Chapter 25: Phylogeny

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Chapter 25 Phylogeny Systematics

• Phylogeny
• Evolutionary history of species or group of
  species
• Attempting to construct the universal tree of
  life

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Information contributing to Phylogenics

• Fossil record
• Substantial but incomplete biased chronicle of
  evolutionary change
• Systematics
• analytical approach to understanding the
  diversity relationships of present day
  extinct organisms through morphological
  biochemical resemblances

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Systematics

• Morphological homologies
• Similar bone structures indicate species share a
  common ancestor
• Molecular homologies
• Similarities in DNA, RNA, other molecules
  indicate species share a common ancestor
• Potential problems for phylogeny Analogous
  structures (homoplasies) convergent evolution

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Taxonomy

• Ordered division of organisms into categories
  based on a set of characteristics used to assess
  similarities differences
• Useful for phylogenic systematics
• Binomial designations (Genus species)
• Hierarchical classifications

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Phylogenetic Trees

• Depict hypothesis about evolutionary
  relationships of a species in relative periods of
  time
• Cladistics
• Analysis of how species may be grouped into
  clades distinguishing analogous from homologous
  structures
• Cladogram
• Depicts patterns of shared characteristics, not
  necessarily evolutionary history
• Can be converted to phylogenetic trees with
  support from fossils, biochemistry, etc.
• Clade
• Group of species in the phylogenetic tree that
  includes an ancestral species all its
  descendants

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Phylogenetic Trees

• Monophyletic
• Clade consists of ancestral species its
  descendants
• Paraphyletic
• Grouping in which information is missing on some
  members of the clade
• Polyphyletic
• Grouping of several species that lack a common
  ancestor

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Preparing phylogenetic trees

• Ingroup
• Species being studied
• Outgroup
• Species or group of species closely related to
  ingroup
• Used to differentiate shared derived shared
  primitive characteristics
• Shared primitive character
• Trait shared beyond the taxon being defined
• Shared derived character
• Novelty trait of a clade
• Maximum parsimony
• Fewest number of evolutionary events occur to
  reach form of shared derived characteristics
• Nature doesnt always follow easiest course ex.
  4 chamber heart
• Maximum liklihood
• Incorporate as much information as possible to
  reflect the most likely sequence of evolutionary
  events

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Evolutionary Diagrams depicting time

• Phylogram
• Present information about the sequence of events
  relative to each other
• Branch length changes in DNA sequence which
  have occurred in that lineage
• Ultrametric trees
• Show sequence of evolutionary events in context
  of geologic time

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Molecular Clocks

• Measures absolute time of evolutionary change
  based on observations that some genes other
  regions of genomes evolve at constant rates
• DNA coding for rRNA changes relatively slowly-
  used to study relationships of distantly related
  species
• DNA in mitochondria (mtDNA) evolves rapidly
  used to study recently diverged species
• Orthologous genes
• Homologous genes passed from one generation to
  the next but end up in different gene pools as a
  result of speciation
• Ex. Beta globin genes in humans mice
• Paralogous genes
• Result from gene duplication in one genome
• Ex. Olfactory genes

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Universal Tree of Life

• Tree consists of 3 great domains
• Bacteria
• Archaea
• Eukarya
• Early history of the domains is not yet clear
• Molecular systemactics clocks used to construct

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