Transcript 17-4 Patterns of Evolution

The History of Life
Patterns of Evolution
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Foothill High School Science Department
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:
1.
2.
3.
4.
5.
6.
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
– Darwin’s 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
–Dolphins
–Seals
- Whales
- Sharks
- 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
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