BIOLOGY 1M03 Lecture Notes - Lecture 19: Antigenic Shift, Stabilizing Selection, Disruptive Selection
2 Aug 2018
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Document Summary
If difference in body size among individuals were due to variation their genotypes. If directional selection of this type continued then the alleles that contribute to small body size would quickly decline in frequency. This is evidence that birth weight was under strong stabilizing selection in humans. Alleles associated with high birth weight or low birth weight were subject to purifying selection alleles associated with intermediate birth weight increased in frequency. Disruptive selection: eliminates phenotypes near the average value and favors extreme phenotypes, overall genetic variation in population is maintained. Disruptive selection can lead to formation of new species: disruptive selection is important because it sometimes play a part in speciation or in formation of new species. If small beaked seed crackers mated with small beaked individuals and if large beaked seed crackers mated with large beak individuals, then there is a possibility of 2 different populations forming.
