Evolution 16

• Charles Darwin


  Father of Evolution
• Descent with modification


  • Every species must have descended by reproduction from preexisting species
  • Species must be able to change over time
• 13 species of finches
• Charles Darwin


  Father of Evolution
• Descent with modification


  • Every species must have descended by reproduction from preexisting species
  • Species must be able to change over time
• Finches


  • 13 species
• Natural selection


  The process by which organisms with genetic variations that are best suited to their environment survive and produce more offspring that will inherit said genes
• "Survival of the fittest"
• Natural selection


  The environment "selects" the best suited organisms, and those are the ones which pass on their genes
• Darwin's reasoning for natural selection

  • Overproduction
  • Gene variation
  • Struggle to survive
  • Differential Reproduction
• Evidence of evolution


  • Fossil records
  • Biogeography
  • Comparative anatomy
  • Embryology
  • Biological molecules
• Fossil record


  • Superposition
  • Relative age
  • Absolute age
• Homologous structure


  Occur in different species, inherited from a structure in the most common ancestor of the species
• Homologous structure


  • Bat's wing and a horse's leg
• Analogous structure


  Closely related functions but do not derive from the same ancestral structure
• Analogous structure


  • Wings of birds, bats, moths
• Vestigial structure


  Serve no function but resemble structures with functional roles in related organisms
• Vestigial structure


  • Human tailbone, vertebrate pelvic bone of whales, human appendix
• Biological Molecules


  • DNA and RNA
  • Amino acid proteins
• Comparing biological molecules to other organisms

  • Similarities and differences can be compared
  • Greater the number of similarities = more similar the organisms
• Phylogeny


  • Phylogenetic tree
  • Trunk represent past species common ancestor to all
  • Branches → separate population or lineage
• Mechanism of evolution


  1. Convergent evolution: Process in which different species evolve similar traits

  2. Divergent evolution: Process in which the descendants of a single ancestor diversify into species that each fit different parts of the environment

  3. Coevolution: When 2 or more species have evolved adaptations to each other
• Convergent evolution


  • Dolphin and shark (fins)
• Divergent evolution


  • Darwin's finches
• Coevolution


  Lion gave the gazelle its speed
• Artificial Selection


  Process occurs when a human breeder chooses individuals that will parent the next generation
• Artificial Selection


  • Plant that yields more grain/stalk
  • Greyhounds that run faster
• How populations evolve


  • Gene drift
  • Mutation
  • Nonrandom genetic mating
  • Gene flow
  • Natural selection
• Mutations are free of a 1.0 in gamete production and random mutation has converted a to A
• Genetic Drift


  Due to chance events, only some individuals leave offspring
• Genetic drift can lead to a bottleneck effect where natural disasters wipe out a majority of a population
• Non-random Mating


  • Assortative mating: preference for similar genotypes or phenotypes
  • Disassortative mating: preference for different genotypes or phenotypes
• Natural Selection


  Selection against light gray beetles that are spotted and eaten by birds more often than dark ones
• Patterns of Natural Selection

  • Directional
  • Stabilizing
  • Disruptive
• Directional Selection


  Selection for one extreme trait, against the other extreme
• Stabilizing Selection


  Selection for moderate traits, against both extremes
• Disruptive Selection


  Selection for both extremes, against moderate traits
• Directional Selection


  • Long wiggly tails look like a snake and scare predators, the longer the tail the more it looks like a snake
• Stabilizing Selection


  • Short tails mess up the rat's balance, long tails drag on the ground, medium tails don't help
• Disruptive Selection


  • Short tails help keep predators from catching you on the ground, long tails are good for balance in the trees