Classification of
Organisms
Mai n Idea
*****Chapter 14*****
Students should be able to:
* Understand why a classification system is important
* Understand that there are a variety of ways to classify
organisms
* Understand the origins of our modern classification system
Why Classify?
To
study the great diversity of
organisms on earth, biologists
must give each organism a name.
But,
a universal naming system
was needed to avoid confusion
caused by regional names.
Why Classify?
Taxonomy
is the
discipline of classifying
and assigning each
organism a universal
name.
Early Naming Systems
 The
first attempts to classify organisms
was to describe the physical
characteristics in great detail.
 This resulted in very long names like:
 “Oak with deeply divided leaves that
have no hairs on their undersides and
no teeth around their edges.”
Binomial Nomenclature
This system, proposed by
Carolus Linnaeus, is still in
use today.
It is a two-word naming
system.
Each species is assigned a
two-part scientific name.
Binomial Nomenclature
A
scientific name is always
written in italics (or
underlined), and the first word
is capitalized and the second
word is lowercase.
Homo sapien is the scientific
name for humans.
(or Homo sapien)
Binomial Nomenclature
Homo
sapien
The first part of a scientific
name is the genus.
A genus is a group of closely
related species.
The second part of the name
is unique to each individual
organism or the species.
Binomial Nomenclature
8
Question?
Do
Ursus arctos and
Ursus maritimus belong
to the same species?
No, they are different
species.
Question?
Do
Ursus arctos and Ursus
maritimus belong to the
same genus?
Yes, they both belong to
the genus Ursus.
System of
Classification
 The
classification system is
hierarchical, or consists of levels.
 They are, from largest to smallest,
domain, kingdom, phylum, class,
order,family, genus, species.
 Each level is called a taxon or
taxonomic category.
The 8 Taxa (plural for taxon)
 Domain
 Kingdom
 Phylum
 Class
 Order
 Family
 Genus
 Species
Did
King
Philip
Cross
Over
For
Good
Spaghetti
Do
Kentucky
People
Climbing
Over
Fences
Get
Shot
The Human Species
(Domain Eukarya)
Kingdom: Animalia (Animal in Latin)
Phylum: Chordata (Spinal Cord)
Class: Mammalia (have mammary glands)
Order: Primates (two mammary glands)
Family: Hominoidea (bipedalism)
Genus: Homo (man)
Species: Sapien (wise, knowing)
Least Specific
Section
(least Section
in common)
18Lea-118-1
Grizzly bear Black bear
Giant
panda
Red fox
Coral Sea star
Abert
squirrel snake
KINGDOM Animalia
PHYLUM Chordata
CLASS Mammalia
ORDER Carnivora
FAMILY Ursidae
GENUS Ursus
Most Specific
(most in common)
SPECIES Ursus arctos
The Classification Game!!
With your partner
In the following few slides, you will find
14 different organisms, each of them labeled
with a letter. In your groups, write down
two main classifications (example red/green)
Then place the corresponding letters under
the correct classification.
For Example
These organisms have been
classified by their color.
Green
Red
ARE
YOU
READY!
B
E
A
D
C
F
G
K
L
J
I
H
M
N
One Possible Solution
Animals
Plants
C
D
A
G
I
J
M
????
B
K
E
N
F
L
H
Did You Have
Problems??
There were actually several different ways to go
about classifying these 14 organisms. You might
have done color, shape, size, number of legs… the
possibilities are endless. You might have encountered
one or two that really did not fit into either of your
two classifications, what should you do when this
happens? Make a new classification of course! And
this is what scientist have done as well through the
years.
Cladistics
A
phylogenetic classification system
that uses shared derived characters
and ancestry as the sole criterion for
grouping taxa
 (Phylogenetic
means evolutionary
development or history)
 Cladogram: an evolutionary “tree”
Cladogram
a diagram that shows
evolutionary
relationships among
organisms based on
shared derived
characteristics.
**Helps scientists understand how one lineage
branched from another in the course of evolution
Derived Characters
A unique trait
of a particular
group of
organisms that
appears in
recent parts of
a lineage but
not in older
members.
Common ancestor