Biology 3466B Lecture : Evolution Notes
3 Feb 2012
School
Department
Course
Professor
Document Summary
If a trait is controlled by a single gene with two alleles, there could be 1, 2, or 3 phenotypic variants in a population. Natural selection: four necessary conditions 1) phenotypic variation among individuals. 3) more individuals are born than will survive and reproduce (individuals have different fitness). 4) fitness is non-random and depends on phenotype. If all of these conditions are met, populations will evolve. Natural selection example 1: geospiza fortis (medium ground finch). Postulate 1 phenotypic variation: there is lots of phenotypic variation (normal distribution). It is not controlled by just two alleles. Postulate 2 heritable variation: one way to measure heritability is to look at parent trait values and offspring trait values. If there is positive correlation, it means the beak depths of parents and offspring are similar. Parents with deep beak depth have offspring with deep beak depth. Postulate 3 differential fitness: after a drought in 1977, the number of finches decreased.
