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Classification of Living Things
Chapter 18
Why Classify
• Classification is used to name organisms and
group them in a logical manner
– Biologists have classified and named over 1.5
million species
– Estimate that 2 million- 100 million have yet to be
discovered
Taxonomy
• A branch of biology where scientists classify
organisms and assign each a universally
accepted name
Taxonomy
• A good classification system puts organisms in
groups with other organisms that are similar
– Originally based on physical characteristics
• Physical traits are shared amongst unrelated
organisms
– Convergent evolution
• Shark vs. dolphin
• Bird vs. bat
Common Names
• Organism were originally referred to by
common names
– Names that are unique to a small group of people
• With out discussion; draw what comes to
mind when you hear the word: cat
Use of common names
• Common names can be misleading
– Given based on physical characteristics and what
the organism reminds us of
jellyFISH
seaHORSE
Sea
CUCUMBER
Use of common names
• Common names vary among languages and
even regions in the same country
– Mountain lion
– Puma
– Cougar
– Panther
Use of common names
• Different species sometimes share a common
name
– What is a buzzard???
United StatesVulture
United Kingdom (England)Hawk
Removing Confusion
• First Naming system
– scientists used detailed physical descriptions
• Names were long and hard to remember
• Carolus Linnaeus (mid 18th century)
– Developed a two word naming system called
Binomial nomenclature
• shows ancestral relation
Binomial Nomenclature
• scientific names are used to avoid confusion
– Universally accepted
Cathartes aura
Buteo jamaicensis
Taxonomic Nomenclature
Hierarchical system (consists of levels)
Each level is a taxon
Kids
Kingdom
Phylum Prefer
Candy
Class
Over
Order
Fried
Family
Green
Genus
Species Spinach
Kingdom- Animalia
Phylum- Chordata
Class-
Mammalia
Order- Carnivora
Family- Felidae
Genus- Panthera
Species- leo
Binomial Nomenclature
Rules to follow
1. Always written in italics (or underlined)
2. First word is capitalized (genus name)
3. Second word is lowercased (species name)
Binomial Nomenclature
• Genus a group of closely related species
Ursus
Binomial Nomenclature
• Species
a group of similar organisms that can breed
and produce fertile offspring
Ursus
arctos
Ursus
maritimus
Ursus
americanis
Modern Evolutionary
Classification
18.2
Modern Evolutionary classification
• Taxonomic groups are invented by scientist to
group organisms with similar characteristics
Which Similarities are most important
• Taxonomists try to group organisms according
to biologically important characteristics
– Linnaeus grouped species based on visible
similarities (Dolphin example: Fish vs. Mammal)
Barnacle
crab
limpet
Evolutionary Classification
Limpet and barnacle larvae
are very different.
• Barnacles have jointed
limbs, Limpets DON’T !
• Barnacles have a
segmented body, Limpets
DON’T !
• Barnacles have an
exoskeleton that molts,
Limpets DON’T !
Evolutionary Classification
Crab and barnacle larvae
are very similar
• Barnacles have jointed
limbs, So do CRABS !
• Barnacles have a
segmented body, So do
CRABS !
• Barnacles have an
exoskeleton that molts,
So do CRABS !
Evolutionary Classification
• Organisms are grouped
together based on
evolutionary decent not
just physical traits (WHY??)
• The higher the level of
the taxon, the further
back in time is the
common ancestor
Lion
• Kingdom: Animalia
• Phylum: Chordata
• Class: Mammalia
• Order: Carnivora
• Family: Felidae
• Genus: Panthera
• Species: leo
Tiger
• Kingdom: Animalia
• Phylum: Chordata
• Class: Mammalia
• Order: Carnivora
• Family: Felidae
• Genus: Panthera
• Species: tigris
Lion
• Kingdom: Animalia
• Phylum: Chordata
• Class: Mammalia
• Order: Carnivora
• Family: Felidae
• Genus: Panthera
• Species: leo
Grey Wolf
• Kingdom: Animalia
• Phylum: Chordata
• Class: Mammalia
• Order: Carnivora
• Family: Canidae
• Genus: Canis
• Species: C. lupus
Cladistic analysis
• Cladogram: a diagram
used to show
evolutionary
relationships
• A way of classifying
organisms using only
new evolutionary
characteristics
• Derived
characteristics- These
characteristics appear
in later organisms but
not earlier ones
Molecular Clock
• Used to compare DNA of organisms
– The more similar the DNA the more recently the
organisms branched off from one another
• Neutral Mutations- are not affected by natural
selection
– Accumulate in the DNA over time (at the same
rate in all species)
Cladogram
• Help us to understand
how one lineage
branched from another
in the course of
evolution. (family tree)
1. ______ Wings
2. ______ 6 Legs
3. ______ Segmented Body
4. ______ Double set of wings
5. ______ Jumping Legs
6. ______ Crushing mouthparts
7. ______ Legs
8. ______ Curly Antennae
Answer
1. ___F___ Wings
2. ___C___ 6 Legs
3. ___A___ Segmented Body
4. ___G___ Double set of wings
5. ___E___ Jumping Legs
6. ___D___ Crushing mouthparts
7. ___B___ Legs
8. ___H___ Curly Antennae
Kingdoms and Domains
The tree of Live “Evolves”
Changes in the classification system
• New biological understanding lead to a more
accurate classification system
• Genes show important similarities at the
molecular level
– Linnaeu’s didn’t know about DNA
• DNA from organisms can be sequenced and
compared to show evolutionary relationships.
Molecular Clocks
• DNA comparisons can be used to estimate
how long 2 species have been evolving
independently.
• Mutations in the genes accumulate at
different rates
– The more similar mutations 2 species have the
closer related they are
Effect on Classification
• Scientist used to believe there were just 2 groups
of living things: plants and animals
• 2 kingdom system doesn’t adequately represent
diversity of life
• 6 kingdom system:
–
–
–
–
–
–
Eubacteria
Archaebacteria
Protista
Fungi
Plantae
Animalia
•
•
•
•
•
Eubacteria
Prokaryote
Unicellular
Autotroph or Heterotroph
Cell wall with peptidoglycan (extra outer layer)
Ecologically diverse (Common Bacteria)
– Free-living soil organisms
– Parasites
– Photosynthetic
– Anaerobic
– aerobic
Archaebacteria
•
•
•
•
•
Prokaryote
Unicellular
Autotroph or Heterotroph
Cell wall without peptidoglycan layer
Live in the most extreme environments (first
living organisms)
– Volcanic hot springs
– Brine pools
– Black organic mud (NO oxygen)
Protista
• Eukaryote
• Most are unicellular
• Autotroph or Heterotroph
• Cell walls of cellulose
• Some have chloroplasts
• Made up of organisms that
cannot be classified elsewhere
Fungi
• Eukaryote
• Most are Multicellular
(some unicellular)
• Heterotrophs
– Feed on dead or
decaying matter
– Secrete digestive
enzymes to break down
food
• Cell wall of chitin
Plantae
• Eukaryote
• Multicellular
• Autotroph
– Carry out photosynthesis
• Chloroplasts
• Cell wall of cellulose
• Non-motile (cannot
move from place to
place)
Animalia
•
•
•
•
•
Eukaryote
Multicellular
Heterotroph
No cell wall
Most can move (at least
at some point in there life
cycle)
• Very diverse group
– Species that exist in almost
every part of the planet
3 Domain System
• Molecular clock analysis allows scientists to
group organisms according to how long they
have been evolving independently
• The domain is a more inclusive category than
any other
• 3 Domains: Bacteria, Archaea, and Eukarya
Domain/ Kingdom Relationship