1. Evolution Unit: Darwin’s Theory of Evolution
Biology Chapter 15
Evolution Unit:
Darwin’s Theory of Evolution

2. 15-1 The Puzzle of Life’s Diversity
I. Background: Evolution and Its Core Principles
Evolution is a
T. Zobzhansky: “Nothing in biology makes sense except in the light of evolution.”
Central theme in biology

3. B. Core principles of evolution:
1. All life is linked through a ___________________
2. Populations of living things ___________________ (evolve).
3. The _______________________
this change (natural selection) so
that advantageous traits are selected over less advantageous traits.
4. The _________________________________ ____________________________________ (descent with modification).
Common ancestor
Change over time
Environment influences
advantageous traits become more
common in the population

4. Peppered Moth Example of natural selection
The evolution of the peppered moth over the last two hundred years has been studied in detail. Originally, the vast majority of peppered moths had light colouration, which effectively camouflaged them against the light-coloured trees and lichens which they rested upon. However, because of widespread pollution during the Industrial Revolution in England, many of the lichens died out, and the trees that peppered moths rested on became blackened by soot, causing most of the light-coloured moths, or typica, to die off from predation. At the same time, the dark-coloured, or melanic, moths, carbonaria, flourished because of their ability to hide on the darkened trees.[1]
Since then, with improved environmental standards, light-coloured peppered moths have again become common, but the dramatic change in the peppered moth's population has remained a subject of much interest and study, and has led to the coining of the term industrial melanism to refer to the genetic darkening of species in response to pollutants. As a result of the relatively simple and easy-to-understand circumstances of the adaptation, the peppered moth has become a common example used in explaining or demonstrating natural selection.[2]

5. II. Voyage of the Beagle A. A sea voyage helped ____________________
1. Darwin was born in England on February 12, 1809.
2. Set sail on the HMS Beagle from England in 1831 for a ____________ around the world.
Darwin frame his theory of evolution.
5 year voyage

6. Darwin’s Journey

7. Tortoise
Marine Iguana

8. 3. Darwin’s Observations:
Patterns of Diversity
a. ___________________: plants and animals seemed remarkably well suited to whatever environment they inhabited.

9. Living Organisms and Fossils
b. ____________________________: Many of the fossils that Darwin discovered resembled living organisms but were not identical to them.
For example, glyptodon, an extinct animal, is an ancient relative of the armadillo of South America. (page 370)

10. c. The Galapagos Islands:
1.) Located 1000 km west of South America.
2.) Islands were close together but had _________________
3.) Hood Island had __________________ Tortoises on this island had _____________ to reach the sparse vegetation.
4.) Isabel Island had _________________.
Tortoises on this island had _____________.
different climates
sparse vegetation
long necks
rich vegetation
shorter necks

11. Giant Tortoises of the Galápagos Islands
Section 15-1
Pinta
Tower
Pinta Island Intermediate shell
Marchena
James
Fernandina
Santa Cruz
Isabela
Santa Fe
Hood Island
Saddle-backed shell
Floreana
Hood
Isabela Island
Dome-shaped shell

12. 5.) Galapagos Finches: striking correlation between form of finches and the environment they inhabit;
similarities and differences with mainland species

13. Beak Adaptations

14. Small Tree Finch
Large Ground Finch
Woodpecker
Finch

15. 15-2 Ideas That Shaped Darwin’s Thinking
I. Evolutionary Thinking before Darwin
A. ________ believed that species were fixed and did not evolve.
B. All species were created in a single act of creation about 6,000 years ago.
C. Buffon (mid-1700’s) suggested that _______________________ and raised the possibility that different species ______________________________
Aristotle
Earth was much older
arose from common ancestors.

16. II. An Ancient Changing Earth
Hutton (1785)
________________
2. Earth is much older than a few thousand years.
Geological processes
operate extremely
slowly.

17. B. Lyell (1833)
1. Wrote Principles of Geology.
2. Promoted the idea of
continual, gradual, consistent geological changes.

18. C. Lamarck (1809) was the
1. Believed organisms acquired or lost certain traits during their lifetime.
Example: giraffe 2.
therefore, this led to a change in a species.
first to support the idea of evolution.
Traits could be passed to offspring

19. Example: Giraffe

20. D. Malthus (1798)
1. If human populations _______________, it would lead to competition for scarce resources, and 2.
increase too fast
only some individuals
would survive.
Limits to population growth.

21. E. Wallace (1858)
1. Conceived of essentially the same theory as Darwin. 2.
Speculates on
evolution by natural selection.

22. 15-3 Darwin Presents His Case
I. Publication of
On the Origin of Species
A. Wallace’s letter outlining basic principles of natural selection spurs Darwin into taking his ideas public.

23. B. After much fierce debate,
Darwin publishes his theory in 1859.
Contains a well-constructed
Backed by
He used the phrase
The book is “sold out” in one day.
argument for natural selection.
considerable evidence.
“descent with
modification.”

