Fossils and Extinction

• What are fossils?

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

  They provide insight into 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 are impressions different from casts?

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

  No decay occurs in amber or tar pits
• Where can fossils be preserved without decay?

  In amber, tar pits, glaciers, or peat bogs
• 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 can destroy ancient fossils?

  Volcanoes, earthquakes, and tectonic activity
• When is a species considered extinct?

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

  Rapid environmental changes
• How can new predators contribute to extinction?

  They can kill off existing species
• How has human activity affected species extinction?

  Human hunting has driven species extinct
• How can diseases lead to extinction?

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

  An asteroid hit Mexico 66 million years ago
• What are the main causes of extinction?

  • Rapid environmental changes
  • Arrival of new predators
  • Spread of diseases
  • Competition from new species
  • Catastrophic events