Introduction to Taxonomy


Do you think the names of each organism pictures are accurate descriptions? Do names of organisms matter?

Taxonomy and Classification

Can you think of a task more daunting than classifying all of Earth’s life forms? There may be as many as 50 million organisms! Too intense? How about classifying a single group of living things, such as the 25,000 species of orchid? Why bother? Keeping track of the amazing diversity of life and being able to compare and contrast different organisms in the tree of life is valuable in and of itself.

There are so many diverse species on Earth that there is a need to organize, name and classify these organisms into categories in a logical way.

Watch the following video introduction to taxonomy. Answer the following questions while watching the video:

  1. What does a taxonomist do?
  2. Who was the first to come with a system for classifying? How did he separate organisms?
  3. Who developed a standard naming system?
  4. What important idea did Darwin put forth that connects all life?
  5. What are the taxa for each level of human?

Taxonomy is the field of biology where organisms are organized (or “classified”) into groups of related individuals, assigning each a scientific name. This field can also lead to surprising insights and discoveries, from finding new drugs to giving scientists a systematic way to monitor the effects of global environmental change.

Classification is a way of separating a large group of closely related organisms into smaller subgroups. The scientific names of organisms are based on the classification systems of living organisms. The identification of an organism is easy with a classification system.

History of Classification

Trying to organize the vast variety of life has been a part of human culture for a long time.


Classification Hierarchy

Linnaeus developed a hierarchy to classify organisms, beginning with kingdom (domain was added later) and working down into phylum, class, order, family, genus, and species.


Each of these levels, or taxa (singular: taxon) is a group of related organisms that is nested in the one above it.

Linnaeus’ original system had 7 taxa: (Domain was added most recently; we will discuss this later in this module.)

  1. Kingdom – broadest and most inclusive level that includes a group of related phyla
  2. Phylum – a group of related classes   (Division is used for Plants)
  3. Class – a group of related orders
  4. Order – a group of related families
  5. Family – a group of related genera
  6. Genus – a group of related species
  7. Species – smallest and most specific level that names one particular type of organism that interbreeds

For those new to this system, it can be a challenge to remember these categories. Here’s a mnemonic referencing something you might read about in Alice in Wonderland:

DKings Play Chess OFunny Green Squares?

You might have fun making up your own silly sentence using the first letter of each taxon!

Take a look at the table below comparing three organisms and where they fit into Linnaeus’ 7 taxa. Compare humans (Homo sapiens) to the other animals.

 Stop and Think: Are humans more closely related to a snail, or a Triceratops? (Hint: we would have the most taxa in common.)  (Answer: triceratops)

Scientific Naming

You may be wondering why it is that we need to provide a scientific name for organisms. Let’s take a look at an example:


We use scientific names because it is an organized way to communicate about the same organism all over the world, regardless of region or language.

What is a scientific name? It is a universally accepted two-word Latin-based name that is given to an organism based on its Genus and Species taxa. This two-word system is called binomial nomenclature (“two-word naming”) and was developed by Carl Linnaeus.

  • The genus and species are always written in italics or it is underlined .
  • The genus name is capitalized and the species name is uncapitalized.
  • The genus name is a noun and the species is an adjective that describes the noun and a trait of the organism

There are 8 species of bears living today. They all have similar features and are recognizable as bears, but they do not interbreed with each other. Therefore, they are classified in the same genus, but as separate species. Take a look at the three bears below and note their common and scientific names.


Lets Review!

Now that you have had the chance to learn about the basics of taxonomy, test your learning with the following interactive. (If one comes up all crazy looking, just guess the answer and keep moving. Try guessing the first one.)