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Natural Selection

Natural Selection. 4.1.2 Outline the mechanism of natural selection as a possible driving force for speciation. What is evolution? What does it mean to you? Do you think it happens? Evidence? (for or against). http://evolution.berkeley.edu/evolibrary/article/evo_25. DEFINITIONS:.

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Natural Selection

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  1. Natural Selection 4.1.2 Outline the mechanism of natural selection as a possible driving force for speciation.

  2. What is evolution? What does it mean to you? Do you think it happens? Evidence? (for or against) http://evolution.berkeley.edu/evolibrary/article/evo_25

  3. DEFINITIONS: Evolution are the changes in the gene pool of a population over time. Natural selection process by which individuals that are better suited to their environment survive and reproduce most successfully. Adaptation is an inherited characteristic that increases an organism’s chance of survival.

  4. Darwin and Evolution 1809-1882

  5. Darwin Wolf Pinta Genovesa Marchena Santiago Bartolomé Seymour Råbida Baltra Pin zon Fernandia Santa Cruz Santa Fe Tortuga San Cristobal Española Floreana EQUATOR Galåpagos Islands Isabela Sailed around world 1831-1836

  6. Each island had its own type of tortoises and birds Through his travels he found that species diversity was much greater than previously known.

  7. Marine Iguana Land Iguana

  8. His observations led to the development of the theory of evolution.

  9. What is a Theory? • A well tested idea that explains an observed phenomena • Supported by multiple sources of evidence

  10. Darwin’s Postulates • Populations have natural Variation • Overproduction of offspring. • Struggle for existence. • Unequal survival and reproduction rates. (Those with traits more likely to help them survive will pass traits to their offspring)

  11. What is a species? • A group of individual organisms that are capable of reproducing and produce fertile offspring. • When organisms can no longer reproduce or do not produce viable offspring then they are no longer the same species.

  12. KONA FINCH extinct KAUAI AKIALAOA AMAKIHI LAYSAN FINCH IIWI AKIAPOLAAU APAPANE MAUI PARROTBILL fruit and seed eaters insect and nectar eaters FOUNDER SPECIES

  13. Based on his observations, Darwin proposed that EVOLUTION occurs by NATURAL SELECTION.

  14. Population of organisms Mutations & Sexual reproduction produces variations among offspring. Overproduction of offspring Limited resources leads to a struggle for survival between offspring. Survivors reproduce more successfully. Population changes over time.

  15. The Genetic Makeup of a Population Can Change • Populations evolve by becoming genetically different • Genetic variations • First step in biological evolution • Occurs through mutations in reproductive cells • Mutations in other cells can happen , but only reproductive cell mutations are passed on • Sometimes a mutation can result in a new genetic trait that gives it a better chance to survive, sometimes not.

  16. Individuals in Populations with Beneficial Genetic Traits Can Leave More Offspring • Natural selection: acts on individuals • Second step in biological evolution • Adaptation may lead to differential reproduction • Genetic resistance in bacteria, cockroaches • When environmental conditions change, populations • Adapt • Migrate • Become extinct

  17. A group of bacteria, including genetically resistant ones, are exposed to an antibiotic Eventually the resistant strain replaces the strain affected by the antibiotic The genetically resistant bacteria start multiplying Most of the normal bacteria die Normal bacterium Resistant bacterium

  18. Evidence Supporting Evolution Fossil Record

  19. Evidence Supporting Evolution Homologous Structures

  20. Evidence Supporting Evolution Vestigial Structures

  21. Evidence Supporting Evolution Embryo Development

  22. Opposing Theory at the TimeLamark: Theory of Acquired Traits • Lamark believed that organisms acquired traits by using their bodies in new ways • These new characteristics were passed to offspring • Why was Lamark’s theory refuted???

  23. Can a fish species willfully grow limbs and fingers if they are needed to crawl out of the water onto dry land?

  24. Origin of Species • Darwin published his book The Origin of Species in 1859 • His findings are still supported today by further evidence and the scientific community.

  25. Activity: • Choose two online natural selection simulations. • Work through the simulation and discuss the strengths and weaknesses of the simulation with regard to modeling natural selection. • Which simulation do you believe does a better job modeling natural selection? Justify your answer. • In your own words, explain how a new species forms. http://phet.colorado.edu/en/simulation/natural-selection (requires shockwave) http://sepuplhs.org/high/sgi/teachers/evolution_act11_sim.html http://biologyinmotion.com/evol/ http://www.techapps.net/interactives/pepperMoths.swf (requires flash) http://www.sciencechannel.com/games-and-interactives/charles-darwin-game.htm

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