1. Chapter 17 The History of Life
Section Patterns of Evolution

3. Macroevolution
Large Scale Evolutionary Changes That Take Place Over Long Periods of Time

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

5. Flowchart SPECIES that are Unrelated Related form in under under in in
Intense environmental pressure
Inter-relationships
Similar environments
Small populations
Different environments
can undergo
can undergo
can undergo
can undergo
can undergo
Convergent evolution
Punctuated equilibrium
Coevolution
Extinction
Adaptive radiation:
Aka:
Divergent
evolution

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

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Extinction
Extinction
More than 99% of all species that have ever lived are now extinct.
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8. Mass Extinctions
It is often difficult to determine exactly when mass extinction events have occurred in the Earth's history - the fossil record is not perfect, and the poorer the record for a particular time frame, the more it is open to different interpretations. Some scientists have suggested that there is a cycle of mass extinctions, with a major die off every 26 million years or so. This would imply that there have been some 23 extinction events since the Cambrian, a figure which is at the upper limit of most estimates. While we remain unsure of the total number, there is general agreement over the existence of 5 major mass extinction events.

10. Mass Extinctions Causes? Effects Asteroids?
Volcanic/Geologic Activity?
Effects
Habitats Left Unoccupied
Ecological Opportunity
Evolution Explosion

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Extinction
What effects have mass extinctions had on the history of life? Mass extinctions have:
provided ecological opportunities for organisms that survived
resulted in bursts of evolution that produced many new species
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12. Adaptive Radiation: aka Divergent evolution
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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14. Convergent Evolution Fish - Whales Dolphins - Sharks Seals - Penguins
Unrelated Species That Look And Act Remarkably Similar To Each Other But Are Not Related:
Fish Whales
Dolphins - Sharks
Seals - Penguins

15. How would you compare the fins in these 2 organisms?
CONVERGENT EVOLUTION
How would you compare the fins in these 2 organisms?

16. In what way are these organisms displaying examples of convergent evolution?

17. Coevolution
The Process By Which Two Species Evolve In Response To Changes In Each Other
Figs & Wasp
Yucca & Bats
Orchids & Moths

18. Punctuated Equilibrium
Evolution Is Sometimes Gradual & Slow (Gradualism, Darwin)
Horseshoe Crabs
Sharks
Cockroaches
BUT When Ecological Equilibrium Is Upset, Evolution Can Become Quite “Rapid

19. Punctuated Equilibrium
Occurs Due To
Small Populations Become Reproductively Isolated
Mass Extinctions

20. Punctuated Equilibrium
Brief Periods of Rapid Evolutionary Change That Interrupt Long Periods of Gradual Evolution

21. Punctuated Equilibrium
Darwin felt that biological change was slow and steady, an idea known as gradualism.
Biologists have considered two different explanations for the rate of evolution, as illustrated in these diagrams. Gradualism involves a slow, steady change in a particular line of descent. Punctuated equilibrium involves stable periods interrupted by rapid changes involving many different lines of descent. 21

22. Punctuated Equilibrium
Punctuated equilibrium is a pattern of evolution in which long stable periods are interrupted by brief periods of more rapid change.
Biologists have considered two different explanations for the rate of evolution, as illustrated in these diagrams. Gradualism involves a slow, steady change in a particular line of descent. Punctuated equilibrium involves stable periods interrupted by rapid changes involving many different lines of descent.
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23. Developmental Genes & Body Plans
Hox Genes: master genes
Homologous Hox Genes Establish Body Plans In Animals As Different As Humans & Insects
Control Number of Wings, Legs, Body Segments, etc.

24. Developmental Genes & Body Plans
Small Changes In Timing of Genetic Control During Embryonic Development, Make Big Changes In The Resulting Organism

25. 17–4 Patterns of Evolution
A. Mass Extinctions- dinosaurs
B. Adaptive Radiation- species evolved into several different forms that live in different ways
C. Convergent Evolution- unrelated organisms come to resemble one another

26. 17–4 Patterns of Evolution
D. Coevolution- process by which two species evolve in response to changes in each other over time
E. Punctuated Equilibrium- patterns of long, stable periods interrupted by brief periods of more rapid change
Gradualism- patterns of slow, gradual change