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Taxonomy Notes
Nowicki Biology, Chapter 17
With a partner discuss why/how we classify things:
17.1: The Linnaean System of Classification
Linnaeus developed the scientific naming system still used today
taxonomy – science of naming and classifying organisms
- hierarchical – multilevel scale in which each level is contained or included in every
level above it
- based on the system developed by Carolus Linnaeus
Figure 1: Animal Hierarchy
Looking at the Figure 1: Animal Hierarchy to the right:
1. Dogs are _____________ and ____________________
2. Are birds animals? ______________
3. Are fish mammals? ___________
Animals
Mammals
Dogs
Fish
Birds
Cats
taxon – a level of classification; the basic level is species; taxa
is the plural
- the diagram below shows 8 taxa in the hierarchical system of classification we use
most general/least specific (includes the greatest
number of organisms)
Domain
Kingdom
Phylum
Class
Order
Family
Genus
most specific – contains only one single kind of organism
Species
Mnemonic
(Dear King Phillip Came Over For Grape Soda)
Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
Come up with your own mnemonic:
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(Domain is not shown in the diagram
to the left)
When looking at the taxonomic
hierarchy (Domain, Kingdom, etc),
Which taxon has the most diverse
group of organisms?
__________________________
Which taxon is the least diverse?
___________________________
Scientific Naming
- Using common names is confusing because many organisms may have several different common
names.
- The cougar is also known as the mountain lion, puma or catamount, thus the need for a
scientific name.
- We use binomial nomenclature to assign scientific names.
The scientific name for a cougar is Felis concolor
binomial nomenclature – a system of naming in which each species has a two-part scientific
name
- Two different species cannot have the same scientific name
- Importance? Binomial nomenclature provides a standard of communication among
biologists, regardless of their native language
scientific name – genus and species names of an organism
- basis for our system of naming organisms.
- two parts:
o genus – first part/word of the scientific name
 always capitalized and italicized (typing) or underlined (handwriting)
 can be used alone
o species – second part/word of the scientific name
 never capitalized
 always italicized (typing) or underlined (handwriting)
 can never be used alone
Helix pomatia
 Typed
Written 
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EXAMPLE: One of the most commonly used scientific names is Escherichia coli. This is the
scientific name of a rod-shaped bacteria that lives in your intestines, helping you digest your
food and produce vitamin K (necessary for blood clotting). It is also used in research involving
bacteria and is sometimes linked to outbreaks of food-poisoning.
When the name has been typed, it should look like this: Escherichia coli
When the name has been handwritten, it should look like this: Escherichia coli
It is okay to abbreviate the full name like this: E. coli or Escherichia, but never like this: coli
Why are all scientific names so weird? Why can’t they just be “in English”?
Scientific names are written in Latin because it is not a language spoken in any
country today; therefore, it is a nonpolitical choice.
There are several divisions of the International Code of Nomenclature that
govern the naming of all organisms.
The Linnaean classification system has limitations
- Linnaeus based his classification on physical similarities
- today we have technology that allows us to look at molecular similarities (amino acid
sequences in proteins that are based on nucleotide sequences in the genes of the DNA)
- remember that organisms can look similar due to analogous characteristics resulting
from convergent evolution (think back to evolution: bird wings and butterfly wings
have the same function, different structure)
- classification should be based on homologous characteristics resulting from divergent
evolution (think back to evolution: homologous characteristics share the same
structure, have a common ancestor but have a different function)
- molecular homology is much more definitive in determining species relationships than
physical analogy
The more taxonomic levels that two organisms share, the more closely related they are.
Which bears are most closely related?
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Ursus maritimus
Ursus arctos
Ailuropoda melanoleuca
Using the chart to the right
1. What type of animal is Musca
domestica?
2. From the table, which 2 animals
are most closely related?
3. At what classification level does
the evolutionary relationship
between cats and wolves diverge
(become different)?
dichotomous key – tool used by scientists to identify organisms in the field based on defining
characteristics
Dichotomous Key for Norns
- arranged in pairs of
1. a. Has pointed ears……………………………………………………. go to 3
questions to which the
b. Has rounded ears………………………………………………..... go to 2
answer is generally yes
2. a. Has no tail……………………………………………………...kentuckyus
or no, followed by a
b. Has tail……………………………………………………………...… dakotus
direction of what pair of
3. a. Ears point upward……………………………………………....... go to 5
questions to go to next
b. Ears point downward…………………………………………....… go to 4
4. a. Engages in waving behavior………………………………….... dallus
until the organism has
b. Has hairy tufts on ears………………………………………californius
been identified
-
key to using this tool is
always starting with the
first pair of questions!
Norns are a very rare and
actually imaginary animals that
belong to the genus Norno.
There are 8 different species of
Norno, generally located in
specific regions of the world. Use
the key to identify the Norns
shown.
