10 27-11

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10 27-11

  1. 1. Lab Intro: Genetic Drift But first….
  2. 2. Evolution Review <ul><li>What is natural selection? </li></ul><ul><li>How does natural selection relate to the struggle to survive? </li></ul><ul><ul><li>What are some environmental factors that create that struggle </li></ul></ul><ul><li>Explain the concept of overproduction of offspring </li></ul><ul><ul><li>How does that relate to the idea of population capacity? </li></ul></ul><ul><li>What is inherited variation? </li></ul><ul><ul><ul><li>Why is it so very important? </li></ul></ul></ul><ul><ul><ul><li>What are some dangers of loosing it? </li></ul></ul></ul><ul><li>How does all of this relate to differential reproductive success? </li></ul>
  3. 3. Biodiversity Review <ul><li>What is biodiversity? </li></ul><ul><li>Explain what “biodiversity = stable ecosystem” really means? </li></ul><ul><ul><li>What constitutes a stable ecosystem? </li></ul></ul><ul><li>How is biodiversity decreased? </li></ul><ul><li>How is biodiversity increased? </li></ul><ul><li>What are some consequences of a loss of biodiversity? </li></ul>
  4. 4. Genetic Variation <ul><li>A loss of genetic variation = a loss of what? </li></ul><ul><li>Why is genetic uniformity so dangerous? </li></ul>
  5. 5. And now.. GENETIC DRIFT!
  6. 6. Genetic Drift is: <ul><li>FLASHCARD ALERT: </li></ul><ul><li>GENETIC DRIFT: Random, non-adaptive change in the gene frequencies (aka genetic variation) of a population </li></ul><ul><ul><li>What do you think they mean by non-adaptive? </li></ul></ul><ul><li>Usually reduces genetic variation </li></ul><ul><ul><li>Which genes get eliminated happens by chance </li></ul></ul><ul><li>Affects smaller populations much more than large populations. </li></ul><ul><li>Two types: Bottleneck Effect & Founders Effect </li></ul>
  7. 7. Example: <ul><li>Population of flowers: Red and White </li></ul><ul><li>Through random chance the elimination of the white flower occurs (I.e it gets trod on) </li></ul><ul><li>This loss in genes to a small population means that certain combinations cannot reproduce </li></ul><ul><li>Over time the small population of flowers will be all red. </li></ul>
  8. 9. Natural Selection vs. Genetic Drift
  9. 11. The Bottleneck Effect <ul><li>FLASHCARD ALERT: BOTTLENECK EFFECT: </li></ul><ul><ul><li>A situation where a large population is drastically reduced in size </li></ul></ul><ul><ul><ul><li>Could be a result of: </li></ul></ul></ul><ul><ul><ul><ul><li>natural disasters </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Invasive species </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Epidemic etc. etc. </li></ul></ul></ul></ul><ul><li>Which does what to the genetic variation of the population? </li></ul>
  10. 13. Example: The California Sea Otter <ul><li>Past 10 years: dying at an alarming rate </li></ul><ul><ul><li>Infected with Toxoplasma Gondii </li></ul></ul><ul><ul><li>Increased pollution </li></ul></ul><ul><ul><li>Loss of habitat </li></ul></ul><ul><li>Almost Extinct </li></ul><ul><ul><li>1990: <100 otters </li></ul></ul><ul><ul><li>1993: 2,200 otters </li></ul></ul><ul><li>Now scientists are again having issues with successful population growth </li></ul><ul><ul><li>Result of the bottleneck effect. </li></ul></ul>
  11. 14. Founder Effect <ul><li>FLASHCARD ALERT: </li></ul><ul><ul><li>FOUNDER EFFECT: colonization of a new habitat by only a few individuals </li></ul></ul><ul><li>Again: reduce of genetic variation </li></ul><ul><li>In the right circumstances it will lead to speciation and eventually evolution of new species </li></ul><ul><ul><li>New environment - new challenges - different adaptations are beneficial - natural selection </li></ul></ul>
  12. 16. Example: The Afrikaner population of Dutch Settlers in Africa <ul><li>Dutch immigrants in 1652 </li></ul><ul><li>One man carried the gene for Huntington’s disease </li></ul><ul><ul><li>Dominant gene </li></ul></ul><ul><li>Now there is an alarmingly high frequency of the disease in that region of Africa </li></ul>

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