1. Chapter 14 Principles of Evolution
14.1 How did evolutionary thought evolve?
14.2 How does natural selection work?
14.3 How do we know that evolution has occurred?
14.4 What is the evidence that populations evolve by natural selection?
14.5 A postscript by Charles Darwin

2. Two Meanings of Evolution
Evolution as a process – change in the features of individuals in a population over generations
Examples:
Head lice resistant to pesticide
Cancer cells resistance to chemotherapy
Plants resistant to Round Up

3. Figure 9.1 The process of evolution.
The evolution of pesticide resistance in lice occurs as a result of natural selection, one of the mechanisms by which traits in a population can change over time.

4. The Process of Evolution
The process of evolution has been widely seen and accepted:
Pesticide resistance in insects
Antibiotic resistance in bacteria
However, acceptance that traits in populations can evolve is not the same as acceptance of the theory of evolution…

5. The Theory of Evolution
The theory of common descent—the idea that all living things on the planet can be traced back to a common ancestor—is what most people (especially opponents) think of when they hear “evolution”

6. Figure 9.2 The theory of common descent.
This theory states that all modern organisms descended from a single common ancestor. Each branching point on the tree represents the origin of a new species from an ancestral form.

7. Evolutionary Thought
Evolution by natural selection is a unifying theme for all of biology
The foundation of evolutionary thought developed gradually over centuries
Main ideas of evolution were not widely accepted until after Charles Darwin published On the Origin of Species in 1859

8. FIGURE 14-1 A timeline of the roots of evolutionary thought
Each bar represents the life span of a key figure in the development of modern evolutionary biology.

9. 14.1 How Did Evolutionary Thought Evolve?
Early biological thought did not include the concept of evolution
Pre-Darwinian science was heavily influenced by theology
All organisms were created simultaneously
Each life-form is distinct and unchanging from the moment of creation
Each life-form was a divinely established “ideal form” (Greek philosophers Plato & Aristotle B.C.)
This view remained unchallenged for ~2,000 years

10. Aristotle’s Ladder of Nature
FIGURE 14-2 Aristotle's Ladder of Nature
In Aristotle's view, fixed, unchanging species could be arranged in order of increasing closeness to perfection, with inferior types at the bottom and superior types above.
Aristotle’s Ladder of Nature

11. 14.1 How Did Evolutionary Thought Evolve?
Exploration of new lands revealed a staggering diversity of life
European naturalists explored new lands (Africa, Asia & the Americas)
They found more species then suspected
Some species closely resembled each other, and/or differed in some characteristics
Maybe species did change, but how?

12. Speculation That Life Had Evolved
Comte de Buffon ( ) proposed that some modern species had evolved through natural processes
Idea was not accepted
Did not provide a mechanism for evolution
Earth was not old enough to allow time for the process of evolution

13. 14.1 How Did Evolutionary Thought Evolve?
Fossil discoveries showed that life had changed over time
As more and more fossils were discovered, it became clear that they were the impressions of plants and animals that had died long ago
The way in which fossils are distributed in the rocks is consistent and show progression in development

14. Layer upon layer of sedimentary rock forms the walls of the Grand Canyon. The layers formed from the accumulation of sediments over more than a billion years.

15. eggs in nest fossilized feces (coprolites) bones footprints
Any part or trace of an organism that is preserved in rock or sediments is a fossil.
eggs in nest
fossilized feces
(coprolites)
bones
footprints
skin impression

16. Fossils Certain fossils were always found in the same layers of rock
Organization of fossils and rock layers was consistent
The deeper (older) the layer, the more dissimilar the fossils from modern organisms
Many fossils were of extinct organisms

17. FIGURE 14-4 Fossils of extinct organisms
Fossils provide strong support for the idea that today's organisms were not created all at once, but arose over time by the process of evolution. If all species were created simultaneously, we would not expect (a) trilobites to be found in older rock layers than (b) seed ferns, which in turn would not be found deeper than (c) dinosaurs, such as Allosaurus. Trilobites became extinct about 230 million years ago, seed ferns about 150 million years ago, and dinosaurs 65 million years ago.

