Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Document
Document related concepts
Heritability of IQ wikipedia , lookup
Gene expression programming wikipedia , lookup
Koinophilia wikipedia , lookup
Fetal origins hypothesis wikipedia , lookup
Human genetic variation wikipedia , lookup
Polymorphism (biology) wikipedia , lookup
Group selection wikipedia , lookup
Dominance (genetics) wikipedia , lookup
Hardy–Weinberg principle wikipedia , lookup
Genetic drift wikipedia , lookup
Transcript
Population: 10 individuals Phenotype frequency: 30% blue eyes (or 0.3) 70% brown eyes (or 0.7) = bb = Bb = BB Population 10 individuals Phenotype frequency: 30% blue eyes (or 0.3) 70% brown eyes (or 0.7) Genotype frequency: f(bb) = 30% (or 0.3) f(Bb) = 50% (or 0.5) F(BB) = 20% (or 0.2) = bb b b b b b b B b B b B b B b B b BB BB = Bb = BB Population 10 individuals Genotype frequency: f(bb) = 30% (or 0.3) f(Bb) = 50% (or 0.5) f(BB) = 20% (or 0.2) Number of alleles: b = 11 B=9 Population 10 individuals b b b b b b b b b b b b Genotype frequency: f(bb) = 30% (or 0.3) f(Bb) = 50% (or 0.5) f(BB) = 20% (or 0.2) B b bB b bB b b B B B Number of alleles: b = 11 B=9 B B BB B B B Allele frequency: f(b) = 11/20 = 0.55 f(B) = 9/20 = 0.45 B b bB b b B B B b b b b = B B b b b b B B b B b B B B b B Gene pool of a population = bb b b b b b b B b B b B b B b B b BB BB = Bb = BB Possible gametes of each individual b b b b = B B b b b b B B b B b B B B b B Possible gametes in the population Population 10 individuals b b b b b b b b b b b b Genotype frequency: f(bb) = 30% (or 0.3) f(Bb) = 50% (or 0.5) f(BB) = 20% (or 0.2) B b bB b bB b b B B B Number of alleles: b = 11 B=9 B B BB B B B Allele frequency: f(b) = 11/20 = 0.55 f(B) = 9/20 = 0.45 B b bB b b B B B Genetic Drift Homozygous for allele A1 Homozygous for allele A2 Heterozygous (a) Founder effect Immigrants establish new population New population is likely to have different allele frequencies than the source population, by chance (b) Genetic bottleneck High mortality strikes individuals at random Time 1 Time 2 Bottlenecked population is likely to have different allele frequencies than original population, by chance Gene Flow Homozygous for allele A1 Homozygous for allele A2 Time 1 At time 1, populations differ in allele frequencies Population 2 Population 1 Time 2 Gene flow Gene flow causes allele frequencies in the two populations to be more alike Gene flow Population 1 Population 2 (a) Directional selection changes the average value of a trait. Normal distribution During selection After selection Number of individuals Before selection Low fitness Change in average value Value of a trait High fitness Figure 25-3 Slide 6 For example, directional selection caused average body size to increase in a cliff swallow population. Percentage of birds Original population (N = 2880) Change in average value Body size class Survivors (N = 1027) (a) Stabilizing selection reduces the amount of variation in a trait. Normal distribution During selection After selection Number of individuals Before selection Low High fitness Low fitness fitness Reduction in variation Value of a trait Mortality Heavy mortality on extremes Birth weight (pounds) Percentage of mortality Percentage of newborn population (b) For example, very small and very large babies are the most likely to die, leaving a narrower distribution of birth weights. (a) Disruptive selection increases the amount of variation in a trait. Normal distribution During selection Number of individuals Before selection High Low fitness fitness High fitness Increase in variation After selection Value of a trait Number of individuals (b) For example, only juvenile black-bellied seedcrackers that had very long or very short beaks survived long enough to breed. Only the extremes survived Only the extremes survived Beak length (mm)
