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Evidence of evolution
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Evidence of evolution






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Evidence of evolution Evidence of evolution Presentation Transcript

  • The Evidence for Evolution
  • Evidence Supporting Darwin  1) Fossil records  2) Anatomy  3) DNA  4) Embryology
  • 1) Fossils Footprints of dead organisms Tracks Insects trapped in tree sap Impressions of skin Traces of dead organisms.
  • Conditions to create fossils  Must be buried by sediments  Swamps, mud, tar pits, ocean bottoms  Hard stuff most likely to be fossilized.
  • How are Fossils Dated? Scientists determine the age of fossils by measuring the amounts of radioactive decay. Half-life describes how long it takes for one- half of the radioactive atoms in a sample to decay. The rate of radioactive decay is constant Scientists can use the amount of radioactive element remaining in a rock or fossil to determine its age. This technique is
  • 2) Anatomy Transitional Species – Evolutionary transitions/ intermediate forms of the organism.  Whales- – Are descendants of 4 legged land animals that are also ancestors of horses and cows.
  •  35 mya 42 mya 50 mya 60 mya
  • Whales- Vestigial Structures -Remnants of an organisms Hind limbs evolutionary past. became smaller Eventually lost Modern whales have a pelvis but, no rear limbs.
  • Structural Evidence cont. Vestigial Structures: Remnants of an organisms evolutionary past. Structures reduce in size and have no present function.
  • Comparative Anatomy
  • Structural Evidence Comparing the way two organisms are put together. Homologous structures: Modified versions of the same structure. Similar in structure differ in functions.
  • 3) DNA Evidence  Structural, fossils, and developmental evidence still posed many questions.  DNA evidence supports the other three.  If species change over time, their DNA will also change.  Similar organisms = similar DNA  Genes accumulate more alterations in their nucleotide sequence over time.
  • DNA Evidence con’t  Compare: chimp, dog, rattlesnake, human  Protein- look at amino acid sequence.  When comparing a.a. sequences chimps vs. humans 0 a.a. differences – Dog vs human 13 a.a. differences – Rattlesnake vs. human 20 a.a. difference
  • 4) Embryology  Early stages of development are similar between organisms.