1. Ch. 15 Notes

2. What evidence did Charles Darwin gather that led to his theory?

3. What is artificial selection
What is artificial selection? How did this concept contribute to Darwin’s ideas on natural selection?

4. Four Principles of Natural Selection
1) Variation - 2) Heritability - 3) Overproduction - 4) Reproductive Advantage -

5. Compare and contrast evolution and natural selection
What is similar?
What is different?
-Evolution
-Natural Selection

6. Evolution Evidence
The theory of evolution states that all organisms on Earth have descended from a common ancestor

7. The Fossil Record (Fig. 15.4 p. 423)
Support for Evolution
The Fossil Record
(Fig p. 423)
Fossils show that ancient species share similarities with species that live on Earth today

8. Glyptodont
Armadillo

9. 2. Comparative Anatomy
(Fig p. 425)
a) Homologous structures develop from similar tissues in early developmental stages of the organism, but meet different needs in the adult.

10. Homologous Structures

11. Fig. 15.6 on p. 425 Q: What is similar about each of these?
Similar bone structure, from same tissue
 Q: What is different about each of these?
Perform different functions – grab, walk, fly

12. b) Vestigial structures are features of ancestors that no longer have a function for that species and will become smaller over time until they are lost
Ex: Humans → appendix, tailbone (Table p. 425)
Snakes →tiny bones where legs used to be

13. Vestigial Structures

14. Other Vestigial Structures
Vestigial Pelvis bone and femur in whales

15. Other Vestigial Structures

16. Ex: eagle wing vs. beetle wing bird wing vs. bat wing
c) Analogous structures look similar in appearance and function, but are developed from anatomically different parts
They are used for the same purpose and similar in construction, but not inherited from a common ancestor.
Ex: eagle wing vs. beetle wing
(Fig. 15.7)
bird wing vs. bat wing

17. Analogous Structures

18. 3. Comparative Embryology (Fig. 15.8 p. 426)
Embryology is the study of embryos
Embryo = early, pre-birth stage of an organism’s development
Vertebrate embryos have similar structures during certain stages of development, but become totally different structures in the adult form.

19. Comparative Embryology

20. Comparative Embryology
Human embryo
Chick embryo (LM)
Pharyngeal
pouches
Post-anal
tail

21. Q: What do similarities in early development indicate?
The organisms have similar genes controlling early development.
Q: What do these similar genes indicate?
These organisms have a common ancestor.
Q: Why do the embryos become different as they develop?
Different genes start to contribute or become “expressed” in the organism.

22. 4. Comparative Biochemistry
(Fig p. 427)
Evolutionary theory predicts molecules in species with a recent common ancestor should share certain amino acid sequences.
The more closely related the species are, the more amino acid sequences they have in common.

24. 5. Geographic distribution
(Fig p. 427)
Evolution is linked to climate and plate tectonics which explains many ancestral relationships and geographic distributions seen in fossils and living organisms.
For example: South American animals are more similar to other South American animals than to animals in Europe.

25. Mara –
South America
Rabbit – Europe

26. Adaptation
An adaptation is a trait influenced by natural selection that increases an organism’s reproductive success.

27. Fitness: The ability of an organisms to survive and reproduce
how much a certain trait appears in the next generation; measured by the amount of offspring

28. Camouflage: adaptation that allows a species to blend in with their environment.
Why?
Hide from predators/prey, more survive to reproduce
Ex: Arctic fox (Fig p. 428)

29. Leafy sea dragon

30. Mimicry: one species changes to look like another species
Ex: Harmless snake “mimics” a poisonous snake so predators leave it alone
(Fig p. 429)

31. California Kingsnake
Western Coral Snake
(poisonous)

32. Antibiotic resistance:
Some species of bacteria that originally were killed by antibiotics (like penicillin) have evolved to be drug resistant
For nearly every antibiotic, there is at least one species of resistant bacteria

33. Example: Tuberculosis (TB)

34. Section 15.3

35. Mechanisms of Evolution
1. Genetic Drift
A random change in the frequency of an allele in a population NOT due to natural selection.
More likely to occur in small populations.

36. a. Why does genetic drift have its greatest effects in small, isolated populations?

37. Mechanisms of Evolution
Genetic Drift
2. Founder effect: a small group separates from the population and lives somewhere else
they carry a subset of the population’s gene
Ex: Amish community

38. Mechanisms of Evolution
Genetic Drift
3. Bottleneck: population declines to a very low number and then rebounds
the gene pool of the rebound population is similar to the original population

39. Northern Elephant Seals

40. Ex: Northern Elephant Seals
3. Bottleneck Effect
Ex: Northern Elephant Seals
Large population  overhunting  20 Total
Population eventually recovered in size
Loss of genetic variation
Could hurt long-term survival of species

41. 3. Bottleneck Effect - Cheetahs

42. Mechanisms of Evolution
4. Remember mutations?
A random change in a sequence of DNA.
A small population with a lot of mutations has the greatest potential for evolution

43. Mechanisms of Evolution
Natural Selection
How does it alter phenotypes?

44. Mechanisms of Evolution
1. Stabilizing selection: selection against extreme expressions of a trait, selection for the average
Ex: birth weight in human babies

45. Mechanisms of Evolution
2. Directional selection: selection toward one extreme of a trait
Ex: Galapagos finches - large beaks during drought
Peppered moths - color

46. Mechanisms of Evolution
3. Disruptive selection: selection against the average, selection for both extremes
Ex: Cichlid fish size - males

47. Mechanisms of Evolution
4. Sexual selection: selection of a trait in males to attract a mate and intimidate other males
Ex: peacocks

48. Isolation 1. Reproductive Isolation
Some members of a population change so much that they can no longer produce offspring with members of the original population.

49. Different mating patterns
Eastern meadowlark
and
Western meadowlark
Different mating patterns
Liger
Sterile

50. 2. Speciation
For speciation to happen, a population has to move away and then be reproductively isolated.

51. 2. Speciation Ex: Allopatric Speciation
A physical barrier divides one population into 2 or more populations
Abert squirrel
South Rim
Kaibab Squirrel
North Rim

52. Patterns of Evolution 1. Adaptive Radiation = Divergent Evolution
The evolution of a new species in a relatively short period of time
one species evolves into several different forms that live in different habitats
homologous structures

53. Adaptive Radiation

54. Patterns of Evolution 2. Coevolution
A close relationship between 2 species
The evolution of one species influences the evolution of the other

55. Coevolution
Datura Plant & Hawk Moth

56. Patterns of Evolution 3. Convergent Evolution
Unrelated species evolve similar traits even though they live in environments that are really far apart
similar ecology and climate
analogous structures

57. 3. Convergent Evolution
Unrelated species evolve similar adaptations, due to environmental pressures (natural selection)
These adaptations may look similar from the outside, but actually evolve independently from each other
Ex: sharks, dolphins, seals, penguins

58. Remember Analogous Structures?
Similar in appearance and function, but are developed from anatomically different parts
Evidence for convergent evolution
Ex: octopus eye versus vertebrate eye (both complex eyes

59. How fast does speciation happen?
1. Gradualism:
Evolutionary change occurs gradually, over long periods of time

60. How fast does speciation happen?
2. Punctuated Equilibrium
Patterns of long periods of stability (no change) interrupted by episodes of rapid change

61. How fast does speciation happen?

62. Evolution can follow both patterns, depending on the situation and the time in evolutionary history