Lecture 7 - Traits evolve in a way that the mean fitness of...

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Traits evolve in a way that the mean fitness of the population increases Fishers Fundamental Theorem of Nat selection - Mean fitness increases at a rate equal to the genetic variance (V G ) for fitness -Key assumption Relative fitness are constant in time Other evolutionary forces are weak Wrights “Adaptive landscape” Pop mean fitness Wbar vs Allele frequency (or mean trait value) -populations evolve uphill the landscape -pop evolve to a peak - The speed of evolution is determined by the steepness of the landscape -selection drives populations to peak How does evolution get populations from one peak to another? Natural selections go uphill not downhill Two big exceptions to the fund theorem and adaptive landscape -Changing environments Finches- As drought hits, only big hard seeds left, strong natural selection for big beaks and pop evolved big beaks. After were huge rains and seeds shifted back and strong natural selection back to smaller beaks. Evolution cannot see into the future - frequency dependent selection- the relative fitness of the individuals depends on the frequencies of phenotypes or genotypes The evolution of trees: 14 trillion years ago there were no trees just bushes with lots of fruit. Mutation caused a bush to make a trunk. It is able to shade out its neighbors and they die. Has a selection advantage and several generations later there is a pop of trees.
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This note was uploaded on 03/29/2012 for the course BIO 370 taught by Professor Edwards during the Spring '08 term at University of Texas.

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Lecture 7 - Traits evolve in a way that the mean fitness of...

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