1. The Theory of Evolution by Natural Selection Charles Darwin
More than anyone else in the history of science, Charles Darwin provided us with an answer to “why are there so many species”?

2. Western Historical Context
Aristotle ( B.C.) – Greek philosopher
Species are permanent, perfect, immutable
Dominant world view for > 2000 yr
See timeline Fig. 22.2

3. Western Historical Context
A.D. – Natural Theology (Creationism)
Species are permanent, perfect, immutable
A.D. = anno Domini, “the year of our Lord”.
See timeline Fig. 22.2

4. Western Historical Context
Carolus Linnaeus ( )
Swedish physician & botanist whose passion was taxonomy
Developed a hierarchical classification scheme & binomial nomenclature
Karl von Linne (Carolus Linnaeus) = Swedish physician & botanist.
Taxonomy = branch of biology concerned with naming and classifying organisms. Binomial composed of genus and specific epithet that refers to one species.
See timeline Fig. 22.2

5. Western Historical Context
Carolus Linnaeus ( )
Canis = genus
lupus = specific epithet that refers to one species in the genus Canis
The binomial is always italicized or underlined, the genus name is always capitalized, and the specific epithet is always lower case
“King Philip Came Over For Gumbo Sunday”
See Fig. 25.8

6. Western Historical Context
Georges Cuvier ( )
French anatomist who largely developed paleontology, the study of fossils
Geoges Cuvier = French anatomist.
Paleontology – The study of fossils.
See timeline Fig. 22.2

7. Western Historical Context
Georges Cuvier ( )
Deeper strata contain older taxa
See timeline Fig. 22.2

8. Western Historical Context
Georges Cuvier ( )
Preferred hypothesis for profound geologic change = catastrophism
See timeline Fig. 22.2

9. Western Historical Context
James Hutton ( )
Scottish geologist who offered an alternative to catastrophism
Preferred hypothesis for profound geologic change = gradualism
James Hutton = Scottish geologist.
Profound changes are the cumulative product of slow but continuous processes; e.g., laying down strata and then carving out river valleys.
See timeline Fig. 22.2

10. Western Historical Context
Charles Lyell ( )
Scottish geologist who incorporated Hutton’s gradualism into the theory of uniformitarianism
Charles Lyell = Scottish geologist.
See timeline Fig. 22.2

11. Western Historical Context
Charles Lyell ( )
Uniformitarianism – geological processes & rates today are those that also operated in antiquity
Charles Lyell = Scottish geologist.
See timeline Fig. 22.2

12. Western Historical Context
Charles Lyell ( )
Uniformitarianism – suggested that the Earth is > 6000 yr old
Charles Lyell = Scottish geologist.
See timeline Fig. 22.2

13. Western Historical Context
Jean Baptiste Lamarck ( )
Invertebrate Curator of the Natural History Museum in Paris
One of the 18th & 19th centuries’ biologists who hypothesized that traits of species are not immutable, i.e., they can evolve
Jean Baptiste Lamarck = Invertebrate Curator of Natural History Museum in Paris.
See timeline Fig. 22.2

14. Western Historical Context
Jean Baptiste Lamarck ( )
Hypothesized mechanism of evolution: Use & disuse alters traits; inheritance of acquired characters results in adaptations to environmental conditions
Jean Baptiste Lamarck = Invertebrate Curator of Natural History Museum in Paris.
See timeline Fig. 22.2

15. Western Historical Context
Thomas Malthus ( )
English demographer
Hypothesis: Plants and animals are capable of producing far more offspring than resources can support; the “struggle for existence” (e.g., famine, war) is an inescapable consequence
English demographer and political economist.
See timeline Fig. 22.2

16. Western Historical Context
Within this context, Charles Darwin ( ) served as Ship’s Naturalist on the HMS Beagle’s circumnavigation of the globe ( )
England
EUROPE
NORTH
AMERICA
Galápagos
Islands
Darwin in 1840,
after his return
SOUTH
Cape of
Good Hope
Cape Horn
Tierra del Fuego
AFRICA
HMS Beagle in port
AUSTRALIA
Tasmania
New
Zealand
PACIFIC
OCEAN
Andes
ATLANTIC

