Reference Text:
Modern Biology
Chapter 18 – Section 2
Modern Phylogenetic
Taxonomy pgs. 342 - 346
• Evidence from morphology, the
fossil record, embryology and
molecular biology is used to
organize organisms in systematic
taxonomy
Linnaeus focused on morphology or features of an
organism when classifying it.
Organisms were classified together because they are
similar; they are similar because chances are they
stem from a common ancestor.
Today we know that those features are largely
influenced by genes, which are inherited, or passed
down from our ancestors.
Squirrel
Prairie Dog
Sciurus
carolinensis
Cynomys
gunnisoni
FAMILY SCIURIDAE
Modern Systematic Taxonomists consider
several lines of evidence when classifying
organisms according to their phylogeny
(a.k.a. evolutionary history)
Four Types of evidence include:
• Morphology (homologous structures)
• Embryological development
• DNA, RNA, Amino acid sequences
• Fossil records
•
PHYLOGENEY
The evolutionary relationships between all
groups of organisms based on
ancestor/descendant relationships.
Pangolin -
The morphology Linnaeus followed holds
true to phylogeny or evolutionary
relationships… in most cases…
Armadillo
The Pangolin and armadillo are two animals
with no close taxonomic relationship.
Modern Systematic Taxonomists construct a
Phylogenetic tree, or family tree to show
these relationships.
A phylogenetic
tree shows the
evolutionary
relationships
between
different groups
of organisms.
Modern Taxonomist consider several lines
of evidence when classifying organisms
according to their evolutionary history:
Four Types of evidence include:
• Morphology (homologous structures)
• Embryological development
• DNA, RNA, Amino acid sequences
• Fossil records
Homologous Structures (BONES in the FORELIMBS) shows
Similarities in the morphology of mammals.
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EVIDENCE - Similarities in DNA
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A relatively new system of
phylogenetic classification is called
cladistics.
•
Based on Derived characteristics:
•
Certain features that evolved only within
the group being studied
• Example: if the group being studied is
birds, having feathers is the derived
character.
In this approach, ancestry diagrams are made
through derived characters analysis.
These diagrams called CLADOGRAMS
Primate
Cladogram
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