Earths Early History

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Earths Early History

• Jan. 22, 2009

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What is a Theory?

• In everyday terms a theory is usually a guess
  or idea.
• In science a theory is well-supported scientific
  explanation.
• The theory of evolution explains through
  observation how life changes over time.

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Section 10.12 main ways life on Earth could have
started

• 1. Divine Creation
• Definition relating to a god or gods
• Common to religions although the account of
  creation varies from 1 religion to another.
• Cannot be explained by science. Science must
  have a scientific hypothesis that can be proven
  true or false.

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How old is the Earth?

• Approximately 4.5 billion years old.
• Age was determined by looking at the layers of
  sediment in the Earths crust.

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Origin of Life

• No one was there to record EXACTLY how life
  began.
• Some scientists are questioning whether or not
  life even originated on Earthcould have
  originated outside of Earth.

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Theories of geologic change set the stage for
Darwins theory

• There were three theories of geologic change.
• 1. catastrophism
• 2. gradualism
• 3. uniformitarianism

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Uniformitarianism is the prevailing theory of
geologic change.
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Fossils

• What are they?
• Preserved remains or remnants of an ancient
  organism.
• Rocks, petrified wood and tree sap, peat bogs,
  tar pits, glaciers.
• Fossil record provides evidence about
• History of life on Earth
• How different groups of organisms have changed
  over time.