Anthropology5_Gradualism - Anth5 18:01 Gradualism

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Anth 5 18:01 Gradualism Not the idea that evolution is always slow The idea that the changes that are incorporated over evolutionary time are  small changes Mutations of small effects are more likely to be helpful that mutations Two implications of Gradualism What about complex adaptations(e.g the eye) Selection has no foresight No allele will spread unless it confers and advantage in the present So complex adaptations must be built of small changes, each of which is  beneficial Microevolution = change in allele frequency How about macroevolution? What happens over millions of years? New species arise (and others go extinct) Can microevolution explain macroevolution? Artificial selection suggests it can Speciation: Where do new species come from? First what is a species o Defined by reproductive isolation o Members of different species don’t share genes; they can’t interbreed o But, all organisms are connected in an unbroken ancestor-descendant 
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This note was uploaded on 08/25/2011 for the course ANTH 5 taught by Professor Gaulin during the Fall '07 term at UCSB.

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Anthropology5_Gradualism - Anth5 18:01 Gradualism

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