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Characteristics of and usefulness of
classification systems
CLASSIFICATION
Evolution has created great diversity of life
More than 2.5 million different kinds of
organisms have been identified.
It is estimated that as many as 20 million more
may be discovered.
Features of a good classification system:
1. Needs to use universally accepted names for organisms
2. Doesn’t use common names--they can be misleading and
confusing.
 Mountain
lion, cougar, puma, panther-same animal
 Starfish, jellyfish, seahorse, groundhog
Organisms should be placed in groups that have
meaning (share important traits)
The science of naming is called taxonomy
Early Classification Systems:
Aristotle-grouped animals by how they moved (fly, swim,
walk).
Even though it had obvious problems, his system was
used for nearly 2000 years.
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18th century scientists began to use Latin but
names were long (20 words or more), some
organisms were given more than one name.
For example, the English translation of the scientific
name of a tree might be “Oak with deeply divided
leaves that have no hairs on their undersides and no
teeth around their edges.”
Carl Linnaeus
He was a Swedish Botanist;
he developed the system for
giving things two names.
His method is called binomial nomenclature
Each organism gets a first and last name.
-the first name is the genus. It is a small group
of very similar organisms.
-the second name is the species. It is all the
same organism
Definition of a species:
John Ray defined a species as organisms that can
interbreed and have fertile offspring.
Examples:
All dogs are the same species because they can
interbreed and have fertile offspring.
Horses and donkeys are not the same species because
their offspring, a mule, is sterile.
Example:
Acer rubrum-red maple
Acer palmatum-palm maple
Example:
Felis tigris
Felis leo
How to write a scientific name:
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The genus name is always capitalized, species is
always small. It must then be underlined or
italicized to be set apart.
Names are in Latin so the meanings won’t change
with use.
Examples:
Ursus arctos horribilus
“horrible artic bear”
for the grizzly bear
Ursus maritimus Polar bear
Ursus americanus Black bear
Some are named for a location:
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Microtus pennsylvanicus
Sphiggurus mexicanus
Atlantic Puffin
Fratercula arctica translates as “little brother of the
Arctic”),
Some are named for people:
Beyonce: Scaptia beyonceae
Barack Obama: Caloplaca obamae
7 Categories:
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Kingdom
Phylum
Class
Order
Family
Genus
Species
A way to remember:
Kathy
Puts
Cheese
On
Fresh
Garden
Salad
Kings
Play
Chess
On
Fine
Grain
Sand
Examples:

Human
 animalia
 chordata
 mammalia
 primate
 homididae
 Homo
 sapien

Housecat
 animalia
 chordata
 mammalia
 carnivora
 felididae
 Felis
 domesticus
Categories go from general to specific
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Animal
Chordata
Mammalia
Carnivora
Ursidae
Ursus
artic horribilus
Modern Classification methods:
Scientists often disagree on how to classify.
The following are often looked at:
1. homologous structures
2. embryos
3. fossils
4. biochemicals
a. DNA
b. RNA
c. proteins-Cytochrome c (found in all living things)
Kingdoms:
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Linnaeus started with 2 kingdoms:
plants and animals.
It became clear that not everything fit into those 2
kingdoms so more were added.
There are now 6 kingdoms:
1. Eubacteria--the
most common bacteria.
“eu” means “true”.
All are prokaryotic.
2. Archaebacteria--have
different cell walls, lipids
and ribosomes. All are
prokaryotic.
3. Protista—all are eukaryotic cells with a nucleus
and other organelles. Some are plant-like and
some are animal-like.
4. Fungi--eukaryotic, plant-like but have different
cell walls from plants, and they do not make their
own food like plants.
5. Plantae—all are multicellular, have cell walls
made of cellulose, and are autotrophic
6. Animalia—all are multicellular, have no cell walls,
and are heterotrophic.