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Charles Darwin (1809-1882)

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Darwin and Wallace independently came up with a credible MECHANISM that could ... Henslow, interested in botany, entomology, chemistry, mineralogy, geology ... – PowerPoint PPT presentation

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Title: Charles Darwin (1809-1882)


1
Charles Darwin (1809-1882) Alfred Wallace
(1823-1913)British Naturalists
2
Foundations of Darwinism
  • Darwin and Wallace independently came up with a
    credible MECHANISM that could produce
    evolutionary changes
  • Both men Stimulated by
  • 1. Observations of diversity of life in the
    tropics
  • 2. An Essay on the Principle of Population as
    it Affects the Future Improvement of Society
    (1798) by Thomas Malthus (1766-1834).
  • Malthus Argued
  • Human populations will always expand until
    famine, war, or disease limits growth

3
Darwins Early Years
  • Mediocre student during early education
  • Loved animals and the outdoors
  • 1825, entered Edinburgh University to study
    medicine, no stomach for surgery
  • Developed fondness for natural science,
    especially Marine Zoology
  • Went to Cambridge, to enter the clergy! 

4
Darwin, the Naturalist
  • Collected beetles!
  • At Cambridge, befriended Professor Henslow,
    interested in botany, entomology, chemistry,
    mineralogy, geology
  • Henslow persuaded Darwin, after graduation, to
    begin a study of geology
  • Arranged for young Darwin to accompany Professor
    Sedgwick on a field trip through North Wales
  • Captain FitzRoy invited D to volunteer as
    naturalist on the Beagle, survey ship about to
    leave on round-the-world mapping and collecting
    expedition

5
Darwins Voyage on the Beagle
  • Read Lyell's The Principles of Geology during
    early weeks
  • Investigated geology of places ship visited,
    understood the slow passage of geologic time
  • Collected fossil bones and faunal specimens
  • 1831-1836 visited Cape Verde Islands, Brazil,
    Tierra del Fuego, Patagonia, Chile, Argentina,
    the Galapagos Islands, Tahiti, New Zealand,
    Australia, Tasmania, Cocos Islands, Mauritius,
    St. Helena, Ascension, and the Azores

6
Formation of Darwins Ideas on Natural Selection
  • Darwin's journal, The Voyage of the Beagle
    (1839), sold well
  • Perceived that SELECTION was key to success in
    breeding domestic plants and animals.
  • Read Malthus observed that animals and plants
    struggled for existence and developed habits and
    variations
  • it at once struck me thatfavorable variations
    would tend to be preserved, and unfavorable ones
    to be destroyed. The result of this would be the
    formation of new species" (Darwin, 1898, p. 68).
  •  

7
Alfred Wallace
  • Family of Modest Means
  • Limited education, worked many jobs
    construction, surveying, assistant to a
    watchmaker, teacher...
  • Loved natural history and the outdoors
  • With naturalist Henry Bates,
  • traveled to Brazil, explored the Amazon, sold
    collections of biological specimens, especially
    insects

8
Wallaces Formative Years
  • 1848 Wallace and Bates sailed for South America,
    gathered large collections
  • 1852 Sailed back to England, ship caught fire
    and sank after 3 weeks! Passengers rescued but
    collections lost!
  • 1859 Bates gathered more than 14,000 species in
    Brazil
  • 1854 Wallace collected in the Malay Archipelago
    recognized the Archipelago as biologically
    divided by a narrow strait, separating Asian
    fauna from Australian fauna, still recognized as
    Wallace's Line.

9
Wallace Forms His Ideas on Natural Selection
  • Applied geological idea of uniformitarianism to
    biology
  • Charts of a species might look more like a tree
    than a straight line
  • No species came into existence unless coexisted
    with another similar species that was its
    predecessor
  • 1855 Wrote paper arguing for evolution of
    species, searching for a MECHANISM. Malthus
    inspired him.

10
Wallace and Darwin
  • June 1858 Wallace drafted his thoughts, sent
    them in letter to Darwin, Darwin was shattered
  • July 1858 Joint credit was given to Darwin
    Wallace at Linnaean Society
  • The announcement attracted no particular
    scientific or public attention!
  • 1859 Darwin worked intensely for the next year
    on his manuscript, On the Origin of Species by
    Means of Natural Selection (1859), sold out on
    day of publication!

11
Natural Selection
  • Theory of Natural Selection was based on 3
    observations and 2 deductions
  •  Observation 1
  • Organisms reproduce in a geometric ratio
    (Actually Malthus was wrong reproduction is
    exponential, not geometric)
  • Observation 2
  • The numbers of any given species tend to remain
    more or less constant through time
  • Observation 3
  • All living things vary
  • Deduction 1
  • There is a universal struggle for survival. More
    organisms of each kind are born than can possibly
    obtain food and survive.
  • Deduction 2
  • Individuals with some kind of advantage have the
    best chance of surviving and reproducing their
    own kind

12
Darwins Grand Contribution
  • NATURAL SELECTION some individuals are more
    successful at reproducing than others
  • Advantageous characteristics become numerous,
    less favorable characteristics disappear
  • NS explains how one species transmutes into
    another species
  • EVOLUTION became a central organizing concept in
    biology a NATURAL (v. supernatural) process
    could produce a new species!
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