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Forces that Drive Evolution

Forces that Drive Evolution. Mutation, Selection, Genetic Drift and Gene Flow. Forces that Drive Evolution Objectives:. Understand that evolution is change over time Understand that there are four main forces that “drive” evolution: Mutation

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Forces that Drive Evolution

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  1. Forces that Drive Evolution Mutation, Selection, Genetic Drift and Gene Flow

  2. Forces that Drive Evolution Objectives: • Understand that evolution is change over time • Understand that there are four main forces that “drive” evolution: • Mutation • Natural selection (and other forms of selection) • Genetic drift • Gene flow • Be able to explain each, and how they work

  3. Evolution – A Definition (or three) • Variation of inherited traits within a population over time* • Descent with modification • Change over time* *time = multiple generations

  4. Charles Darwin – The Theory of Evolution • English naturalist (1809-1882) • Traveled the world (including the Galapagos Islands) on the Beagle, making observations, collecting samples, formulating the Theory of Evolution • Published On The Origin of Species over 20 years after his voyage on the Beagle. • It was meant to explain the diversity of life, not the origin.

  5. Why is Darwin so important? • Provided evidence for descent with modification (i.e., change over time, i.e., evolution) • Proposed a natural mechanism for how species evolve (i.e., natural selection)

  6. Evolution helps explain… • The diversity of life on Earth • How new species are formed • Why organisms look and behave the way they do • How organisms respond to changes in their environment • Why some groups of organisms are more diverse than others

  7. Darwin’s Evidence for Evolution • Animal distributions - Closely related organisms found in geographical proximity

  8. Darwin’s Evidence for Evolution • Fossils - Sequential emergence of different groups and transitional forms

  9. Darwin’s Evidence for Evolution • Homology - The spatial and developmental equivalence of traits that may look quite different

  10. Darwin’s Evidence for Evolution • Vestigial features - Speaks to imperfect “design”. Best explained by the persistence of shared traits.

  11. Yeah, but what actually causes evolution, anyway?!?

  12. Forces That Drive Evolution • Mutation • Selection • Genetic Drift • Gene Flow

  13. Mutations Affect Genes, Proteins, Traits U.S. Department of Energy Human Genome Program, http://www.ornl.gov/hgmis

  14. Mutations Affect Genes, Proteins, Traits

  15. Mutation Leads to Variation, Diversity…

  16. Natural Selection From “Understanding Evolution”

  17. How Does Evolution Work? Through a process called “Natural Selection” Individuals in a population that are better adapted for a particular environment, survive and pass their traits on to their offspring H.E. Hoekstra

  18. Natural Selection The Pocket Mouse Example

  19. Natural Selection The Pocket Mouse Example What can we conclude? The mice that blend in have an advantage over those that stand out. They survive and reproduce.

  20. What other types of selection are there besides Natural Selection?

  21. Sexual Selection (Sexual Dimorphism)

  22. What is sexual selection? Competition for mates

  23. What is sexual selection? Competition for mates Armaments (intrasexual selection) Ornaments (intersexual selection)

  24. Sexual Selection The Birds of Paradise Example

  25. Sexual Selection The Birds of Paradise Example What can we conclude? The birds that stand out have an advantage over those that blend in. They have more chances to reproduce.

  26. Natural Selection suggests it is better to blend in… Sexual Selection suggests it is better to stand out… Can you come up with an hypothesis (or theories) to explain this?!?

  27. Are there any other types of selection?

  28. Artificial Selection

  29. Artificial Selection Moruga Scorpion Pepper

  30. Genetic Drift Genetic Drift – Change in gene pool due to chance From “Understanding Evolution”

  31. Genetic Drift Genetic Drift – Change in gene pool due to chance The “jar of marbles” example From “Understanding Evolution”

  32. Genetic Drift Genetic Drift – Change in gene pool due to chance The “jar of marbles” example From “Understanding Evolution”

  33. Genetic Drift- Bottlenecks A population’s size is reduced for at least one generation

  34. Genetic Drift– Founder Effect Establishment of a new population (colony) by just a few individuals

  35. Question:Why are genetic drift, bottlenecks and founder effects important in evolution? Answer:They result in reduced genetic variation. And why does this matter???

  36. Because reduced genetic variation can mean decreased ability to adapt to new selective pressures, such as… or… Climate change Evolving pathogens

  37. Gene Flow Change in gene pool due to migration

  38. Natural Selection Activities • Survival of the Skittleshttp://salsa.nescent.org/activity-2-survival-of-the-skittles/) • “Clip Birds” (http://www.ucmp.berkeley.edu/education/lessons/clipbirds/) • Teddy Graham Evolution • Several online simulations… • EvoDots (http://faculty.washington.edu/herronjc/SoftwareFolder/EvoDots.html) • AIPOTU (http://aipotu.umb.edu/) • PhET NS Simulator (http://phet.colorado.edu/en/simulation/natural-selection) • McGraw-Hill Natural Selection Simulator http://www.mhhe.com/biosci/genbio/virtual_labs/BL_12/BL_12.html • ENSI Evolution Lessons (http://www.indiana.edu/~ensiweb/evol.fs.html)

  39. Any Questions?!?

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