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Chapter 17.2 Genetic Change 17.3 Speciation

Chapter 17.2 Genetic Change 17.3 Speciation. Definitions. Gene pool : All alleles of the population’s genes. Allelic frequency : % of a specific allele in the gene pool. Example: See Figure 5 Page 404 Snapdragon Flower

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Chapter 17.2 Genetic Change 17.3 Speciation

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  1. Chapter 17.2 Genetic Change 17.3 Speciation

  2. Definitions • Gene pool: All alleles of the population’s genes. • Allelic frequency: % of a specific allele in the gene pool. Example: See Figure 5 Page 404 Snapdragon Flower • Genetic Equilibrium: This exists when the frequency of alleles remains the same over generations. The population is not evolving.

  3. 5 Different “Forces” That Can Cause Evolution 1. Gene Flow 2. Non-random Mating (Sexual Selection) 3. Mutation 4. Genetic Drift 5. Natural Selection

  4. Gene Flow • Gene Flow occurs when genes are added or removed from a population • Example: Migration • These caribou are migrating from one place to another. If they meet other groups of caribou and interbreed, gene flow may occur.

  5. Non-random Mating (Sexual Selection) Females sometimes select mates based on the male’s size, color, ability to gather food, or other characteristics. Example: The vibrant red stripe of the blue muzzle of this male (right) mandrill baboon does not appear in females (left).

  6. Non-random Mating (Sexual Selection)

  7. Mutation When the DNA code of organisms changes randomly (Creates new alleles)

  8. Genetic Drift Chance events, such as fires, floods or storms, can cause rare alleles to be lost. This occurs more often in populations that are small in size. Genotypes can change as a result. Example: A wildflower population ... consisted of only 25 plants. Assume that 16 of the plants have the genotype AA for flower color, 8 are Aa, and only 1 is aa. Now imagine that three of the plants are accidently destroyed by a rock slide before they have a chance to reproduce. By chance, all three plants lost from the population could be AA individuals.

  9. Natural Selection • Can remove individuals with certain traits from a population. • The alleles for those traits may become less common in the population over time. • Example: Horse Evolution

  10. Evolutionary Fitness How long an individual can survive and how many offspring they can produce to pass genes to future generations??? This is their “Evolutionary Fitness”.

  11. Who has the Higher Evolutionary Fitness?

  12. 3 Types of Natural Selection Directional Selection– favors one of the extreme variations of a trait Stabilizing Selection– favors average individuals Disruptive Selection– favors individuals with both extremes of a trait (eliminates intermediate phenotypes)

  13. 17.3 Biological Species Concept When Males and Females of the same species reproduce and their offspring are fertile and can pass on their genes they are considered a species.

  14. Sterile Hybrids Mule Liger

  15. Speciation Speciation occurs when members of similar populations no longer interbreed to produce fertile offspring within their natural environment. Example: Squirrels that live in the Grand Canyon

  16. Species definition does not always apply Some organisms reproduce Asexually: Bacteria and Archaebacteria

  17. Types of Speciation a. Geographic Barrier- A physical barrier that prevents interbreeding (Mountain, River, Island) b. Change in Mating Behavior and Timing c. Change in Niche (Food source)

  18. a. Geographic Isolation

  19. Geographic Isolation Examples of how this can happen: A pond dries up somewhat to make two ponds, A river becomes re-routed so that it cuts through a field, Two land masses drift apart over time, A few seeds stuck on a bird's feather fall by chance on a new island A new road goes up between 2 fields, A flood washes a small population of lizards to an island....etc

  20. Geographic Isolation

  21. Change in b. Mating Behavior and Timing • Many species that sexually reproduce have specific behaviors for attracting mates, such as a pattern of sounds or actions. • Example: The pickerel frog and the leopard frog are closely related species. Differences in mating times may have caused their reproductive isolation.

  22. Timing • Similar species have different breeding seasons Eastern Spotted Western Spotted Skunk Skunk

  23. Bizarre Mating Rituals The male anglerfish latches onto the female like a parasite, living off her food and fertilizing her when she's ready to lay eggs. The male octopus's penis breaks off during mating, but don't worry, it will grow back the following season.

  24. Bizarre Mating Rituals Emperor Penguins travel as far as 70 miles on foot to reach the breeding site. They look for their mates by making a bugling call. Once they find one another, they stand breast to breast, repeatedly bow to each other and sing.

  25. c. Change in Niche • Divergence can happen when populations use different niches • Example: The members of a particular population of insects live and feed high up in the trunks of trees. As time passes, some members of the population begin to feed on different parts of the trees. Eventually the 2 groups diverge and no longer interbreed.

  26. Artificial Speciation Diane Dodd’s fruit fly lab, 1989

  27. What is Extinction? Wooly Mammoth T Rex Dodo Bird Tasmanian Tiger When a species fails to produce any offspring 99% of all species that have ever lived on Earth are now extinct

  28. The End

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