Development of Evolutionary Thought

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Development of Evolutionary Thought
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Law vs. Theory

• Laws are facts. Simple statements of what
  happens.
• Ex. Law of Gravity when I drop a pen it lands on
  the floor
• Theories are attempts to explain laws
• Ex. Theory of Gravity spacetime warping or
  gravitons

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Evolve change over time
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What is Evolution?

• Evolution - a change in the genetic composition
  of a population over time.

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Paleontology Evolution

• Before evolution there was Geology
• Older layers of sedimentary rock (the layers on
  the bottom) contain fossil species very
  dissimilar from modern life.
• Each layer (stratum) is characterized by a unique
  group of fossil species.
• As you move upward through the layers, you find
  species more and more similar to modern life.

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James Hutton - 1795

• A Scottish geologist
• proposed that it was possible to explain the
  various landforms by looking at mechanisms
  currently operating in the world
• Proposed that the earth was much more than a few
  thousand years old

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What about life?

• Originally people believed that life was
  generated by spontaneous generation
• If you leave a piece of meat out, maggots will
  appear inside the meat
• In the mid 1800s Louis Pasteur proved only living
  organisms can produce more living organisms

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Modern Ideas

• The primordial soup hypothesis
• Simple organic molecules resulted from
  interactions with compounds in the earth and
  natural forces
• The first cells were prokaryotic
• Eukaryotic cells appear about 1.8 billion years
  ago

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Endosymbiotic Theory

• Endosymbiotic Theory states that eukaryotic cells
  were formed when some prokaryotic cells started
  living inside other prokaryotic cells
• Eventually these other cells became organelles
  like mitochondria or chloroplasts
• Margulis proposed this to explain why
  mitochondria and chloroplasts contain their own
  DNA