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Lecture 8

BIO SCI 94 Lecture Notes - Lecture 8: Phylogenetic Tree, Synapomorphy, Natural SelectionPremium


Department
Biological Sciences
Course Code
BIO SCI 94
Professor
Brad Hughes
Lecture
8

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1/23/19
Introduction
Over large periods of time, nature of life on Earth has experienced many
changes
Two analytical tools to reconstruct history of life:
Phylogenetic tree
Fossil record
Tools for Studying History: Phylogenetic Trees
Phylogeny-evolutionary history of group of organisms
Phylogenetic tree
Graphical summary of evolutionary history
Shows ancestor-descendant relationships among taxa
Clarifies sho is related to whom
Tree of life-universal phylogenetic tree
Reading a Phylogenetic Tree
Root-most ancestral branch in tree
Branch-population through time
node(fork)-hypothetical ancestor
Representation of Traits/Groups on the Tree
Ancestral trait-trait that existed in an ancestor
Derived trait- modified ancestral trait, found in descendant
Synapomorphies
Traits in two or more taxa;present only in most recent ancestors
Allow recognition of monophyletic groups-called clades or lineages
Includes only ancestral population and descendants
How can Biologist Distinguish Homology from Homoplasy?
Homology- shared ancestry leads to similar traits
Homoplasy- similar traits due to reasons other than common ancestry
Convergent evolution-common cause of homoplasy
Natural selection favors similar solutions to similar environmental
pressures
Some traits may be homologous with traits in another species while others may
be convergent
Are Streamlined Bodies Homologous or Convergent?
Ichthyosaurs(extinct aquatic reptiles) and dolphins(extant mammals) are simir
Streamlined bodies
Flippers
Dorsal fins
Phylogenetic analysissimilarities not due to common ancestry
Result from convergent evolution
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