Classification
and Taxonomy
Classifying Organisms
• Taxonomy: the science of describing,
naming, and classifying organisms
Ways to Classify Organisms
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Unicellular vs. multicellular
Prokaryote vs. eukaryote
Autotroph vs. heterotroph
Linnean system and binomial
nomenclature (today)
Old Systems of Classification
• Aristotle (Greek, 2400 years ago): classified
only as plant or animal
…but where does this stuff go? 
A better system
• Carolus Linnaeus
(1707-1778)
• “Father of Taxonomy”
• His work is the basis
of classification
systems used today
Modern Classification
• Can classify all life into 3 main domains
– Most general/most inclusive category
– Bacteria, archaea, eukarya (written in chart)
Characteristics of Domain Bacteria
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Prokayote
Small
Unicellular
Have cell wall
Example: E. coli
Characteristics of Domain Archaea
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Prokayote
Small
Unicellular
Have cell wall
Live in harsh
environments
• Example: Pyrococcus
abyssi
Some of the first
Archaea were
found in the hot
springs of
Yellowstone Park
Characteristics of Domain Eukarya
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Eukaryote
Small or large
Uni. or multi.
Some have cell walls
Ex: protists, fungi,
plants, animals
Be ready to answer!
• How did Aristotle classify organisms?
• Who came along and improved Aristotle’s
method?
• Which domain of life has organisms that live in
very harsh environments?
• Which domain are humans contained in?
• Which 2 domains have prokaryotes?
Domains can be broken into 6 kingdoms
The 6 kingdoms:
• Kingdom Eubacteria (“true” bacteria)
– Prokayote
– Unicellular
– Includes autotrophs and heterotrophs
The 6 kingdoms:
• Kingdom Archaebacteria (“ancient” bacteria)
– Prokayote
– Unicellular
– Autotrophs (chemosynthesis), heterotophs
The 6 kingdoms:
• Kingdom Protista (protists)
– Eukaryote
– Majority are unicellular
– Autotrophs, heterotophs
The 6 kingdoms:
• Kingdom Fungi
– Eukaryote
– Majority are multicellular
– Heterotrophs
The 6 kingdoms:
• Kingdom Plantae (plants)
– Eukaryote
– Multicellular
– Autotrophs
The 6 kingdoms:
• Kingdom Animalia (animals)
– Eukaryote
– Multicellular
– Heterotrophs
“Domain” and “kingdom”
are still too broad.
We continue to break organisms into
more and more specific categories.
Same
information,
just presented
in a different
way
Classification of Humans
Domain: Eukarya
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Family: Hominidae
Genus: Homo
Species: Homo sapeins
Guess the organism!
To remember the order:
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Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
Dear
King
Phillip
came
over
for
great
spaghetti
Classifying
organisms
• Taxon: any particular
group within a
taxonomic system
– “Taxa” is plural
– Examples of taxa:
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Kingdom
Phylum
Class
etc.
In order, the taxa go from general to specific.
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Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
General
Specific
Same genusvery closely
related
Species- the
most unique
Be ready to answer!
• Which kingdom has “true” bacteria?
• Which kingdom has organisms like Volvox, a
protist?
• Which kingdom has mushrooms?
• Which kingdom has organisms that are ALL
autotrophs?
• Which kingdom has “ancient” bacteria?
• Which kingdom has ants?
Why do scientists use Latin to classify
and name organisms?
HERE’S AN EXAMPLE WHY.
What is this? 
This organism can be
called a:
• Cougar
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• Mexican lion •
• Mountain
•
lion
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• Deer tiger
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• Mountain
•
screamer
• Puma
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• Florida
•
panther
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• Catamount •
• Panther
Silver lion
Devil cat
Indian devil
Sneak cat
King cat
Mountain
devil
Red tiger
Deercat
Fire cat
Plain lion
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Grey lion
Caracajou
Klandagi
Catawampus
Quinquajou
Long Tail
Swamp lion
Problem!
• There are at least 50 common names for the
cougar. The same issue arises with many other
organisms!
Why classify with a scientific name?
• Since common names vary,
scientific names ensure
you’re talking about the
correct organism
• Some names are
misleading (“jellyfish”)
Scientific naming system
• Binomial nomenclature- a two-part name
system for writing scientific names. Based on
Latin.
Rules
• Genus name written first
– ALWAYS capitalized
• Species name is written second
– NEVER capitalized
– NEVER by itself
• Both words are italicized if typed, underlined
if handwritten
Find the errors!
• Taxidea Taxus
• procyon lotor
• Delphinidae Delphis
Sidenote with an example:
• Cannis vulpes is a fox
– Writing C. vulpes is acceptable.
– Writing Cannis v. is not.
– Writing vulpes (by itself) is
BAD…need genus + species.