1. Unit 11: Evolution & Natural Selection
Biology 10

2. Unit 11: Evolution Table of Contents
Lesson 11.1: Camouflage & Mimicry
Lesson 11.2: Mutation & Adaptation
Lesson 11.3: Darwin’s Finches
Lesson 11.4: Natural Selection
Lesson 11.5: Evidence for Evolution

3. Lesson 11.3: Charles Darwin
I can describe how Darwin came to describe natural selection while observing finches (birds) in the Galapagos Islands.

4. Darwin’s Voyage of Discovery
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A reconstruction of the HMS Beagle sailing off Patagonia.

5. Voyage of the Beagle Charles Darwin Born Feb. 12, 1809
Joined Crew of HMS Beagle, 1831
Naturalist
5 Year Voyage around world
Avid Collector of Flora & Fauna
Astounded By Variety of Life
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6. Darwin returned 5 years later in 1836
Darwin Left England in 1831
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Darwin returned 5 years later in 1836

7. The Galapagos Islands
Small Group of Islands 1000 km West of South America
Very Different Climates
Animals On Islands Unique
Tortoises
Iguanas
Finches

8. copyright cmassengale

9. The Galapagos Islands
Finches on the islands resembled a mainland finch
More types of finches appeared on the islands where there was a variety of available food (seeds, nuts, berries, insects…)
Finches had different types of beaks adapted to their type of food gathering

10. Darwin’s Finches

11. copyright cmassengale

12. Distribution of Food on The Galapagos Islands

13. Predicted Finch Distribution
Predict the distribution (presence or absence) of each type of finch on each of the various Galapagos Islands.
Fill in the table on your handout.
HINT: Compare the preferred food type & beak shape of each bird with the type of food available on each island.

14. Actual Finch Distribution

15. What if . . . The seeds on Espanola started to increase in size?
What would you expect to happen immediately to the population of Small Ground Finches?
What would you expect to see happen to the population over the next 20 years?
What would happen if the size of the seeds decreased again in the future?

16. Darwin’s Conclusions
The environment determined which animals would survive and which would die off.
Those adapted to the new environment survived and became different from their mainland relatives.
Examples: Iguanas & Finches

17. Lesson 11.4: Natural Selection
I can describe how variation can provide populations an advantage for survival
I can identify examples of adaptations that may have resulted from variations favored by natural selection.

18. Natural Selection
Natural Selection: Organisms that are better adapted to an environment survive and reproduce more than others.

19. Natural Selection
The Theory of Natural Selection is based on four concepts:
Overproduction
Variation
Competition
Selection

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

21. 2. Variation
Each individual has a unique combination of inherited traits.
Adaptation: an inherited trait can increase an organism’s chances of survival

22. What adaptations do you see?

23. What adaptations do you see?

25. Why is Variation Important?
Because the environment changes.
The more variation within a species, the more likely it will survive.
EX: A deadly disease strikes an area, and only those who are immune survive.
The more variation of types of species in an habitat, the more likely at least some will survive.
EX: Dinosaurs replaced by mammals

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

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

28. 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)

29. 4. Selection
Individuals with traits that are not well adapted 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 that carried them.

34. Q: WHO selects the traits for wild plants and animals?

35. Natural Selection is Survival of the Fittest
NOBODY!!
There is no agent involved in natural selection.
Natural selection is a process of elimination
INDIVIDUALS THAT HAVE TRAITS THAT ARE BEST ADAPTED FOR THE CURRENT ENVIRONMENT ARE THE ONES THAT SURVIVE TO BREED AND PASS ON THEIR GENES TO THE NEXT GENERATION.
Organisms that do not have the beneficial traits either die or don’t have as many offspring.
Natural Selection is Survival of the Fittest

36. “Survival of the Fittest”
Evolutionary fitness isn’t a measure of physical fitness but of reproductive fitness.
Fitness- Ability to survive and produce offspring in an environment *

37. What acts as a selection pressure on a population?
Competition for food
Competition for a mate
Changes in the environment
Predators
Parasites
Human-caused changes to the environment (deforestation, climate change, pollution, etc.)

38. Sexual Dimorphism
Sexual Dimorphism: Differences between individuals of different sex of the same species
Male is larger in most mammals
In insects, spiders, birds, reptiles, amphibians the female is usually larger
In almost every species except for humans, the male is more colorful, as it is his job to attract a mate.

39. Sexual Dimorphism
Female Male

40. Sexual Dimorphism - Males

41. Sexual Dimorphism - Females

42. Sexual Selection
Sexual selection: selection towards male/female characteristics that leads to sexual dimorphism
How does this happen?
Female mate choice
Male-Male competition

43. Sexual Selection – The Bower Bird

44. Factors Affecting Natural Selection:
This is the perfect tool for the job!
Overproduction: the more offspring born, the more mouths to feed which equals fewer resources available to all
Variation: if there is no variation within species, all individuals will have the same traits and an equal chance of surviving and reproducing
Remember that natural selection does not grant organisms what they “need,” it only works with what they are “born” with…

45. Factors Affecting Natural Selection:
Competition: different species compete or fight over resources which can affect the number of organisms that survive from generation to generation
Environmental change: changes in the environment may favor certain characteristics over others – ex. Having thick fur during a particularly cold winter may favor an organism’s survival

46. Lesson 10.4: Evidence for Evolution
I can give several examples of evidence supporting the theory of evolution.

47. Evolution Evolution = change in populations over time.
More specifically, evolution is genetic change in populations, often leading to observable changes, over time.

48. Evolution Several key points:
Evolutionary change does not happen overnight.
2. Changes must be heritable – able to be passed on from one generation to the next.

49. Evidence for Evolution:
Fossil Record
Homologous Body Structures
Vestigial Organs
Embryology
Biochemical Evidence (DNA)

50. The Fossil Record
Fossils: the impression in the earth left by the remains of dead organisms.
Fossil Record: a record of the history of life on Earth, documented by fossils.

52. Archaeopteryx
Similarities between different fossil species and between fossil species and modern species illustrate a relationship
Missing link between reptiles and birds

53. Geological and fossil evidence show that the Earth has evolved (changed over time) too.

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

56. Analogous Body Structures
Analogous Body Structures: similar anatomy in different types of animals because similar environmental pressures, NOT an ancestral relationship.

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

59. Embryology
Embryology: embryos of all vertebrates are very similar early in their development.

61. 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

62. Review Questions 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 genotype? Explain!
5. List the 5 evidences that support the Theory of Evolution.