Evolution: Basic Principles and Our Heritage

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Chapter 22

• Evolution Basic Principles and Our Heritage

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Life Evolved on the Earth about 3.8 Billion Years
Ago
Atmosphere mostly contained H2, Methane, CO2,
Carbon Monoxide and not much O2
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Life Evolved on the Earth about 3.8 Billion Years
Ago

• Inorganic molecules formed small organic molecules

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Miller and Urey Experiment
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Life Evolved on the Earth about 3.8 Billion Years
Ago

• Small organic molecules joined to form larger
  molecules
• Genetic material originated
• Organic molecules aggregated into droplets

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Fig 22.4
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Evidence of Evolution Comes from Diverse Sources

• The fossil record provides evidence of evolution
• Preserves only hard tissues

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Evidence of Evolution Comes from Diverse Sources

• Geographic distributions reflect evolutionary
  history
• Shows impact of geographic barriers and
  continental drift

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Evidence of Evolution Comes from Diverse Sources

• Comparative anatomy and embryology reveal common
  descent
• Comparative anatomy and embryology reveal
  Homologous, Analogous and Vestigial structures

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Homologous Structures are Related Through Common
Ancestry
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Analogous Structures Are not related
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Embryology Common Developmental pathways Are
revealed
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Embryology
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Evidence of Evolution Comes from Diverse Sources

• Comparative molecular biology also reveals
  evolutionary relationships

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Natural Selection A Mechanism of Evolution

• Random mutations underlie evolution, introduces
  allelic (gene) variations
• Natural selection encourages survival of the
  fittest
• Individuals with traits that make them better
  suited to their environments
• More likely to survive and reproduce
• Not necessarily the biggest and the strongest

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Human Roots Trace Back to the First Primates

• Primates have distinct characteristics

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Human Roots Trace Back to the First Primates

• Walking on two feet was a critical step in
  hominid evolution

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Proposed Homo sapien Evolution
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Brain Capacities
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