1. Chapters 15-17
Evolution

2. Science Definitions

3. Theory
A well-substantiated explanation of some aspect of the natural world that typically incorporates many confirmed observations, laws and successfully verified hypotheses.
Modified from

4. Evolution
Book definition = Gradual accumulation of adaptations over time.
In genetic terms, the change in the frequency of alleles in populations from generation to generation. (change over time)
Modified from

5. Adaptation
Any heritable characteristic (determined from alleles) of an organism that improves its ability to survive and reproduce in its environment.
Note: not all characteristics are adaptive
Modified from

6. Adaptations

7. Fitness
The success of an individual in surviving and reproducing, measured by that individual’s genetic contribution to subsequent generations.
Modified from

8. Natural Selection Charles Darwin’s Theory
Mechanism for change in populations.
Occurs when organisms with certain traits survive, reproduce and pass their variations to the next generation.
“Survival of the Fittest”

9. Natural Selection
1. Variations exist in a population

10. Sweet! I’m better at surviving because I blend into my surroundings!
Natural Selection
2. Some variations improve the ability to survive and reproduce in the particular environment
Sweet! I’m better at surviving because I blend into my surroundings!
Dang!

11. I have more fitness than you!
Natural Selection
3. The individuals with the adaptive traits are more likely to pass on their genes to future generations
Dang!
I have more fitness than you!

12. Natural Selection
4. Over time, the frequency of adaptive alleles increases = evolution.

13. Tenants of Natural Selection
OVERPRODUCTION: Organisms produce more offspring than their environment can support.
HERITABLE VARIATION: Offspring vary in their appearance and function; some of these variations are heritable.
COMPETITION: Offspring must compete for survival, food and reproduction.
*SURVIVAL OF THE FITTEST: Offspring who have the highest fitness for their environment will live longer and/or leave more offspring than those less suited for the environment.

14. Can we see natural selection in one generation?
This process occurs very slowly, over many generations
Natural selection can only be observed as changes in the characteristics or behaviors in populations over time.

15. Is there any variation in pinto beans???

16. Bean Variation Mini-Lab
Create Data Table with two three columns: Bean Number, Mass (g), and Qualitative Observations
Work with a partner and choose 10 random beans from the beakers at your station. Try not to be selective for any properties whatsoever
Measure each bean’s mass and record, along with qualitative observations
Share your data with two other groups to get a total of 30 beans recorded.

17. Bean Variation Mini-Lab
In your journal, create a frequency distribution graph as modeled on the whiteboard. For the x-axis, use bean mass (g), and put number of beans on the y-axis
Answer the following questions in your journal:
How does your graph compare to the overall class data?
What factors do you think are responsible for causing the variation in the pinto beans?
What could be advantages of being bigger or smaller for a bean seed? Identify several.

18. Natural Selection…
Caterpillars… what is the benefit of looking like bird poop?

19. Overproduction & Heritable Variation in butterflies…
How many offspring do butterflies produce?
1000+ offspring … not that many survive
What kind of variation could we see in larva (caterpillars)?
Different color patterns
Different sizes
Diet
Is this variation in color patterns heritable?
Genes control color patterns in all organisms…
Offspring from a butterfly (caterpillar) that was green as a larva?
Offspring from a butterfly (caterpillar) that was brown and white as a larva?

20. Competition & Survival of the Fittest…
Caterpillars have competition for food, survival & reproduction.
Who will survive the longest?
Best camouflage = less likely to be seen by predators = longer survival = more reproduction
If those that look like bird poop survive longer, what will the population start to look like over many generations?
Like bird poop!
NATURAL SELECTION – the natural selection of characteristics that allow an animal to survive and reproduce (sometimes because of their ability to blend in with their environment)– makes them more fit.

21. Other examples of selection for survival…

22. Natural Selection…
Cheetahs… why can they run so fast?

23. Overproduction & Heritable Variation in cheetahs…
How many offspring do cheetahs produce?
5-6 offspring per year … not that many survive
What kind of variation could we see in cheetahs?
Size of the heart
Length of the legs
Color patterns
+ many others
Is this variation in length of legs heritable?
Genes control length of limbs …
Offspring from a cheetah with long legs?
Offspring from a cheetah with short legs?

24. Competition & Survival of the Fittest…
Cheetahs have competition for food, survival & reproduction.
Who will survive the longest?
Those that can run fast enough to catch prey to survive = longer survival = more reproduction.
If those that run faster eat more, what will the population start to look like over many generations?
Fast runners!
NATURAL SELECTION – the natural selection of characteristics that allow an animal to get more food within their environment – makes them more fit.

25. Sexual Selection…
The male peacock… why waste so much energy producing feathers?

26. Overproduction & Heritable Variation in peacocks
How many offspring do they produce?
6-8 per year are hatched… not that many survive
What kind of variation could we see in male peacocks?
Different color patterns
Different feather sizes
Size of bird
Is this variation in feather size heritable?
Genes control how large feathers will get…
Offspring from a peacock with large feathers?
Offspring from a peacock with short feathers?

27. Competition & Survival of the Fittest…
Peacocks have competition for food, survival & reproduction.
Who will reproduce the most?
Largest feathers = more reproduction
If those with large feathers reproduce more, what will the population start to look like over many generations?
Larger feathers, on average.
SEXUAL SELECTION – the natural selection of secondary sex characterizes in males is WORTH the energy they spend because it increases levels of reproduction – makes them more fit.

