1. Evolution of populations
Chapter 21

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

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

4. (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

5. (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

6. Genetic VariATION
HOW DO WE MEASURE GENETIC VARIATION?

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

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

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

10. Independant Assortment
Crossing Over

12. 21.3 NAtural Selection, genetic drift, and gene flow
alter allele frequencies in a populations

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

14. 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

15. Founder Effect Old Order Amish of PA

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

17. (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.

18. 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.

19. 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.

20. (b) Florida panther (Puma concolor coryi)
Figure 21.10b The bottleneck effect (part 2: photo)
(b) Florida panther (Puma concolor coryi)
vhttp://

21. Greater prairie chicken
Figure 21.11
Pre-bottleneck
(Illinois, 1820)
Post-bottleneck
(Illinois, 1993)
Greater prairie chicken
Range
of greater
prairie
chicken
(a)
Figure 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)

22. 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)

23. 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)

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

25. 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%

26. 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

27. Gene Flow
Transfer of alleles into or out of a population

28. 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 Gene flow and local adaptation
Eastern 40
Survival rate (%) 30 20 10
Females born in
central population
Females born in
eastern population

29. 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

30. 21.4
Natural Selection is only mechanism of evolution that leads to inreased relative fitness