BIOL 123 Lecture Notes - Lecture 10: Disruptive Selection, Stabilizing Selection, Speciation
Document Summary
Directional selection favors organisms with phenotypes that are at one extreme relative to the average phenotype. Simple kinds of selection that encompass selection processes. Idea that there is a genetically based phenotype and natural selection favors a large or small value of that phenotype. Distribution of that phenotype, where the medium value is most frequent. But only individuals that are large/small has a cutoff, where only those individuals above those cutoffs will survive. Ones that do the best (in the large range) This is to pass on their genes to the next generation. When you favor an extreme, you expect the next population to be big, and you can later lose the big alleles. This tends to lose genetic variation, as you are only favoring one extreme. Due to unfavorable environment at the time. Happens in nature, and happens in the background. Stabilizing selection favors organisms that have intermediate characteristics.
