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Evolution of Populations

Evolution of Populations. Populations are the units of evolution. Population. A group of individuals of the same species living in the same place at the same time. Species. A group of populations whose members are capable of interbreeding and producing fertile offspring.

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Evolution of Populations

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  1. Evolution of Populations

  2. Populations are the units of evolution

  3. Population • A group of individuals of the same species living in the same place at the same time.

  4. Species • A group of populations whose members are capable of interbreeding and producing fertile offspring.

  5. Population genetics An important turning point for evolutionary theory the 1920’s. Developed in the 1920’s A field that combines Darwin’s and Mendel’s ideas by studying how populations change over time.

  6. The Gene Pool • In studying evolution at the population level, geneticists focus on the GP • Total collection of genes in a population at any one time.

  7. The Gene Pool

  8. Sources of Genetic Variation • Mutations • Gene Shuffling • Crossing over • Sexual reproduction

  9. Single Gene Traits • The number of phenotypes produced for a given trait depends on how many genes control the trait

  10. Polygenic traits are controlled by two or more genes

  11. Natural Selection can affect the distributions of phenotypes in 3 ways: • Directional selection • Disruptive selection • Stabilizing selection

  12. Directional Selection • When individuals at one end of the curve have higher fitness than individuals in the middle or at the other end.

  13. Disruptive Selection • When individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle.

  14. Stabilizing Selection • Takes place when individuals near the center of a curve have higher fitness than individuals at either end

  15. The Process of Speciation Isolating Mechanisms Behavioral Geographic Temporal

  16. Behavioral

  17. Geographical Sciurus aberti kaibabenesis Sciurus aberti

  18. Temporal Bufo fowleri Bufo americanus

  19. The Hardy–Weinberg principle states: • Both allele and genotype frequencies in a population remain constant or are in equilibriumfrom generation to generation unless… • Disturbing influences happen such as non-random mating, mutations, selection, limited population size, random genetic drift and gene flow. • Genetic equilibrium is a basic principle of population genetics.

  20. Hardy-Weinbergprinciple is like a Punnett square for populations, instead of individuals.

  21. p2 + 2pq + q2 = 1; p + q = 1 Hardy-Weinberg Principle

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