Phylogeny and theTree of Life      Chapter 26
Phylogeny   The evolutionary history of a species or    a group of related species   Systematics       classifying and ...
Taxonomy   Natural way to group organisms   Linnaeus – 18th century   Binomial nomenclature (Genus species)   Hierarch...
Phylogenetic tree   Branching diagram that shows evolutionary    history   Hypothesis about evolutionary relationship   ...
How to read a phylogenetictree
Homology vs Analogy   Homology - similarities due to shared    ancestry   Analogy – similarities due to convergent    ev...
Molecular Systematics   Comparisons of proteins and DNA   DNA with many similar base sequences    = homologies
Cladistics   Common descent is primary way to classify    organisms   Clade – ancestral species and all    descendents ...
Example of groups
Shared vs. Derived   Shared ancestral character –       originated in an ancestor of the taxon       Backbone in mammal...
Derived Characters   Outgroup –       species from an evolutionary lineage that is        known to have diverged before ...
Genome comparisons   More common DNA = more closely related   Different genes evolve at different rates,    even in the ...
Genome Evolution   Living organisms share many    biochemical and development pathways   The # of genes seems not to hav...
Molecular clocks   Different proteins and DNA evolve at different    rates, but at a relatively constant rate for    each...
Molecular clocks
2 Kingdoms to 3 Domains   Plants & Animals   More than 2 kingdoms did not gain    acceptance until the late 1960s   5 k...
3 Domains
Chapter 26 - Phylogeny and the Tree of Life
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Chapter 26 - Phylogeny and the Tree of Life

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Chapter 26 - Phylogeny and the Tree of Life

  1. 1. Phylogeny and theTree of Life Chapter 26
  2. 2. Phylogeny The evolutionary history of a species or a group of related species Systematics  classifying and determining the evolutionary relationship between organisms  Data from fossils, comparative anatomy, molecules and genes
  3. 3. Taxonomy Natural way to group organisms Linnaeus – 18th century Binomial nomenclature (Genus species) Hierarchical System  Domain  Species  Taxon – each unit
  4. 4. Phylogenetic tree Branching diagram that shows evolutionary history Hypothesis about evolutionary relationship  Branch points – divergence of 2 lineages from a common ancestor  Sister taxa – groups of organisms that share an immediate common ancestor  Rooted – branch point within the tree representing the last common ancestor of all taxa in the tree  Polytomy – branch point from which more than two descendant groups emerge
  5. 5. How to read a phylogenetictree
  6. 6. Homology vs Analogy Homology - similarities due to shared ancestry Analogy – similarities due to convergent evolution (similar environmental pressure)  Homoplasies When determining closeness of relatedness, you must only use homology
  7. 7. Molecular Systematics Comparisons of proteins and DNA DNA with many similar base sequences = homologies
  8. 8. Cladistics Common descent is primary way to classify organisms Clade – ancestral species and all descendents Monophyletic grouping  Single ancestor gave rise to all species in taxon Polyphyletic  Members are derived from two or more forms Paraphyletic  Does not include all members from ancestral form
  9. 9. Example of groups
  10. 10. Shared vs. Derived Shared ancestral character –  originated in an ancestor of the taxon  Backbone in mammals Shared derived character –  an evolutionary novelty unique to a particular clade  Hair in mammals
  11. 11. Derived Characters Outgroup –  species from an evolutionary lineage that is known to have diverged before the lineage that includes the species we are studying.  Used to determine when traits were derived Ingroup  species of study
  12. 12. Genome comparisons More common DNA = more closely related Different genes evolve at different rates, even in the same lineage Orthologous genes – homologous genes that are found in different species  Cytochrome c gene (ETC) Paralogous genes – gene duplications, more than one copy in the same genome  Olfactory receptor genes
  13. 13. Genome Evolution Living organisms share many biochemical and development pathways The # of genes seems not to have increased through duplication at the same rate as perceived phenotypic complexity  Humans 4xs more genes as yeast
  14. 14. Molecular clocks Different proteins and DNA evolve at different rates, but at a relatively constant rate for each Ex: # of amino acid substitutions in a protein is proportional to elapsed time since divergence Nucleotide substitutions more accurate Assumes mutation rates are constant Less reliable if more distant
  15. 15. Molecular clocks
  16. 16. 2 Kingdoms to 3 Domains Plants & Animals More than 2 kingdoms did not gain acceptance until the late 1960s 5 kingdoms  Problem – some prokaryotes differed as much from other prokaryotes as eukaryotes 3 domains – Bacteria, Archaea, Eukarya
  17. 17. 3 Domains

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