24. C. Advances in genetics in the twentieth century yield the mechanism through which natural selection operates, vindicating Darwin’s ideas.
DNA Fingerprinting

25. II. Inherited Variation and Artificial Selection
Nature provided the variation,
B. Variation existed both in nature and in farms. This variation was inherited.
1. Cows that __________________________ were selected by breeders.
2. Plants that __________________________ were selected.
and humans
selected those variations that they found useful.
produced the most milk
produced the largest and most
flavorful fruit

26. Artificial Selection: Dogs

27. Artificial Selection: Plants

28. III. Evolution by Natural Selection
A. The Struggle for Existence
1. High birth rates and a shortage of life’s basic needs would force organisms to compete.
2. Result:
or better protected, such as a porcupine can avoid being caught. Those predators that are faster or have a better mechanism to catch prey survive.
Those prey that are better camouflaged,

29. B. Survival of the Fittest
ability of an organism to survive and reproduce.
Fitness –
2. Darwin proposed that
3. Adaptation – any _________________ characteristic that increases an organism’s chance of survival.
fitness is a result of adaptation.
inherited

30. Examples of Adaptations
a. Waxy coating on the surface of leaves
prevents against water loss
Ability to climb trees - spider monkey
- Tree boa
Coloration
- Octopus

31. Look closely: It’s an Insect!
4. Those individuals best suited to their environment survive and reproduce most successfully. Darwin called this process “survival of the fittest” or natural selection.
Mantids exhibit camouflage.

32. C. Descent with Modification1.
2. Common descent: all species –__________________– were derived from common ancestors. 3.
All living organisms are related to
one another.
living and extinct
A single “tree of life” links all living
things.

33. The “Tree of Life”

34. IV. Evidence of Evolution
Example
1. Fossil Record
Fossils – the bones, shells, teeth, and other remains of organisms.
Fossils of simpler organisms are found in older rocks.
Newer strata contain more complex organisms.

35. Strata of sedimentary rock at the Grand Canyon.

36. Figure 17-2 Formation of a Fossil
Section 17-1
Water carries small rock particles to lakes and seas.
Dead organisms are buried by layers of sediment, which forms new rock.
The preserved remains may later be discovered and studied.
Go to Section:

37. Formation of sedimentary rock and deposition
of fossils from different time periods.

38. Leaf Fossil
Insect in Amber
Ammonites
Dinosaur Fossil

39. IV. Evidence of Evolution
Example
2. Geographic Distribution of Animals
1. All 13 species of Galapagos finches descended with modification from a common mainland ancestor.
2. Similar ecological conditions cause different animals to end up evolving striking features in common.

41. Darwin’s Finches

42. The continent of Australia is home to unique animals,
such as these marsupials, that evolved in isolation.

43. IV. Evidence of Evolution
Example
3. Current Evolution
Experimental evidence can demonstrate natural selection at work.
Example: Peppered moths, antibiotic resistance of bacteria.

44. Overuse of Antibiotics
has lead to Antibiotic
Resistance in bacteria.
Evolution of Pesticide Resistance in insect populations.

45. IV. Evidence of Evolution
Example
4. Artificial Selection
Humans select from among the naturally occurring genetic variations in species.
Example: Wheat, corn, cows, race horses, domestic breeding of dogs – poodles.

46. Evidence
Example
5. Comparative Anatomy
Similarities in form and structure between otherwise different-appearing structures.
Homologous structures: Same structure but different function. (organization of bones in fins of whales, wings of bat, paws of cat and gorilla point to their common evolutionary origin)
Vestigial Structures: Useless structures. (in humans – appendix, wisdom teeth, muscles that move the ears and nose.)

47. Evolution Evidence: Comparative Anatomy
Homologous structures (homology)
Descent from a common ancestor
Vestigial organs Ex: whale/snake hindlimbs; wings on flightless birds

48. Comparative Anatomy: Whale hind limb
Fossilized leg bones of Basilosaurus, an ancient whale.
A transitional fossil linking past and present.

49. Whales are mammals that evolved from land dwellers.

50. Evidence
Example
6. Comparative Embryology
Early embryo development in all animals goes through similar stages, to the extent of producing structures not seen in adults.
Example: The fish, bird, rabbit, and human embryos are similar in appearance and all have a two-chambered heart, pharyngeal slits, and a tail with muscles to move it.

51. Evolution Evidence: Comparative Embryology

52. Evolution Evidence: Comparative Embryology
Pharyngeal pouches, ‘tails’ as embryos

53. IV. Evidence of Evolution
Example
7. Comparative Biochemistry
Similarity in genes that control cellular function in very different organisms.
Example: Same set of genes controls many early events in the development of the fruit fly and mouse.
*All living things contain DNA.

54. Evolution Evidence: Molecular Biology
Similarities in DNA, proteins, genes, and gene products
Common genetic code

55. V. Summary of Darwin’s Theory
A. Individual organisms
B. More organisms
C. Individual organisms
for limited resources.
differ from one another
in a population.
are produced than can survive.
must compete

56. A few of the color variations
in a population of Asian lady
beetles.
Overproduction of offspring.

57. D. Individuals best suited to their environment survive and reproduce most successfully. These “best fit” individuals pass their heritable traits to their offspring.
E. Natural selection, the environment selecting the best traits (phenotype) under the current conditions, causes species to change over time.

58. THE END!

61. Homologous Structures