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Evolution Change in life on Earth Evolution • Phylogeny : the evolutionary history of a group of organisms. • Often drawn as a tree Jean Baptiste Lamarck • Early contributor to the theory of evolution. • His ideas are summarized as “use and disuse”. Charles Darwin • English naturalist • Traveled the world for 5 years on the HMS Beagle • Darwin first produced evidence of evolution of living things from a common ancestor Charles Darwin • Darwin identified natural selection as the process for evolution. • Natural selection : mechanism for change in populations. Natural Selection • Natural selection proceeds in steps • 1. In nature, organisms produce more offspring than can survive. Natural Selection • 2. Individuals have variations. • This may be color, size, or speed Natural Selection • 3. Individuals with certain useful characteristics (variation) survive in a struggle for existence. Natural Selection • 4. Over time, the more successful variations are “selected” and the species will gradually change. Natural Selection • This gradual change in characteristics changes the population’s gene pool. • Gene pool : all available genes for a population Evidence of Evolution • Fossils provide a record of early life. • Fossils of a species can show change over time. Evidence of Evolution • Homologous structures: structures with the same evolutionary origin. • Can be the same in arrangement, function or both. Evidence of Evolution • Embryology : the study of the developing embryo. • The shared features of the young embryos suggest evolution from a common ancestor. Evidence of Evolution • Vestigial structures : a structure in a present day organism that no longer serves its original purpose. • Probably useful to its ancestor Evidence of Evolution • Biochemical : nearly all organisms share DNA, ATP and many enzymes. • The code for amino acids is the same in organisms. • The more similar the DNA between 2 organisms, the more closely related Results of Natural Selection • Speciation : new species is formed when similar populations no longer interbreed. • Species: group of organisms that can breed and reproduce • Some obstacle may separate populations. Results of Natural Selection Results of Natural Selection • Diversity : a large variety of organisms. • The more diversity the healthier the ecosystem. Results of Natural Selection • Genetic Drift : Change in gene frequency. (how often you see a trait) • Especially in small populations. • Recessive trait is expressed • Results in a decrease in diversity. Polydactyl Results of Natural Selection • Divergent evolution: related species become less alike. Results of Natural Selection • Convergent evolution: unrelated species become more alike. Results of Natural Selection • Extinction : species may vanish • Can be a mass extinction like dinosaurs. Paths of Evolution • Gradualism : gradual change over time in a species Paths of Evolution • Punctuated equilibrium : relatively quick evolution followed by long periods of equilibrium. • Big change in environment, or new predator