18. Nonevolutionary Explanations
Georges Cuvier ( ) proposed theory of catastrophism which hypothesized that
High numbers of species were created originally
A series of catastrophes produced rock layers and destroyed many species, preserving some as fossils
Modern day species are the survivors of these catastrophes

19. Catastrophism
If true, the oldest rock layers should contain fossils of present-day species, but the vast majority of fossils are of extinct species
So, French geologist Louis Agassiz ( ) proposed new creations after each catastrophe
Even with just the fossils known at that time, Agassiz had to include 50 separate catastrophes and creations

20. 14.1 How Did Evolutionary Thought Evolve?
A few scientists speculated that life had evolved
In the early 1700s, most people thought the earth was only 4,000-10,000 old – and evolution cannot happen that quickly

21. Earth Is Exceedingly Old
James Hutton ( ) and Charles Lyell ( ) studied geologic processes (wind, water, earthquakes, volcanism)
Developed theory of uniformitarianism: geologic change resulting from slow, continuous actions similar to those at work today
Now the earth could be very old.
In fact, Lyell thought the earth was eternal

22. Earth Is Exceedingly Old
Rock formations reflect repeated cycles of geologic change occurring over vast periods of time
Conclusions:
Earth was older than the 6,000 years proposed by theologians
There was enough time for evolution to occur
Most scientists now think the earth is about 4.5 billion years old

23. Pre-Darwin Proposal
Jean Baptiste Lamarck ( ) proposed that organisms evolved through inheritance of acquired characteristics
Organisms are modified during their lifetime through use or disuse of different parts
These modifications are passed to offspring

24. Pre-Darwin Proposal
Inheritance of acquired characteristics mechanism was rejected when it was determined that acquired characteristics are not heritable

25. Darwin and Wallace
By mid-1880s the concept of evolution was increasingly accepted
1858 Charles Darwin and Alfred Russel Wallace independently
Provided evidence for its occurrence
Proposed the mechanism through which it occurs

26. Darwin and Wallace
Darwin and Wallace shared experiences that shaped their thinking
Aware that fossils showed a trend of increasing complexity
Aware of Hutton and Lyell’s proposal that Earth is extremely old

27. Darwin and Wallace
Darwin and Wallace shared experiences, continued
Traveled extensively studying tropical plants and animals
Observed that similar species differed only in a few ecologically important features
Darwin had collected 30 years of data but was afraid to tell people. Why?

28. Large ground finch, beak suited to large seeds
Small ground finch, beak
suited to small seeds
Darwin studied a group of closely related species of finches on the Galapagos Islands. Each species specializes in eating a different type of food and has a beak of characteristic size and shape, because natural selection has favored the individuals best suited to exploit each food source efficiently. Aside from the differences in their beaks, the finches are quite similar.
Warbler finch, beak
suited to insects
Vegetarian tree finch, beak
suited to leaves

29. Darwin and Wallace
Darwin and Wallace independently proposed that organisms evolved by natural selection
Both presented papers to the Linnaean Society in London (1858)
Darwin published On the Origin of Species by Means of Natural Selection in 1859

30. Thomas Malthus English economist and clergyman (1766-1834)
His writings were extremely influential
In his essay on population, he wrote
“It may safely be pronounced, therefore that [human] population, when unchecked, goes on doubling itself every 25 years, or increases in a geometric ratio.”

31. Section 14.2 Outline 14.2 How Do We Know That Evolution Has Occurred?
Fossils Provide Evidence of Evolutionary Change Over Time
Comparative Anatomy Gives Evidence of Descent with Modification
Embryological Similarity Suggests Common Ancestry
Modern Biochemical and Genetic Analyses Reveal Relatedness Among Diverse Organisms

32. Evidence from Fossils
Fossils of ancient species tend to be simpler in form than modern species
Several series of fossils have been found that exhibit the evolution of body structures over time
One series reveals that modern whales evolved from land-dwelling ancestors

33. FIGURE 14-6 The evolution of the whale
Over the past 50 million years, whales have evolved from four-legged land dwellers, to semiaquatic paddlers, to fully aquatic swimmers with shrunken hind legs, to today's sleek ocean dwellers.

34. Comparative Anatomy
Homologous structures provide evidence of common ancestry
Homologous structures are structures that have the same evolutionary origin despite their current appearance or function
Bird and mammalian forelimbs are homologous structures

35. FIGURE 14-7 Homologous structures
Despite wide differences in function, the forelimbs of all these animals contain the same set of bones, inherited through evolution from a common ancestor. The different colors of the bones highlight the correspondences among the various species.

36. Comparative Anatomy
Vestigial structures are remnants of structures that are inherited from ancestors
Had important functions in ancestors
Serve no obvious purpose in present day organism
Vestigial structures include:
Molar teeth in vampire bats
Pelvic bones in whales and certain snakes

37. Figure 14-8 Vestigial structures
Many organisms have vestigial structures that serve no apparent function. The (a) salamander, (b) whale, and (c) snake all inherited hindlimb bones from a common ancestor; the bones remain functional in the salamander but are vestigial in the whale and snake.

