Classification/Taxonomy
Chapter 18
Why Classify?
To study the diversity of life, biologists use a
classification system to name organisms &
group them in a logical manner.
Taxonomy
Discipline of classifying
organisms and assigning each
organism a universally
accepted name.
Defined:
In other words, naming things.
Why common names don’t work
Common names vary among languages.
Example:
United Kingdom – Buzzard refers to a hawk
United States – Buzzard refers to a vulture
Red-tailed Hawk
Honey Buzzard
Turkey Vulture
Early Taxonomists
2000 years ago,
Aristotle (384 BC-322 BC)
was the first
taxonomist
 Aristotle divided
organisms into plants
& animals
 He subdivided them
by their habitat ---land,
sea, or air dwellers

Carolus Linnaeus
(1707 – 1778)
 Classified organisms by their structure
 Created the system of naming we use today.
 His classification system includes 7 levels.
 In taxonomy, a group or level of organization is
called a taxonomic category or taxon.

Binomial Nomenclature

“Bi” means 2

“nomial” means naming

Nomenclature means “the system of”
Defined:
In binomial nomenclature, each
species is assigned a two-part
scientific name.
Example of Binomial Nomenclature
 Polar Bear is Ursus maritimus

Ursus: genus
Ursus contains 5 other kinds of bears

maritimus: species
The Latin word, maritimus, refers to the sea.
Polar bears often live on pack ice that floats in the sea.
Definitions to know
 Genus: is a group of closely related species
 Species: Group of similar organisms that can
breed and produce fertile offspring
 Kingdom:
 Phylum:
 Class:
 Order:
 Family:
Largest taxonomic group,
consisting of closely related
phyla.
Group of closely related
classes
Group of similar orders
Group of similar families
Group of genera that share
many characteristics
Here We Go…
Polar Bear
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Ursidae
Genus: Ursus
Species: maritimus
What do these mean?...lets see
What they mean
Species: maritimus (lives in marine environment)
Genus: Ursus (kind of bear)
Family: Ursidae (larger category of bears)
Order: Carnivora (meat-eating animals)
Class: Mammalia (warm-blooded, hair, & milk)
Phylum: Chordata (vertebrates)
Kingdom: Animalia (there are 6 kingdoms)
How to remember:
King Phillip Came Over For Green Salad
Kingdom Phylum Class Order Family Genus Species
Rules of the Game
Uniqueness: Every name has to be unique.
Universality: Zoologists have adopted, by international
agreement, a single language to be used on a
worldwide basis. All animals are given a generic
(common name) and specific name in Latin (scientific
name).
These names are in italics or are underlined
(i.e. Homo sapiens).
Phylum
Chordata
Class
Mammalia
Order
Carnivora
Family
Ursidae
Genus
Ursus
Species
maritimus
Genus species
If these three species belong to the same
genus, they are descended from a common
ancestor.
Felis domestica
domestica
Felis
Domestic
Cat
Felis leo
leo
Lion
Felis margarita
margarita
Sand cat`
Which TWO are more closely
related?
A Problem with Traditional
Classification

Traditional classification systems relied on
body structure comparisons only

Due to convergent evolution, organisms that
are quite different from each other evolve
similar body structures.
Convergent Evolution: Process by which
unrelated organisms independently evolve
similarities when adapting to similar
environments.
A Problem with Traditional Classification
Example: The Crab, The barnacle, & The limpet
•
The barnacle and the limpet have similarly
shaped shells & look alike
•
The crab has a very different body form
•
Based on anatomy, the barnacle & limpet could
be classified together and the crab in a different
group.
Related
This incorrect because
crabs and barnacles
are actually related
Crustaceans
Gastropods
Molted Exoskeleton
Segmentation
Free swimming Larva
Even though they do
not look a like, crabs &
barnacles are actually
related
Evolutionary Classification

Biologists now group organisms into categories
that represent lines of evolutionary descent, not
just physical similarities
Evolutionary Classification: Is the
strategy of grouping organisms together based
on their evolutionary history.
Classification Using Cladograms
Cladogram: A diagram that shows the
evolutionary relationships among a group of organisms.
Crustaceans
Gastropods
Molted Exoskeleton
Segmentation
Free swimming Larva
Using Cladograms, you can
see that crabs and barnacles
share similar characteristics
because they both molt & are
segmented
Crustaceans
Gastropods
Molted Exoskeleton
Segmentation
Free swimming Larva
You can also see that
ALL have a free
swimming larva stage
Classification History
1700s
Plantae
1800s
1950s
Protista
Monera
1990s Eubacteria
Animalia
Plantae
Animalia
Protista
Fungi
Plantae
Animalia
Archaebacteria Protista
Fungi
Plantae
Animalia
The Three-Domain System

Recently, as evidence about microorganisms
continue to accumulate, biologists came to
realize that the Kingdom Monera were
composed of 2 distinct groups.

The 6-Kingdom system of classification
includes kingdoms:
1. Eubacteria
4. Fungi
2. Archaebacteria
5. Plantae
3. Protista
6. Animalia
6 Kingdoms
Eubacteria
Prokaryote
Autotroph or
heterotroph
Archaebacteria
Prokaryote
Autotroph or
heterotroph
“Ancient Bacteria”
Most
common
bacteria
E. ecoli
Protista
Fungi
Plantae
Animalia
Eukaryote
Eukaryote
Eukaryote
Eukaryote
Autotroph
Heterotroph
Autotroph/ Heterotroph
heterotroph
Includes
Algae
Live in very
hot places
Don’t
belong in
other euk
Pyrococcus furiosus
Paramecium
No cell wall
Release
enzymes
to digest
food
Cell walls
&
Chloroplasts
H. coccinea
Fern frod
No
chloroplasts
Multicellular
Homo sapiens
Where do viruses go?
Viruses: Are particles of nucleic acid, protein,
and in some cases lipids that can reproduce
ONLY by infecting living cells.
Viruses are made of a core of either DNA or RNA
surrounded by a protein coat.
These are T4 Bacteriophage
A bacteriophage is a
virus which infects
bacteria
Where do viruses go? (continued)
Viruses are not considered alive because they
don’t have ALL the characteristics of life.
Example: They can’t reproduce independently
These are the Influenza Viruses
Influenza or "flu" is an
infection of the respiratory
tract that can affect millions
of people every year.
The End.
Visuals
Taxonomy Video