BIO E121 Lecture Notes - Lecture 6: Gene Pool, Birth Weight, Allele Frequency
Document Summary
Hw assumes all individuals have equal ability to mate and produce viable offspring. Almost never true variation exists, resources limited. Another way to state: nonrandom changes in allele frequency. Results from different alleles present at locus or loci. Morphs: contrasting phenotypes (e. g. red and white flower) Polymorphic: population with 2 or more morphs at detectable frequencies. Populations must be polymorphic for natural selection to operate. 3 types of selection can change phenotype distribution. Intermediate states selected for, extremes selected against. Examples: antibiotic resistance, beak size in finches. Selection for both phenotypic extremes over intermediate state, occurs when environment is highly variable. Chance events that alter frequency mating, etc. Small number of individuals colonize a new habitat. Gene pool of new population probably different allele frequencies from parent population due to small sample size. Size of population drastically reduced, survival random. Small surviving population have allele frequencies different from: gene flow ancestral population.
