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17.2 Classification Based on Evolutionary Relationships
Organization of all that speciation!
• Patterns of evolution…..
17.2 Classification Based on Evolutionary Relationships
17.2 Classification Based on Evolutionary Relationships
Taxonomy gets an over haul! Using more than
morphology!
3 domains, 6 kingdoms
17.2 Classification Based on Evolutionary Relationships
17.2 Classification Based on Evolutionary Relationships
KEY CONCEPT
Modern classification is based on evolutionary
relationships. Called Systematics/Cladistics
17.2 Classification Based on Evolutionary Relationships
Cladistics is classification based on common ancestry.
• Phylogeny is the evolutionary history for a group of species.
– evidence from living species, fossil record, and
molecular data
– shown with branching tree diagrams
17.2 Classification Based on Evolutionary Relationships
• A cladogram is 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.
17.2 Classification Based on Evolutionary Relationships
Plants?
• Bryophyte
• Tracheophyte
• Gymnosperm
• Angiosperm
17.2 Classification Based on Evolutionary Relationships
• Derived characters are traits shared in different degrees by
clade members (synapomorphies).
– basis of arranging
species in
cladogram
– more closely
related species
share more
derived characters
– represented on
cladogram as hash
marks on the “x”
axisFOUR LIMBS WITH DIGITS
Tetrapoda clade1
Amniota clade2
Reptilia clade3Diapsida clade4
Archosauria clade5
EMBRYO PROTECTED BY AMNIOTIC FLUID
OPENING IN THE SIDE OF
THE SKULL
SKULL OPENINGS IN
FRONT OF THE EYE &
IN THE JAW
FEATHERS &
TOOTHLESS
BEAKS.
SKULL OPENINGS BEHIND THE EYE
DERIVED CHARACTER
17.2 Classification Based on Evolutionary Relationships
FOUR LIMBS WITH DIGITS
• Nodes represent
the most recent
common ancestor
of a clade.
• Clades can be
identified by
snipping a branch
under a node.
Tetrapoda clade1
Amniota clade2
Reptilia clade3Diapsida clade4
Archosauria clade5
EMBRYO PROTECTED BY AMNIOTIC FLUID
OPENING IN THE SIDE OF
THE SKULL
SKULL OPENINGS IN
FRONT OF THE EYE AND
IN THE JAW
FEATHERS AND
TOOTHLESS
BEAKS.
SKULL OPENINGS BEHIND THE EYE
NODE
DERIVED CHARACTER
CLADE
17.2 Classification Based on Evolutionary Relationships
CLADE/MONOPHYLETIC TAXON: A group of organisms, that are derived
from a common ancestor.
EX: Birds and reptiles and the reptilian ancestor
TAXON (TAXA): Group of organisms
PARAPHYLETIC TAXON: A group of organisms that does not include all
possibly related organisms. EX: Looking at just birds and then reptiles separately
Out-group is the least related group on the far left!
17.2 Classification Based on Evolutionary Relationships
Outcomes?
17.2 Classification Based on Evolutionary Relationships
Steps to making a cladogram:
1. Determine the traits to assess in order of evolutionary complexity.
2. Create a table of who has the traits and who does not
3. Arrange the traits along the bottom of the diagram and the
organisms coming off that line .(Most advanced organism will be
on the top right when done)
4. Determine common ancestry along the way to determine if new
branch is needed or if one organism derives but does not have new
ancestry.
17.2 Classification Based on Evolutionary Relationships
17.2 Classification Based on Evolutionary Relationships
17.2 Classification Based on Evolutionary Relationships
17.2 Classification Based on Evolutionary Relationships
17.2 Classification Based on Evolutionary Relationships
Anatomical tools
• Homologous structures (shared homology)-structure has
same ancestry and anatomy, even though immediate
function differs:
17.2 Classification Based on Evolutionary Relationships
• Vestigial- structure has huge function in one group, little
or no function in another
17.2 Classification Based on Evolutionary Relationships
• Analogous structure (analogy)-structure has same
immediate function but not ancestry or anatomy. Ex: bee
wings and bird wings
17.2 Classification Based on Evolutionary Relationships
• Molecular clock- once divergence from a common
ancestor occurs and each species lineage continues to
evolve separately, DNA mutations can be compared to
measure genetic differences between the group.
• Tend to use proteins that have plasticity without losing
function. (Ex: not hemoglobin)
• Cytochrome C is better choice. EX: Species A has a 6%
base pair difference in molecule from B, A and C have a
32% difference, who is more closely related? Why?