Chapter 17 The History of Life Section 17- 4 Patterns of Evolution

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

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

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

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

Copyright Pearson Prentice Hall Extinction Extinction More than 99% of all species that have ever lived are now extinct. Copyright Pearson Prentice Hall 7

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.

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

Copyright Pearson Prentice Hall 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 Copyright Pearson Prentice Hall 11

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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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

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

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

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

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

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

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

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

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. Copyright Pearson Prentice Hall 22

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.

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

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

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