1. Darwin’s Theory of Evolution *
Evolution, is change over time, OR is the process by which modern organisms have descended from ancient organisms.
A scientific theory is a well-supported testable explanation of phenomena that have occurred in the natural world.

2. Evolution is a Theory – Just like Gravity!
Evolution is a well supported explanation of phenomena that have occurred in the natural world
A theory in science is a well tested hypothesis, not just a guess

3. Evolution is when organisms change over time
Evolution is when organisms change over time. So, modern organisms descended from ancient ones

4. Charles Darwin: Father of evolution.* Sailed around the world 1831-1836

5. How do you think Darwin came up with his theory?
Voyage of the Beagle

6. What did Darwin’s Travels reveal. *
The diversity of living species was far greater than anyone had previously known!!
These observations led him to develop the theory of evolution!!

7. Patterns of Diversity
Darwin visited Argentina and Australia which had similar grassland ecosystems.
those grasslands were inhabited by very different animals.
neither Argentina nor Australia was home to the sorts of animals that lived in European grasslands.

8. Living Organisms and Fossils.*
Fossils are the preserved remains of ancient organisms.
Some of those fossils resembled organisms that were still alive today.

9. Living Organisms and Fossils
Others looked completely unlike any creature he had ever seen.
As Darwin studied fossils, new questions arose.
Why had so many of these species disappeared?
Mass extinction
How were they related to living species?
Observation from their fossils.

10. Fossils Types of fossils Trace fossils Imprints
Cast mold
Trace fossils Imprints
Frozen or amber Petrified fossils

11. Imprint

12. The Galapagos Islands
A group of islands of the west coast of South America
The islands are close together but have very different climates
Darwin noticed that the characteristics of many plants and animals varied among islands.

13. The Galapagos Island
The smallest, lowest islands were hot, dry, and nearly barren-Hood Island-sparse vegetation
The higher islands had greater rainfall and a different assortment of plants and animals-Isabela- Island had rich vegetation.

15. Animal on the Galapagos Islands
Land tortoises
Galapagos finches
Blue footed booby
Marine Iguanas

18. The Journey Home Darwin Observed that
Many islands close together with different climates.
Characteristics of many plants and animals vary greatly among the islands

19. Darwin finally published his ideas in in his book “The Origin of Species” that summarized all his findings from his trip around the world.

20. Lamarck Theory of acquired characteristics
Lamarck said organisms acquired traits by using their bodies in new ways
These new characteristics were passed to offspring
Lamarck was totally wrong!

22. Evidence of Evolution Fossil Record
Geographic Distribution of Living Species
Homologous Body structures
Similarities in Embryology

23. Evidence of Evolution
Fossil Record provides evidence that living things have evolved
Fossils show the history of life on earth and how different groups of organisms have changed over time

24. Relative vs. Absolute Dating

25. Relative Dating Can determine a fossil’s relative age
Performed by estimating fossil age compared with that of other fossils
Drawbacks – provides no information about age in years

26. Primate Fossils
Australopithecus Homo erectus Homo sapien

27. Homo habilis = handy human 1.5 to 2 mya
Homo erectus 1.6 mya
Modern Homo sapien
(fully modern fossils 100,000 ya)
bipedal

28. Geographic Distribution of Living Species
Similar animals in different locations were the product of different lines of descent

29. Homologous body structures
Structures that have different mature forms but develop from the same embryonic tissues.
Wings and legs all descended from fish fins.
e.g. Wing of bat, human arm, leg of turtle
Turtle
Alligator
Bird

30. Homologous Body Structures

31. Vestigial Organs e.g. Appendix in man
Vestigial structure: It is a structure without function or no use.
e.g. Appendix in man

32. Similarities in Embryology
In their early stages of development, chickens, turtles and rats look similar, providing evidence that they shared a common ancestry.

33. Embryological development

34. Evolution by Natural Selection
Selection means to choose
What do you think natural selection mean?
(“Nature chooses”, chooses what?
Best adaptations for survival)
The Struggle for Existence-members of each species have to compete for food, shelter, other life necessities in order to survive.
Survival of the Fittest-Some individuals are better suited for the environment. Organisms with most favorable adaptation will survive.

35. Natural Selection
Natural selection is the process by which individual organisms with favorable traits are more likely to survive and reproduce.
Fitness is the ability of an individual to survive and reproduce in its specific environment.
Adaptation: an inherited characteristic that increases an organism’s chance of survival.

36. Artificial Selection
Nature provides variation, humans select variations that are useful.
Example - a farmer breeds only his best livestock.

38. Components of Natural Selection
Not all individuals will be able to reproduce.
Due to environmental issues, illness, etc…
DIFFERENTIAL REPRODUCTION
Birds eat green beetles, not brown ones.
What’s Left?
What’s the end result?