5. a. Engages in waving behavior……………………………….
walawala
b. Does not engage in waving behavior…………………....... go to 6
6. a. Has hair on head…………………………………………………. beverlus
b. Has no hair on head (may have ear tufts)………………. go to 7
7. a. Has a tail……………………………………………………………….... yorkio
b. Has no tail, aggressive……………………………………………….rajus
A
B
C
17.2: Classificaiton Based on Evolutionary Relationships
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phylogeny – evolutionary history for a group of species
- can be shown as branching “family trees”
- think back to evolution and phylogenetic trees: does this reflect convergent or
divergent evolution? _________________________________
Cladistics is classification based on common ancestry
cladistics – classification based on common ancestry
- goal is to place species in the order in which they descended from a common ancestor
cladogram – diagram based on patterns of shared, derived traits that shows the evolutionary
relationships between groups of organisms
- clade – group of species that share a common ancestor
derived characters – traits that can be used to figure out evolutionary relationships among a
group of species; traits are shared by some species but are not present in others
- the more closely related species are, the more derived characters they will share
outgroup – group of species that shares no derived characters with the other groups being
studied
1. Which are the derived characters in the cladogram below?
2. Circle the Hagfish and label it, “outgroup.” Explain why it’s the outgroup.
Complete Quicklab: Classifying – Construct a Cladogram, p. 511
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1. Use the following words to appropriately label the 5 blanks at the top of the cladogram.
airplane
bicycle
car
motorcycle
walking
2. What are the derived characters in this cladogram?
3. What mode of transportation may be considered an “outgroup?”
4. A species that has evolved a new trait is not better than a species without that trait.
Each species is just adapted to a certain way of life. When might riding a bike have an
advantage over flying in an airplane?
Cladograms are important tools in classification because they represent true evolutionary
relationships based on all available data, especially molecular homology--DNA &/or amino acids.
Interpreting a Clagogram:
CLADE – group of organisms that share certain traits derived from a common
ancestor. On many cladograms, a clade is marked by lines looking like the letter
V. The dotted line marks the amniote clade shown in this diagram
DERIVED CHARACTERS –
shared trait of all species
above the name of the
character or the hash
mark for it
NODE – intersection of 2 branch
points representing the most
recent common ancestor
What derived traits do groupers have? _______________________________________________
Do Lancelet’s contain a vertebral column? _______________
What organism is closely related to the wolf? _________________________
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17.3: Molecular Clocks
Molecular clocks use mutations to estimate evolutionary time
molecular clocks – models that use mutation rates to measure evolutionary time
- basis for using molecular data to determine relatedness of 2 organisms
o more differences between the genes or proteins of 2 organisms means they are
more distantly related they are (they shared a common ancestor a long, long
time ago)
o fewer differences between the genes or proteins of 2 organisms means they are
more closely related (they shared a common ancestor more recently)
(Read pages 516-518 for more information on Molecular Clocks)
17.4: Domains and Kingdoms
Classification is always a work in progress:
Two Kingdoms
Three Kingdoms
Five Kingdoms
Four Kingdoms
Six Kingdoms
Current system of 3 domains and 6 kingdoms
The three domains in the tree of life are Bacteria, Archaea, and Eukarya
Bacteria – includes single-celled prokaryotes in the kingdom Bacteria
- cell wall contains peptidoglycan
- includes bacteria that live in/on organisms, soil decomposers, disease causing bacteria
(everyday bacteria)
Archaea – includes single-celled prokaryotes in the kingdom Archaea
- cell wall does not contain peptidoglycan, has lipids
- includes bacteria that live in extreme environments such as deep sea vents, hot
geysers, salt lakes, etc.

classifying Bacteria and Archaea is difficult because they so frequently transfer genes among
themselves that defining a “species” is nearly impossible; this process is just beginning and will
continue as we learn more about these organisms
Eukarya – made up of all organisms with eukaryotic cells – distinct nucleus and membrane-bound
organelles
- can be single-cells, colonial, or multicellular
- includes the kingdoms Protista, Plantae, Fungi, and Animalia
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Fill in this graphic
organizer for the 3
domains and the 6
kingdoms under each.
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CHARACTERISTICS OF DOMAINS AND KINGDOMS
DOMAIN
KINGDOM
Archaea
Archaea
Bacteria
Bacteria
CELL TYPE
Prokaryotes
BODY FORMS unicellular
Prokaryotes
unicellular
CELL WALL
cell walls with
peptidoglycan
heterotroph &
autotroph
everyday
bacteria,
includes
decomposers
and Nitrogen
fixers
E.coli, Strep,
Staph
NUTRITION
FACTS
EXAMPLES
cell walls with
lipids
heterotroph &
autotroph
live in extreme
environments
thermophiles,
halophiles
Eukarya
Plantae
Protista
Fungi
Eukaryotes
mostly
unicellular
some have
cell walls
heterotroph &
autotroph
live in
water/moist
places;
produce about
1/3 of Earth’s
oxygen
algae,
amoeba,
paramecium
Eukaryotes
mostly
multicellular
cell walls with
chitin
heterotroph
only
decomposers;
making food
and medicine
Eukaryotes
multicellular
mushrooms,
yeast, mold
grass, trees,
shrubs
Animalia
Eukaryotes
multicellular
cell walls with NO cell walls
cellulose
autotroph only heterotroph
only
produce about most
2/3 of Earth’s physically
oxygen
diverse
kingdom
sponges,
worms,
insects, fish,
birds, reptiles,
mammals
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