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Mechanisms of Evolution

Mechanisms of Evolution. Evolution. Changes in a population over time . Mechanisms of evolution (8) Mutations Gene flow Genetic drift Natural Selection (survival of the “fittest”) Artificial Selection Recombination Non-Random Mating Isolations (speciation). Mutations.

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Mechanisms of Evolution

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  1. Mechanisms of Evolution

  2. Evolution • Changes in a population over time. • Mechanisms of evolution (8) • Mutations • Gene flow • Genetic drift • Natural Selection (survival of the “fittest”) • Artificial Selection • Recombination • Non-Random Mating • Isolations (speciation)

  3. Mutations • Mutations are random changes in DNA, which if favorable, can be passed down from one generation to the next. • These random mutations play an important role in evolution

  4. Mechanism of Evolution: Mutations Original Population

  5. Mechanism of Evolution: Mutations After Mutation

  6. Mechanism of Evolution: Mutations Many Generations Later

  7. Gene Flow • Genes move with individuals when they move (emigrate or immigrate) into and out of a population…and it changes the gene pool

  8. Genetic Drift • Genetic Drift – the random fluctuation due to chance occurrences alone • It is more significant in smaller populations • It increases the chance of any given allele becoming more or less prevalent when the number of individuals is small • Ex.) Founder Effect and Bottleneck Effect

  9. Natural Selection Section 15.1 Summary – pages 393-403 • Natural selection is the idea that organisms with favorable/beneficial traits survive, reproduce, and pass those traits to the next generation “Survival of the Fittest”. ENVIRONMENTALLY CONTROLLED • Organisms without these variations/traits are less likely to survive and reproduce.

  10. NATURAL SELECTION Section 15.2 Summary– pages 404-413 • There are three different types of natural selection: stabilizing, directional, and disruptive. • Stabilizing selection is a natural selection that favors average individuals in a population. Evolution will not occur Middle sized Siberian Huskies are selected for

  11. NATURAL SELECTION Section 15.2 Summary– pages 404-413 • Directional selection occurs when natural selection favors one of the extreme variations of a trait. • This type of selection can lead to rapid evolution of a population.

  12. NATURAL SELECTION Section 15.2 Summary– pages 404-413 • In disruptive selection, individuals with either extreme of a trait’s variation are selected for. • This results in eventually having no intermediate form of a trait, and leading to two separate species.

  13. Natural Selection • Shifts to middle range • Shifts to 2 extremes • Shifts to 1 extreme

  14. Section 15.1 Summary – pages 393-403 ARTIFICIAL SELECTION • Breeding organisms with specific traits in order to produce offspring with ideal (Intentional breeding for certain traits) A Goldendoodle (Golden retriever/ Poodle)

  15. Recombination (Crossing over) • As we learned in the genetics unit, CROSSING OVER leads to genetic material being shuffled. • This shuffling, along with sexual reproduction, leads to variation within populations. This variation leads to selection, which ultimately leads to evolution.

  16. Non-Random Mating Blue = BB or Bb Red = bb Original Population The red coated birds traits are favored in choosing a mate x Most species do not just mate randomly… there are desired or favorable traits that they look for when choosing a mate (ex..peacocks)

  17. Non-Random Mating Over time, you would see the favored traits more prevalent than the undesired traits. Many Generations Later

  18. Reproductive Isolation Two ways reproductive isolation occur: • Prezygotic mechanisms • Geographic • Temporal • Mechanical • Behavioral • Postzygotic mechanisms • Infertility

  19. SPECIATION Section 15.2 Summary– pages 404-413 • Theevolution of new species, a process called speciation. • This occurs when members of similar populations change so much from each other that they no longer interbreed to produce fertile offspring.

  20. SPECIATION Section 15.2 Summary– pages 404-413 • In nature, physical barriers can break large populations into smaller ones. • Geographic isolationoccurs whenever a physical barrier divides a population and over time they change and become two different species. • Reproductive isolation…

  21. SPECIATIONwithout a physical barrier Section 15.2 Summary– pages 404-413 • Some speciation occurs while the organisms still exist in the same area… • Reproductive Isolation • Behavioral, Temporal, Mechanical

  22. Adapted to cold through heavier fur, short ears, short legs, short nose. White fur matches snow for camouflage. Northern population Arctic Fox Spreads northward and southward and separates Different environmental conditions lead to different selective pressures and evolution into two different species. Early fox population Adapted to heat through lightweight fur and long ears, legs, and nose, which give off more heat. Southern population Gray Fox Speciation

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