Evidence of Evolution: Fossils

• According to the video, what should you be able to do by the end?

  Discover fossils provide evidence for evolution and how fossils are formed
• What is another learning objective mentioned in the introduction?

  Describe why there are very few fossils for early life-forms
• What is the final learning objective mentioned in the video's introduction?

  Explain how species can become extinct
• What do scientists believe about species alive today?

  They evolved from species in the past
• What provides good evidence for evolution?

  Fossils
• What are fossils?

  The remains of organisms from millions of years ago
• Where are fossils found?

  In rocks
• What are the three ways fossils can form?

  • When parts of organisms have not decayed
  • When parts of the organism are slowly replaced by minerals during the decay process
  • As the preserved traces of organisms
• When can parts of organisms not decay to form fossils?

  When the conditions needed for decay are absent
• What conditions, if absent, can lead to the formation of fossils?

  Not enough oxygen or water
• How can fossils form even if an organism decays?

  If parts are slowly replaced by minerals
• Why are there very few fossils for early life forms?

  Many were soft bodied organisms
• What does it mean if an organism is soft bodied?

  They didn't have a shell or skeleton
• Why do soft bodied organisms rarely form fossils?

  They decay too quickly
• What destroys many fossils that did form?

  Changes to rocks in the Earth's crust
• Why can't scientists be certain how life on Earth began?

  There are very few fossils of the early forms of life
• What do fossils definitely show about species?

  A huge number have become extinct
• What does it mean for a species to be extinct?

  There are no remaining individuals of that species still alive
• What catastrophic event is mentioned that led to extinction?

  An asteroid colliding with the earth
• What are some reasons why species can become extinct?

  • Due to a catastrophic event
  • When the environment changes
  • If a new more successful species evolves and competes with it
• How can changing weather patterns lead to extinction?

  It could kill all of the individuals of a species
• How can a new disease lead to the extinction of a species?

  It could kill all of the individuals of a species
• How can a new predator make a species extinct?

  It could kill all of the individuals of a species
• How does competition lead to the extinction of a species?

  For scarce food or water