Evolution4

Evolution4 - Evolution #6: Tempo & Mode in Macroevolution...

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Speciation can take place w/ or w/out geographic separation allopatric speciation: new species forms while geographically isolated from its present pop o as the isolated pop evolves by natural selection & genetic drift, reproductive isolation from the ancestral species may arise as a byproduct of the genetic change o such reproductive barriers prevent interbreeding w/ the parent pop, even if pop’s come back in contact sympatric speciation: requires emergence of a reproductive barrier that isolates a subset of a pop w/out geographic isolation from the parent pop o allopolyploidy: hybridization betwn closely related species coupled w/ errors during cell division that lead to fertile polyploidy individs (common mech, esp in plants) o when subset of pop becomes reproductively isolated b/c of switch to habitat, food source, or other resource not used by parent pop o sexual selection in a polymorphic pop (animals)} Adaptive radiation definition = the evolution of many diversely adapted species from a common ancestor occurs when a few organisms make their way to new, often distant areas occurs when envtal changes cause numerous extinctions, opening up ecological niches for the survivors ex) fossil evidence shows mammals underwent dramatic adaptive radiation after mass extinctions of dinosaurs 65mya ex) Hawaiian archipelago o volcanic islands are progressively younger as the we follow the chain toward the SE o youngest island is Hawaii w/ still active volcanoes o born “naked,” each island varies in physical diversity (altitude, rainfall) providing many opportunities for evolutionary divergence by natural selection o multiple invasions, allopatric & sympatric speciation events explosion of adaptive radiation o most are endemic species found nowhere else on Earth Studying the Genetics of Speciation to pinpoint genes that play key roles in speciation 2 species of monkey flower: Mimulus lweisii & Mimulus cardinalis pollinated by
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This note was uploaded on 09/24/2009 for the course BIO 1B taught by Professor Carlson,mischel,power during the Fall '07 term at Berkeley.

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Evolution4 - Evolution #6: Tempo & Mode in Macroevolution...

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