Bio Notes - • The essential ingredient of diversification...

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Bio Notes February 19, 2008 Normalizing Selection Also known as “stabilizing selection” Reduces variation around mean or average Does NOT change the mean or average Characteristic of most populations Directional Selection Selection for “extreme” individuals May occur in either direction When changing environment Stabilizing selection may set in Direction of directional selection may change Disruptive Selection Occurs when two or more phenotypes are favored British land snail example Low vegetation with lots of light – dark eaten Forested areas with little light – light ones eaten Speciation Speciation (df.): process by which one species splits into two and thereafter distinct lineages evolve A gradual process Has occurred millions (hundreds of millions) of times
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Unformatted text preview: • The essential ingredient of diversification • Shift of concern from population to species creationism means concern is now with MACROEVOLUTION Macroevolution and Kinds of Speciation • Macroevolution: evolutionary change on grand scale, that encompassing origin of new taxonomic groups, and dealing with evolutionary trends and mass extinctions • Allopatric speciation: most common type • Sympatric speciation: much less common • Parapatric speciation: Species: Reminder and a Bit More • Species (df.): individuals capable of breeding with one another but not with members of another species • Species (refined df): Groups of actually or potentially interbreeding natural populations which are reproductively isolated from one another •...
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This note was uploaded on 04/10/2008 for the course BIOL 1a taught by Professor Symanski during the Winter '08 term at UC Irvine.

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