classes such as mammalia (mammals) and reptilia (reptiles).


Orders are even more specific than classes. For instance, there are 26 orders within the class mammalia.


Each order is made up of multiple families. For example, grasses in the order Poales belong in the family Poaceae.


After family comes the level of genus. In some cases, there are genera that only contain one species. These are called monotypic. Others are polytypic, such as the genus Panthera, which includes several species of tigers and lions.


The species is the lowest level of organization. There are over 8.7 million species of organisms on Earth.

Binomial Nomenclature

An organism’s scientific name is also known as its binomial nomenclature, which means two names. The first part of the name is the genus, and the second part is the species. As we saw earlier, the scientific name for the cougar is Puma concolor. This means that is belongs in the genus Puma, and the species concolor. When we write a scientific name in binomial nomenclature, the first letter of the genus is always capitalized, but never for the species. When typed, the scientific name is written in italics. When handwritten, it is underlined.

In the end, taxonomy is an incredibly important part of how scientists study organisms. The ability to categorize organisms based on similar characteristics helps scientists better study the world around us. So far, scientists have only given scientific names to about 1.78 million species, so there is still a long way to go until every species in the world is properly identified. Never the less, taxonomy is an invaluable tool that helps us explore the diversity of life.

Works Cited:

Admin. “Taxonomic Hierarchy In Biological Classification.” BYJUS, BYJU’S, 23 Oct. 2019,

Bailey, Regina. “The Six Kingdoms of Life.” ThoughtCo, ThoughtCo, 11 Feb. 2020,

“Cougar.” National Geographic, 21 Sept. 2018,

Rosenberger, Alfred L. “Taxonomy I: Biology.” Visionlearning, Visionlearning, Inc., 12 Feb. 2017,

“Taxonomy.” Basic Biology, 6 Apr. 2019,

Unit, Biosafety. “What Is Taxonomy?” Convention on Biological Diversity, Secretariat of the Convention on Biological Diversity, 6 Apr. 2010,

VanCleave, Janice. “History Of Classification.” VanCleave’s Science Fun, 16 Sept. 2017,

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