10/2/2012
Classifying Organisms
What are living
things, and how
can they be
classified?
• binomial nomenclature
• species
• genus
• dichotomous key
• cladogram
Classifying Living Things
Classification: organizing information
based on characteristics or traits
There have been many different ideas
about how to organize, or classify, living
things.
Aristotle: Greek philosopher 384-322 BC
2 large groups plants and animals
Carolus Linnaeus classified organisms into
two main groups, called kingdoms, based on
similar structures. Animal and Plant
Binomial nomenclature is a system for
naming organisms with two-word scientific
name
Ex. Ursus arctos
Robert H. Whitaker- 1969 created 5 kingdom
system for classifying organisms
Based groups on size, shape,
environment, presence of red blood
cells
Systematics- current system
Carl Woese and George Fox
uses all known evidence to classify organisms,
including cell type, how food and energy are
obtained, structure and function of features,
common ancestry, and molecular analysis.
Domain-A broad category of living things based on
Domaincharacteristics of the cell
A level above Kingdom in classification – created in
1977 based on DNA and cell type
Prokaryotic cells: no nucleus, simple and small in size
Eukaryotic cells: nucleus, complex and larger in size
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Domain: Archaea
Means ancient –
Ancient Earth
Prokaryotic cells
Unicellular
Extremeophyles: live in
extreme conditions such
as thermal vents deep in
the ocean, hot
geysers,with no oxygen,
acidic conditions, salt,
extreme cold
Domain: Bacteria
Prokaryotic
Unicellular
Live in most environments
Helpful and harmful
Genetically and
chemically different than
Archaea
Domain Eukarya
Eukaryotic cells
cells with a nucleus
and other organelles
Multi-cellular and
unicellular organisms
More complex
Larger
Kingdoms: Animalia,
Plantae, Fungi, Protista
Organisms are now classified into
one of three domains and then into
one of six kingdoms.
Determining Domains (cont.)
What evidence is used to classify living things into
groups?
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Scientific Names
Binomial nomenclature is a system for
naming organisms with two-word
scientific name:
• A species is a group of
organisms that have similar
traits and are able to produce
fertile offspring.
• A genus is a group of similar
species.
Domain
Kingdom
Phylum
Scientific Names (cont.)
genus
from Greek genos, means “race, kind”
Class
Order
Family
Genus
Species
Scientific Names (cont.)
Binomial nomenclature was
developed by Linnaeus and is still
used today.
Scientific names are important
because each species has its own
scientific name and those names
are the same worldwide.
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Help to avoid errors in communication
Genus – group of
species that have
similar
characteristics
Members of a genus
are closely related
Organisms with similar evolutionary
history are group together
Allows information to be organized and
easily found
Descriptive information about species
Elaphe guttata, Huernia
guttata, Stephanorrhina
guttata
(guttata spotted)
Ex. Ursus –bears
Ursus americanus
Ursus maritimus
When naming an organism use both
the genus and species name
Writing names: Genus comes first &
is capitalized and in italics
Scientific Names (cont.)
Why does every species
have a scientific name?
species name comes second in lower
case and italicsBoth underlined when hand written
Homo sapiens - humans
A dichotomous key is a series of
descriptions arranged in pairs that
lead the user to the identification of
an unknown organism.
A cladogram is a branched diagram
that shows the relationships among
organisms, including common
ancestors.
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10/2/2012
• All organisms are classified into one
of three domains: Bacteria, Archaea,
or Eukarya.
• Every organism has a unique species
name.
• A dichotomous key helps to identify an
unknown organism through a series of
paired descriptions.
How many scientific names does each
organism have?
Which of these refers to the system for
naming organisms with two identifying
scientific terms?
1
B. 2
C. 3
D. Many
A.
B.
C.
D.
A.
genus
cladogram
binomial domains
binomial nomenclature
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Which of these refers to the system for
naming organisms with two identifying
scientific terms?
A.
B.
C.
D.
genus
cladogram
binomial domains
binomial nomenclature
Do you agree or disagree?
3. A dichotomous key can be used to
identify an unknown organism.
4. Physical similarities are the only
traits used to classify organisms.
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