MICROEVOLUTION

POPULATION GENETICS

PHET NATURAL SELECTION Mutation  Variation  Natural Selection  Speciation

QUICK REVIEW: NATURAL SELECTION Mutation  Variation  Natural Selection  Speciation Organisms better suited to the environment SURVIVE & REPRODUCE at a greater rate than those less suited to the environment and this is how… SPECIES EVOLVE

HOW A SPECIES CHANGES OVER TIME Mutation  Variation  Natural Selection  Speciation

 Any generational change in allele frequency w/in a population  Results in a change in phenotypes of that population MICROEVOLUTION

 House sparrows were introduced to North America in Since that time the sparrows have evolved different characteristics in different locations. Sparrow populations in the north are larger-bodied than sparrow populations in the south. HOUSE SPARROWS

 Mutation & Recombination:  Changes on a molecular level MECHANISMS OF MICROEVOLUTION

 Genetic Drift  Shifts in allele frequencies over time MECHANISMS OF MICROEVOLUTION

 Gene Flow  Introduction of alleles from surrounding populations MECHANISMS OF MICROEVOLUTION

 Natural Selection  Environment selecting for specific traits MECHANISMS OF MICROEVOLUTION

HARDY WEINBERG

HOW A SPECIES CHANGES OVER TIME Mutation  Variation  Natural Selection  Speciation

QUICK REVIEW: NATURAL SELECTION Mutation  Variation  Natural Selection  Speciation Organisms better suited to the environment SURVIVE & REPRODUCE at a greater rate than those less suited to the environment and this is how… SPECIES EVOLVE

HARDY & WEINBERG Mutation  Variation  Natural Selection  Speciation We can study changes in phenotypes/genotypes of one trait in a population over time We will use math to show if evolution is occurring

EX: ALLELE FREQUENCIES IN SNAPDRAGONS  Collect data of phenotypes of a population  320 red flowers, 160 pink flowers, & 20 white flowers  Convert phenotypes to genotypes  320 RR  160 RW  20 WW  Calculate allele frequencies  R alleles = = 800  W alleles = = 200

EX: ALLELE FREQUENCIES IN SNAPDRAGONS  Allele Frequency  800 R alleles / 1000 total alleles (80% or 0.8)  200 W alleles / 1000 total alleles (20% or 0.2)

EX: ALLELE FREQUENCIES IN SNAPDRAGONS  Hardy-Weinberg:  If evolution is not occurring in this population  Then allele frequency will remain constant over time  Therefore at any moment the population will have:  80% R alleles & 20% W alleles  If 10 years later:  50% R alleles  50 % W alleles  Then microevolution is occurring

APPLYING H.W.E.  This happens to nearly all populations for all traits  p represents the dominant allele (R)  q represents the recessive allele (W) p =.8 & q =.2 p + q = 1

SOLVE THIS STORY PROBLEM  In certain Native American groups, albinism is due to a homozygous recessive condition. The frequency of the allele for this condition is currently.06 of the Native American population.  What is the frequency of the dominant allele? p + q = 1 P +.06 = 1 p =.94

EXTRAPOLATING H.W.E.  H.W.E. Equation 1:  p + q = 1 (shows allele frequencies)  H.W.E. Equation 2:  (1) * (1) = 1  (p + q) * (p + q) = 1  p 2 +2pq + q 2 = 1  500 Snapdragon Example  p =.8 & q =.2  (.8) 2 +2(.8*.2) + (.2) 2 = 1  = 1  = 500

APPLYING H.W.E.  p 2 = homozygous dominant condition  2pq = heterozygous condition  q 2 = homozygous recessive condition p 2 +2pq + q 2 = 1 RR + 2RW + WW = 1

SOLVE THIS STORY PROBLEM  In a certain flock of sheep, 4 percent of the population has black wool (recessive condition) and 96 percent has white wool.  What % of sheep are heterozygous for wool color? p 2 +2pq + q 2 = 1

H.W.E. CONDITIONS  Our equations are great for:  Finding allele frequencies: p + q = 1  Finding genotype frequencies: p 2 +2pq + q 2 = 1  Showing microevolution if values change over time  When would allele frequencies not change over time?

H.W.E. CONDITIONS  No Mutations  No new genotypes/phenotypes  Very large population size  No minor population disruptions (genetic drift)  Isolation from other populations  No immigration/emigration (gene flow)  Random Mating  No picky females choosing one allele over another  No natural selection  No environmental pressures selecting one allele over another