Evidence of Evolution

  • Fossils
    • Evidence of an organism that lived long ago
    • The deeper down in the ground a fossil is found, the older it is
    • Fossils can be dated using carbon dating
  • Homologous Structures
    • Similar structures found in different species, but with different purposes
    • Ex: Bones in the flippers of a whale, arms of humans, and wings of a bat
  • Vestigial Structures
    • Structures that organisms have, but do not serve a purpose
    • Ex: Appendix, tailbone
    • Presumed to have been useful in ancestral species

   

  • Analogous Structures
    • Structures used for similar purposes, but they are very different in structure

     

  • Molecular Biology
    • Closely related organisms have very similar DNA and amino acid sequences
    • Many similarities in DNA are seen between closely related species
  • Cladograms
    • Chart used to show the evolutionary relationships among organisms

   

  • Evolution
    • Gradual change in a species over many generations
    • Divergent evolution
    • @@Two closely related species develop different traits to survive in different@@ @@environments@@
    • Convergent evolution
    • ^^Two unrelated species develop similar traits to survive in similar environments^^
  • Jean-Baptiste Lamarck
    • Hypothesized that acquired traits could be passed on to offspring through use and disuse
    • Traits are inheritable
    • Different from Darwin, Lamarck said if a giraffe stretches its neck for leaves, then its neck would become longer and its offspring would inherit the longer neck
    • This is wrong because acquired traits do not change the DNA and cannot be passed down to offspring

     

  • Charles Darwin
    • Went on a five-year voyage to map the coast of South America to investigate organisms and fossils
    • From his observations he developed a theory about evolution called @@natural selection@@
  • Natural Selection
    • 4 principles
    • In a population, more individuals are produced than the environment can support
      • They compete for food and shelter
      • Overpopulation - struggle for survival
    • Members of a population have inheritable variations
      • Variations arise from random, inheritable mutations
    • Some individuals have characteristics that enable them to survive and reproduce better than other individuals
      • Survival of the fittest
    • The ability to survive and reproduce better leads to gradual change in a population over time