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Evolution

Explore the fascinating evolution of life on Earth through the lens of natural selection, fossils, homologous structures, and more. Understand genetic drift, speciation, and the paths of evolution, from gradualism to punctuated equilibrium.

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Evolution

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  1. Evolution Change in life on Earth

  2. Evolution • Phylogeny : the evolutionary history of a group of organisms. • Often drawn as a tree

  3. 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

  4. Charles Darwin • Darwin identified natural selection as the process for evolution. • Natural selection : mechanism for change in populations.

  5. Natural Selection • Natural selection proceeds in steps • 1. In nature, organisms produce more offspring than can survive. (overproduction)

  6. Natural Selection • 2. Individuals have variations. • This may be color, size, or speed

  7. Natural Selection • 3. Individuals with certain useful characteristics (variation) survive in a struggle for existence.

  8. Natural Selection • 4. Over time, the more successful variations are “selected” and the species will gradually change.

  9. Natural Selection • This gradual change in characteristics changes the population’s gene pool. • Gene pool: all available genes for a population

  10. Evidence of Evolution • Fossils provide a record of early life. • Fossils of a species can show change over time.

  11. Evidence of Evolution • Homologous structures: structures with the same evolutionary origin. • Can be the same in arrangement, function or both.

  12. Evidence of Evolution • Embryology : the study of the developing embryo. • The shared features of the young embryos suggest evolution from a common ancestor.

  13. Evidence of Evolution • Vestigial structures: a structure in a present day organism that no longer serves its original purpose. • Probably useful to its ancestor

  14. Evidence of Evolution • Biochemical : nearly all organisms share DNA, ATP and many enzymes. • The code for aminoacids is the same in organisms. • The more similar the DNA between 2 organisms, the more closely related

  15. 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.

  16. Results of Natural Selection

  17. Results of Natural Selection • Diversity : a large variety of organisms. • The more diversity the healthier the ecosystem.

  18. Results of Natural Selection • Genetic Drift: Change in genefrequency. (how often you see a trait) • Especially in small populations. • Recessive trait is expressed • Results in a decrease in diversity.

  19. Polydactyl

  20. Results of Natural Selection • Divergent evolution: related species become less alike.

  21. Results of Natural Selection • Convergent evolution: unrelated species become more alike.

  22. Results of Natural Selection • Extinction : species may vanish • Can be a mass extinction like dinosaurs.

  23. Paths of Evolution • Gradualism : gradual change over time in a species Which fossils are the oldest?

  24. Paths of Evolution • Punctuated equilibrium: relatively quick evolution followed by long periods of equilibrium. • Big change in environment, or new predator

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