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Chapter 23

Chapter 23. The Evolution of Populations. Key Concepts. 1. Genetic variation makes evolution possible. The Hardy-Weinberg equation can be used to test whether a population is evolving. 3. Natural selection , genetic drift , and gene flow can alter frequencies in a population.

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Chapter 23

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  1. Chapter 23 The Evolution of Populations

  2. Key Concepts 1. Genetic variation makes evolution possible • The Hardy-Weinberg equation can be used to test whether a • population is evolving. 3. Natural selection, genetic drift, and gene flow can alter frequencies in a population. • Natural selection is the ONLY mechanism that consistently causes • ADAPTIVE evolution.

  3. Framework POPULATIONS may be in consists of individuals that show are units that undergo Hardy- Weinberg equilibrium genetic variation Evolution is substrate for change in large population, natural selection allele frequencies no gene flow, equation is no mutations, random mating, estimated by may change due to mechanism of no natural selection p + q=1 (alleles) P2 + 2pq + q2=1 (genotypes) adaptive evolution natural selection, genetic drift, gene flow

  4. True/False Individual organisms evolve. 1. How does natural selection act on individuals? Each individual organism’s trait affects its survival and reproductive success compared with other individuals. 2. What is microevolution? Change in allele frequencies in a population over generations. 3. What are the three main causes of microevolution? 1. Natural selection 2. genetic drift (chance events) 3. gene flow (transfer of alleles between populations)

  5. Genetic variation makes evolution possible Natural selection is the mechanism for evolution. Individuals differ in their inherited traits and selection acts on the differences 4. What are the sources of genetic variation? Mutation and sexual reproduction

  6. 5. What is genetic variation? Differences among individuals in the composition of their genes or other DNA segments. GENOTYPE 6. Phenotype is the product of ____________ and _______________. THE ENVIRONMENT

  7. Nemoria arizonaria Raised on a diet of oak flowers resemble the flowers Raised on a diet of oak leaves resemble twigs EC: Is there a difference in phenotype in the adult moth?

  8. TRUE/FALSE Without genetic variation, evolution cannot occur. TRUE!!!!!! Genetic variation provides the raw material for evolutionary change

  9. 7. Characters that vary in a population may be ____________ or ____________ DISCRETE QUANTITATIVE Discrete characters: either-or basis

  10. single gene locus with different alleles 8. Discrete characteristics are determined by ________________________________

  11. 9. Quantitative characters usually results from the ________________________ __________________________. influence of two or more genes on single phenotype Variation in quantitative characters involve a continuum. Hair color

  12. Eye color

  13. Skin color Guess this genotype. AABBCC

  14. You will NOT need to know AVERAGE HETEROZYGOSITY A way to measure variation within a population

  15. 10. What is geographic variation? Differences in the genetic composition of separate populations. The Kaibab was separated by the Colorado River. The Kaibab squirrel evolved from the Abert squirrel. The source of variation here is the pattern of fused chromosomes.

  16. Variation here is a result of chance events (genetic drift).

  17. Sources of genetic variation Mutation Gene duplication Process that produce new alleles and new genes Sexual reproduction

  18. http://goose.ycp.edu/~kkleiner/ecology/EvolEcologyimages.htm

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