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Classification
There are around 2 million species that
have been described and scientists believe
there are anywhere from 4 million to over
100 million different kinds of life forms on
this planet. How do we figure this out?
Mathematical models!
Classification is…the process of grouping
things together based upon their
similarities.
Scientists do this in order to make it easier
to study living things.
 Taxonomy is…the study of how living things
are classified. Taxonomists are the scientists
that do this.
How Did this all Start?
Dude #1
 Aristotle was a Greek philosopher and
scientist who lived in the 300B.C.’s; he took a
shot at classifying critters. He observed animals
and grouped them into…swimming, walking, and
flying things. Nice try…but we don’t use these
groups…they’re too general.
More About Aristotle…for inquiring
minds
 Aristotle also grouped animals into: those
with blood and those without blood. That’s
sorta close to our vertebrate (backbone)
and invertebrate (no backbone) thing.

Even though we have made some
changes, We still DO use his basic
approach.
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Dude #2
Carolus Linnaeus was a Swedish scientist
(mid-1700’s) who followed up on Aristotle’s
work.
He developed the system of using two names,
so that scientists could communicate regardless
of the language they spoke. We call this:
BINOMIAL NOMENCLATURE.

The first word is the genus and the second is
usually an adjective that describes the
organism (or where its from or who
discovered it). More on this in a few slides.
Eight Levels of Classification
(and one way to remember them)
Domain…Dumb
 Kingdom…Kings
 Phylum…Play
 Class…Chess
 Order…On
 Family…Fancy
 Genus…Glass
 Species…Stools
 Kingdoms are the broadest category and
species the most…ummm…specific.

Domains
Domains were added to the taxonomic
system to take evolutionary differences
and differences in DNA.
 This level is the broadest in scope.
 There are three DOMAINS: Archaea,
Bacteria, and Eukarya.

The Six Kingdoms
We’ll look at each in more detail later.
Archaebacteria
Bacteria (formerly Eubacteria)
3. Protists
4. Fungi
5. Plants
6. Animals
1.
2.
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In this system of naming living things using
two names, we use the genus and species
names.
Genus: a grouping that contains several similar
organisms.
Species: an even smaller group within which
organisms can mate and produce fertile
offspring.
Example: Crocodylus porosus (salt water
crocodile), Crocodylus niloticus (Nile
crocodile)…same genus; different species.
Notice that the genus name is upper case and
the species name…lower case.
Dichotomous Keys
AKA: Taxonomic Key
 A bunch of paired statements that
describe the physical characteristics of
living things.
 You make observations; follow the key;
and BINGO! Instant identification 
 Turn to page 226 and figure out what
organisms are pictured by using the
dichotomous (taxonomic) key.
Checkpoint Question #1!?!?!?
What were the three main groups of animals
in Aristotle’s system of classification?
A) Large animals, small animals, and
medium-sized animals
B) Mammals, fish, and reptiles
C) Those that fly, those that swim, and
those that can walk, crawl, or run
Checkpoint Question #2!?!?!?!?
In a scientific name, the genus name is
similar to
A) Your species name.
B) Your family name.
C) Your nickname.
Checkpoint Question #3!?!?!?!?
What are the seven levels of classification
from the broadest to the most specific?
A) Domain, kingdom, phylum, class, order,
family, genus, species
B) Kingdom, phylum, order, class, family,
genus, species
C) Kingdom, phylum, family, order, genus,
species
Checkpoint Question #4!?!?!?!?
Who developed one of the earliest
classification system for organisms?
A) Aristotle
B) Linnaeus
C) Darwin
Checkpoint Question #5!?!?!?!?
In the scientific name of a house cat, Felis
domesticus, “felis” is the name of the
animal’s
A) Species
B) Family
C) Genus
Checkpoint Question #6!?!?!?!?
A taxonomic key is
A) a book with illustrations that highlights
differences between similar-looking
organisms.
B) a process for determining the
evolutionary history of an organism.
C) a series of paired statements that
describe the physical characteristics of
different organisms.
Answers!!!
1-C
2-B
3-A
4-A
5-C
6-C