Classification
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Why Classify?
•Classification is the
arrangement of organisms into
orderly groups based on their
similarities in DNA.
Life is so diverse, that
scientists use classification to
group organisms in a logical
way.
•
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Taxonomy
The science of
classification is known as
taxonomy.
Taxonomists are scientists
that identify & name
organisms
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Why does it matter?
What is this?
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Cougar?
Mountain Lion?
Panther?
Puma?
Felis concolor
For many species, there are regional
differences in their common name.
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Assigning Scientific Names
•To eliminate confusion, 18th
century scientists agreed to a
single name for each
organism.
•The languages that were
chosen to use were Greek and
Latin because they were
widely understood.
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Early Attempts at Naming
•The first attempts at naming
were descriptions of physical
characteristics.
•But they were WAY TO
LONG and still caused
confusion.
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Example: name this in 10 words:
Oak with rounded edges three
fingered top and narrow bottom
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Binomial Nomenclature
Binomial Nomenclature is the
system still used today in which a
species is given a two-part
scientific name.
RULES:
1) Written in italics
2) 1st word capitalized
3) 2nd word is lower case
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What does each word stand for?
1st Word- Genus- group of closely
related species.
2nd Word- Species Specificimportant trait or reflection of
habitat.
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Example: Polar Bear
Scientific Name: Ursus maritimus
Ursus = genus the polar bear
belongs to
maritimus = Latin for “sea”
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Carolus Linnaeus
1707 – 1778
• 18th century
taxonomist
• Classified
•
organisms by
their structure
Developed
naming system
still used
today
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Linnaeus’s system of classification
includes seven Taxa (levels)
(singular- taxon).
They are (from largest to smallest):
Kingdom
Phylum
Class
Order
Family
Genus
Species
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King
Phillip
Came
Over
For
Good
Spaghetti
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Example: Polar Bear
Kingdom- Animalia
Phylum- Chordata
Class- Mammalia
Order- Carnivora
Family- Ursidae
Genus- Ursus
Species- maritimus
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Read pg. 449 in your text. Then answer the
following questions:
1) What would NOT share a kingdom with
a polar bear?
2) Name one animal that shares a phylum
with the polar bear.
3) Name one animal that shares a class
with the polar bear.
4) Name one animal that shares an order
with the polar bear.
5) Name one animal that shares a family
with the polar bear.
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18-2 Modern Evolutionary Classification
Q: What was the problem with
Linnaeus’s system of classification?
A: Which similarities and differences
were most important when classifying?
Example: Dolphins- what is more
important? Live in water with fins
or breathe air and feed their
young with milk?
A better system was developed based on
Darwin’s ideas of descent with
modification.
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Evolutionary Classification
Phylogeny- study of evolutionary
relationships among organisms.
Biologists now place organisms into
categories that represent lines of
evolutionary descent, or phylogeny, not
just physical similarities.
This strategy is called evolutionary
classification.
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The larger the level of the taxon, the
farther back in time is the common
ancestor of all organisms in that taxon.
Share a common
ancestor further back
in time. Therefore,
more differences.
Share a common
ancestor more
recently. Therefore,
more similarities.
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Classification Using Cladograms
Derived Characters-characteristics that
appear in recent parts of the lineage as a
result of evolution/adaptations over time,
that don’t appear in older parts of the
lineage.
Derived characters can be used to construct
a cladogram- a diagram that shows
evolutionary relationships among a group of
organisms.
Derived characters are the point at which
one organism breaks from another on a
cladogram.
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Example Cladogram
Derived characters
appear on the
branch in the
evolutionary order
they first appeared.
Examples: jaws, lungs,
claws/nails, feathers,
fur, mammary glands
Outgrou
p
Questions: What characteristics do both lizards and
pigeons share? _________________________________
What two characteristics appeared around the same
time?
