Wiens-lecture 6-7April - Todays Lecture Finish molecular...

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Today’s Lecture Finish molecular evolution Introduction to phylogeny
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Molecular Evolution Genome size varies widely among species; partly due to number of functional genes, but also amount of non-functional DNA
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Molecular Evolution Gene duplication (evolution of one or more additional copies of a gene) is a key aspect of molecular evolution Gene duplication can allow origin of new functions One copy performs old function, while new copy can evolve new function One copy may also evolve to become functionless pseudogene
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Molecular Evolution When more than one copy of a gene is present in a genome, genes belong to same “gene family” May be duplication of entire genome through polyploidization Early vertebrates are thought to have gone through one or more rounds of polyploidization Many genes in vertebrates belong to gene families with four copies; may be important part of our complexity!
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Molecular Evolution “duplication and individualization” is an important principle for creating diversity in evolution Applies to morphology (phenotype) as well as genes; duplicate a structure, let one version diverge while the other keeps its old function Mammals differ from other vertebrates in having teeth with different structure and function What other examples are there on your body?
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Introduction to Phylogeny Phylogeny = history of evolutionary branching and descent (family tree) Systematics = branch of biology dedicated to reconstructing phylogeny (also called “phylogenetics”)
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Answers the question: What is it? Why phylogeny is important
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Why phylogeny is important? Phylogenies are necessary to tell us what evolutionary changes have occurred. group of 8 species: 4 species have a trait, 4 do not What happened? Did the trait evolve once? Did it evolve 4 times? Was it lost 4 times?
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Phylogenies tell us: what happened? Evolution of male display ornaments. Major question in evolutionary biology: what explains the origin of elaborate male ornaments? peacock stalk-eyed fly
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Phylogenies tell us: what happened? Evolution of male display ornaments. Phylogenies show that in many groups ornaments are lost 4-5 times more often than gained present lost
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Introduction to Phylogeny Why phylogeny is important Phylogeny answers the question “what is it?” Is a whale a mammal or a fish?
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