Classification & Taxonomy 10-1
An organized system to classify all
living things
Biology is the study of life…
• But how do we know
something is “alive”?
– Metabolism
• Consume molecules
• Produce wastes
• Exchange gases
– Reproduction
– Cells
– DNA
The Need for a Classification System…
• Organizing and categorizing all of the organisms that
exist on earth today is quite a task!
A system of classification must be…
- organized and logic
- universal (used by all scientists)
• Our current system breaks down organisms into more & more
closely-related groups until only one group is left…the
“species”!
Taxonomy…
• Taxonomy is the study, practice, and science of
the classificiation of organisms.
Binomial Nomenclature
(“to name with 2 names”)
• Each species is named with 2 words
– The first word is the “genus”
– The second word is the “specific epithet”
– When written together, this name is called the
“species”
– Ex: Homo sapiens or Homo sapiens
• Homo = genus of humans
• sapiens = specific epithet of humans
• Note: genus is capitalized, other is not…both
underlined or italicized
Taxons
• Groups of related genera are classified together
in the same family
• Groups of related families for an order
• This follows the pattern…
Orders  Class  Phylum  Kingdom
• We usually memorize these from the largest to
smallest direction:
– KPCOFGS
Test Yourself!
Name the 7 major taxons in order…
•
•
•
•
•
•
•
Kingdom
Phylum
Class
Order
Family
Genus
Species
Dichotomous Keys
• Rules:
– Always start at clue set #1
– One of the choices must be correct…the other
must be incorrect
– Identify the correct one and go where it says
– When creating a key, it is better to use
“is…is not” format for clues
– Will always have one fewer clue than # of
objects
Dichotomous Key Example
• Example:
• 1. A. contains ink……………..…..go to 2
•
B. does not contain ink………..go to 3
• 2. A. point made of metal………..pen
•
B. point not made of metal……marker
3. A. made of plastic…..mechanical pencil
B. not made of plastic…...regular pencil
All organisms have been placed
into one of 6 kingdoms.
• This is a generally agreed-upon standard,
but is subject to change
• We have not always had 6 kingdoms, and
some scientists use fewer or more
• What criteria are used to place an
organism in a kingdom?
Basic Criteria for Kingdoms
(The Big 5!) 10-2
• # of Cells
– Unicellular or Multicellular
• Type of Cell
– Prokaryotic or Eukaryotic
• Cell Wall
– Yes or No
• Nutrition
– Autotrophic or Heterotrophic
• Motility
– Yes or No
Test Yourself!
What do the following mean?
•
•
•
•
•
•
•
•
•
Unicellular
Multicellular
Prokaryotic
Eukaryotic
Autotrophic
Heterotrophic
Motile
Nonmotile
Cell Wall
Bacteria
• The Big 5:
• K. Archaebacteria
–
–
–
–
Harsh environments
Methanogens (anerobic)
Thermophiles (high heat)
Halophiles (salt)
• K. Eubacteria
– “common” bacteria
– Ex: E.coli; Staphylococcus aureus
– Unicellular
– Prokaryotic
– The other 3
traits are
variable…
examples of
bacteria exist
for each trait
K. Protista
• The most diverse and
oft-changing kingdom!
• The Big 5:
– Unicellular***
– Eukaryotic
– The other 3 traits are
variable…protists of
various types exhibit
both versions.
K. Fungi
• Often seem plant-like…but
cannot make food!
• The Big 5:
– Multicellular
– Eukaryotic
– Cell wall – of chitin
– Heterotrophic – absorb food
– Nonmotile
K. Plantae
• Usually green due to
chlorophyll
• The Big 5:
– Multicellular
– Eukaryotic
– Cell wall – of cellulose
– Autotrophic
– Nonmotile
K. Animalia
• Large, motile creatures
that eat!
• The Big 5:
– Multicellular
– Eukaryotic
– No cell wall
– Heterotrophic – ingest
food
– Motile
Taxonomic Tree 10-3
• Cladistics- classification system based on
phylogeny; assumes that as groups of
organisms diverge and evolve from a common
ancestral group, they retain derived traits.
• Cladogram is the diagram used to represent the
phylogeny of a species based on those derived
traits.
Taxonomic Tree
Which group of organisms are most closely related?
Butterflies, moths and flies
X
Y
Z
1. A. Is multicellular………………………………..go to 2
B. Is unicellular……………………….…………go to 3
2. A. Contains chlorophyll; is green…………….Chlorella
B. Contains erythrophyll; is red………………Hemalia
3. A. Cell is oblong with tiny cilia………………...Paramecium
B. Cell is blob-like with slender extensions….Amoeba