The History of Life

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The History of Life

• Patterns of Evolution

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Macroevolution

• Large Scale Evolutionary Changes That Take Place
  Over Long Periods of Time

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Macroevolution

• Key Concept
• There Are Six Important Patterns of
  Macroevolution
• Mass Extinctions
• Adaptive Radiation
• Convergent Evolution
• Coevolution
• Punctuated Equilibrium
• Developmental Gene Changes

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Mass Extinctions

• Extinction
• Occurs Constantly
• 99 Earths Life Forms Extinct
• Mass Extinctions
• Wipe Out Ecosystems
• Disrupt Energy Flow
• Collapse Food Webs

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Mass Extinctions

• Causes?
• Asteroids?
• Volcanic/Geologic Activity?
• Effects
• Habitats Left Unoccupied
• Ecological Opportunity
• Evolution Explosion

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Adaptive Radiation

• Single Species or Small Group of Species Evolve
  Into Several Different Forms That Live In
  Different Ways
• Darwins Finches
• Age of Reptiles
• Age of Mammals

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Convergent Evolution

• Unrelated Species That Look And Act Remarkably
  Similar To Each Other But Are Not Related
• Fish - Whales
• Dolphins - Sharks
• Seals - Penguins

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Coevolution

• The Process By Which Two Species Evolve In
  Response To Changes In Each Other
• Figs Wasp
• Yucca Bats
• Orchids Moths

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Punctuated Equilibrium

• Evolution Is Sometimes Gradual Slow
  (Gradualism, Darwin)
• Horseshoe Crabs
• Sharks
• Cockroaches
• BUT When Ecological Equilibrium Is Upset,
  Evolution Can Become Quite Rapid

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Punctuated Equilibrium

• Occurs Due To
• Small Populations Become Reproductively Isolated
• Mass Extinctions

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Punctuated Equilibrium

• Brief Periods of Rapid Evolutionary Change That
  Interrupt Long Periods of Gradual Evolution
• Still Controversial

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Developmental Genes Body Plans

• Hox Genes
• Homologous Hox Genes Establish Body Plans In
  Animals As Different As Humans Insects
• Control Number of Wings, Legs, Body Segments, etc.

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Developmental Genes Body Plans

• Small Changes In Timing of Genetic Control During
  Embryonic Development, Make Big Changes In The
  Resulting Organism