Linnaean Classification
Douglas Wilkin, Ph.D.
Jean Brainard, Ph.D.
Say Thanks to the Authors
Click http://www.ck12.org/saythanks
(No sign in required)
To access a customizable version of this book, as well as other
interactive content, visit www.ck12.org
CK-12 Foundation is a non-profit organization with a mission to
reduce the cost of textbook materials for the K-12 market both in
the U.S. and worldwide. Using an open-source, collaborative, and
web-based compilation model, CK-12 pioneers and promotes the
creation and distribution of high-quality, adaptive online textbooks
that can be mixed, modified and printed (i.e., the FlexBook®
textbooks).
Copyright © 2015 CK-12 Foundation, www.ck12.org
The names “CK-12” and “CK12” and associated logos and the
terms “FlexBook®” and “FlexBook Platform®” (collectively
“CK-12 Marks”) are trademarks and service marks of CK-12
Foundation and are protected by federal, state, and international
laws.
Any form of reproduction of this book in any format or medium,
in whole or in sections must include the referral attribution link
http://www.ck12.org/saythanks (placed in a visible location) in
addition to the following terms.
Except as otherwise noted, all CK-12 Content (including CK-12
Curriculum Material) is made available to Users in accordance
with the Creative Commons Attribution-Non-Commercial 3.0
Unported (CC BY-NC 3.0) License (http://creativecommons.org/
licenses/by-nc/3.0/), as amended and updated by Creative Commons from time to time (the “CC License”), which is incorporated
herein by this reference.
Complete terms can be found at http://www.ck12.org/about/
terms-of-use.
Printed: July 15, 2015
AUTHORS
Douglas Wilkin, Ph.D.
Jean Brainard, Ph.D.
www.ck12.org
C HAPTER
•
•
•
•
Chapter 1. Linnaean Classification
1
Linnaean Classification
Define taxonomy and binomial nomenclature.
Explain the importance of classifying organisms.
Outline the Linnaean classification system.
Describe a domain and list the three domains of life.
In biology, what would classification refer to?
There are millions and millions of species, so classifying organisms into proper categories can be a difficult task. To
make it easier for all scientists to do, a classification system had to be developed.
Linnaean Classification
The evolution of life on Earth over the past 4 billion years has resulted in a huge variety of species. For more than
2,000 years, humans have been trying to classify the great diversity of life. The science of classifying organisms
is called taxonomy. Classification is an important step in understanding the present diversity and past evolutionary
history of life on Earth.
All modern classification systems have their roots in the Linnaean classification system. It was developed by
Swedish botanist Carolus Linnaeus in the 1700s. He tried to classify all living things that were known at his time.
He grouped together organisms that shared obvious physical traits, such as number of legs or shape of leaves. For
his contribution, Linnaeus is known as the “father of taxonomy.” You can learn more about Linnaeus and his system
of classification by watching the video at this link: http://teachertube.com/viewVideo.php?video_id=169889 .
The Linnaean system of classification consists of a hierarchy of groupings, called taxa (taxon is singular). Taxa
range from the kingdom to the species (see Figure 1.1). The kingdom is the largest and most inclusive grouping.
It consists of organisms that share just a few basic similarities. Examples are the plant and animal kingdoms. The
species is the smallest and most specific grouping. It consists of organisms that can produce fertile offspring together.
Closely related species are grouped together in a genus.
1
www.ck12.org
FIGURE 1.1
Linnaean Classification System: Classification of the Human Species. This chart
shows the taxa of the Linnaean classification system. Each taxon is a subdivision
of the taxon below it in the chart. For
example, a species is a subdivision of a
genus. The classification of humans is
given in the chart as an example.
Binomial Nomenclature
Perhaps the single greatest contribution Linnaeus made to science was his method of naming species. This method,
called binomial nomenclature, gives each species a unique, two-word Latin name consisting of the genus name
and the species name. the genus is capitalized an the species is not. The entire binomial nomenclature is written in
italics. An example is Homo sapiens, the two-word Latin name for humans. It literally means “wise human.” This
is a reference to our big brains.
Why is having two names so important? It is similar to people having a first and a last name. You may know several
people with the first name Michael, but adding Michael’s last name usually pins down exactly which Michael you
are referring to. In the same way, having two names uniquely identifies a species. Another example would be
Tyrannosaurus rex. To abbreviate a scientific name, the genus is represented by a capital letter with a period after it.
The species is spelled out in lower case letter. the entire abbreviation is still written in italics. Examples include: H.
sapiens and T. rex.
Revisions in Linnaean Classification
Linnaeus published his classification system in the 1700s. Since then, many new species have been discovered. The
biochemistry of many organisms has also become known. Eventually, scientists realized that Linnaeus’s system of
classification needed revision.
A major change to the Linnaean system was the addition of a new taxon called the domain. A domain is a
taxon that is larger and more inclusive than the kingdom. Most biologists agree there are three domains of life
on Earth: Bacteria, Archaea, and Eukaryota (see Figure below). Both Bacteria and Archaea consist of single-celled
2
www.ck12.org
Chapter 1. Linnaean Classification
prokaryotes (having no nucleus). Eukaryota consists of all eukaryotes (having a true nucleus), from single-celled
protists to humans. This domain includes the Animalia (animals), Plantae (plants), Fungi (fungi), and Protista
(protists) kingdoms.
Vocabulary
Taxonomy-the method scientists use to identify, classify, and name organisms
Linnaean classification-a classification system for grouping organisms originally created by Carolus Linnaeus
Taxa-heirachy of groupings
Kingdom-largest group
Species-most specific group
Binomial nomenclature-two names (the genus and species)
Domain-a taxon where organisms are grouped based mainly on whether cells have a nucleus
Summary
• Classification is an important step in understanding life on Earth.
• All modern classification systems have their roots in the Linnaean classification system.
• The Linnaean system is based on similarities in obvious physical traits. It consists of a hierarchy of taxa, from
the kingdom to the species.
• Each species is given a unique two-word Latin name consisting of the Genus and species.
• The recently added domain is a larger and more inclusive taxon than the kingdom.
Review
1.
2.
3.
4.
5.
What is taxonomy?
Define taxon and give an example.
What is binomial nomenclature? Why is it important?
What is a domain? What are the three domains of life on Earth?
Create a taxonomy, modeled on the Linnaean classification system, for a set of common objects, such as motor
vehicles, tools, or office supplies. Identify the groupings that correspond to the different taxa in the Linnaean
system.
Explore More
Use this resource to answer the questions that follow.
• Categorizing Mother Nature: The Linnaean Taxonomic System at http://www.dummies.com/how-to/co
ntent/categorizing-mother-nature-the-linnaean-taxonomic-.html .
1.
2.
3.
4.
Why is the Linnaean taxonomic system useful as a classification system?
Because wolves and dogs share many similarities, they also share what part of their scientific name?
Mammalia is what category of classification?
What is necessary for two species to be in the same genus?
3
www.ck12.org
References
1. Christopher Auyeung (based on image by Peter Halasz). Levels in the Linnaean classification system. CC
BY-NC 3.0 (original image in public domain)
4