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Section 19-2: Patterns and Processes of Evolution 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 Paleontologists study fossils, put them into clades based on derived characters Learn history of life 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 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 Gradualism – slow, steady change in a line of descent Punctuated equilibrium – equilibrium interrupted by brief periods of rapid change New species created Small population becomes isolated from main population, and can evolve faster Small group of organisms migrates (finches) Organisms survive mass extinction 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 Migration Mass extinction New adaptation Examples in fossil record after extinction of dinosaurs Finches Process of evolution that produces similar structures and characteristics in distantlyrelated organisms Similar environments and selection pressures Body parts with similar functions, may look similar (analogous) Two species evolving in response to changes in each other over time Flowers and pollinators Plants and herbivorous insects
