BIOL 1108 FINAL

• Charles Darwin


  Naturalist who wrote the Origin of Species
• Origin of Species


  • Proposed that organisms have descended with modification from common ancestors
  • The main cause of descent with modification is natural selection acting on heritable variation
  • Traveled to Galapagos
• 3 Pillars to support Darwin's ideas

  • Fossils
  • Structural homology
  • Artificial selection
• Darwin's ideas challenged traditional views of a young Earth inhabited by unchanging species
• Greeks believed the world was eternal and did not have a fixed age (spontaneous generation)
• Middle ages believed in "The Great Chain of Being" – Ladder
• Natural selection


  A process which individuals that have certain inherited traits tend to survive and reproduce at higher rates because of those traits
• Artificial selection


  Demonstrated that some traits can be passed on from parent to offspring, and wanted characteristics can be established if they are selected for
• Fitness


  An organism's ability to survive and reproduce in a particular environment. The contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals
• Adaptation


  Inherited characteristic of an organism that enhances its survival and reproduction in a specific environment
• Evidence for evolution


  • Direct observation
  • Homologous structures
  • Fossils
  • Biogeography
• Homologous structures


  • Shows common ancestry
  • Can be both genetic and phenotypic
  • Embryonic homologies: similar early development
  • Vestigial organs: that have lost their ancestral function
  • Molecular homologies: similar DNA and amino acid sequences
• Extinct


  Species no longer alive
• Extant

  Surviving species
• Biogeography

  • The study of the distribution of plants and animals
  • Consistent with the hypothesis that life-forms evolved in a particular locale
  • Endemic species: not found anywhere else in the world
• Microevolution

  A change in allele frequencies in a population over generations
• Microevolution

  • Small-scale variation
  • Descendants are in the same taxonomic group
  • Can happen over a short period
• Macroevolution


  Large-scale variation allele variation
• Macroevolution


  • Descendants are in a different taxonomic group
  • Results in speciation
  • Happens over an extended period
• Biological population


  A group organisms of a the same species living in the same geographic area at the same time. Interbreed, producing fertile offspring
• Gene Pool


  All copies of every type of allele at all loci in every individual in a population
• Hardy Weinberg principle


  The state of a population in which frequencies of alleles and genotypes remain constant from generation to generation, provided that only Mendelian segregation and recombination of alleles are at work
• The Chi-Square test for Hardy-Weinberg equilibrium assumes the "null hypothesis" - that is, the observed genotype frequencies are not significantly different from those predicted for a population in equilibrium
• Assumptions of Hardy Weinberg principle

  • No mutations
  • Random mating
  • No natural selection
  • Extremely large population size
  • No gene flow
• Natural selection


  Which individuals that have certain inherited traits tend to survive and reproduce at higher rates because of those traits and become favored in a population and will pass on those genes that aided their success
• Genetic drift


  Random change in allele frequency from one generation to another
• Genetic drift


  • Bottleneck effect: drastic reduction in population size due to sudden environmental change
  • Founder effect: when a few individuals become isolated from larger population
• Gene flow


  Gene movement between populations
• Gene flow


  • Reduces variation between populations
  • Can increase diversity within a population
• Biological species


  Composed of individuals who can interbreed and produce viable, fertile offspring
• Benefits of biological species concept

  • Groups members by their reproductive capability
  • Not subjective
• Limitations of biological species concept

  • We do not know the reproductive isolation of all organisms
  • Not applicate to asexual
  • Mainly focused on the absence of gene flow
  • Hybrids exist
• Morphological species


  A species is categorized by shape and other physical features
• Benefits of morphological species concept

  • Can apply to asexual
  • Useful for when gene flow is unknown
• Limitations of morphological species concept

  • Relies on subjective parameters
• Ecological species


  Defined by the terms of its ecological niche
• Benefits of ecological species concept

  • Can accommodate asexual organisms
  • Can accommodate the rapid changes that occur during disruptive selection
• Limitations of ecological species concept

  • Gene flow is not accounted for
• Phylogenetic species concept


  A group of individuals with unique genetic history
• Benefits of phylogenetic species concept


  • Emphasizes unity in a species
  • Smallest group that share a common ancestor =species
  • Branch in the "tree of life"
  • Includes asexual species