1. Origins of Life and Darwin’s Theory of Evolution

2. How did life begin? Miller & Urey’s Experiment
- produced amino acids by passing hydrogen,
methane, ammonia, and water through
electric sparks.
- demonstrates how simple compounds could
form organic compounds.

3. Miller & Urey’s Experiment

4. (*endosymbiotic theory*)
Progression of Life
1. Anaerobic prokaryotes (no oxygen)
2. Photosynthetic bacteria (produce oxygen)
3. Aerobic prokaryotes
4. Prokaryotes join together to form eukaryotes*
(*endosymbiotic theory*)
5. Protists, plants, fungi, & animals
- occurred due to sexual reproduction

5. - Idea that eukaryotes formed from groups of prokaryotes
Endosymbiotic Theory
- Idea that eukaryotes formed from groups of prokaryotes

6. Charles Darwin Charles Darwin(1809-1882) - the father of evolution
- believed environment determined traits
Darwin traveled around the world for 5 years on the HMS Beagle collecting data on many unique organisms.

7. Darwin’s Journey

8. Giant Tortoises of the Galápagos Islands
Pinta
Tower
Marchena
Pinta Island Intermediate shell
James
Fernandina
Santa Cruz
Isabela
Santa Fe
Hood Island
Saddle-backed shell
Floreana
Hood
Isabela Island
Dome-shaped shell

9. Evidence for Evolution
1) Fossil Record
Shows species that once existed.
Comparing fossils and rock layers one can find relationships showing change.

10. Evidence: Fossils

11. Evidence: 2) Geographic Distribution
Different continents have different species.
Species may evolve similar traits if environments are the similar.

12. Geographic Distribution
Beaver
Beaver
Muskrat
Beaver and Muskrat
Coypu
Capybara
Coypu and Capybara
NORTH AMERICA
Muskrat
Are these the same two animals?
SOUTH AMERICA
Capybara
Coypu

13. Evidence 3) Homologous structures
Structures in different species that share similar design/function.
Shows species have common ancestors.

14. Homologous Body Structures
Turtle
Alligator
Bird
Mammal
Ancient lobe-finned fish

15. Homologous Structures

16. Cladogram Shows evolutionary relationships

17. Evidence:
4) Vestigial structure structure with no function in present-day organisms, but was useful to an ancestor.
Natural selection does not get rid of the organ.

18. Evidence: Embryology
5) Embryology- comparing early growth stages of organisms.
Fish chicken rabbit human

19. Embryology

20. 6) Biochemical Evidence - Comparing DNA of organisms - shows how closely organisms are related - can link organisms to common ancestors

21. A Summary of Darwin’s Theory
1. Differences are inherited.
2. Organisms produce more offspring than can survive.
3. Increase in organisms causes competition.
4. Best adapted organisms survive & reproduce.
5. Today’s species are descended with modifications from their ancestors.

22. Genetics and Evolution
Gene pool = all the alleles in a population.
Ex- Pea plants:
- Height alleles: T = tall t = short
Relative frequency = % of each allele
- Height alleles: T = 70% t = 30%
Evolution = change in relative frequency.

23. Relative Frequencies of Alleles
Section 16-1
 Relative Frequencies of Alleles
Sample Population
Frequency of Alleles
allele for brown fur
allele for black fur
48% heterozygous black
16% homozygous black
36% homozygous brown

24. Sources of Evolution 1. Mutations
2. Genetic variation due to sexual reproduction
3. Environmental changes

25. Phenotypes for Single-Gene Trait
100 80 60 40 20
Frequency of Phenotype
(%)
Widow’s peak
No widow’s peak
Phenotype

26. Single trait mutation
Observe this population of delicious spiny puffs in pond water.
Imagine there’s a predator that loves to eat delicious blue spiny puffs instead of green spiny puffs. What would happen to the color of spiny puffs over time?

27. Year # 1

28. Year # 2

29. Year #3

30. Bell Curve for Polygenic Trait Phenotypes
Frequency (%) of Phenotype
Phenotype (height)
5 ft ft 8 in ft 6 in

31. Natural Selection of Polygenic traits
Changes create 3 types of selection
1. Directional selection
2. Stabilizing selection
3. Disruptive selection

32. Directional Selection
One trait is favored.
Shifts the population’s average toward that trait.
Key
Low mortality, high fitness
High mortality, low fitness
Food becomes scarce.

33. Stabilizing Selection
Average traits are favored.
Stabilizing Selection
Selection against both extremes keep curve narrow and in same place.
Key
Low mortality, high fitness
High mortality, low fitness
Percentage of Population
Birth Weight

34. Disruptive Selection Only organisms with extreme traits survive.
Creates two different extreme phenotypes.
Largest and smallest seeds become more common.
Key
Beak Size
Beak Size
Low mortality, high fitness
Population splits into two subgroups specializing in different seeds.
Number of Birds in Population
High mortality, low fitness
Number of Birds in Population

35. Genetic Drift (Founder’s Effect)
Sample of
Original Population

36. Genetic Drift (Founder’s Effect)
Sample of
Original Population
Founding Population A
Founding Population B

37. Genetic Drift(Founder’s Effect)
Sample of
Original Population
Descendants
Founding Population A
Founding Population B

38. Speciation Evolution of new species
- Large allele changes can create new species
- Isolation can cause allele changes:
Types
1. Behavioral Isolation
2. Geographic Isolation

39. Behavioral Isolation
A change of behavior within a population that creates 2 new gene pools.
Example :
Birds with different mating songs.

40. Geographic Isolation
If a geographic barrier splits a population, then two new genetic pools may form.