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Lecture

ANTH222 Lecture Notes - Daphne Major, Phenotype

1 pages98 viewsFall 2012

Department
Anthropology
Course Code
ANTH222
Professor
Dr.Francis Allard

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Notes: 9/7 Evolution/Natural Selection “In Action”
Phenotype (form evolutionary perspective)
Ex. skin color, finches beaks
Peter and Rosemary Grant- Galapagos experiment on natural selection “in action” on Medium
Ground Finches on Daphne Major (an island) 1976-78
1. During drought, finches with “small” beaks didn’t reproduce as much because they were
unable to break the larger/harder seeds (population dropped from 1200 to 180)
2. Before drought, larger variation in beak depth, after increasingly “bigger” to eat
larger/harder seeds
3. Offspring tended to have beak depth of parents
(*Fits all Postulates of Darwin’s Theory)
Directional Selection- normal distribution of traits shifts right or left on graph
Stabilizing Selection- pressure at either side of variation, no evolution happening but natural
selection still continues (species cannot be static)
Figure 1.9 on Worksheet (H1)
1. Height of bar goes down, aka less birds (population drop)
2. Average beak depth shifts to the right, aka average beak depth is larger than before
drought
3. Curve shape of bars didn’t change, variation still exsists
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