40. Components of Natural Selection
The brown beetles that are left will mate and have brown offspring.
The brown trait has a genetic basis.
This is called HEREDITY.

41. Eventually, all beetles in this population will be brown.
Finally, the brown trait (which is more advantageous) allows the beetle to survive in order to reproduce.
Eventually, all beetles in this population will be brown.
This PHENOTYPE has been SELECTED over the green phenotype.
Image courtesy of

42. Descent with Modification
Descent with Modification- Natural selection produces organisms that have different structures, establish different niches or occupy different habitats. This causes today’s species to look different from their ancestors.
Common Descent- were derived from common ancestors

43. Summary of Darwin’s Theory
Organisms differ; variation is inherited.
2. Organisms produce more offspring than survive.
3. Organisms compete for resources.
4. Organisms with advantages survive to pass those advantages to their children.
5. Species alive today are descended with modifications from common ancestors.

44. Evolution of Populations
Occurs when there is a change in relative frequency of alleles

45. VOCABULARY REVIEW Evolution – change over time NATURAL SELECTION –
Individuals better adapted to the environment are able to survive and reproductive.
“SURVIVAL OF THE FITTEST”

46. NEW VOCABULARY POPULATION –
Group of individuals of same species that interbreed.
GENE POOL –
Common group of all genes present in a population.

47. Variation and Gene Pool
Combined genetic information of all members.
Allele frequency is number of times alleles occur in the population.
Evolution: Any change in the relative frequency of alleles in a population

48. Single-Gene vs. Polygenic Traits
Single-Gene trait: any trait controlled by one gene (example: tongue rolling)
Natural selection on single-gene traits can lead to change in allele frequencies and thus evolution. Distinct phenotype
Polygenic traits: any trait controlled by two or more genes (example: height in human) Many Phenotypes

49. Natural selection can affect the distribution of phenotypes in any of three ways:
1.Directional selection- Individuals at one end of the curve have higher fitness than those in the middle. (Example: seed size and birds beak size)

50. 2. Stabilizing selection-Individuals near the center of the curve have higher fitness than those at either ends of the curve. (Example: weight of human infants at birth).

51. 3.Disruptive selection-Individuals at the upper and lower ends of the curve have higher fitness than those near the middle. (Eample: seed size and bird beak size).

52. PHENOTYPE SELECTION http://www.youtube.com/watch?v=aTftyFboC_M

53. Natural Selection on Polygenic Traits

54. Genetic Variation Gene Flow Mutation Sexual Reproduction
Movement of genes from one population to another.
Mutation
Changes in DNA
Sexual Reproduction
Sexual reproduction causes new combinations of genes.
Gene flow, sexual reproduction (meiosis), and mutations are major causes of genetic variation.

55. Sources of genetic Variation in Populations
processes can
lead to this:
Mutations -
change in DNA
sequence
Gene Shuffling –
from sexual
reproduction

56. What causes genetic variation?
The forces that causes population and species to evolve are:
1. Natural selection
2. Migration
Genetic drift
Mutation

57. Genetic Drift Genetic drift occurs only in small population
What is genetic drift?
It is a random change in allele frequency causes an allele to become common.

58. Effects of genetic Drift
Genetic drift has two main effects on population:
Bottle necking effect
Founder effect

59. Reduction in a small population due to chance event.
Bottle necking effect
Reduction in a small population due to chance event.
The surviving population does not represent the true original population.
Use white/brown beans to explain this.

60. Founder Effect: genetic drift due to the migration of a small subgroup of a population. (example: fruit flies migrating from mainland to different Hawaiian islands and)

61. Hawaiian Honeycreepers
An example of adaptive radiation –
these species all diverged from a
common ancestor (founder species)
FOUNDER SPECIES

62. Conditions needed for Genetic Equilibrium
Hardy Weinberg ‘s principle for the population to remain constant:
Population must be large
There must be no mutation
No sexual selection
No struggle for survival
No movement into and out of the popution(emmigration).

63. GENETIC EQUILIBRIUM http://www.youtube.com/watch?v=AU2XCDMdR9k

64. SPECIATION Speciation is the formation of new species
As new species evolve, population become reproductively isolated.
1. Reproductive Isolation – Members of two population cannot interbreed & produce fertile offspring.

65. ISOLATING MECHANISMS
Behavioral Isolation - capable of breeding but have differences in courtship rituals (EX. Mead

66. Table 23.1a
Geographical Isolation – Separated by geographic barrier like rivers ,mountains, or bodies of water (ex: squirrel)

67. Temporal Isolation – Two or more species reproduce at different times

68. ISOLATING MECHANISMS……..
2. Behavioral Isolation - capable of breeding but have differences in courtship rituals (EX. Meadowlarks)
3. Geographical Isolation – Separated by geographic barrier like rivers ,mountains, or bodies of water (ex: squirrel)
4. Temporal Isolation – Two or more species reproduce at different times.

69. Table 23.1a