38. Comparative Anatomy
Analogous structures are structures that are outwardly similar in appearance, but differ in their evolutionary origin
Analogous structures include
Wings of insects and birds

39. Figure 14-9a Analogous structures
Convergent evolution can produce outwardly similar structures that differ anatomically. The wings of (a) insects and (b) birds and the sleek, streamlined shapes of (c) seals and (d) penguins are examples of such analogous structures.

40. Figure 14-9b Analogous structures
Convergent evolution can produce outwardly similar structures that differ anatomically. The wings of (a) insects and (b) birds and the sleek, streamlined shapes of (c) seals and (d) penguins are examples of such analogous structures.

41. Comparative Anatomy Analogous structures include
Streamlined shapes of seals and penguins

42. Figure 14-9c Analogous structures
Convergent evolution can produce outwardly similar structures that differ anatomically. The wings of (a) insects and (b) birds and the sleek, streamlined shapes of (c) seals and (d) penguins are examples of such analogous structures.

43. Figure 14-9d Analogous structures
Convergent evolution can produce outwardly similar structures that differ anatomically. The wings of (a) insects and (b) birds and the sleek, streamlined shapes of (c) seals and (d) penguins are examples of such analogous structures.

44. Comparative Anatomy
Analogous structures result from convergent evolution rather than descent from a common ancestor
Convergent evolution occurs when similar environmental pressures and natural selection give rise to similar (analogous) structures in distantly related organisms

45. Figure 9.6 Divergence from a common ancestor.
(a) Prickly pear cactuses, like this Opuntia on continental South America, are shrub-like and low to the ground.

46. Figure 9.6 Divergence from a common ancestor.
(b) On the Galápagos Islands, some prickly pears are tree-sized, such as this variety of Opuntia echios. The overall similarity of these two species despite their difference in form supports the hypothesis that they descended from a common ancestral prickly pear.

47. Embryology
All vertebrate embryos, resemble one another in their early development

48. Embryology
All vertebrate embryos possess genes that direct development of gill slits and a tail
These genes were inherited from a common ancestor

49. Embryology
Adult fish retain gills and tail because the genes are active throughout their embryonic development
Humans are born without gills and a tail because the genes are active only during early embryonic development

50. Biochemistry and Genetics
All organisms share related biochemical processes:
All cells use DNA as genetic blueprint
All use RNA, ribosomes, and approximately the same genetic code for translation
All use roughly the same set of 20 amino acids to build proteins
All use ATP to transfer energy

51. Biochemistry and Genetics
Striking genetic similarities between organisms imply evolutionary relatedness
For example, the DNA nucleotide sequence of the human and mouse cytochrome c gene is very similar, suggesting shared ancestry

52. Figure 14-11 Molecular similarity shows evolutionary relationships
The DNA sequences of the genes that code for cytochrome c in a human and a mouse. Of the 315 nucleotides in the gene, 30 (shaded in blue) differ between the two species.

53. Biochemical Evidence Similar organisms have similar DNA sequences
DNA sequences reflect evolutionary relationships

54. 08-11
Title:
DNA sequences reflect evolutionary relationships.
Caption:
DNA sequences evolve over time. Species that share more recent common ancestors have undergone less evolution separately than species that share more distant common ancestors, and thus have DNA that is more similar.

55. Figure 9.17 Similar organisms have similar DNA sequences.
(a) The order of DNA bases contains information about the traits of an organism. We can compare the DNA of various organisms by looking at similarities and differences in the DNA sequences for various genes. The number of nucleotide differences between species is exaggerated in this example for illustration purposes.
Mathematical models can be used to determine the distance between organisms

56. Figure 9.18 Using DNA evidence to test an evolutionary hypothesis.
Scientists comparing several physical features hypothesized a tree of relationships among swallowtail butterflies; a small portion of the tree is illustrated here. When another group of scientists measured similarity in DNA sequences for several genes in these species, the results supported the original hypothesis.

57. Section 14.3 Outline 14.3 How Does Natural Selection Work?
Darwin and Wallace’s Theory Rests on Four Postulates
Natural Selection Modifies Populations Over Time

58. Evolution by Natural Selection
Darwin and Wallace proposed that life’s diverse forms arose through process of descent with modification
Individuals in each generation differ slightly from the members of the preceding generation
Over long time periods, small differences accumulate to produce major transformations

59. Evolution by Natural Selection
Postulate 1: Individual members of a population differ from one another in many respects
Variations arise purely by chance resulting from random mutations in DNA
Differences are obvious in many physical characteristics and extend to molecular level

60. Figure 14-12 Variation in a population of snails
Although these snails are all members of the same population, no two are exactly alike.

