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Lecture #30: POPULATION & EVOLUTION

Learn about populations, gene pools, genetic drift, mutations, and natural selection in evolution. Explore how populations evolve over generations due to various causes. Discover mechanisms like gene flow, mating preferences, and environmental adaptations.

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Lecture #30: POPULATION & EVOLUTION

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  1. Lecture #30: POPULATION & EVOLUTION Ms. Day Honors Biology http://glencoe.mheducation.com/sites/9834092339/student_view0/chapter20/animation_-_mechanisms_of_evolution.html

  2. Population & Evolution • Population: • Group of the same species living in the same place at the same time that can interbred • Species: • a group of populations whose individuals can to interbreed and produce living offspring that can reproduce themselves • Gene pool: • ALL of the genes (alleles) in a population at any one time

  3. “Individuals are selected, but populations evolve.” • Populations = smallest unit of evolution

  4. A change in the gene pool of a population over many generations There are 5 reasons why populations can evolve. Causes of Microevolution

  5. #1: Small Populations How can this happen? Genetic Drift • Genetic drift: changes in the gene pool of a SMALL population due to chance (reduces genetic variability) • http://highered.mcgraw-hill.com/sites/0072835125/student_view0/animations.html# • 2nd to last video

  6. Genetic Drift Example #1 Bottleneck Effect • Caused by a natural disaster • Leaves surviving population with less genetic variation than original population

  7. Ex: NORTHERN ELEPHANT SEAL

  8. Genetic Drift Example #2 Founder Effect: • a result of colonization by a few individuals from a parent population finding a new place to live http://nortonbooks.com/college/biology/animations/ch16a01.htm http://bcs.whfreeman.com/thelifewire/content/chp24/2402002.html

  9. Cause #2: Migration of Alleles Gene Flow: • alleles/genes migrate (move) between populations (reduces differences between populations)

  10. Cause #3: Mutations Mutations: • a change in an organism’s DNA • original source of genetic variation (raw material for natural selection) • Mutations can immediately lead to NEW variation in a population

  11. Cause #4: “Picky” Mating Nonrandom mating • “picky” mating • Unequal chances of each egg getting fertilized • Assortative mating - choosing individuals more like self

  12. results in sexual dimorphism differences between the sexes in secondary sexual characteristics Sexual Selection

  13. Cause #5: Natural Selection • Different survival and reproductive success due to variation https://highered.mheducation.com/sites/9834092339/student_view0/chapter20/animation_-_mechanisms_of_evolution.html

  14. LIGHT/DARK ROCK HABITAT DARK ROCK HABITAT MEDIUM COLOR ROCK HABITAT

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