Chapter 15 Darwins Theory of Evolution

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Chapter 15Darwins Theory of Evolution

• Section 15-2Ideas That Shaped Darwins Thinking

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An Ancient, Changing Earth

• Key Concept
• Hutton Lyell Helped Scientists Recognize That
  Earth Is Many Millions of Years Old, And The
  Processes That Changed Earth In The Past Are The
  Same Processes That Operate In The Present

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Huttons Theory of Geological Change

• James Hutton, 1795
• Described The Geological Forces That Have Changed
  The Earth Over Millions of Years
• Sedimentary Deposits
• Volcanic
• Displacement
• Erosion

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Lyells Principles of Geology

• Published Just Before The Beagle Set Sail
• Explained Geological Processes That Shaped The
  Earth
• Helped Darwin Understand Sea Shells In The Andes
  Mountains At 12,000 Feet
• Expanded Earths Age

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Lamarcks Theory of Evolution

• Jean-Baptiste Lamarck, 1809
• One Of First Scientists To Understand That Change
  Occurs Over Time
• Changes Are Adaptations To Environment
• Almost On The Right Track, Almost

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Lamarcks Theory of Evolution

• Key Concept
• Lamarck 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.

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Lamarcks Theory of Evolution

• Tendency Toward Perfection
• Organisms Are Continually Changing and Acquiring
  Features That Help Them Live More Successfully In
  Their Environment
• Bird Ancestors Desired To Fly So They Tried Until
  Wings Developed

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Lamarcks Theory of Evolution

• Use Disuse
• Organisms Could Change The Size Or Shape Of
  Organs By Using Them Or Not Using Them
• Blacksmiths Their Sons
• Giraffes Necks

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Lamarcks Theory of Evolution

• Inheritance Of Acquired Traits
• Traits Acquired During Ones Lifetime Would Be
  Passed To Offspring

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Lamarcks Theory of Evolution

• Lamarcks Errors
• Did Not Know About Inheritance of Traits
• Genes Are Not Changed By Activities In Life
• Change Occurs Through Mutation To The DNA of a
  Germ Cell, And Occurs Before An Organism Is Even
  Fertilized.

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Population Growth

• Thomas Malthus, 1798
• Economist
• Observed Babies Being Born Faster Than People
  Were Dying
• Population vs. Food Supply
• Unless Controlled, Would Result In Disaster

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Population Growth

• Key Concept
• Malthus Reasoned That If The Human Population
  Continued To Grow Unchecked, Sooner or Later
  There Would Be Insufficient Living Space Food
  For Everyone
• Famine, Pestilence
• Political Instability, War
• Death Rate Will Increase To Balance Population
  Food Supply

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Four Horseman of the Apocalypse
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Population Growth

• Darwin Realized Malthuss Principles Were Visible
  In Nature.
• Plants Animals Produce Far More Offspring Than
  Can Be Supported.
• Most Die
• If They Didnt Earth Would Be Overrun