Foothill High School Science Department The History of Life Patterns of Evolution

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.Mass Extinctions 2.Adaptive Radiation 3.Convergent Evolution 4.Coevolution 5.Punctuated Equilibrium 6.Developmental Gene Changes

Foothill High School Science Department Mass Extinctions ExtinctionExtinction –Occurs Constantly –99% Earths Life Forms Extinct Mass ExtinctionsMass Extinctions –Wipe Out Ecosystems –Disrupt Energy Flow –Collapse Food Webs

Foothill High School Science Department Mass Extinctions Causes?Causes? –Asteroids? –Volcanic/Geologic Activity? EffectsEffects –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- Whales –Dolphins- Sharks –Seals- Penguins

Foothill High School Science Department The Process By Which Two Species Evolve In Response To Changes In Each OtherThe Process By Which Two Species Evolve In Response To Changes In Each Other –Figs & Wasp –Yucca & Bats –Orchids & Moths Coevolution

Foothill High School Science Department Punctuated Equilibrium Evolution Is Sometimes Gradual & Slow (Gradualism, Darwin)Evolution Is Sometimes Gradual & Slow (Gradualism, Darwin) –Horseshoe Crabs –Sharks –Cockroaches BUT When Ecological Equilibrium Is Upset, Evolution Can Become Quite “RapidBUT When Ecological Equilibrium Is Upset, Evolution Can Become Quite “Rapid

Foothill High School Science Department Punctuated Equilibrium Occurs Due ToOccurs 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 GenesHox 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