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Chapter 19

Chapter 19. Section 19-2: Patterns and Processes of Evolution. Speciation and Extinction. Fossil record shows that 99% of species that have ever existed have gone extinct

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Chapter 19

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  1. Chapter 19 Section 19-2: Patterns and Processes of Evolution

  2. Speciation and Extinction • Fossil record shows that 99% of species that have ever existed have gone extinct • Macroevolutionary patterns are grand transformations in anatomy, phylogeny, ecology, and behavior, usually taking place in clades not individual species • Includes speciation, extinction, emergence of larger clades

  3. Macroevolution and Cladistics • Paleontologists study fossils, put them into clades based on derived characters • Learn history of life

  4. Adaptation and Extinction • As environments have changed, species either adapt or go extinct • Rates at which species appear, adapt, and become extinct vary • Emergence of new species in a clade impacts macroevolution of the clade • If “birth” of species is equal to “death” of species , clade will survive • Sometimes the more varied the clade more likely it will continue

  5. Patterns of Extinction • Background extinction – species goes extinct because of slow, steady natural selection • Mass extinction – many species go extinct over a short period of time • Entire ecosystems/food webs collapse • Change is too quick • Caused by asteroids, volcanoes, changing sea levels • Severely decreases biodiversity – some may survive then flourish • Eventually recover in 5 to 10 million years

  6. Rate of Evolution • Gradualism – slow, steady change in a line of descent

  7. Rate of Evolution • Punctuated equilibrium – equilibrium interrupted by brief periods of rapid change • New species created

  8. Rapid Evolution After Equilibrium • Small population becomes isolated from main population, and can evolve faster • Small group of organisms migrates (finches) • Organisms survive mass extinction

  9. Adaptive Radiation • Evolutionary process by which a single species or a small group of species evolves over a relatively short time into several different forms that live in different ways • Diversification of a clade

  10. Adaptive Radiation • Migration • Mass extinction • New adaptation • Examples in fossil record after extinction of dinosaurs • Finches

  11. Convergent Evolution • Process of evolution that produces similar structures and characteristics in distantly-related organisms • Similar environments and selection pressures • Body parts with similar functions, may look similar (analogous)

  12. Coevolution • Two species evolving in response to changes in each other over time • Flowers and pollinators • Plants and herbivorous insects

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