Fossils

• how are fossils formed?

  • parts of organisms that haven’t decayed due to conditions needed for decay being absent
  • parts of organisms that have been replaced by minerals as they decayed
  • traces of organisms are preserved, covered in sediment and becoming rock
• why are there few traces of early life-forms left behind?

  mostly soft-bodied
• how do fossils act as evidence for evolution?

  scientists can identify the ages of the fossils and use them to show how organisms change over time
• what do branches in evolutionary trees indicate?

  where speciation has occurred