17-4 Patterns of Evolution Macroevolution refers to large-scale evolutionary patterns and processes that occur over long periods of time. Copyright Pearson Prentice Hall

Patterns in Evolution Evolution through natural selection is not random. Natural selection can have direction. The effects of natural selection add up over time.

Copyright Pearson Prentice Hall Macroevolution Six important topics in macroevolution are: extinction divergent evolution convergent evolution coevolution punctuated equilibrium adaptive radiation Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Extinction Extinction is the elimination of a species from the earth More than 99% of all species that have ever lived are now extinct. Copyright Pearson Prentice Hall

Background Extinction Background extinctions occur continuously at a very low rate. occur at roughly the same rate as speciation usually affects a few species in a small area caused by local changes in environment

Copyright Pearson Prentice Hall Mass Extinction Mass extinctions are rare but much more intense. destroy many species at global level thought to be caused by catastrophic events at least five mass extinctions in last 600 million years 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

Copyright Pearson Prentice Hall Convergent Evolution Convergent Evolution Different organisms undergo adaptive radiation in different places or at different times but in similar environments. Convergent evolution describes evolution toward similar traits in unrelated species. Results in analogous structures. Copyright Pearson Prentice Hall

Divergent Evolution Divergent evolution describes evolution toward different traits in closely related species. How do convergent and divergent evolution illustrate the directional nature of natural selection? ancestor red fox kit fox

Copyright Pearson Prentice Hall Coevolution Coevolution Sometimes organisms that are closely connected to one another by ecological interactions evolve together. The process by which two species evolve in response to changes in each other over time is called coevolution. Copyright Pearson Prentice Hall

Benefits of Coevolution Coevolution can occur in beneficial relationships. Both species receive benefits from the other as a result of adaptations that each species has evolved over many generations

Evolutionary arms races Both species respond to competitive pressure from the other through adaptations over many generations

Copyright Pearson Prentice Hall Adaptive Radiation Adaptive Radiation Adaptive radiation is the process by which a single species or a small group of species evolves into several different forms that live in different ways and adapt to a wide range of environments. For example, in the adaptive radiation of Darwin's finches, more than a dozen species evolved from a single species. Copyright Pearson Prentice Hall

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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

Gradualism (left) vs Punctuated equilibrium (right) In contrast to the concept that life forms change slowly over time in response to their environment, punctuated equilibrium is a theory that those changes occur in spurts of time periodically. Copyright Pearson Prentice Hall

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Copyright Pearson Prentice Hall 17-4 Darwin's species of finches were very similar but different in beak size and feeding habits. This is an example of convergent evolution. coevolution. adaptive radiation. stabilizing selection. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 17-4 A slow steady change in a particular line of descent is called coevolution. gradualism. punctuated equilibrium. convergent evolution. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 17-4 Master control genes are called hox genes. developmental genes. embryonic genes. regulatory genes. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 17-4 Some evidence suggests that species do not change much over long periods of time and then undergo relatively short periods of rapid speciation. This kind of change is called coevolution. genetic equilibrium. adaptive radiation. punctuated equilibrium. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 17-4 Fossil evidence shows that mass extinctions ended the existence of many species in a short period of time. occurred mainly when the dinosaurs disappeared. require an asteroid strike to occur. caused convergent evolution among animals. Copyright Pearson Prentice Hall

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