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MECHANISMS FOR EVOLUTION

MECHANISMS FOR EVOLUTION. Honors Biology. REVIEW. Evidence for Evolution and Examples What is Natural Selection? How did Darwin develop theory of Natural Selection?. PATTERNS OF EVOLUTION. Coevolution: 2 or more species evolve in association with one another

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MECHANISMS FOR EVOLUTION

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  1. MECHANISMS FOR EVOLUTION Honors Biology

  2. REVIEW • Evidence for Evolution and Examples • What is Natural Selection? • How did Darwin develop theory of Natural Selection?

  3. PATTERNS OF EVOLUTION • Coevolution: • 2 or more species evolve in association with one another • Predators and Prey • Plants and Pollinators • Bats and Flowers

  4. PATTERNS OF EVOLUTION • Convergent Evolution: • Organisms that look similar but are not related • Analogous features • Similar environments • Sharks and Dolphins

  5. PATTERNS OF EVOLUTION • Divergent Evolution • 2 or more related populations or species become more and more dissimilar • Usually a response to new habitat • Can result in new species • Adaptive radiation • Artificial Breeding • Humans and Chimps

  6. POPULATION GENETICS AND EVOLUTION • What did Darwin know? • Environment is important • Competition for Resources • Natural Selection: Individuals with traits more suitable for a particular environment are more likely to survive AND reproduce • What did Darwin not know? • Where does variation come from

  7. POPULATION GENETICS • We now know that variation comes from genetics; no variation  extinction • Population genetics: study of evolution from genetic point of view

  8. WHAT CAUSES VARIATION • Need to think about variation in GENOTYPE • Mutation: change in DNA/chromosomes • Recombination: during meiosis • Random fusion of gametes

  9. OTHER MECHANISMS FOR EVOLUTION • Things that upset genetic equilibrium • Using Hardy Weinberg you can predict genotypes; Only in hypothetical populations

  10. MUTATION • Change in DNA or chromosomes • Make new alleles for a trait • Many are harmful • Can be neutral (code for same amino acid) • Some are beneficial

  11. MIGRATION/GENE FLOW • Call it gene flow • Populations exchange genes • Increases within group variation • Decreases between group variation • DOESN’T HAVE TO BE MIGRATION

  12. GENETIC DRIFT • Occurs in small populations • Allele frequencies shift as a result of RANDOM events • Coin Toss • Founders Effect; Bottleneck

  13. NONRANDOM MATING • Sexual Selection • Positive assortative mating – mate with someone similar • Negative assortative mating: redheads!

  14. NATURAL SELECTION • Darwin and neoDarwinians believe is the most important way evolution occurs • Types of Selection

  15. STABILIZING SELECTION • Average form are selected for • Lizards: • Predators caught slow small and large visible • Select for medium size

  16. DIRECTIONAL SELECTION • Individuals with an extreme trait are selected for • Anteaters with long tongues

  17. DISRUPTIVE SELECTION • Individuals with either extreme are selected for • Limpet shell color; light and dark on different surfaces

  18. SEXUAL SELECTION • Choosing mates based on traits • Intersexual Selection • Intrasexual Selection • Bird Color

  19. SPECIATION • If enough changes accumulate  new species • Biological concept of species: organisms can mate and produce fertile offspring; not just morphological (what they look like) • Isolating mechanisms  speciation • Geographic isolation • Reproductive isolation

  20. SPECIATION • Rates of speciation • Gradualism: species evolve gradually over time • Punctuated equilibrium: species go through times of fast change and slow or no change

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