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Warm Up 2/27

Warm Up 2/27. What is allele frequency ? What are the four ways evolution occurs?. Evolution Island. Finish the lab now!!. After the Lab. Staple all Teammates’ papers together. I will grade 1 of them…. You don’t know whose it is. Quick Review…. EVOLUTION.

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Warm Up 2/27

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  1. Warm Up 2/27 • What is allele frequency? • What are the four ways evolution occurs?

  2. Evolution Island • Finish the lab now!!

  3. After the Lab • Staple all Teammates’ papers together. • I will grade 1 of them…. You don’t know whose it is.

  4. Quick Review… EVOLUTION • Change in allele frequency in a population is called • Change in allele frequency due to random/chance is called (remember the coywolves) • A change in the DNA sequence that offers an advantage and results in that change being passed on to other generations is evolution by Mutation • Change in allele frequency in a population due to MIGRATION is: Gene Flow • Change in allele frequency due to selection pressures in their environment is called: Natural Selection Genetic Drift

  5. 3 Different Types of Natural Selection • Disruptive • Directional • Stabilizing

  6. Disruptive Selection • Disruptive selection– FAVORS EXTREMES • It is a type of natural selection that selects against the average individual in a population. • Disruptive selection is the rarest of the three types of natural selection.

  7. Disruptive Selection • Remember, it favors EXTREMES. London Peppered Moth Industrial areas – black moths. Rural areas – light colored moths. Very few medium colored moths.

  8. Stabilizing Selection • Stabilizing selection – FAVORS AVERAGE • It is a type of natural selection that favors the average individuals in a population. • This process selects against the extreme phenotypes • Diversity in a population is decreased due to stabilizing selection

  9. Stabilizing Selection - Example • Stabilizing selection works mostly on traits that are polygenic. • Since stabilizing selection favors the middle of the road, a blend of the genes is often what is seen. • Many human characteristics are a result of stabilizing selection. Human birth weight is not only a polygenic trait, but it is also controlled by environmental factors. Infants with average birth weight are more likely to survive than a baby that is too small or too large.

  10. Directional Selection • Directional Selection – FAVORS *ONE* EXTREME • Think – this drives selection in one DIRECTION over the other • This phenomena is usually seen in environments that have changed over time. Changes in weather, climate, or food availability lead to directional selection.

  11. Directional Selection - Example The Texas Longhorn is an example of the effects of directional selection.  The long horns were advantageous for defending young calves from predators - so horn length increased in feral herds in the American Southwest between the early 1500s-1860's.  The trend is now maintained through artificial selection by ranchers.  Do you think the horn length would change if the now predator-free cattle were not being selected for artificially?

  12. So when you think of DIRECTIONAL Selection… • Think of…

  13. Moon Bounce Choose one person to be the astronaut. The other teammates hold each elbow and waist of the astronaut. Count 3-2-1, the astronaut jumps and the teammates boost the astronaut at the top of their jump.

  14. Types of Natural Selection • http://education-portal.com/academy/lesson/types-of-natural-selection.html

  15. Scenario 1 • Tongue length in anteaters in polygenetic and therefore tongues come in a range of lengths. Give (1) example of how directional selection might be acting upon this trait, with a graph and pictorial representation.

  16. If it was particularly hot one summer and ants were making their hills farther below the surface, anteaters with shorter tongues wouldn’t be able to find food.

  17. Practice Scenarios • You will receive a scenario – work it in your spiral. • When everyone at your table is done, rotate the scenarios. • Once you have completed all 4, compare with your team.

  18. Teams for your scenarios….

  19. Teams for your scenarios

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