Ch. 17:
Classification
Who is Carolus Linnaeus?
• Linnaeus developed the
scientific naming system
still used today.
What is…?
• Taxonomy…
–the science of naming and
classifying organisms.
• A taxon…
–group of organisms in a
classification system.
Linnaean Taxonomy
• Organisms are grouped based on physical
and structural similarities.
• Basic taxon is the species
–Defined as a group of organisms that
can breed and produce offspring that
can reproduce
• Each species is given a scientific name
Binomial Nomenclature
• Two-part scientific naming system
–uses Latin words
–scientific names always written in
italics
–two parts are the genus name and
species descriptor
Binomial Nomenclature
• A genus includes one or more physically similar species.
– Species in the same genus are thought to be closely
related.
– Genus name is always capitalized.
• A species descriptor is the second part of a scientific
name.
– always lowercase
– always follows genus
name; never written alone
– (1) Genus (2) species
Seven Levels
• Kingdom, Phylum, Class, Order,
Family, Genus, Species
• Each level is included in the level
above it.
• Levels get increasingly specific from
kingdom to species.
Taxonomy of Lions
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Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Felidae
Genus: Panthera
Species: leo
Taxonomy of Leatherback Sea
Turtles
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Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Testudines
Family: Cheloniidae
Genus: Dermochelys
Species: coriacea
Taxonomy of Humans
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Family: Hominidae
Genus: Homo
Species: sapiens
The Linnaean classification system has
limitations.
• Linnaeus taxonomy doesn’t account for
molecular evidence, only on physical
similarities…
– The technology didn’t exist during Linneaus’
time.
– Physical similarities are not always the
result of close relationships.
– Genetic similarities more accurately show
evolutionary relationships.
Dichotomous Keys
• Used to identify objects or organisms that
have already been described by another
scientist.
• Made up of paired statements.
– Pair of statements divides the objects to be
classified into one category or the other, but not
both.
• As you proceed from step to step, the
classification is narrowed down.
http://cbe.wisc.edu/assets/docs/pdf/biolearn/Classification/WhatIsLife/dichotomous_key.pdf
Cladistics
• is a common method to make
evolutionary trees.
• classification based on
common ancestry
• species placed in order that
they descended from
common ancestor
Cladogram
• an evolutionary tree made using
cladistics.
• A clade is a group of species that
shares a common ancestor.
–Each species in a clade shares
some traits with the ancestor.
–Each species in a clade has traits
that have changed.
Derived Characters
• are traits shared in different
degrees by clade members.
–basis of arranging species in
cladogram
–more closely related species share
more derived characters
–represented on cladogram as hash
marks
Cladogram
• Nodes represent
the most recent
common
ancestor of a
clade.
• Clades can be
identified by
snipping a branch
under a node.
CLADE
1 Tetrapoda clade
2 Amniota clade
3 Reptilia clade
4 Diapsida clade 5 Archosauria clade
FEATHERS AND
TOOTHLESS
BEAKS.
SKULL OPENINGS IN
FRONT OF THE EYE AND
IN THE JAW
OPENING IN THE SIDE OF
THE SKULL
SKULL OPENINGS BEHIND THE EYE
EMBRYO PROTECTED BY AMNIOTIC FLUID
NODE
FOUR LIMBS WITH DIGITS
DERIVED CHARACTER
Domains and Kingdoms
• The three domains in the tree of life are
Bacteria, Archaea, and Eukarya.
• Domains are above the kingdom level.
–proposed by Carl Woese based on
rRNA studies of prokaryotes
–domain model more clearly shows
prokaryotic diversity
Domain Bacteria
• Domain Bacteria
includes singlecelled prokaryotes
in the kingdom
Bacteria.
– one of largest
groups on Earth
– classified by
shape, need for
oxygen, and
diseases caused
Domain Archaea
• Domain Archaea includes single-celled
prokaryotes in the kingdom Archaea.
– cell walls chemically different from
bacteria
– differences discovered by studying RNA
• known for living in extreme
environments
– Can live areas that lack oxygen, an area with
a high salt concentration, or extremely hot
environments.
Domain Eukarya
• Domain Eukarya includes
all eukaryotes (cells have a
distinct nucleus and
membrane-bound
organelles).
• Eukarya may be:
– Single-celled: protists
– Colonial: some algae
– Multicellular: You!!
• Domain includes the
following kingdoms:
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kingdom Protista
kingdom Plantae
kingdom Fungi
kingdom Animalia