Charles Darwin and Natural Selection

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Charles Darwin and Natural Selection

• Objectives
• To explain Darwins theories of evolution by
  natural selection
• To discuss descent with modification

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I. Darwins Ideas Influenced by

• A. Lamarcks Theory of Evolution
• B. Voyage on the Beagle (1831-1836)

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Lava lizard
Swimming Lizard
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Land Iguana - Galapagos
Marine Iguana - Galapagos
Green Iguana S. America
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Influences on Darwin
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TIME was very important to Darwins theory

• C. Geologists James Hutton and Charles Lyell
• 1. Earth is much older than a few thousand
  years
• 2. Processes shaping Earth have occurred for
  millions of years

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D. Thomas Malthus, Economist

• 1. Human population is increasing competition
  for food, water, space
• 2. War, famine and disease prevents this

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E. Artificial Selection

• 1. Breeders select best traits to produce next
  generation

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II. Darwins Theory of Evolution by Natural
Selection

• A. Over time, the number of individuals that
  carry advantageous traits will increase in a
  population
• B. Occurs in 4 steps

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Darwins Theory of Evolution by Natural Selection

• 1. Living things overproduce

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Darwins Theory of Evolution by Natural Selection

• 2. There is variation among offspring

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Darwins Theory of Evolution by Natural Selection

• 3. There is a struggle to survive

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Darwins Theory of Evolution by Natural Selection

• 4. Those that survive are most fit

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C. Natural Selection Survival of the Fittest

• 1. Fitness ability to survive and reproduce
• 2. Fitness is the result of adaptations
  inherited characteristics that increase an
  organisms chance of survival

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Adaptation
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III. Descent with Modification

• A. Over time, natural selection produces
  organisms with different structures
• B. Todays species look different from their
  ancestors
• C. Each species descended with changes over time

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1965
1975
FORD MUSTANG
2005
1985
1995
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Descent with Modification

• D. Implies that all living things are related to
  one another
• E. COMMON ANCESTOR