Evidence for the Theory of Evolution

Evidence for the Theory of Evolution

1. The Fossil Record

   • Showed that
     • Species existed in the past which were different from those existing today
     • Old species have died out
     • New species have arisen
     • The new species that have appeared are often similar to older ones found in the same place
   • Problems
     • Incomplete fossil evidence
     • Fossils form only under certain conditions, so most organisms decay without preservation before they die
     • Soft bodied organisms rarely become fossilised
     • Most fossils are never found
     • Fossils can be destroyed through earthquakes or other environmental problems

2. Biological Molecules

   • Certain molecules can be found throughout the living world, suggesting that all organisms had a common ancestor
   • Organisms which share a more recent common ancestor are more likely to have similar or identical biological molecules
   • Organisms which diverged along separate evolutionary paths longer ago are more likely to differ more
   • Molecules, such as DNA, cytochrome c (respiration), DNA polymerase (replication) and RNA polymerase (proteins) are examples of universal molecules being studied