61. Evolution by Natural Selection
Postulate 2: At least some of the differences among members of a population are due to characteristics that may be passed from parent to offspring
However, the mechanism of inheritance was not understood at this point in time

62. Evolution by Natural Selection
Postulate 3: In each generation, some individuals in a population survive and reproduce successfully but others do not
Darwin observed that many more individuals are born than survive
Some individuals have more offspring than others

63. Evolution by Natural Selection
Postulate 4: Individuals with advantageous traits survive longest and leave the most offspring, a process known as natural selection

64. Evolution by Natural Selection
Gregor Mendel’s theories of inheritance (1865) confirmed Darwin’s assumption that certain traits are heritable
New variations arise by chance as a result of random mutations in DNA
New variations may be good, bad, or neutral

65. Section 14.4 Outline
14.4 What Is the Evidence That Populations Evolve by Natural Selection?
Controlled Breeding Modifies Organisms
Evolution by Natural Selection Occurs Today

66. Controlled Breeding
Artificial selection is selective breeding to produce plants and animals that possess desirable traits
Modern dogs descended from wolves
In only a few thousand years, humans artificially selected for all breeds of modern dogs

67. Figure 14-13a Dog diversity illustrates artificial selection
A comparison of (a) the ancestral dog (the gray wolf, Canis lupus) and (b) various breeds of modern dogs. Artificial selection by humans has caused a great divergence in size and shape of dogs in only a few thousand years.

68. Figure 14-13b Dog diversity illustrates artificial selection
A comparison of (a) the ancestral dog (the gray wolf, Canis lupus) and (b) various breeds of modern dogs. Artificial selection by humans has caused a great divergence in size and shape of dogs in only a few thousand years.

69. Controlled Breeding
Humans have created tremendous variation in several species over relatively short periods of time through artificial selection
Isn’t it plausible that much larger changes could result from hundreds of millions of years of natural selection?

70. Natural Selection Today
Examples include:
Coloration in Trinidadian guppies
Pesticide resistance
Experimental introductions of Anolis sagrei lizards

71. Coloration
Female guppies prefer to mate with brightly colored males; however, brightly colored males are more likely to be eaten by predators
Males found in areas lacking predators were brightly colored
Males found in areas with predators were duller by comparison (predators eliminated brightly colored males before they could reproduce)
Copyright © 2005 Pearson Prentice Hall, Inc.

72. Coloration
Conclusion: When fewer predators are present, brighter coloration can evolve
Conclusion was confirmed
Predators were introduced to previously predator-free areas (males were brightly colored)
Within a few generations male guppies in those areas evolved to become less colorful
Copyright © 2005 Pearson Prentice Hall, Inc.

73. Copyright © 2005 Pearson Prentice Hall, Inc.
Figure Guppies evolve to become more colorful in predator-free environments
Male guppies (top) are more brightly colored than females (bottom). Some male guppies are more colorful than others. In some environments, brighter males are naturally selected; in other environments, duller males are selected.
Copyright © 2005 Pearson Prentice Hall, Inc.

74. Pesticide Resistance
Numerous insect pests have evolved resistance to pesticides
Roaches developed resistance to Combat®, an insecticide bait that acted as an agent of natural selection
Resistant roaches possessed a rare mutation that caused them to dislike glucose, the main attractant in Combat®
At least one insect species is resistant to every pesticide in existence

75. Experiments
Small groups of Anolis sagrei lizards were introduced onto 14 small Bahamian islands with thinly-branched bushes and no trees
Lizards were originally from Staniel Cay, an island with thickly-branched trees
Their long legs were adaptive for maneuvering in these trees
The introduced lizards thrived and reproduced

76. Experiments
After 14 years, comparisons were made between lizards on the Bahamian islands and those of Staniel Cay
Lizards on all 14 Bahamian islands had shorter, thinner legs

77. FIGURE 14-15 Anole leg size evolves in response to a changed environment

78. Experiments
Conclusion: Individuals with shorter, thinner legs evolved because they were able to escape predators better than their longer-legged ancestors in the new environment

79. Natural Selection of Phenotypes
The variations on which natural selection works are produced by mutations that arise spontaneously

80. Natural Selection of Phenotypes
Natural selection selects for organisms that are best adapted to a particular environment
If the environment changes, a previously advantageous trait may become disadvantageous

81. 14.4 What Is the Evidence That Populations Evolve by Natural Selection?
Evolution by natural selection occurs today
Experiments can demonstrate natural selection

82. Natural Selection Today?
Selection acts on random variation to favor the traits that work best in particular environments
Environments are constantly changing
Organisms are not perfect, and natural selection can only work on traits already present
Evolution by natural selection occurs today
Experiments can demonstrate natural selection