FA2008 - BILD 3 - Lecture 04 (Natural Selection - 02)

FA2008 - BILD 3 - Lecture 04 (Natural Selection - 02) -...

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10/9/08 1 Lecture 4 Natural Selection Reading Text Ch. 23 Heritability of human height is well studied. Here are estimates of heritability for height in different human populations: Australia = 0.8 Finland = 0.78 China = 0.65 western Africa = 0.65 What is a reasonable hypothesis for why the results for Aussies and Finns are so different from Chinese and west Africans? a. There are different genes controlling height in Aussies and Finns compared to Chinese and Africans b. There is more environmental variation contributing to height in Chinese and Africans c. Chinese and Africans are naturally shorter than Aussies and Finns d. all of the above heritability = genetics genetics and environment B. Variation in beak size is heritable heritability = slope of line How does evolution happen? 1. individuals vary 2. variation is heritable (genetic) 3. individuals with certain traits survive longer and reproduce more (natural selection) Result- evolution C. Is there natural selection on beak size/shape Do individuals with one type of beak survive longer and have more offspring (differential survival or reproduction) than individuals with another type of beak?
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10/9/08 2 Daphne Major averages 130 mm rain / year 1977 - 24 mm rain serious drought During 20 months of drought, birds died. Why? What happened? The Grants and colleagues sifted through dirt and counted # seeds Drought - abundance of seeds plummeted The Grants measured size & hardness of seeds During drought most seeds were eaten soft seeds disappeared 1st Only seeds left were: Tribulus cistoides Very large and very hard seeds Again, finches died. Is this natural selection?
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10/9/08 3 Again, finches died. Is this natural selection? NO! Death Natural selection - differential survival and/or reproduction of phenotypes Birds with larger beaks were more likely to survive drought This is evidence of natural selection. How does evolution happen? 1. individuals vary 2. variation is heritable (genetic) 3. individuals with certain traits survive longer and/or reproduce more (natural selection) Result- evolution D. Did the population evolve? We know all these things were true: 1. individuals vary 2. variation is heritable (genetic) 3. individuals with certain traits survive longer and reproduce more (natural selection) Result- evolution Why don’t all finches all have bigger and bigger and bigger bills?
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10/9/08 4 Why don’t all finches all have bigger and bigger and bigger bills? a. Variation was exhausted b. They attained the perfect beak size, thus natural selection ceased c. The environment is constantly changing d. Estimates of heritability were incorrect e. There was stabilizing selection on bill size 1977 - drought 1983 - El Niño - 1359 mm rain (10x average) Super abundance of small seeds 2003/4 - another drought 1977 drought - red line - beaks got bigger Changes in average beak size 1970 - 2000 1883 - rain Beaks got smaller
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This note was uploaded on 03/31/2009 for the course BILD 632282 taught by Professor Henter during the Spring '08 term at UCSD.

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FA2008 - BILD 3 - Lecture 04 (Natural Selection - 02) -...

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