Evolution 3a

Evolution 3a - The most carefully documented example...

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1 The most carefully documented example… Long-term studies of the medium ground finch Daphne Major Island
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2 Not much there! An old cinder cone, some boobies, and…
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3 Grass seed Morning glory seed Goat head thorn Ground finch food Mechanical advantage to a wider beak! 1. Beak size is heritable 2. Beaks do not grow wider with use!
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4 Grants’ Rainfall Data (Daphne Major Island) 1977 Drought! 1977 Drought! Small seeds get scarce!
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5 Small seeds get scarce! Small seeds get scarce! Medium ground finch population decreases Small seeds get scarce! Compare to cactus finch
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6 Which finches --a lot of medium ground finches in 1976 --a few in 1978… survived?? Big beak: a clear survival advantage! Next generation: this difference persists…
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7 In conclusion, the finches show: 1. A survival differential causes a shift in average beak size; 2. Lasting evolutionary change can occur in a single year of drought; 3. If drought persists across multiple years,
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This note was uploaded on 11/08/2009 for the course HUMBIO 2A taught by Professor Boggs,c;durham,w during the Spring '08 term at Stanford.

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Evolution 3a - The most carefully documented example...

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