Evidence for Evolution: Fossils

• What should you be able to do by the end of this video?

  Discover fossils, evidence for evolution, and extinction
• How do fossils provide evidence for evolution?

  They are remains of ancient organisms
• What are fossils?

  Remains of organisms from millions of years ago
• What are the three ways fossils can form?

  Decayed parts, mineral replacement, preserved traces
• How can fossils form when parts of organisms have not decayed?

  Conditions for decay are absent
• What conditions can prevent decay to form fossils?

  Cold temperatures, low oxygen, low water
• How can fossils form if an organism decays?

  Parts replaced by minerals during decay
• What are preserved traces of organisms?

  Footprints or spaces left by roots
• Why are there very few fossils of early life-forms?

  Soft-bodied organisms rarely form fossils
• What happens to many fossils of early life-forms?

  They have been destroyed by rock changes
• What does the lack of early life-form fossils imply?

  Uncertainty about how life on Earth began
• What is a species considered when no individuals are alive?

  Extinct
• What can cause a species to become extinct?

  Catastrophic events, environmental changes, competition
• What catastrophic event led to the extinction of dinosaurs?

  An asteroid colliding with the Earth
• How can environmental changes lead to extinction?

  New diseases or predators can kill species
• How can competition with new species lead to extinction?

  New species compete for scarce resources
• What are the key points about fossil formation?

  • Fossils can form from non-decayed parts.
  • Fossils can form from mineral replacement during decay.
  • Fossils can be preserved traces like footprints.
• What are the reasons for the scarcity of early life-form fossils?

  • Soft-bodied organisms rarely fossilize.
  • Many fossils have been destroyed by geological changes.
  • Uncertainty about the origins of life due to few fossils.
• What are the main causes of species extinction?

  • Catastrophic events (e.g., asteroid impacts).
  • Environmental changes (e.g., new diseases, predators).
  • Competition with more successful species.