BGYB51H3 Lecture 12 Notes Oct 20

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BGYB51H3 Lecture 12 Notes
-migration is the change in allele frequencies due to movement between populations
-migration adds alleles to a population
-mechanisms of migration are transported by wind, long distance dispersal by juveniles, or
dispersal due to human activity
-in migration, even if allele frequencies are the same, genotype frequencies become
unpredictable
-migration can maintain variation and is a very useful mechanism in small populations
-migration homogenizes and slows down divergence of species
-migration decreases adaptation to local conditions due to maladaptive traits moving between
populations
-mutation and migration reintroduce deleterious alleles through mutation-selection balance
and migration-selection balance
-in genetic drift, the chances of getting a smaller representative sample of a population with the
same allele frequencies p and q is low (refer to figure 7.15)
-genetic drift has the strongest effect on small populations
-selection effects counteracts the effects of genetic drift
-founder effect is a change in allele frequencies when a new population is established by
individuals with different allele frequencies
-migration assumes allele frequencies between two populations is the same while in founder
effect, the allele frequencies are between the two populations is different
-bottleneck involves a change in allele frequencies due to a new population established after a
catastrophic event
-non-random mating changes genotype frequencies without changing allele frequencies
-non-random mating has an indirect effect on evolution
-self-fertilization decreases heterozygosity and increases homozygosity
-inbreeding causes increased homozygosity and increases in smaller populations
-deleterious alleles are expressed more in the homozygote form as a result of increased
inbreeding
(refer to red bladder campion example on pg230)
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Document Summary

Migration is the change in allele frequencies due to movement between populations. Mechanisms of migration are transported by wind, long distance dispersal by juveniles, or dispersal due to human activity. In migration, even if allele frequencies are the same, genotype frequencies become unpredictable. Migration can maintain variation and is a very useful mechanism in small populations. Migration homogenizes and slows down divergence of species. Migration decreases adaptation to local conditions due to maladaptive traits moving between populations. Mutation and migration reintroduce deleterious alleles through mutation-selection balance and migration-selection balance. In genetic drift, the chances of getting a smaller representative sample of a population with the same allele frequencies p and q is low (refer to figure 7. 15) Genetic drift has the strongest effect on small populations. Selection effects counteracts the effects of genetic drift. Founder effect is a change in allele frequencies when a new population is established by individuals with different allele frequencies.

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