Evidence for Evolution

• The Fossil Record

  • Fossils are a record of the history of life on Earth
  • Some fossils look like organisms that are alive, with slight differences
  • Some fossils don't look like any organisms that are alive
• Similarities in Embryos

  • the Embryos of many different animals species with backbones look very similar
  • Similarities in structure and development provides evidence of a common ancestor
• Cellular Evidence: The Endosymbiotic Theory

  • Eukaryotic cells: complex cells with mitochondria & chloroplasts
  • The endosymbiotic Theory states that eukaryotic cells arose from symbiotic relationship with prokaryotic organisms
  • It's theorized that they evolved when a simple eukaryote engulfed prokaryotes and they survived after being eaten and lived symbiotically inside the larger cell
  • Over time, they became the mitochondrion and chloroplast
  • Mitochondria and chloroplasts have properties of bacteria like DNA and ribosomes
  • The Endosymbiotic Theory was recognized in the 1960's by Lynn Margulis
• Geographic Distribution of Organisms: The Galapagos Islands

  • all the different species of finches on the Galapagos Islands could have evolved from a common mainland ancestor once they relocated on different Galapagos Islands
• Homologous Structures and Vestigial Organs

  • Structures that have different mature forms and functions but develop from the same embryonic tissues are called homologous structures
  • Shows a common ancestor
  • Similarities and differences in homologous structures help biologists group animals according to how recently they last shared a common ancestor
  • Vestigial organs are reduced in size that they are just vestiges, or traces of homologous organs in other species
  • Ex: Whales have left over pelvic bones but don't walk!
• Similar DNA and Proteins

  • Organisms that share more recent common ancestors and are closely related in evolutionary history have DNA sequences and Proteins that are more similar.