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NATURAL SELECTION

NATURAL SELECTION. The ideas that shaped Darwin…. Hutton, Lyell, Lamarck and Malthus. Evidence of a Changing Earth. Scientists Hutton and Lyell studied the organisms found in fossils. The older the fossil, the deeper it was buried

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NATURAL SELECTION

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  1. NATURAL SELECTION

  2. The ideas that shaped Darwin… Hutton, Lyell, Lamarck and Malthus

  3. Evidence of a Changing Earth • Scientists Hutton and Lyell studied the organisms found in fossils. • The older the fossil, the deeper it was buried • Changes in the appearance of the organisms could be seen between layers.

  4. Lamarck’s Evolution Hypothesis • In 1809, Lamarck proposed that an animal’s behavior could change the traits passed down to their babies. • He thought, the more you use it, the more it grows. • He did not know about how genes were passed down.

  5. Malthus’ Population Growth • Population growth is limited by the resources available, such as food and living space. • Once the food or the space starts to run out, then the growth rate will have to slow and then stop.

  6. Darwin’s Work

  7. Inherited Variation • Slight mutations in the genetic code happen • Before Darwin, scientists did not think this was important • Darwin claimed that differences matter and can change the direction of a species

  8. Artificial Selection • Nature provides genetic variation • Humans often select for traits that they find most useful. • Example: We like larger, sweeter tomatoes, so we will selectively breed plants for those traits.

  9. Struggle for Existence • Species have to compete for the best food, living space and mates • This drives the selection process

  10. Survival of the Fittest • Organisms with the best adaptations for the environment will survive. • These adaptations are passed down through the genes from parents to babies. • The others will die off. • Darwin called this, “Natural Selection.”

  11. Evidence for Evolution

  12. The Fossil Record • There are many marine life fossils • They saw many species with shells • The shells got increasingly complex, suggesting evolution took place over time

  13. Homologous Body Structures • Same bones, but different uses • Mammal Examples: • Human Arm w/Hand • Horse Leg w/Hoof • Whale Flipper • Bat Wing

  14. Similarities in Embryos

  15. Types of Selection

  16. Directional Selection • Individuals at one end of the curve are better fitted for the situation, so all shift.

  17. Stabilizing Selection • Individuals in the middle of the curve are best fitted for the situation, so ends drop off.

  18. Disruptive Selection • Individuals at either extreme are better fitted for the situation than an average individual.

  19. Genetic Drift • Certain traits many become more common in a population by chance, rather than by a type of purposeful selection.

  20. Hardy-Weinberg Principle • There are 5 was to have a population at equilibrium (where there is no change) • Random Mating • Large Population • No Movement into or out of the population • No Mutations • No Natural Selection

  21. The Process of Speciation

  22. Reproductive Isolation • Only individuals of the same species can mate ?

  23. Behavioral Isolation • Individuals could breed, but their styles of behavior or courtship make them not attracted to one another.

  24. Geographic Isolation • Individuals could mate, but they are separated by distance

  25. Temporal Isolation • Individuals could mate, but they naturally mate at different time periods.

  26. Process for the Evolution of Darwin’s Finches

  27. How Speciation Occurred… • Founders Arrive: A few finches flew to one of the islands from South America and mated • Separation of Populations: Some of these finches flew to a neighboring island • Changes in Gene Pool: Adapting to new island • Reproductive Isolation: Now the finches on the different islands are too different to mate! • Ecological Competition: need food & nests • Continued Evolution: natural selection continues

  28. Patterns of Macro-Evolution

  29. Extinction • Species that cannot adapt to their environment will die out.

  30. Adaptive Radiation • Many species evolve from a single species

  31. Convergent Evolution • Some species look similar • However, they are not closely related genetically • Similar environmental factors cause the species to evolve in similar ways. Beaver Coypu

  32. Coevolution • The process when two species evolve in response to changes in each other over time • Example: Flowers change to keep attracting the bees needed to pollinate them.

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