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Systematics and the Phylogenetic Revolution

Systematics and the Phylogenetic Revolution. Chapter 23. Systematics. The Study of Evolutionary Relationships Bases relationships of similarities Does similarity always imply relation?. Cladistics. Makes relationships based on shared derived Characteristics NOT ancestral!

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Systematics and the Phylogenetic Revolution

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  1. Systematics and the Phylogenetic Revolution Chapter 23

  2. Systematics • The Study of Evolutionary Relationships • Bases relationships of similarities • Does similarity always imply relation?

  3. Cladistics • Makes relationships based on shared derived Characteristics NOT ancestral! • Ancestral vs Derived • Derived- Hair in mammals, because all mammals have it but not amphibians etc • Ancestral- Lungs all mammals have it but then so do some amphibians

  4. How to construct a Cladogram • Step 1- Create a chart listing all organisms in question and traits that you would like to look at.

  5. Step 2- Mark off Traits that exist in each species

  6. Step 3 – Construct Cladogram Using the traits you marked. Animal with the most traits will be at the top of the Cladogram, animal with the least will be at the bottom. Humans Dog Fish

  7. Is it that Simple? • Nope! • Homoplasy- a shared character that has not been inherited from a common ancestor – can occur due to convergent evolution or evolutionary reversal • Frogs- Lack a tail but does that mean they are more closely related to humans than salamanders?

  8. How do we draw our cladogram for the Frog? • Parsimony- draw the cladogram that requires the least number of changes

  9. Creating a Phylogenetic Tree

  10. Types of Phyla • Monophyletic-Consists of the most recent common ancestor and all of its descendants • Paraphyletic- Consists of the most recent common ancestor and some of its descendants. • Polyphyletic- Does not contain the most recent common ancestor of the group

  11. Homologous vsAnalagous Structures

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