Download 17-4 Patterns of Evolution

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