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Making a Cladogram
Step 1: Create a table
Perch
Lizard
Chimp
Hagfish
Salamander
Pigeon
Mouse
Fur,
Mammary
glands
Lungs
Jaws
Claws/
Nails
Feathers
Step 2: Mark derived Characters and total them
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Step 3: Create Cladogram from Data
• The organism with the least amount of
checked derived characters is the first to
evolve, etc.
• The derived character with the most amount of
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Similarities in DNA Help Classify
•The genes of many organisms show
important similarities at the
molecular level.
•Similarities in DNA are used to
classify organisms and show if
there is a common ancestor.
•The more DNA there is in
common, the more recent they
shared a common ancestor.
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Even organisms as different
as a multicellular organism
(like a human) and a
unicellular organism (like
yeast) can have similarities in
their genes!
The study of these genes can
help determine if there is any
degree of relatedness.
(common ancestor?)
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A molecular clock is a model that uses DNA
comparisons to estimate the length of time
two species have been evolving
independently.
It shows when new mutations occur in the
DNA.
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18-3: Kingdoms and Domains
There are 3 Domains that scientists
have created that are broader
categories than kingdoms.
The 3 Domains are:
1) Eukarya
2) Bacteria
3) Archaea
Each Kingdom fits into these
domains.
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Domain 1: Bacteria
•Contains the Kingdom Eubacteria.
•Cell Type: prokaryotic
•Cell Structures: cell walls with
peptidoglycan
•Number of Cells: unicellular
•Mode of Nutrition: autotroph or
heterotroph
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Domain 2: Archaea
•Contains the Kingdom Archaebacteria.
•Cell Type: prokaryotic
•Cell Structures: cell walls without
peptidoglycan
•Number of Cells: unicellular
•Mode of Nutrition: autotroph or
heterotroph
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Domain 3: Eukarya
•Contains the Kingdoms
Protista, Fungi, Plantae,
Animalia
•Each kingdom must be broken
down separately to describe
differences in this domain.
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Kingdom Protista
Cell Type: Eukaryote
Cell Structures:
Cell walls with cellulose;
chloroplasts
Number of Cells: most
unicellular
Nutrition: Autotroph or
heterotroph
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Kingdom Fungi
Cell Type: Eukaryote
Cell Structures:
Cell walls with chitin
Number of Cells: most
multicellular
Nutrition: heterotroph
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Kingdom Plantae
Cell Type: Eukaryote
Cell Structures:
Cell walls with cellulose;
chloroplasts
Number of Cells:
multicellular
Nutrition:Autotroph
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Kingdom Animalia
Cell Type: Eukaryote
Cell Structures:No cell
wall, no chloroplasts
Number of Cells:
multicellular
Nutrition:Heterotroph
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Classification Table
Domain
Bacteria Archaea
Eukarya
Kingdom
Cell Type
Cell
Structures
Number
of Cells
Nutrition
Examples
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Dichotomous Keying
•Used to identify organisms
•Characteristics given in
pairs that are “opposites”
•Read both characteristics
and either go to another
set of characteristics OR
identify the organism
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Turn to pages
462-463 in
Textbook
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Example of Dichotomous Key
1a
1b
2a
2b
3a
3b
4a
4b
Tentacles present – Go to 2
Tentacles absent – Go to 4
Eight Tentacles – Octopus
More than 8 tentacles – Go to 3
Tentacles hang down – Go to 4
Tentacles upright–Sea Anemone
Balloon-shaped body–Jellyfish
Body NOT balloon-shapedGo to 5
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Creating a Dichotomous Key
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1) Brainstorm characteristics
of the items:
Long and tubular For writing
Short non-tubular Not for writing
Plastic
has a cap
Not plastic
no cap
Green and gray
Blue and clear
Black and silver
Silver
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2) Make a spider key
2 Main groups
Further breakdown
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3) Using your spider key as a
guide, construct your
dichotomous key. When
something can no longer be
divided, name it!
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Let’s practice!
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