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Classification
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What is Classification?
Classification is the arrangement of
organisms into orderly groups based
on their similarities.
Taxonomy is the scientific discipline
that deals with classification.
Taxonomists are scientists that
identify & name organisms.
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Benefits of Classifying
•organisms.
Accurately & uniformly names
•starfish
Prevents misnomers such as
& jellyfish that aren't
really fish.
Uses the same language (Latin)
for all names.
•
Sea”horse”??
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Confusion in Using Different
Languages for Names
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Latin Names are Understood by
all Taxonomists
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History of Classification
•2000 years ago,
the Greek
philosopher, Aristotle
developed the first
widely accepted
classification system.
•Organisms were
classified as either
plants or animals.
(394-322 B.C.)
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•He subdivided plants into three
groups: herbs, shrubs, and trees.
•He classified animals by their
habitat -- land, sea, or air
dwellers.
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Carolus Linnaeus
• 18th century
1707 – 1778
Swedish botanist.
• Called the
“Father of
Taxonomy.”
• Developed naming
system still used
today.
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Carolus Linnaeus
•Developed the modern
system of naming known as
binomial nomenclature
•Two-word scientific name
(Genus & species)
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Standardized Naming
•Binomial nomenclature
•Genus species
•Language: Latin
•Italicized in print
•Capitalize genus, but
NOT species
•Underline when writing
Turdus migratorius
American Robin
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Binomial Nomenclature
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Classification Groups
• Taxon (taxa-plural) is a
•
•
category into which related
organisms are placed.
There is a hierarchy of groups
(taxa) from broadest to most
specific.
Domain, Kingdom, Phylum, Class,
Order, Family, Genus, species
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Hierarchy-Taxonomic Groups
BROADEST TAXON
Domain
Kingdom
Phylum (Division – used for plants)
Class
Order
Family
Genus
Species
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Hierarchy-Taxonomic Groups
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King
Phillip
Came
Over
For
Grape
Soda!
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Modern Classification
•Classification is based on
evolutionary relationships.
•Phylogeny is the evolutionary
history of a species.
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Basis for Modern Taxonomy
•Homologous structures (same
structure, different function)
•Similar embryo development
•Similarity in DNA, RNA, or
amino acid sequence of
Proteins
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Homologous Structures show Similarities in mammals.
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Similarities in Vertebrate Embryos
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Cladogram
Diagram showing how organisms are
related based on shared, derived
characteristics such as feathers,
hair, or scales.
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Domains
• Broadest, most inclusive taxon
• Three domains
• Archaea are extremophiles.
• Eubacteria are unicellular
•
prokaryotes (no nucleus or
membrane-bound organelles)
Eukarya are more complex and
have a nucleus and membranebound organelles.
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Archaea live in harsh environments and may
represent the first cells to have evolved.
Sewage
treatment
plants, thermal
vents, etc.
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Eubacteria, some of which cause
human diseases, are present in
almost all habitats on earth.
Live in the
intestines
of animals
Bacteria play an important role in
the environment and food production.
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Domain Eukarya is Divided
into four Kingdoms
•Protista (protozoans, kelp,
amoebas…)
•Fungi (yeasts, mushrooms …)
•Plantae (multicellular plants)
•Animalia (multicellular animals)
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•Most are
unicellular
•Some are
multicellular
•Some are
Protista
autotrophic, while
others are
heterotrophic
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Fungi
• Multicellular,
except yeast
• Absorptive
•
heterotrophs
(digest food
outside their
body & then
absorb it)
Cell walls
made of chitin
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Plantae
•Multicellular
•Autotrophic
•Absorb sunlight
to make glucose –
Photosynthesis
Cell walls made of
cellulose
•
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• Multicellular
• Ingestive
•
Animalia
heterotrophs
(consume food
& digest it
inside their
bodies)
Feed on plants
or animals
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Viruses—An Exception
 A virus is a nucleic acid surrounded by a
protein coat.
 Viruses do not possess cells.
 Viruses cannot live on their own they
need to live inside a host cell.
 Are they living?
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Dichotomous Keying
•Used to identify organisms
•Characteristics given in pairs
•Read both characteristics and
either go to another set of
characteristics OR identify
the organism.
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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 3
Eight Tentacles – Octopus
More than 8 tentacles – 3
Tentacles hang down – go to 4
Tentacles upright–Sea Anemone
Balloon-shaped body–Jellyfish
Body NOT balloon-shaped - 5
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