19_Mechanisms_of_Evolution_Nat_Sel_Feb_15_

Why 116 fitness tradeos 2 fitness tradeo male

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Unformatted text preview: duces •  2 consequences: 1.  2.  106 Natural Selec+on: Disrup+ve •  Opposite to stabilising selec+on •  Eliminates phenotypes near average value & favours extreme phenotypes •  Maintains gene+c varia+on within a popula+on 110 Natural Selec+on at Work: Galápagos Finches 111 Natural Selec+on: Stabilizing • Can occur when direc%onal selec%on acts in opposing direc%ons. 112 Gene+c Constraints 1977 drought – birds with •  deep beaks survived beber than shallow •  BUT narrow beaks beber than wider beaks b/c can concentrate twis+ng force more efficiently BUT narrower beaks didn’t evolve! Why? 116 Fitness Trade ­offs 2.  Fitness trade ­off: •  Male guppies  ­ sport gonopodia (modified anal fin used in breeding) Fitness Trade ­offs •  1977 drought: •  Finches with larger bodies won fights over remaining seed sources •  BUT •  Fitness trade ­offs exist because selec+on acts on many traits at once. Historical constraints 3.  Evolu+on is a remodelling process…acts on exis+ng varia+on • All tr...
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This note was uploaded on 08/29/2012 for the course BIO 1001 taught by Professor Kelly during the Winter '12 term at York University.

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