1. Darwin & Natural Selection
Unit 3: Evolution

2. Learning Goals 1. Define "Evolution" & "Natural Selection".
2. Describe the 4 steps of Natural Selection, giving an example of each.
3. Explain the importance of "Variation".
4. Does Natural Selection act on an organism phenotype or genotoype? Explain!
5. List the 5 evidences that support the Theory of Evolution.

3. Theory of Evolution
Evolution: The process of change over time. Any change in the heritable traits
Specifically, a change in the frequency of a gene or allele in a population over time

4. Charles Darwin Father of Evolution
Proposed a mechanism for evolution, natural selection
Darwin went on a 5-year trip around the world on the ship, the HMS Beagle
As the ship’s naturalist, he made observations of organisms in South America and the Galapagos Islands
Wrote a book, “Origin of the Species”

5. Voyage of the Beagle

6. Voyage of Beagle Dates: February 12th, 1831 Captain: Charles Darwin
Ship: H.M.S. Beagle
Destination: Voyage around the world.
Findings: evidence to propose a revolutionary hypothesis about how life changes over time

8. 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.

9. Patterns of Diversity Darwin posed challenging questions.
Why were there no rabbits in Australia, despite the presence of habitats that seemed perfect for them?
Why were there no kangaroos in England?

10. Living Organisms and Fossils
Darwin collected the preserved remains of ancient organisms, called fossils.
Some of those fossils resembled organisms that were still alive today.

11. 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?
How were they related to living species?

12. Fossils

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.

14. The Galapagos Island
Darwin was fascinated in particular by the land tortoises and marine iguanas in the Galápagos.
Giant tortoises varied in predictable ways from one island to another.
The shape of a tortoise's shell could be used to identify which island a particular tortoise inhabited.

16. Animals found in the Galapagos
Land Tortoises
Darwin Finches
Blue-Footed Booby
Marine Iguanas

17. Animals

18. The Journey Home
Darwin Observed that characteristics of many plants and animals vary greatly among the islands
Hypothesis: Separate species may have arose from an original ancestor

19. Lamarck

20. Lamarck’s Theory of Evolution
He came up with the theory of Inheritance of Acquired Traits in 1809
His theory was that if an organism continually used a structure to carry out a certain task, the structure used would become physically modified over time to make the task easier.
This modified structure would then be passed on to any offspring.

21. Lamarck’s Theory of Evolution
Lamarck also believed that when body parts were not being used, such as the human appendix, they gradually disappear. Eventually, people will be born without these parts. Lamarck believed that evolution happens according to a prearranged plan and that the results have already been decided.

24. Darwin’s Finches

25. Natural Selection
Natural Selection: Organisms that are best adapted to an environment survive and reproduce more than others
“Survival of the fittest”

26. Natural Selection
Darwin’s Theory of Natural Selection occurs in four steps:
Overproduction
Variation
Competition
Selection

27. 1. Overproduction
Each species produces more offspring that can survive

28. 2. Variation
Each individual has a unique combination of inherited traits.
Adaptation: an inherited trait that increases an organism’s chances of survival

29. What adaptations do you see?

30. What adaptations do you see?

32. Why is Variation Important?
Because the environment changes.
The more variation within a species, the more likely it will survive
EX: If everyone is the same, they are all vulnerable to the same environmental changes or diseases
The more variation of types of species in an habitat, the more likely at least some will survive
EX: Dinosaurs replaced by mammals

33. Which community has a better chance of surviving a natural disaster?
Community A
Community B

34. 3. Competition Individuals COMPETE for limited resources:
Food, water, space, mates
Natural selection occurs through “Survival of the fittest”
Fitness: the ability to survive and reproduce
Not all individuals survive to adulthood

35. 4. Selection
The individuals with the best traits / adaptations will survive and have the opportunity to pass on it’s traits to offspring.
Natural selection acts on the phenotype (physical appearance), not the genotype (genetic makeup)
Ex: When a predator finds its prey, it is due to the prey’s physical characteristics, like color or slow speed, not the alleles (BB, Bb)

36. Individuals with traits that are not well suited to their environment either die or leave few offspring.
Evolution occurs when good traits build up in a population over many generations and bad traits are eliminated by the death of the individuals.

41. Peppered Moth A
Which moth will the bird catch? B

42. Descent with Modification
Descent with Modification – each living species has descended, with changes, from other species over time.
Common Descent – all living organisms are related to one another

44. Evidence for Evolution:
Fossil Record
Homologous Body Structures
Vestigial Organs
Embryology
Biochemical Evidence

45. The Fossil Record
Fossils: a record of the history of life on Earth

46. Archaeopteryx
Missing link between reptiles and birds

48. Homologous Body Structures
Homologous Body Structures: similar anatomy in different types of animals because of common ancestor

50. Evidence for Evolution
Vestigial organs-organs that serve no useful function in an organism
i.e.) appendix, hip bones in whales

51. Vestigial Organs
Vestigial Organs: “leftover” traces of evolution that serve no purpose

53. Embryology
Embryology: embryos of all vertebrates are very similar early on

55. Biochemical Evidence
Biochemistry: DNA with more similar sequences suggest species are more closely related
EX: Humans and chimpanzees share more than 98% of identical DNA sequences

56. Learning Goals 1. Define "Evolution" & "Natural Selection".
2. Describe the 4 steps of Natural Selection, giving an example of each.
3. Explain the importance of "Variation".
4. Does Natural Selection act on an organism phenotype or genotoype? Explain!
5. List the 5 evidences that support the Theory of Evolution.

58. Coral Snake (Poisonous)
Milk Snake (Not poisonous)

65. Stick Mantid

66. Flower Mantid