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EVOLUTION of POPULATIONS

EVOLUTION of POPULATIONS. B-SC: Students will demonstrate an understanding of the history of life on Earth. . defintions. gene pool : combined genetic information of all members of a particular population

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EVOLUTION of POPULATIONS

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  1. EVOLUTION of POPULATIONS B-SC: Students will demonstrate an understanding of the history of life on Earth.

  2. defintions • gene pool: combined genetic information of all members of a particular population • relative frequency: # of times an allele occurs in a gene pool compared with the # of times other alleles occur

  3. In genetic terms, evolution is any change in the relative frequency of alleles in a population

  4. Sources of Genetic Variation • 2 main sources due to sexual reproduction (homologous chromosome independently assort in meiosis)

  5. Sources of Genetic Variation • MUTATIONS +/- changes phenotype +/- changes fitness

  6. 2. Gene Shuffling 2. Gene Shuffling • Cause of most heritable differences • Humans have 8.4 million different combinations of genes

  7. Single Gene Traits • When a single gene controls a phenotype • There are only 2 alleles: dominant & recessive

  8. Natural selection on single-gene traits can lead to changes in allele frequencies which leads to evolution

  9. Polygenic Traits • Controlled by 2 or more genes • Each gene has 2 or more alleles

  10. Natural Selection on Polygenic Traits • 3 different ways natural selection can affect phenotypes: • DIRECTIONAL SELECTION • STABILIZING SELECTION • DISRUPTIVE SELECTION

  11. DIRECTIONAL SELECTION • When individuals at either end of the bell-shaped curve have an advantage the curve moves in direction of advantage

  12. Stabilizing Selection • When individuals near the mean of the graph have advantage (higher fitness) the bell shape becomes taller

  13. Disruptive Selection • When individuals at both extremes have advantage (or middle has decreasing fitness)the middle decreases

  14. Genetic Drift • seen in small populations • may see a particular allele producing more offspring than would happen by chance • over time a series of chance occurrences can make an uncommon allele common

  15. Founder Effect • when small sampling of large population colonizes new habitat & allele frequencies not representative of original population

  16. Hardy-Weinberg Principle • states that allele frequencies in a population will remain constant unless 1 or more factors cause those frequencies to change • when allele frequencies remain constant population is said to be in genetic equilibrium

  17. 5 conditions necessary to maintain genetic equilibrium • Random Mating • Large Population • No Immigration or Emigration • No Mutations • No Natural Selection (all genotypes have same chance of survival)

  18. Hardy-Weinberg Equation

  19. CLASSIFICATION • Classification systems used to name organisms & to group them in a logical manner. • Linnaeus (Swedish botanist ) developed binomial nomenclature: 2 part name for every species (Genus species) • Man: Homo sapiens

  20. Evolutionary Classification TAXONOMY PHYLOGENY • discipline of classifying organisms & assigning each organism a universally accepted name • the study of evolutionary relationships among organisms

  21. Taxonomy Phyogeny

  22. Cladograms • diagram that shows evolutionary relationships among a group of organisms • an evolutionary tree of life

  23. Quick Lab page 453 Hand in for grading

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