1. LECTURE 1: EVOLUTIONARY THEORY

2. Why are there so many species?
How many species do you think there are on Earth?
There may be as many as 30 million species of beetles alone! 2

3. ~ 1000 species of bats 3

4. Introduction
On November 24, 1859, Charles Darwin published On the Origin of Species by Means of Natural Selection.
Darwin’s book drew a cohesive picture of life by connecting what had once seemed a bewildering array of unrelated facts.
Darwin made two points in The Origin of Species:
Today’s organisms descended from ancestral species.
Natural selection provided a mechanism for evolutionary change in populations.
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5. What is the difference between Hypothesis and Theory?5

6. Tentative explanation of
Hypothesis
Tentative explanation of
observations 6

7. Theory
General explanation of important natural phenomena, developed through extensive & reproducible observations & experiments 7

8. What is a Scientific Theory?
A theory in science is not a “guess”
It represents the best model for making sense out of all the evidence.
Germ theory, Electrical theory, Cell theory, etc.
Evolution is a well-supported theory drawn from a variety of sources of data:
Observation of the fossil record
Genetic information
Distribution of plants and animals
Similarities across species of anatomy and development 8

9. Western Historical Context
Aristotle ( B.C.) – Greek philosopher
Species are permanent, perfect, immutable
With Increasing complexity
Dominant world view for > 2000 yr 9

10. Western Historical Context
A.D. – Natural Theology (Creationism)
Species are permanent, perfect, immutable
A.D. = anno Domini, “the year of our Lord”. 10

11. 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. 11

12. 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” 12

13. Western Historical Context
Georges Cuvier ( )
French anatomist who largely developed paleontology, the study of fossils
Geoges Cuvier = French anatomist.
Paleontology – The study of fossils. 13

14. Deeper strata contain older taxa
Western Historical Context
Georges Cuvier ( )
Deeper strata contain older taxa
Preferred hypothesis for profound geologic change = catastrophism = Stated that species disappear due to a catastrophic event of the earth’s crust (volcano, earthquake…) 14

15. Western Historical Context
James Hutton ( )
Scottish geologist who offered an alternative to catastrophism
Proposed that the Earth was millions of years instead of a few thousand years old
Preferred hypothesis for profound geologic change = gradualism
Changes in Earth’s crust due to slow continuous processes(erosion, earthquakes, volcanoes…)
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. 15

16. Western Historical Context
Charles Lyell ( )
Scottish geologist who incorporated Hutton’s gradualism into the theory of uniformitarianism
Charles Lyell = Scottish geologist. 16

17. Western Historical Context
Charles Lyell ( )
Geological processes at uniform rates building & wearing down Earth’s crust
Proposed that the Earth was millions of years instead of a few thousand years old
Charles Lyell = Scottish geologist. 17

18. Principles of Geology
Published by Lyell Just Before The Beagle Set Sail & read by Darwin
Explained Geological Processes That Shaped The Earth
Helped Darwin Understand Sea Shells In The Andes Mountains At 12,000+ Feet
Expanded Earth’s Age 18 18

19. 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. 19

20. Western Historical Context
Jean Baptiste Lamarck ( )
Stated that Changes Are Adaptations To Environment
acquired in an organism’s lifetime
Said acquired changes were passed to offspring
Jean Baptiste Lamarck = Invertebrate Curator of Natural History Museum in Paris. 20

21. LAMARCK Hypothesized mechanism of evolution: Law of Use & disuse
If a body part were used, it got stronger
If body part NOT used, it deteriorated
Inheritance of acquired characters
Proposed That By Selective Use Or Disuse Of Organs, Organisms Acquired Or Lost Certain Traits During Their Lifetime
These Traits Could Then Be Passed On To Their Offspring
Over Time This Led To New Species

22. 22 22

23. Will his kids be born with big muscles?

24. What were Lamarck’s Mistakes?
Lamarck Did NOT Know how traits were inherited (Traits are passed through genes)
Genes Are NOT Changed By Activities In Life
Change Through Mutation Occurs Before An Organism Is Born

25. 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. 25

26. Thomas Malthus (1766-1834) Each Species Struggles For: Food
Living Space
Mates

27. Western Historical Context
Charles Darwin ( )
English gentleman who conceived of natural selection as the principal mechanism of adaptive evolution 27

28. Western Historical Context
Alfred Russel Wallace ( )
English biologist who also (independently) conceived of natural selection as the principal mechanism of adaptive evolution
Species evolved from common ancestor 28

29. Western Historical Context
Lyell presented the independently derived hypothesis to the Linnaean Society of London on July 1, 1858 29

30. Western Historical Context
Charles Darwin ( )
The Origin of Species
(1859) 30

31. In Summation Evolutionary history
Linnaeus: taxonomy
Hutton: gradualism
Lamarck: evolution
Malthus: populations
Cuvier: paleontology/catastrophism
Lyell: uniformitarianism
Darwin: evolution
Mendel: inheritance
Wallace: evolution 31

32. 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. 32

33. inheritance from selected population
Lamarckism
Use
Inheritance of
acquired
characteristics
Darwinism
Genetic
inheritance from selected population
Natural
selection
Generation 1
Generation 2 33

34. What is theoretical about the Darwinian view of life?
Arguments by individuals dismissing the Darwinian view as “just a theory” suffer from two flaws.
First, it fails to separate Darwin’s two claims: that modern species evolved from ancestral forms and that natural selection is the main mechanism for this evolution.
The conclusion that life has evolved is supported by an abundance of historical evidence.
To biologists, Darwin’s theory of evolution is natural selection - the mechanism that Darwin proposed to explain the historical facts of evolution documented by fossils, biogeography, and other types of evidence.
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35. As Darwin said, “There is grandeur in this view of life.”
Fig
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings 35