  Fossil record is not complete!  Pretty good “general” information  But there are “missing” gaps  Could be missing only because they haven’t been found yet  Fossils take many factors to form  Radiometric Dating  Use Carbon-14 for ages 50,000 years or less  Half-life is 5730 years The Fossil Record-Issues

  Suppose an organism has 20 grams of 14 C at its time of death. Approximately how much 14 C remains after 11,400 years?  Half-Life=5730 years  1 half-life would take us to 10 grams (5,730 years)  2 half-lifes would take us to 5 grams (11,460 years)  ~5 grams 14 Carbon Question

  Current debate: Does speciation happen gradually or rapidly? Or both?  Gradualism  Punctuated equilibrium  Stasis Rate of Speciation

  Gradual divergence over long spans of time  assume that big changes occur as the accumulation of many small ones  Series of transitional forms between ancestor and current species Gradualism

 Gradualism Graph

  What other process that we’ve previously discussed would fit within the gradualism model for evolutionary change?  What about the fossil record? Can the incomplete fossil record support gradualism for evolution?  Would the evolution of humans be an example of gradualism? Why or why not? (I think that…because…) Questions to consider

 Punctuated Equilibrium  Rate of speciation is not constant  rapid bursts of change  long periods of little or no change  species undergo rapid change when they 1 st bud from parent population  Not well-preserved in the fossil record because of rapid changes  More info see: vosite/evo101/VIIA1bPunctuate d.shtml vosite/evo101/VIIA1bPunctuate d.shtml

 Punctuated Equilibrium Graph

  What are some issues with punctuated equilibrium? Punctuated Equilibrium- Questions

  Situation when evolutionary lineages persist for long periods without change.  common but it has recently taken on a new importance with the punctuated equilibrium debate. Stasis

  Both theories claim that they can explain the gaps in the fossil record. The Gradualism theory states that the fossil record is incomplete and that it is unlikely that all stages of evolution would be preserved let alone found. However there have been a few species that show Gradualism through the fossil record. Humans for example.  Punctuated Equilibrium claims the gaps in the fossil record are not just missing links but the actual process of evolution. They claim that he evolution happens to rapidly to be found in a fossil record. As shown before this has been proven countless times from T rexes to shell fish.  So in the aftermath what theory holds true?  In the present it is still difficult to decide which statement is true concerning the gaps in the fossil record since a limited number of fossils have been collected and recorded. Research is ongoing today and possible in the next few hundred years we may have an answer. But remember these are both just theories and one or both could be proven wrong. So which theory is true?