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1. Natural Selection Summarized :

1. Natural Selection Summarized :. Darwin’s theory suggests that in a species: A. There is a tendency towards over-production Variation exists Variations are inherited Individuals survive in their environments with varying degrees of success

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1. Natural Selection Summarized :

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  1. 1. Natural Selection Summarized: Darwin’s theory suggests that in a species: A. There is a tendency towards over-production • Variationexists • Variations are inherited • Individuals survive in their environments with varying degrees of success B. The best adapted survive and pass favorable variations on to next generation • In time, great differences arise, until a new species • Evolves from an old species

  2. Alfred Wallace • Studied the way geography limited or facilitated the extension of species range • How ecology influenced the shaping of adaptations • In 1858, shared with Darwin on the Theory of Evolution by means of Natural Selection

  3. Charles Darwin (1809-1882) • Voyaged around the world 1831-1836 • Wrote On the Origin of Species which reveals his ideas on Evolution by means of Natural Selection

  4. Homologous Structures Analogous structures

  5. Convergent Evolution A kind of evolution wherein organisms evolve structures that have similar (analogous) structures or functions in spite of their evolutionary ancestors being very dissimilar or unrelated. This is due to the demands of their environment.

  6. Adaptive Radiation

  7. Adaptative Radiation

  8. Coevolution: • Mutual evolutionary influence between two species • Typically evolution of two species totally dependent on each other. • Exert selective pressure on the other, so they evolve together. • Extreme example of mutualism.

  9. Biological fitness The contribution an individual makes to the gene pool of the next generation relative to contributions of other individuals Offspring should be fertile

  10. Evolution of Populations

  11. Populations are the units of evolution

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

  13. Biological definition of a species • A group of populations whose members are capable of interbreeding and producing fertile offspring.

  14. 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.

  15. 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.

  16. The Gene Pool

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

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

  19. Polygenic traits are controlled by two or more genes

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

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

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

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

  24. Isolating Mechanisms Behavioral Geographic Temporal The Process of Speciation

  25. Behavioral

  26. Geographical

  27. Temporal

  28. 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.

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

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

  31. Resource partitioning

  32. Competitive Exclusion Principle states that no 2 species can occupy the exact same niche in the exact same habitat at the exact same time?

  33. Biological Magnification

  34. Primary Ecological Succession What would happen if the climax community was burned?

  35. Food Web Showing 5 trophic levels

  36. Starting with primary producer, 10% of energy available will move up to the next trophic level.

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