What Are Fossils?#78

• What are fossils?

  Remains of long dead organisms
• Why is studying fossils important?

  They provide evidence of extinct organisms
• How do fossils provide evidence for evolution?

  They show incremental changes over time
• What are the three main ways fossils can form?

  1. Gradual replacement by minerals
  2. Casts and impressions
  3. Preservation without decay
• How do gradual replacement fossils form?

  Body parts decay and are replaced by minerals
• What types of body parts commonly form fossils?

  Bones, teeth, and shells
• What are casts in fossil formation?

  Impressions left by decayed organisms
• How do impressions differ from casts?

  Impressions are marks left on the ground
• What conditions lead to fossil preservation?

  No decay occurs in amber or tar pits
• What is the age range of the oldest fossils found?

  3.5 to 4 billion years old
• Why is there an incomplete fossil record?

  Many early life forms were soft-bodied
• What geological events can destroy ancient fossils?

  Volcanoes, earthquakes, and tectonic movement
• When can we say a species has gone extinct?

  No individuals of that species remain
• What is a common reason for species extinction?

  Rapid environmental changes
• How can human hunting lead to extinction?

  It drives entire species to extinction
• How can diseases contribute to extinction?

  They can spread and kill populations
• What catastrophic event wiped out the dinosaurs?

  An asteroid hit Mexico
• What are the main reasons for species extinction?

  • Rapid environmental changes
  • New predators
  • Human hunting
  • New diseases
  • Competition from new species
  • Catastrophic events