Charles Robert Darwin (1809-1882)

1
Charles Robert Darwin (1809-1882)

• Chapter 14, Section 1
• nothing in biology makes sense except in the
  light of evolution-Theodosius Dobzhansky

2
Evolution

• On the grandest scale, is all the changes that
  have transformed life over time.
• Essentially, it is the biological history of life
  on Earth.

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Ideas that set the Stage for Darwin

• There were 2 prevailing ideas about life on
  Earth
• Life was created in its complexity and has
  remained fixed (or unchanging) since this time
• The Earth was believed to be about 10,000 years
  old and also relatively unchanging
• However, these ideas were challenged as explorers
  traveled and observed the incredible diversity of
  life (past and present) and the nature of Earths
  geological processes

4
Early Influences

• George Buffon (mid-1700s) French naturalist
  collected fossils and noticed similarities and
  differences suggests Earth is older than
  10,000yrs
• James Hutton (1785) English Geologist suggest
  geological forces that shape Earths surface are
  slow and require long periods of time (Earth must
  be millions of years old)
• Jean Baptiste Lamarck (1809) French naturalist
  Explains Buffons observations by making a
  hypothesis that life evolves through the
  inheritance of acquired characteristics

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Lamarcks Hypothesis
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The Voyage

• In 1831, a 22-yr-old Darwin set sail on the HMS
  Beagle on a 5 year cruise around the world
• As a naturalist, he studied the geology, plants,
  and animals encountered on the voyage

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Darwins Observations

• He observed an immense amount of diversity in the
  South American plants, animals, and fossils
• Some fossils resembled modern life forms, some
  had no resemblance
• Life seemed well suited for the environment
• The Galapagos Islands- islands had similar life
  forms but varied in climate and vegetation
• Darwin inferred that the species on the different
  islands had once been part of the same mainland
  species

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The Galapagos Tortoises
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Geological Influence

• On the voyage of the Beagle, Darwin read the
  writings of geologist Charles Lyell
• Lyell proposed that the geological processes that
  shape the Earths surface today (erosion,
  deposition, earthquakes, etc.) are the same
  processes that shaped the Earth in the past
• Encouraged explaining the past in terms of
  observable present day processes
• Darwin personally witnessed an earthquake in the
  Andes Mtns and observed marine fossils move
  centimeters above the water line
• He realized that slow, gradual processes could
  cause enormous change over vast periods of time

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A Mechanism for Change

• When Darwin returned to England, he could no
  longer accept the idea of unchanging life
• He began contemplating a mechanism for
  evolutionary change
• In 1838, he read the work of Thomas Malthus (an
  economist who wrote an essay on human
  populations)
• Malthus suggested that human warfare, famine, and
  disease would limit the growth of the population

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Darwin Publishes His Ideas

• In 1844, Darwin wrote a 200-page essay that
  outlined his idea, but did not publish it in fear
  of controversy and doubt
• Instead he spent the next decade collecting
  evidence to support his idea
• Darwin received an essay from a young naturalist,
  Alfred Wallace, in 1858 proposing the same idea
  for evolutionary change with similar evidence
• In 1859, Darwin published his book The Origin of
  Species by Means of Natural Selection

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Darwins Two Main Ideas

• Natural Selection
• His mechanism for evolutionary change
• Organisms with inherited traits best suited for
  the environment will survive and reproduce more
  often

• Descent with Modification
• The species living on Earth today descended from
  common ancestral species
• This is the most controversial part of his
  publication because it is often misunderstood and
  its religious conflict