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The History of Life Patterns of Evolution Foothill High School Science Department Foothill High School Science Department Macroevolution Large Scale Evolutionary Changes That Take Place Over Long Periods of Time Foothill High School Science Department Macroevolution Key Concept: There Are Six Important Patterns of Macroevolution: 1. 2. 3. 4. 5. 6. Mass Extinctions Adaptive Radiation Convergent Evolution Coevolution Punctuated Equilibrium Developmental Gene Changes Foothill High School Science Department Mass Extinctions • Extinction – Occurs Constantly – 99% Earths Life Forms Extinct • Mass Extinctions – Wipe Out Ecosystems – Disrupt Energy Flow – Collapse Food Webs Foothill High School Science Department Mass Extinctions • Causes? – Asteroids? – Volcanic/Geologic Activity? • Effects – Habitats Left Unoccupied – Ecological Opportunity – Evolution Explosion Foothill High School Science Department Adaptive Radiation • Single Species or Small Group of Species Evolve Into Several Different Forms That Live In Different Ways – Darwin’s Finches – Age of Reptiles – Age of Mammals Foothill High School Science Department Convergent Evolution • Unrelated Species That Look And Act Remarkably Similar To Each Other But Are Not Related: –Fish –Dolphins –Seals - Whales - Sharks - Penguins Foothill High School Science Department Coevolution • The Process By Which Two Species Evolve In Response To Changes In Each Other – Figs & Wasp – Yucca & Bats – Orchids & Moths Foothill High School Science Department Punctuated Equilibrium • Evolution Is Sometimes Gradual & Slow (Gradualism, Darwin) – Horseshoe Crabs – Sharks – Cockroaches • BUT When Ecological Equilibrium Is Upset, Evolution Can Become Quite “Rapid Foothill High School Science Department Punctuated Equilibrium • Occurs Due To –Small Populations Become Reproductively Isolated –Mass Extinctions Foothill High School Science Department Punctuated Equilibrium Brief Periods of Rapid Evolutionary Change That Interrupt Long Periods of Gradual Evolution Still Controversial Foothill High School Science Department 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. Foothill High School Science Department Developmental Genes & Body Plans Small Changes In Timing of Genetic Control During Embryonic Development, Make Big Changes In The Resulting Organism Foothill High School Science Department