Eeb 120 - Lecture 4

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Evolution as a growing tree

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Problems with the first evolutionary tree

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Focused off the theory that organisms evolve to form more complicated forms (Hitchcock 1840). Other trees were based off of similarities (Haeckel 1866)

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Taxonomy + Phylogenetics = Systematics

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*Systematics is the common way it's done

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Phylogenies

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Phylogeny is the true evolutionary history of a group of organisms. A phylogenetic tree is a visual hypothesis of evolutionary relationships based on one or more genetically determined traits (morphology, physiology, development or molecules (DNA/aa).

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Of the 4 traits, which is the most commonly used class of data for building trees?

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Molecules (DNA or amino acid sequences) because every living thing has DNA

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Phylogeny Tree diagram

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B. Common Ancestor

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Lineages: From Populations to Species

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Anatomy of a phylogeny: Nodes, Branches, Root, Lineage, Tip

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Phylogenetic trees can be drawn any ways, but what must always be shown?

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•No matter what, they shouldrepresent a branching pattern that reflects common descent and splitting oflineages through time

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Rooting phylogenetic trees

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Unrooted taxon tree with different rootings

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As taxa are added to a study,the number of possible phylogenetic trees grows exponentially

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Each phylogenetic tree is a hypothesis that can be tested using the organisms’ characteristics

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Trees can be drawn with fewer taxa...

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Branches can be rotated around nodes without changing the topologyof the tree

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Systematics: Clade

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Systematics: Paraphyletic Group

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Clade does not = Paraphyletic Group

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Systematics: Polyphyletic Group

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Why are reptiles a polyphyletic group?

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Reptiles are a paraphyletic group because the name does not include their avian descendants. To be monopyletic, must include birds in clade.

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Why are flying vertebrates a polyphyletic group?

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Flying vertebrates (bats &birds) are a polyphyletic group becauseyou can’t include theircommonancestor without includingmany othertaxa

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B. 5

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Taxonomic Revision

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Fish are not a monophyletic group unless you include all other vertebrates

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Ancestral vs Derived: Synapomorphy and Outgroup

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Internal Egg: Ancestral vs Derived

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Are monotremes primitive?

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No they aren't

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Why aren't monotremes primitive?

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Not primitive because still alive

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How can we use synapomorphies to build phylogenetic trees?

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Build a data matrix using severalmorphologicalcharacters

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Character Matric

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Maxium Parsimony

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*Least steps doesn't always mean correct tree

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What would a tree look like if we had 3 equally parsimonious trees?

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Branch length and cladogram

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Branch Length & Phylogram

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Branch Length & Chronogram

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Using Gobies to test evolutionary hypothesis...

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Consistent with convergent evolution. This is a phylogram cuz tips aren't same length and because it's a scale bar.

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Convergence has led to smaller eyes and elongated bodies when organisms live in dark regions where eyes aren't required

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It's an old structure, but new function

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