28. Other interesting secondary sex characteristics….

29. Natural Selection in recent years…

30. Bt-resistant Cotton Bollworm

31. Antibiotic Resistance

32. AZT-Resistant HIV (AIDS virus)

33. AZT-Resistant HIV (AIDS virus)
Resistance to AZT has evolved in all patients taking the drug (usually in ~6 months)!
How does HIV evolve so rapidly?
1. High mutation rate
• HIV’s mutation rate is 106 higher than ours!
2. Short generation time
• 1 year ≅ 300 viral generations.
10 years of viral ≅ 2-3 x 106 years of human evolution!

34. Natural Selection
Over the past few weeks we did a lab demonstrating natural selection… you just didn’t know about it. ?

35. What is a species?
A group of interbreeding populations that cannot breed with other groups.
Giraffes and Elephants?
German Shepards and Poodles?

36. Speciation
Hurricane

37. Speciation
The populations diverge: Ecological conditions are slightly different on the island, and the island population evolves under different selective pressures and experiences different random events than the mainland population does. Morphology, food preferences, and courtship displays change over the course of many generations of natural selection.

38. Speciation
So we meet again: When another storm reintroduces the island flies to the mainland, they will not readily mate with the mainland flies since they’ve evolved different courtship behaviors. The few that do mate with the mainland flies, produce inviable eggs because of other genetic differences between the two populations. The lineage has split now that genes cannot flow between the populations.

39. Speciation Because of “geographic” isolation,
“maltose flies” preferred other “maltose flies,” and “starch flies” preferred other “starch flies” when choosing mates

40. Speciation
One species splits into two due to isolation (geographic, reproductive, etc…)
Also known as Divergent Evolution… results in homologous structures between groups

41. Speciation

42. Direction of Natural Selection and Species Formation
Stabilizing – extremes not favored (example – human birth weight)
Disruptive – extremes favored (example - short or long beaks not medium beaks)
Directional – extremes at one end favored

43. Isolation
Geographic Isolation: separated by a physical barrier of some kind
Behavioral Isolation: Differences in courtship displays prevent reproduction
Temporal Isolation: separated by differences in the timing of reproduction

44. Genetic Drift
Random changes in numbers of individuals in a population can lead to allele frequency changes in a population
This is called Genetic Drift

45. Directional Selection Stabilizing Selection
Assignment #1
Complete the following chart using pages 398 & 399
Definition
Example
Picture
Directional Selection
Stabilizing Selection
Disruptive Selection

46. Assignment #2 Complete the following chart using pages 404 & 405
Definition
Example
Picture
Behavioral Isolation
Geographic Isolation
Temporal Isolation

47. Phylogeny
Figure 1: A diagram of Mimi's immediate family. The passage of genes from parents to offspring is indicated by the green lines.

48. Figure 2: The genetic relationships for the last three generations of beetles under Mimi's log.

49. Figure 3: Genetic relationships for a segment of Mimi's beetle population over a number of generations. The last three generations of beetles under Mimi's log are shown in the blue frame.

50. Figure 4: Genetic relationships between two closely related species, Bembidion levettei and Bembidion zephyrum. Recent generations of beetles in Mimi's species are indicated with the blue frame. The arrow points to the common ancestor of the two beetle species.

51. Figure 5: A phylogenetic tree of beach beetles
Figure 5: A phylogenetic tree of beach beetles. Some branches have gone extinct in the past, while others represent species living today.

52. Figure 6: Genetic connections flowing along the branches of the Tree of Life.

53. Figure 7: The Tree of Life
???
Figure 7: The Tree of Life

54. Some Evidence of Evolution
Geographic Locations
Anatomical Similarities
Developmental Similarities
Molecular (biochemical) Similarities

55. Some Evidence of Evolution
Geographic Locations (and Convergent Evolution)

56. Convergent Evolution – when species become more alike
Animals live apart but in similar environments
Desirable traits are same
Example – rabbit and squirrel color

57. Some Evidence of Evolution
Anatomical Similarities
Homologous Structures = structural features with a common evolutionary origin (inherited from same common ancestor). Similar in arrangement, function or both.

58. Some Evidence of Evolution
Anatomical Similarities
Homologous Structures—inherited from the same ancestors

59. Not the same thing as…
Analogous Structure = A structural or functional similarity of a body feature, but not related.
Example: Insect & bird wings are similar in function, but not structure
*Instead, this would demonstrate convergent evolution

60. Some Evidence of Evolution
Anatomical Similarities
Can also be seen in fossils
Evidence of an organism that lived long ago.
Most fossils are found in sedimentary rock.
Many different types

61. Trace Fossils

62. Imprints

63. Cast/Molds

64. Petrified

65. Amber-Preserved & Frozen

66. Some Evidence of Evolution
Fossils can show homologous structures
Pteranodon—same sequence of bones in forelimb as other vertebrates, suggesting common ancestry

67. Some Evidence of Evolution
Anatomical Similarities
Homologous Structures
Archaeopteryx—shared characteristics of reptiles and birds (e.g. teeth and feathers). “Transitional species” with homologous structures to existing species can suggest possible common ancestry of two different groups

68. Some Evidence of Evolution
Anatomical Similarities
Vestigial Structures = a body structure that has no function in a present-day organism but was probably useful to an ancestor.

69. Some Evidence of Evolution
Anatomical Similarities
Vestigial Structures

70. Some Evidence of Evolution
Developmental Similarities
Comparative embryology
Early developmental stages are compared.
Related embryos look similar, suggesting common use of the same hox genes during development

71. Some Evidence of Evolution
Developmental Similarities
Comparative embryology

72. Some Evidence of Evolution
Molecular (biochemical) Similarities

73. Some Evidence of Evolution
Molecular (biochemical) Similarities

74. Geologic Time Scale – Page 421 Notice the short amount of time that humans have been a part of Earth’s history.