Fossils and extinction

• 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?

  Gaps left by decayed organisms in clay
• What are impressions in fossil formation?

  Marks left by organisms on the ground
• How can fossils be preserved without decay?

  By being trapped in amber or tar pits
• What conditions prevent decay in fossils?

  No oxygen or moisture present
• How old are the oldest fossils found?

  Between 3.5 and 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
• What does it mean for a species to be extinct?

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

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

  By hunting species to extinction
• How can diseases contribute to extinction?

  By spreading rapidly through populations
• What catastrophic event wiped out the dinosaurs?

  An asteroid hit Mexico
• What can happen when a new species arrives?

  It may outcompete existing species for resources
• How do rapid environmental changes affect species survival?

  They can lead to extinction if species can't adapt