Evolution of populations Chapter 21

evolution on the smallest Scale =A Change in Gene Frequency Microevolution evolution on the smallest Scale =A Change in Gene Frequency

Genetic VariATION WHAT CAUSES VARIATION? MUTATIONS! SEX! Environment?

(a) Caterpillars raised on a diet of oak flowers Figure 21.5a Figure 21.5a Nonheritable variation (part 1: oak flower diet) (a) Caterpillars raised on a diet of oak flowers

(b) Caterpillars raised on a diet of oak leaves Figure 21.5b Figure 21.5b Nonheritable variation (part 2: oak leaf diet) (b) Caterpillars raised on a diet of oak leaves

Genetic VariATION HOW DO WE MEASURE GENETIC VARIATION?

Genetic VariATION WHAT CAUSES VARIATION? MUTATIONS! - NEW ALLELLES SEX! - NEW COMBINATION OF ALLELES

MUTATIONS Point mutations Exons Introns Wobble Hypothesis Duplications Olfactory genes - see Shubin Translocations

Sex No new alleles, just new combinations by Crossing over Independant Assortment Fertilization

Independant Assortment Crossing Over

21.3 NAtural Selection, genetic drift, and gene flow alter allele frequencies in a populations

NAtural Selection allele frequency change to make population a better fit for environment —> Adaptive Evolution Beak of the Finch

Genetic Drift Chance events alter genetic frequency from one generation to the next This fluctuation due to chance, not necessarily leaving more fit individuals for environment to survive and reproduce 2 situations that result in genetic drift are the bottleneck effect and founder effect

Founder Effect Old Order Amish of PA

Original population Bottlenecking event Surviving population Figure 21.10 Original population Bottlenecking event Surviving population Figure 21.10 The bottleneck effect (a) By chance, blue marbles are overrepresented in the surviving population. (b) Florida panther (Puma concolor coryi)

(a) By chance, blue marbles are overrepresented in the Figure 21.10a-1 Figure 21.10a-1 The bottleneck effect (part 1, step 1) Original population (a) By chance, blue marbles are overrepresented in the surviving population.

Original population Bottlenecking event Figure 21.10a-2 Figure 21.10a-2 The bottleneck effect (part 1, step 2) Original population Bottlenecking event (a) By chance, blue marbles are overrepresented in the surviving population.

Original population Bottlenecking event Surviving population Figure 21.10a-3 Figure 21.10a-3 The bottleneck effect (part 1, step 3) Original population Bottlenecking event Surviving population (a) By chance, blue marbles are overrepresented in the surviving population.

(b) Florida panther (Puma concolor coryi) Figure 21.10b The bottleneck effect (part 2: photo) (b) Florida panther (Puma concolor coryi) vhttp://www.floridapanthernet.org/index.php/handbook/history/florida_panther_genetics/#.VdU2EmDB4UU

Greater prairie chicken Figure 21.11 Pre-bottleneck (Illinois, 1820) Post-bottleneck (Illinois, 1993) Greater prairie chicken Range of greater prairie chicken (a) Figure 21.11 Genetic drift and loss of genetic variation Number of alleles per locus Percentage of eggs hatched Population size Location Illinois 1930–1960s 1993 1,000–25,000 <50 5.2 3.7 93 <50 Kansas, 1998 (no bottleneck) 750,000 5.8 99 Nebraska, 1998 (no bottleneck) 75,000– 200,000 5.8 96 (b)

Greater prairie chicken Figure 21.11a Pre-bottleneck (Illinois, 1820) Post-bottleneck (Illinois, 1993) Figure 21.11a Genetic drift and loss of genetic variation (part 1: map) Greater prairie chicken Range of greater prairie chicken (a)

Number of alleles per locus Percentage of eggs hatched Population size Figure 21.11b Number of alleles per locus Percentage of eggs hatched Population size Location Illinois 1930–1960s 1993 1,000–25,000 <50 5.2 3.7 93 <50 Figure 21.11b Genetic drift and loss of genetic variation (part 2: table) Kansas, 1998 (no bottleneck) 750,000 5.8 99 Nebraska, 1998 (no bottleneck) 75,000– 200,000 5.8 96 (b)

Greater prairie chicken Figure 21.11c Figure 21.11c Genetic drift and loss of genetic variation (part 3: photo) Greater prairie chicken

Researchers used DNA from museum specimens to compare genetic variation in the population before and after the bottleneck The results showed a loss of alleles at several loci Researchers introduced greater prairie chickens from populations in other states and were successful in introducing new alleles and increasing the egg hatch rate to 90%

Effects of Genetic Drift: A Summary Genetic drift is significant in small populations Genetic drift can cause allele frequencies to change at random Genetic drift can lead to a loss of genetic variation within populations Genetic drift can cause harmful alleles to become fixed

Gene Flow Transfer of alleles into or out of a population

Females born in central population Females born in eastern population Figure 21.12 Central population NORTH SEA Eastern population Vlieland, the Netherlands 2 km Population in which the surviving females eventually bred 60 Parus major Central 50 Figure 21.12 Gene flow and local adaptation Eastern 40 Survival rate (%) 30 20 10 Females born in central population Females born in eastern population

Females born in central population Females born in eastern population Figure 21.12a Population in which the surviving females eventually bred 60 Central 50 Eastern 40 Survival rate (%) Figure 21.12a Gene flow and local adaptation (part 1: graph) 30 20 10 Females born in central population Females born in eastern population

21.4 Natural Selection is only mechanism of evolution that leads to inreased relative fitness