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Ch. 15 Classification Systems
Taxonomy
Why Classify?
• 2.5 million known species!• Another 20 million unknown species!• We need a system of biological
classification that names and ordersorganisms in a logical manner.– Universally accepted name.– Groups with real biological meaning
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Biological Classification• Early biological classification used a lot
of detail.– Example: “Oak with deeply divided leaves
that have no hairs on their undersides andno teeth around their edges”
– Problems with this system• Too difficult to use.• Different scientists used different descriptions
for the same organism.
• Latin is used in classification.– Understood by scientists everywhere.
Carolus Linnaeus (Carl von Linne)• Binomial nomenclature –
Each organism has a twopart name.– Genus species– Must be italicized– The first letter of the genus
must be capital.– Examples: Acer rubrum (red
maple), Acer palmatum (leafthat resembles a humanhand)
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Carolus Linnaeus
• Organisms that share characteristics aregrouped together.
• Taxa – the group to which an organism isassigned.
• Taxonomy – the science of namingorganisms and assigning them to thesegroups.
• Current classification rules governed by theInternational Codes of Zoological or ofBotonical Nomenclature (ICZN or ICBN)
Linnaeus’ Classification System – Hierarchy• Species – population of organisms that
share similar characteristics and thatcan breed with one another.**
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Linnaeus’ Classification System – Hierarchy• Genus – Similar species but cannot breed
with one another.– Examples: Felis domesticus (house cat) and Felis
concolor (mountain lion)– Examples: Ursus arctos (Grizzly bear) and Ursus
americanus (Black bear)• Similar feet, teeth and claws but are distinct species.
Linnaeus’ Classification System – Hierarchy• Families – Groups of genera (genus plural)
which share many common characteristics.– Examples: Panthera leo (lions) , Panthera tigris
(tigers), Felis domesticus (house cat), and Felisconcolor (mountain lion)
• Belong to the family Felidae (catlike animals)– Examples: Ursus arctos (Grizzly bear), Ursus
americanus (Black bear) and Ailuropodamelanoleuca (Giant panda)
• Belong to the family Ursidae (Bear like animals)
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Linnaeus’ Classification System – Hierarchy• Order – Several families of similar
organisms.– Example: Felidae (cats) and Canidae (dogs).– Examples: Ursus arctos (Grizzly bear), Ursus
americanus (Black bear), Ailuropodamelanoleuca (Giant panda) and Vulpes vulpes(Red fox)
• Belong to the order Carnivora (meat eaters)
Linnaeus’ Classification System – Hierarchy
• Class – Grouping of orders– Examples: Ursus arctos (Grizzly bear), Ursus americanus
(Black bear), Ailuropoda melanoleuca (Giant panda),Vulpes vulpes (Red fox) and Sciurus carolinensis (greysquirrel)
• Belong to the class Mammalia• A “class of vertebrate, air-breathing animals whose females are
characterized by the possession of mammary glands while bothmales and females are characterized by sweat glands, hair and/orfur, three middle ear bones used in hearing, and a neocortex regionin the brain.” - Wikipedia
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Linnaeus’ Classification System – Hierarchy• Phylum – several classes can be
placed into a phylum– Examples: Ursus arctos (Grizzly bear),
Ursus americanus (Black bear), Ailuropodamelanoleuca (Giant panda), Vulpes vulpes(Red fox), Sciurus carolinensis (greysquirrel) and Aspidelaps lubricus (coralsnake)
– Belong to the phylum chordata (Have anerve cord)
Linnaeus’ Classification System – Hierarchy
• Kingdom – All phyla belong to one ofthe six kingdoms.
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The Species Dilemma.• There is a debate among scientists on the
definition of a species.• Some closely related species interbreed.
– Example: Different species of mice mayinterbreed, some species of monkey interbreed.
• Some organisms within a species are slightlydifferent and some may consider them aseparate species.– Example: Birds of the same species may have
slightly different coloration.
The Species Dilemma.
• Some organisms reproduce asexually.– Example: bdelloid rotifers are all female and
produce embryos without the need for sperm.• What about microorganisms such as
bacteria?– Classifying them by what they eat (metabolism) is
not easy.• Example: Some E.Coli are harmless while others are
deadly. Both eat the same type of food.– They all look alike.– Rarely reproduce sexually.
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Phylocode
• Linnaeus lived a century before Darwin’spublication of Origin of the Species.
• Push for a new system based on evolutionaryrelationships not based on commoncharacteristics.
• Phylocode – Names organized based onevolutionary relationships– Look for common ancestors and group into
“clades”– International Society for Phylogenic Nomenclature
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The Species Dilemma
• The solution may be to define a speciesusing several approaches.
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