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Enjoy your journey!

Enjoy your journey!. LINK: http://dingo.care2.com/cards/flash/5409/galaxy.swf. Today’s Date _______. Evolution of Populations. Chapter 16. Warm-up ?’s. What is a trait? What is an Allele? How many Alleles do MOST traits have?. I. Genes and Variation.

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Enjoy your journey!

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  1. Enjoy your journey! LINK: http://dingo.care2.com/cards/flash/5409/galaxy.swf

  2. Today’s Date _______ Evolution of Populations Chapter 16

  3. Warm-up ?’s • What is a trait? • What is an Allele? • How many Alleles do MOST traits have?

  4. I. Genes and Variation • Relative (allelic) frequency - the percentage of a particular allele (trait) in a gene pool. • Natural Selection- In nature, unequal ability to survive and reproduce • Artificial Selection- Mankind “selects” for desired traits

  5. Camouflage- organisms blend-in with surrounding environment • Mimicry- species copy another to insure their own survival

  6. I. Genes and Variation • gene pool - all the genes that exist within a population

  7. gene flow – movement of alleles into or out of a population

  8. B. Genetic drift - change in allelic frequencies by chance Ex: sudden extinction of a dominant species; small populations most affected

  9. C. Genetic equilibrium - when alleles stay the same from generation to generation • The Hardy Weinberg Principle: Allele frequencies will remain constant under five conditions • Random Mating • Large Population • No movement (immigration or emigration) • No Mutations • No Natural Selection: equal change of survival

  10. Hardy-Weinberg Equation (p + q)2 = 1, which is the same as p2 + 2pq + q2 = 1 • p = frequency of “A” allele and q = frequency of “a” allele • p2 = expected freq. of homozygotes for one allele • 2pq = expected freq. of heterozygotes • q2 = expected freq. of homozygotes for the other allele

  11. II. Natural Selection as Genetic Change A. Natural Selection has 3 affects on phenotype distribution • Directional Selection- Individuals on one end of a curve are “better fitted” than the middle or other end Peccaries naturally choose to consume those cactus plants with the fewest spinesAs a result, at flowering time there are more cacti with higher spine numbers; thus, there are more of their alleles going into pollen, eggs, and seeds for the next generation.

  12. Natural Selection has 3 affects on phenotype distribution • Stabilizing Selection- Individuals near center of a curve are “better fitted” than both ends Peccaries are consuming the low-spine number plants, and the insects are killing the high-spine-number plants. As these gene combinations are removed from the cactus gene pool, there is less and less variety possible in subsequent generations.

  13. Natural Selection has 3 affects on phenotype distribution • Disruptive Selection- Individuals at upper and lower ends are “better fitted” the ones in the middle Years of collecting have left their toll on the roadside cacti. In this environment, it is maladaptive to be good looking and have a reasonable number of spines. Low spine-number plants are not picked because they don't "look right", and high spine-number varieties are left alone because they are too hard to pick. Gradually, the gene pool changes in favor of the two extreme spine number types.

  14. III. Evidence of Evolution • homologous structures - similar structures found in related organisms that are adapted for    different purposes. Ex: human arm and bat wing or whale flipper ---DIVERGENT EVOLUTION---

  15. analogous structures - structures found in unrelated organisms that have a similar function Ex: bird wing and insect wing ---CONVERGENT EVOLUTION---

  16. IV. Process of Speciation Isolating Mechanisms • Reproductive Isolation: Two populations cannot interbred and produce fertile offspring • Behavioral Isolation: Two populations capable of breeding but cannot b/c of courtship rituals speciation - evolution of a new species

  17. C. Geographic Isolation: Two populations are separated by geographic barriers Ex: Rivers, Oceans, Mountains D. Temporal Isolation: Two or more populations reproduce at different times

  18. Class Data • Can you roll your Tongue?

  19. Geographical Isolation???? http://www.pbs.org/wgbh/evolution/library/11/2/e_s_4.html Whale Evolution http://www.pbs.org/wgbh/evolution/library/03/4/l_034_05.html

  20. I. Genes and Variation cont. • Sources of Mutation: • Mutations- change in DNA sequence • Gene Shuffling- random assortment of genes during gamete production • Gene Expression Variation • Single-gene trait- controlled by one gene • Ex: Widow’s Peak • Polygenic trait- controlled by many genes • Skin color, eye color

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