17. Galapagos Islands, Ecuador

18. Galapagos Islands, Ecuador

19. Galapagos Islands, Ecuador

20. Galapagos Islands, Ecuador

21. Darwin was a good observer of both wild and domesticated organisms (e
Darwin was a good observer of both wild and domesticated organisms (e.g., birds)

22. Darwin was a good observer of both wild and domesticated organisms (e
Darwin was a good observer of both wild and domesticated organisms (e.g., birds)

23. Western Historical Context
Charles Darwin ( )
English gentleman who conceived of natural selection as the principal mechanism of adaptive evolution
See timeline Fig. 22.2

24. Western Historical Context
Alfred Russel Wallace ( )
English biologist who also (independently) conceived of natural selection as the principal mechanism of adaptive evolution
See timeline Fig. 22.2

25. Western Historical Context
Lyell presented the independently derived hypothesis to the Linnaean Society of London on July 1, 1858

26. Western Historical Context
Charles Darwin ( )
The Origin of Species
(1859)

27. The Origin of Species Final paragraph:
“It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us…
There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed laws of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.”
Darwin recognizes the mystery of the origin of life, but provides a key mechanistic explanation for the continual, ever-present process of evolution.

28. Darwinian Theory of Evolution
Descent with modification
Descent implies common ancestry
Modification to better suite the environment = adaptation
“Descent with modification” is evolution by natural selection in Darwin’s own words years of rigorous research have proven that Darwin hypothesis was essentially correct; his hypothesis has become the “Darwinian Theory of Evolution”.
Natural selection is the principal process that drives adaptive evolution
See Fig. 22.7

29. Darwinian Theory of Evolution
Organisms have enormous potential for population increase, but the potential is rarely reached
Generalized sigmoidal population growth curve

30. Potential for rapid population growth when resources are not limiting
Resource availability generally limits population size
Competition for resources
(“struggle for existence”)
Phenotypic variability (morphology, physiology, behavior, etc.)
Natural Selection: Survival and reproduction of the “fittest” individuals
Some variability results from heritable differences
Evolution by natural selection in modern terms. See next lecture (Chapt. 23) for a modification of this!
Adaptive evolution: A change in the phenotypic constitution of a population owing to selection on heritable variation among phenotypes

31. inheritance from selected population
Lamarckism
Use
Inheritance of
acquired
characteristics
Darwinism
Genetic
inheritance from selected population
Natural
selection
Generation 1
Generation 2

32. Evidence for the Theory of Evolution by Natural Selection
Darwin used artificial selection to illustrate the modifying potential of selection

33. Evidence for the Theory of Evolution by Natural Selection
Darwin used artificial selection to illustrate the modifying potential of selection

34. Evidence for the Theory of Evolution by Natural Selection
Darwin used artificial selection to illustrate the modifying potential of selection

35. Rapid changes in populations under strong selection
Evidence for the Theory of Evolution by Natural Selection
Rapid changes in populations under strong selection
E.g., pesticide resistance

36. Evidence for the Theory of Evolution by Natural Selection
Homologous traits (a.k.a. characters, attributes) = traits in different species that arose from the same ancestral trait (may or may not have similar function)
Human
Cat
Whale
Bat
See
Fig.
22.14

37. Evidence for the Theory of Evolution by Natural Selection
Even when homologies are not obvious in adults, they may be quite apparent in embryonic stages
Lemur Pig Human
Which one is the human?

38. Evidence for the Theory of Evolution by Natural Selection
Analogous traits = traits in different species that have similar function, but arose from different ancestral traits

39. To distinguish homologous vs
To distinguish homologous vs. analogous traits, the relatedness of the organisms
doesn’t matter as much as the evolutionary history of the traits themselves

40. Evidence for the Theory of Evolution by Natural Selection
Analogous traits = traits in different species that have similar function, but arose from different ancestral traits

41. These examples happen to be homologous leg and foot bones
Evidence for the Theory of Evolution by Natural Selection
Vestigial organs = remnants of organs that had important functions in ancestors
These examples happen to be homologous leg and foot bones

42. Evidence for the Theory of Evolution by Natural Selection
Vestigial organs = remnants of organs that had important functions in ancestors

43. Biochemical homologies
Evidence for the Theory of Evolution by Natural Selection
Biochemical homologies
Common use of DNA, RNA, amino acids, ribosomes, genetic code, ATP, electron carriers, electron transport system, etc.