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Review— Evolution and Phylogeny

Review— Evolution and Phylogeny. Lecture 6a. Phylogeny. Phylogeny —the evolutionary history of groups of species Ranges from major lineages (e.g. orders) to species Primitive groups at right, more recently evolved groups at left. Ancestor (extinct). Phylogenetic Tree. Phylogeny.

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Review— Evolution and Phylogeny

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  1. Review—Evolution and Phylogeny Lecture 6a

  2. Phylogeny • Phylogeny—the evolutionary history of groups of species • Ranges from major lineages (e.g. orders) to species • Primitive groups at right, more recently evolved groups at left Ancestor (extinct) Phylogenetic Tree

  3. Phylogeny • Groups arranged based on evolutionary relatedness • Branching points represent common ancestral species • Almost always extinct • Evolutionary time  millions of years Ancestor (extinct)

  4. Phylogeny—outgroups • All groups have shared ancestral characters • Example: chordates  notochord, bilateral symmetry, etc. • Outgroups branch off to right • Represent groups with ancestral traits • Primitive—“living fossils” Ancestor (extinct)

  5. Phylogeny—synapomorphy • Synapomorphy—a newly evolved trait that all descendent groups possess • Derived Trait—not present in outgroups • Arise slowly—one at a time • Phylogentic trees simplified Ancestor (extinct) Ctenoid scales Thoracic pelvics Physoclistous

  6. Phylogeny—secondary losses/gains • Secondarily lost or gained traits occur in outgroups • While outgroups represent ancestral condition, they have still evolved • They are not the original species Ancestor (extinct) Lost: eyes Gained: slime glands

  7. Phylogeny—vertebrate evolution • Fish are essential to understanding vertebrate evolution • Outgroups represent a snapshot • Incremental steps • Most major lineages (outgroups) are extinct Ancestor (extinct)

  8. Fish Fossil Record • Extinct lineages studied from fossils may be added to phylogenetic trees

  9. Monophyletic vs. Paraphyletic • Monophyletic—a group of organisms that share a common ancestor, and all descendents of that ancestor are in the group • Paraphyletic—sharing a common ancestor, but not all descendents in group F F Families A A C C D D E E B B Monophyletic Paraphyletic

  10. Monophyletic vs. Paraphyletic Ancestor (extinct) • Arranging a phylogeny is a matter of perspective • Lobed finned fishes often the ingroup • Major split in vertebrate evolution

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